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Diffstat (limited to 'contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 3167 |
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diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp new file mode 100644 index 0000000..903a0b5 --- /dev/null +++ b/contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -0,0 +1,3167 @@ +//===- InstructionCombining.cpp - Combine multiple instructions -----------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// InstructionCombining - Combine instructions to form fewer, simple +// instructions. This pass does not modify the CFG. This pass is where +// algebraic simplification happens. +// +// This pass combines things like: +// %Y = add i32 %X, 1 +// %Z = add i32 %Y, 1 +// into: +// %Z = add i32 %X, 2 +// +// This is a simple worklist driven algorithm. +// +// This pass guarantees that the following canonicalizations are performed on +// the program: +// 1. If a binary operator has a constant operand, it is moved to the RHS +// 2. Bitwise operators with constant operands are always grouped so that +// shifts are performed first, then or's, then and's, then xor's. +// 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible +// 4. All cmp instructions on boolean values are replaced with logical ops +// 5. add X, X is represented as (X*2) => (X << 1) +// 6. Multiplies with a power-of-two constant argument are transformed into +// shifts. +// ... etc. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/InstCombine/InstCombine.h" +#include "InstCombineInternal.h" +#include "llvm-c/Initialization.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/StringSwitch.h" +#include "llvm/Analysis/AssumptionCache.h" +#include "llvm/Analysis/CFG.h" +#include "llvm/Analysis/ConstantFolding.h" +#include "llvm/Analysis/EHPersonalities.h" +#include "llvm/Analysis/GlobalsModRef.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/LoopInfo.h" +#include "llvm/Analysis/MemoryBuiltins.h" +#include "llvm/Analysis/TargetLibraryInfo.h" +#include "llvm/Analysis/ValueTracking.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/DataLayout.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/GetElementPtrTypeIterator.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/PatternMatch.h" +#include "llvm/IR/ValueHandle.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Utils/Local.h" +#include <algorithm> +#include <climits> +using namespace llvm; +using namespace llvm::PatternMatch; + +#define DEBUG_TYPE "instcombine" + +STATISTIC(NumCombined , "Number of insts combined"); +STATISTIC(NumConstProp, "Number of constant folds"); +STATISTIC(NumDeadInst , "Number of dead inst eliminated"); +STATISTIC(NumSunkInst , "Number of instructions sunk"); +STATISTIC(NumExpand, "Number of expansions"); +STATISTIC(NumFactor , "Number of factorizations"); +STATISTIC(NumReassoc , "Number of reassociations"); + +Value *InstCombiner::EmitGEPOffset(User *GEP) { + return llvm::EmitGEPOffset(Builder, DL, GEP); +} + +/// Return true if it is desirable to convert an integer computation from a +/// given bit width to a new bit width. +/// We don't want to convert from a legal to an illegal type for example or from +/// a smaller to a larger illegal type. +bool InstCombiner::ShouldChangeType(unsigned FromWidth, + unsigned ToWidth) const { + bool FromLegal = DL.isLegalInteger(FromWidth); + bool ToLegal = DL.isLegalInteger(ToWidth); + + // If this is a legal integer from type, and the result would be an illegal + // type, don't do the transformation. + if (FromLegal && !ToLegal) + return false; + + // Otherwise, if both are illegal, do not increase the size of the result. We + // do allow things like i160 -> i64, but not i64 -> i160. + if (!FromLegal && !ToLegal && ToWidth > FromWidth) + return false; + + return true; +} + +/// Return true if it is desirable to convert a computation from 'From' to 'To'. +/// We don't want to convert from a legal to an illegal type for example or from +/// a smaller to a larger illegal type. +bool InstCombiner::ShouldChangeType(Type *From, Type *To) const { + assert(From->isIntegerTy() && To->isIntegerTy()); + + unsigned FromWidth = From->getPrimitiveSizeInBits(); + unsigned ToWidth = To->getPrimitiveSizeInBits(); + return ShouldChangeType(FromWidth, ToWidth); +} + +// Return true, if No Signed Wrap should be maintained for I. +// The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C", +// where both B and C should be ConstantInts, results in a constant that does +// not overflow. This function only handles the Add and Sub opcodes. For +// all other opcodes, the function conservatively returns false. +static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) { + OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I); + if (!OBO || !OBO->hasNoSignedWrap()) { + return false; + } + + // We reason about Add and Sub Only. + Instruction::BinaryOps Opcode = I.getOpcode(); + if (Opcode != Instruction::Add && + Opcode != Instruction::Sub) { + return false; + } + + ConstantInt *CB = dyn_cast<ConstantInt>(B); + ConstantInt *CC = dyn_cast<ConstantInt>(C); + + if (!CB || !CC) { + return false; + } + + const APInt &BVal = CB->getValue(); + const APInt &CVal = CC->getValue(); + bool Overflow = false; + + if (Opcode == Instruction::Add) { + BVal.sadd_ov(CVal, Overflow); + } else { + BVal.ssub_ov(CVal, Overflow); + } + + return !Overflow; +} + +/// Conservatively clears subclassOptionalData after a reassociation or +/// commutation. We preserve fast-math flags when applicable as they can be +/// preserved. +static void ClearSubclassDataAfterReassociation(BinaryOperator &I) { + FPMathOperator *FPMO = dyn_cast<FPMathOperator>(&I); + if (!FPMO) { + I.clearSubclassOptionalData(); + return; + } + + FastMathFlags FMF = I.getFastMathFlags(); + I.clearSubclassOptionalData(); + I.setFastMathFlags(FMF); +} + +/// This performs a few simplifications for operators that are associative or +/// commutative: +/// +/// Commutative operators: +/// +/// 1. Order operands such that they are listed from right (least complex) to +/// left (most complex). This puts constants before unary operators before +/// binary operators. +/// +/// Associative operators: +/// +/// 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. +/// 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. +/// +/// Associative and commutative operators: +/// +/// 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. +/// 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. +/// 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" +/// if C1 and C2 are constants. +bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) { + Instruction::BinaryOps Opcode = I.getOpcode(); + bool Changed = false; + + do { + // Order operands such that they are listed from right (least complex) to + // left (most complex). This puts constants before unary operators before + // binary operators. + if (I.isCommutative() && getComplexity(I.getOperand(0)) < + getComplexity(I.getOperand(1))) + Changed = !I.swapOperands(); + + BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0)); + BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)); + + if (I.isAssociative()) { + // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. + if (Op0 && Op0->getOpcode() == Opcode) { + Value *A = Op0->getOperand(0); + Value *B = Op0->getOperand(1); + Value *C = I.getOperand(1); + + // Does "B op C" simplify? + if (Value *V = SimplifyBinOp(Opcode, B, C, DL)) { + // It simplifies to V. Form "A op V". + I.setOperand(0, A); + I.setOperand(1, V); + // Conservatively clear the optional flags, since they may not be + // preserved by the reassociation. + if (MaintainNoSignedWrap(I, B, C) && + (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) { + // Note: this is only valid because SimplifyBinOp doesn't look at + // the operands to Op0. + I.clearSubclassOptionalData(); + I.setHasNoSignedWrap(true); + } else { + ClearSubclassDataAfterReassociation(I); + } + + Changed = true; + ++NumReassoc; + continue; + } + } + + // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. + if (Op1 && Op1->getOpcode() == Opcode) { + Value *A = I.getOperand(0); + Value *B = Op1->getOperand(0); + Value *C = Op1->getOperand(1); + + // Does "A op B" simplify? + if (Value *V = SimplifyBinOp(Opcode, A, B, DL)) { + // It simplifies to V. Form "V op C". + I.setOperand(0, V); + I.setOperand(1, C); + // Conservatively clear the optional flags, since they may not be + // preserved by the reassociation. + ClearSubclassDataAfterReassociation(I); + Changed = true; + ++NumReassoc; + continue; + } + } + } + + if (I.isAssociative() && I.isCommutative()) { + // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. + if (Op0 && Op0->getOpcode() == Opcode) { + Value *A = Op0->getOperand(0); + Value *B = Op0->getOperand(1); + Value *C = I.getOperand(1); + + // Does "C op A" simplify? + if (Value *V = SimplifyBinOp(Opcode, C, A, DL)) { + // It simplifies to V. Form "V op B". + I.setOperand(0, V); + I.setOperand(1, B); + // Conservatively clear the optional flags, since they may not be + // preserved by the reassociation. + ClearSubclassDataAfterReassociation(I); + Changed = true; + ++NumReassoc; + continue; + } + } + + // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. + if (Op1 && Op1->getOpcode() == Opcode) { + Value *A = I.getOperand(0); + Value *B = Op1->getOperand(0); + Value *C = Op1->getOperand(1); + + // Does "C op A" simplify? + if (Value *V = SimplifyBinOp(Opcode, C, A, DL)) { + // It simplifies to V. Form "B op V". + I.setOperand(0, B); + I.setOperand(1, V); + // Conservatively clear the optional flags, since they may not be + // preserved by the reassociation. + ClearSubclassDataAfterReassociation(I); + Changed = true; + ++NumReassoc; + continue; + } + } + + // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" + // if C1 and C2 are constants. + if (Op0 && Op1 && + Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode && + isa<Constant>(Op0->getOperand(1)) && + isa<Constant>(Op1->getOperand(1)) && + Op0->hasOneUse() && Op1->hasOneUse()) { + Value *A = Op0->getOperand(0); + Constant *C1 = cast<Constant>(Op0->getOperand(1)); + Value *B = Op1->getOperand(0); + Constant *C2 = cast<Constant>(Op1->getOperand(1)); + + Constant *Folded = ConstantExpr::get(Opcode, C1, C2); + BinaryOperator *New = BinaryOperator::Create(Opcode, A, B); + if (isa<FPMathOperator>(New)) { + FastMathFlags Flags = I.getFastMathFlags(); + Flags &= Op0->getFastMathFlags(); + Flags &= Op1->getFastMathFlags(); + New->setFastMathFlags(Flags); + } + InsertNewInstWith(New, I); + New->takeName(Op1); + I.setOperand(0, New); + I.setOperand(1, Folded); + // Conservatively clear the optional flags, since they may not be + // preserved by the reassociation. + ClearSubclassDataAfterReassociation(I); + + Changed = true; + continue; + } + } + + // No further simplifications. + return Changed; + } while (1); +} + +/// Return whether "X LOp (Y ROp Z)" is always equal to +/// "(X LOp Y) ROp (X LOp Z)". +static bool LeftDistributesOverRight(Instruction::BinaryOps LOp, + Instruction::BinaryOps ROp) { + switch (LOp) { + default: + return false; + + case Instruction::And: + // And distributes over Or and Xor. + switch (ROp) { + default: + return false; + case Instruction::Or: + case Instruction::Xor: + return true; + } + + case Instruction::Mul: + // Multiplication distributes over addition and subtraction. + switch (ROp) { + default: + return false; + case Instruction::Add: + case Instruction::Sub: + return true; + } + + case Instruction::Or: + // Or distributes over And. + switch (ROp) { + default: + return false; + case Instruction::And: + return true; + } + } +} + +/// Return whether "(X LOp Y) ROp Z" is always equal to +/// "(X ROp Z) LOp (Y ROp Z)". +static bool RightDistributesOverLeft(Instruction::BinaryOps LOp, + Instruction::BinaryOps ROp) { + if (Instruction::isCommutative(ROp)) + return LeftDistributesOverRight(ROp, LOp); + + switch (LOp) { + default: + return false; + // (X >> Z) & (Y >> Z) -> (X&Y) >> Z for all shifts. + // (X >> Z) | (Y >> Z) -> (X|Y) >> Z for all shifts. + // (X >> Z) ^ (Y >> Z) -> (X^Y) >> Z for all shifts. + case Instruction::And: + case Instruction::Or: + case Instruction::Xor: + switch (ROp) { + default: + return false; + case Instruction::Shl: + case Instruction::LShr: + case Instruction::AShr: + return true; + } + } + // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z", + // but this requires knowing that the addition does not overflow and other + // such subtleties. + return false; +} + +/// This function returns identity value for given opcode, which can be used to +/// factor patterns like (X * 2) + X ==> (X * 2) + (X * 1) ==> X * (2 + 1). +static Value *getIdentityValue(Instruction::BinaryOps OpCode, Value *V) { + if (isa<Constant>(V)) + return nullptr; + + if (OpCode == Instruction::Mul) + return ConstantInt::get(V->getType(), 1); + + // TODO: We can handle other cases e.g. Instruction::And, Instruction::Or etc. + + return nullptr; +} + +/// This function factors binary ops which can be combined using distributive +/// laws. This function tries to transform 'Op' based TopLevelOpcode to enable +/// factorization e.g for ADD(SHL(X , 2), MUL(X, 5)), When this function called +/// with TopLevelOpcode == Instruction::Add and Op = SHL(X, 2), transforms +/// SHL(X, 2) to MUL(X, 4) i.e. returns Instruction::Mul with LHS set to 'X' and +/// RHS to 4. +static Instruction::BinaryOps +getBinOpsForFactorization(Instruction::BinaryOps TopLevelOpcode, + BinaryOperator *Op, Value *&LHS, Value *&RHS) { + if (!Op) + return Instruction::BinaryOpsEnd; + + LHS = Op->getOperand(0); + RHS = Op->getOperand(1); + + switch (TopLevelOpcode) { + default: + return Op->getOpcode(); + + case Instruction::Add: + case Instruction::Sub: + if (Op->getOpcode() == Instruction::Shl) { + if (Constant *CST = dyn_cast<Constant>(Op->getOperand(1))) { + // The multiplier is really 1 << CST. + RHS = ConstantExpr::getShl(ConstantInt::get(Op->getType(), 1), CST); + return Instruction::Mul; + } + } + return Op->getOpcode(); + } + + // TODO: We can add other conversions e.g. shr => div etc. +} + +/// This tries to simplify binary operations by factorizing out common terms +/// (e. g. "(A*B)+(A*C)" -> "A*(B+C)"). +static Value *tryFactorization(InstCombiner::BuilderTy *Builder, + const DataLayout &DL, BinaryOperator &I, + Instruction::BinaryOps InnerOpcode, Value *A, + Value *B, Value *C, Value *D) { + + // If any of A, B, C, D are null, we can not factor I, return early. + // Checking A and C should be enough. + if (!A || !C || !B || !D) + return nullptr; + + Value *V = nullptr; + Value *SimplifiedInst = nullptr; + Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); + Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); + + // Does "X op' Y" always equal "Y op' X"? + bool InnerCommutative = Instruction::isCommutative(InnerOpcode); + + // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"? + if (LeftDistributesOverRight(InnerOpcode, TopLevelOpcode)) + // Does the instruction have the form "(A op' B) op (A op' D)" or, in the + // commutative case, "(A op' B) op (C op' A)"? + if (A == C || (InnerCommutative && A == D)) { + if (A != C) + std::swap(C, D); + // Consider forming "A op' (B op D)". + // If "B op D" simplifies then it can be formed with no cost. + V = SimplifyBinOp(TopLevelOpcode, B, D, DL); + // If "B op D" doesn't simplify then only go on if both of the existing + // operations "A op' B" and "C op' D" will be zapped as no longer used. + if (!V && LHS->hasOneUse() && RHS->hasOneUse()) + V = Builder->CreateBinOp(TopLevelOpcode, B, D, RHS->getName()); + if (V) { + SimplifiedInst = Builder->CreateBinOp(InnerOpcode, A, V); + } + } + + // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? + if (!SimplifiedInst && RightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) + // Does the instruction have the form "(A op' B) op (C op' B)" or, in the + // commutative case, "(A op' B) op (B op' D)"? + if (B == D || (InnerCommutative && B == C)) { + if (B != D) + std::swap(C, D); + // Consider forming "(A op C) op' B". + // If "A op C" simplifies then it can be formed with no cost. + V = SimplifyBinOp(TopLevelOpcode, A, C, DL); + + // If "A op C" doesn't simplify then only go on if both of the existing + // operations "A op' B" and "C op' D" will be zapped as no longer used. + if (!V && LHS->hasOneUse() && RHS->hasOneUse()) + V = Builder->CreateBinOp(TopLevelOpcode, A, C, LHS->getName()); + if (V) { + SimplifiedInst = Builder->CreateBinOp(InnerOpcode, V, B); + } + } + + if (SimplifiedInst) { + ++NumFactor; + SimplifiedInst->takeName(&I); + + // Check if we can add NSW flag to SimplifiedInst. If so, set NSW flag. + // TODO: Check for NUW. + if (BinaryOperator *BO = dyn_cast<BinaryOperator>(SimplifiedInst)) { + if (isa<OverflowingBinaryOperator>(SimplifiedInst)) { + bool HasNSW = false; + if (isa<OverflowingBinaryOperator>(&I)) + HasNSW = I.hasNoSignedWrap(); + + if (BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS)) + if (isa<OverflowingBinaryOperator>(Op0)) + HasNSW &= Op0->hasNoSignedWrap(); + + if (BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS)) + if (isa<OverflowingBinaryOperator>(Op1)) + HasNSW &= Op1->hasNoSignedWrap(); + + // We can propagate 'nsw' if we know that + // %Y = mul nsw i16 %X, C + // %Z = add nsw i16 %Y, %X + // => + // %Z = mul nsw i16 %X, C+1 + // + // iff C+1 isn't INT_MIN + const APInt *CInt; + if (TopLevelOpcode == Instruction::Add && + InnerOpcode == Instruction::Mul) + if (match(V, m_APInt(CInt)) && !CInt->isMinSignedValue()) + BO->setHasNoSignedWrap(HasNSW); + } + } + } + return SimplifiedInst; +} + +/// This tries to simplify binary operations which some other binary operation +/// distributes over either by factorizing out common terms +/// (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this results in +/// simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is a win). +/// Returns the simplified value, or null if it didn't simplify. +Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) { + Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); + BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); + BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); + + // Factorization. + Value *A = nullptr, *B = nullptr, *C = nullptr, *D = nullptr; + auto TopLevelOpcode = I.getOpcode(); + auto LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B); + auto RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D); + + // The instruction has the form "(A op' B) op (C op' D)". Try to factorize + // a common term. + if (LHSOpcode == RHSOpcode) { + if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, C, D)) + return V; + } + + // The instruction has the form "(A op' B) op (C)". Try to factorize common + // term. + if (Value *V = tryFactorization(Builder, DL, I, LHSOpcode, A, B, RHS, + getIdentityValue(LHSOpcode, RHS))) + return V; + + // The instruction has the form "(B) op (C op' D)". Try to factorize common + // term. + if (Value *V = tryFactorization(Builder, DL, I, RHSOpcode, LHS, + getIdentityValue(RHSOpcode, LHS), C, D)) + return V; + + // Expansion. + if (Op0 && RightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) { + // The instruction has the form "(A op' B) op C". See if expanding it out + // to "(A op C) op' (B op C)" results in simplifications. + Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; + Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' + + // Do "A op C" and "B op C" both simplify? + if (Value *L = SimplifyBinOp(TopLevelOpcode, A, C, DL)) + if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, DL)) { + // They do! Return "L op' R". + ++NumExpand; + // If "L op' R" equals "A op' B" then "L op' R" is just the LHS. + if ((L == A && R == B) || + (Instruction::isCommutative(InnerOpcode) && L == B && R == A)) + return Op0; + // Otherwise return "L op' R" if it simplifies. + if (Value *V = SimplifyBinOp(InnerOpcode, L, R, DL)) + return V; + // Otherwise, create a new instruction. + C = Builder->CreateBinOp(InnerOpcode, L, R); + C->takeName(&I); + return C; + } + } + + if (Op1 && LeftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) { + // The instruction has the form "A op (B op' C)". See if expanding it out + // to "(A op B) op' (A op C)" results in simplifications. + Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); + Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op' + + // Do "A op B" and "A op C" both simplify? + if (Value *L = SimplifyBinOp(TopLevelOpcode, A, B, DL)) + if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, DL)) { + // They do! Return "L op' R". + ++NumExpand; + // If "L op' R" equals "B op' C" then "L op' R" is just the RHS. + if ((L == B && R == C) || + (Instruction::isCommutative(InnerOpcode) && L == C && R == B)) + return Op1; + // Otherwise return "L op' R" if it simplifies. + if (Value *V = SimplifyBinOp(InnerOpcode, L, R, DL)) + return V; + // Otherwise, create a new instruction. + A = Builder->CreateBinOp(InnerOpcode, L, R); + A->takeName(&I); + return A; + } + } + + // (op (select (a, c, b)), (select (a, d, b))) -> (select (a, (op c, d), 0)) + // (op (select (a, b, c)), (select (a, b, d))) -> (select (a, 0, (op c, d))) + if (auto *SI0 = dyn_cast<SelectInst>(LHS)) { + if (auto *SI1 = dyn_cast<SelectInst>(RHS)) { + if (SI0->getCondition() == SI1->getCondition()) { + Value *SI = nullptr; + if (Value *V = SimplifyBinOp(TopLevelOpcode, SI0->getFalseValue(), + SI1->getFalseValue(), DL, TLI, DT, AC)) + SI = Builder->CreateSelect(SI0->getCondition(), + Builder->CreateBinOp(TopLevelOpcode, + SI0->getTrueValue(), + SI1->getTrueValue()), + V); + if (Value *V = SimplifyBinOp(TopLevelOpcode, SI0->getTrueValue(), + SI1->getTrueValue(), DL, TLI, DT, AC)) + SI = Builder->CreateSelect( + SI0->getCondition(), V, + Builder->CreateBinOp(TopLevelOpcode, SI0->getFalseValue(), + SI1->getFalseValue())); + if (SI) { + SI->takeName(&I); + return SI; + } + } + } + } + + return nullptr; +} + +/// Given a 'sub' instruction, return the RHS of the instruction if the LHS is a +/// constant zero (which is the 'negate' form). +Value *InstCombiner::dyn_castNegVal(Value *V) const { + if (BinaryOperator::isNeg(V)) + return BinaryOperator::getNegArgument(V); + + // Constants can be considered to be negated values if they can be folded. + if (ConstantInt *C = dyn_cast<ConstantInt>(V)) + return ConstantExpr::getNeg(C); + + if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) + if (C->getType()->getElementType()->isIntegerTy()) + return ConstantExpr::getNeg(C); + + return nullptr; +} + +/// Given a 'fsub' instruction, return the RHS of the instruction if the LHS is +/// a constant negative zero (which is the 'negate' form). +Value *InstCombiner::dyn_castFNegVal(Value *V, bool IgnoreZeroSign) const { + if (BinaryOperator::isFNeg(V, IgnoreZeroSign)) + return BinaryOperator::getFNegArgument(V); + + // Constants can be considered to be negated values if they can be folded. + if (ConstantFP *C = dyn_cast<ConstantFP>(V)) + return ConstantExpr::getFNeg(C); + + if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) + if (C->getType()->getElementType()->isFloatingPointTy()) + return ConstantExpr::getFNeg(C); + + return nullptr; +} + +static Value *FoldOperationIntoSelectOperand(Instruction &I, Value *SO, + InstCombiner *IC) { + if (CastInst *CI = dyn_cast<CastInst>(&I)) { + return IC->Builder->CreateCast(CI->getOpcode(), SO, I.getType()); + } + + // Figure out if the constant is the left or the right argument. + bool ConstIsRHS = isa<Constant>(I.getOperand(1)); + Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS)); + + if (Constant *SOC = dyn_cast<Constant>(SO)) { + if (ConstIsRHS) + return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand); + return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC); + } + + Value *Op0 = SO, *Op1 = ConstOperand; + if (!ConstIsRHS) + std::swap(Op0, Op1); + + if (BinaryOperator *BO = dyn_cast<BinaryOperator>(&I)) { + Value *RI = IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1, + SO->getName()+".op"); + Instruction *FPInst = dyn_cast<Instruction>(RI); + if (FPInst && isa<FPMathOperator>(FPInst)) + FPInst->copyFastMathFlags(BO); + return RI; + } + if (ICmpInst *CI = dyn_cast<ICmpInst>(&I)) + return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, + SO->getName()+".cmp"); + if (FCmpInst *CI = dyn_cast<FCmpInst>(&I)) + return IC->Builder->CreateICmp(CI->getPredicate(), Op0, Op1, + SO->getName()+".cmp"); + llvm_unreachable("Unknown binary instruction type!"); +} + +/// Given an instruction with a select as one operand and a constant as the +/// other operand, try to fold the binary operator into the select arguments. +/// This also works for Cast instructions, which obviously do not have a second +/// operand. +Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) { + // Don't modify shared select instructions + if (!SI->hasOneUse()) return nullptr; + Value *TV = SI->getOperand(1); + Value *FV = SI->getOperand(2); + + if (isa<Constant>(TV) || isa<Constant>(FV)) { + // Bool selects with constant operands can be folded to logical ops. + if (SI->getType()->isIntegerTy(1)) return nullptr; + + // If it's a bitcast involving vectors, make sure it has the same number of + // elements on both sides. + if (BitCastInst *BC = dyn_cast<BitCastInst>(&Op)) { + VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); + VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); + + // Verify that either both or neither are vectors. + if ((SrcTy == nullptr) != (DestTy == nullptr)) return nullptr; + // If vectors, verify that they have the same number of elements. + if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) + return nullptr; + } + + // Test if a CmpInst instruction is used exclusively by a select as + // part of a minimum or maximum operation. If so, refrain from doing + // any other folding. This helps out other analyses which understand + // non-obfuscated minimum and maximum idioms, such as ScalarEvolution + // and CodeGen. And in this case, at least one of the comparison + // operands has at least one user besides the compare (the select), + // which would often largely negate the benefit of folding anyway. + if (auto *CI = dyn_cast<CmpInst>(SI->getCondition())) { + if (CI->hasOneUse()) { + Value *Op0 = CI->getOperand(0), *Op1 = CI->getOperand(1); + if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || + (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) + return nullptr; + } + } + + Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this); + Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this); + + return SelectInst::Create(SI->getCondition(), + SelectTrueVal, SelectFalseVal); + } + return nullptr; +} + +/// Given a binary operator, cast instruction, or select which has a PHI node as +/// operand #0, see if we can fold the instruction into the PHI (which is only +/// possible if all operands to the PHI are constants). +Instruction *InstCombiner::FoldOpIntoPhi(Instruction &I) { + PHINode *PN = cast<PHINode>(I.getOperand(0)); + unsigned NumPHIValues = PN->getNumIncomingValues(); + if (NumPHIValues == 0) + return nullptr; + + // We normally only transform phis with a single use. However, if a PHI has + // multiple uses and they are all the same operation, we can fold *all* of the + // uses into the PHI. + if (!PN->hasOneUse()) { + // Walk the use list for the instruction, comparing them to I. + for (User *U : PN->users()) { + Instruction *UI = cast<Instruction>(U); + if (UI != &I && !I.isIdenticalTo(UI)) + return nullptr; + } + // Otherwise, we can replace *all* users with the new PHI we form. + } + + // Check to see if all of the operands of the PHI are simple constants + // (constantint/constantfp/undef). If there is one non-constant value, + // remember the BB it is in. If there is more than one or if *it* is a PHI, + // bail out. We don't do arbitrary constant expressions here because moving + // their computation can be expensive without a cost model. + BasicBlock *NonConstBB = nullptr; + for (unsigned i = 0; i != NumPHIValues; ++i) { + Value *InVal = PN->getIncomingValue(i); + if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal)) + continue; + + if (isa<PHINode>(InVal)) return nullptr; // Itself a phi. + if (NonConstBB) return nullptr; // More than one non-const value. + + NonConstBB = PN->getIncomingBlock(i); + + // If the InVal is an invoke at the end of the pred block, then we can't + // insert a computation after it without breaking the edge. + if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) + if (II->getParent() == NonConstBB) + return nullptr; + + // If the incoming non-constant value is in I's block, we will remove one + // instruction, but insert another equivalent one, leading to infinite + // instcombine. + if (isPotentiallyReachable(I.getParent(), NonConstBB, DT, LI)) + return nullptr; + } + + // If there is exactly one non-constant value, we can insert a copy of the + // operation in that block. However, if this is a critical edge, we would be + // inserting the computation on some other paths (e.g. inside a loop). Only + // do this if the pred block is unconditionally branching into the phi block. + if (NonConstBB != nullptr) { + BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); + if (!BI || !BI->isUnconditional()) return nullptr; + } + + // Okay, we can do the transformation: create the new PHI node. + PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues()); + InsertNewInstBefore(NewPN, *PN); + NewPN->takeName(PN); + + // If we are going to have to insert a new computation, do so right before the + // predecessor's terminator. + if (NonConstBB) + Builder->SetInsertPoint(NonConstBB->getTerminator()); + + // Next, add all of the operands to the PHI. + if (SelectInst *SI = dyn_cast<SelectInst>(&I)) { + // We only currently try to fold the condition of a select when it is a phi, + // not the true/false values. + Value *TrueV = SI->getTrueValue(); + Value *FalseV = SI->getFalseValue(); + BasicBlock *PhiTransBB = PN->getParent(); + for (unsigned i = 0; i != NumPHIValues; ++i) { + BasicBlock *ThisBB = PN->getIncomingBlock(i); + Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB); + Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB); + Value *InV = nullptr; + // Beware of ConstantExpr: it may eventually evaluate to getNullValue, + // even if currently isNullValue gives false. + Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)); + if (InC && !isa<ConstantExpr>(InC)) + InV = InC->isNullValue() ? FalseVInPred : TrueVInPred; + else + InV = Builder->CreateSelect(PN->getIncomingValue(i), + TrueVInPred, FalseVInPred, "phitmp"); + NewPN->addIncoming(InV, ThisBB); + } + } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) { + Constant *C = cast<Constant>(I.getOperand(1)); + for (unsigned i = 0; i != NumPHIValues; ++i) { + Value *InV = nullptr; + if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) + InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C); + else if (isa<ICmpInst>(CI)) + InV = Builder->CreateICmp(CI->getPredicate(), PN->getIncomingValue(i), + C, "phitmp"); + else + InV = Builder->CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i), + C, "phitmp"); + NewPN->addIncoming(InV, PN->getIncomingBlock(i)); + } + } else if (I.getNumOperands() == 2) { + Constant *C = cast<Constant>(I.getOperand(1)); + for (unsigned i = 0; i != NumPHIValues; ++i) { + Value *InV = nullptr; + if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) + InV = ConstantExpr::get(I.getOpcode(), InC, C); + else + InV = Builder->CreateBinOp(cast<BinaryOperator>(I).getOpcode(), + PN->getIncomingValue(i), C, "phitmp"); + NewPN->addIncoming(InV, PN->getIncomingBlock(i)); + } + } else { + CastInst *CI = cast<CastInst>(&I); + Type *RetTy = CI->getType(); + for (unsigned i = 0; i != NumPHIValues; ++i) { + Value *InV; + if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) + InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy); + else + InV = Builder->CreateCast(CI->getOpcode(), + PN->getIncomingValue(i), I.getType(), "phitmp"); + NewPN->addIncoming(InV, PN->getIncomingBlock(i)); + } + } + + for (auto UI = PN->user_begin(), E = PN->user_end(); UI != E;) { + Instruction *User = cast<Instruction>(*UI++); + if (User == &I) continue; + ReplaceInstUsesWith(*User, NewPN); + EraseInstFromFunction(*User); + } + return ReplaceInstUsesWith(I, NewPN); +} + +/// Given a pointer type and a constant offset, determine whether or not there +/// is a sequence of GEP indices into the pointed type that will land us at the +/// specified offset. If so, fill them into NewIndices and return the resultant +/// element type, otherwise return null. +Type *InstCombiner::FindElementAtOffset(PointerType *PtrTy, int64_t Offset, + SmallVectorImpl<Value *> &NewIndices) { + Type *Ty = PtrTy->getElementType(); + if (!Ty->isSized()) + return nullptr; + + // Start with the index over the outer type. Note that the type size + // might be zero (even if the offset isn't zero) if the indexed type + // is something like [0 x {int, int}] + Type *IntPtrTy = DL.getIntPtrType(PtrTy); + int64_t FirstIdx = 0; + if (int64_t TySize = DL.getTypeAllocSize(Ty)) { + FirstIdx = Offset/TySize; + Offset -= FirstIdx*TySize; + + // Handle hosts where % returns negative instead of values [0..TySize). + if (Offset < 0) { + --FirstIdx; + Offset += TySize; + assert(Offset >= 0); + } + assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset"); + } + + NewIndices.push_back(ConstantInt::get(IntPtrTy, FirstIdx)); + + // Index into the types. If we fail, set OrigBase to null. + while (Offset) { + // Indexing into tail padding between struct/array elements. + if (uint64_t(Offset * 8) >= DL.getTypeSizeInBits(Ty)) + return nullptr; + + if (StructType *STy = dyn_cast<StructType>(Ty)) { + const StructLayout *SL = DL.getStructLayout(STy); + assert(Offset < (int64_t)SL->getSizeInBytes() && + "Offset must stay within the indexed type"); + + unsigned Elt = SL->getElementContainingOffset(Offset); + NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), + Elt)); + + Offset -= SL->getElementOffset(Elt); + Ty = STy->getElementType(Elt); + } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) { + uint64_t EltSize = DL.getTypeAllocSize(AT->getElementType()); + assert(EltSize && "Cannot index into a zero-sized array"); + NewIndices.push_back(ConstantInt::get(IntPtrTy,Offset/EltSize)); + Offset %= EltSize; + Ty = AT->getElementType(); + } else { + // Otherwise, we can't index into the middle of this atomic type, bail. + return nullptr; + } + } + + return Ty; +} + +static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) { + // If this GEP has only 0 indices, it is the same pointer as + // Src. If Src is not a trivial GEP too, don't combine + // the indices. + if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() && + !Src.hasOneUse()) + return false; + return true; +} + +/// Return a value X such that Val = X * Scale, or null if none. +/// If the multiplication is known not to overflow, then NoSignedWrap is set. +Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) { + assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!"); + assert(cast<IntegerType>(Val->getType())->getBitWidth() == + Scale.getBitWidth() && "Scale not compatible with value!"); + + // If Val is zero or Scale is one then Val = Val * Scale. + if (match(Val, m_Zero()) || Scale == 1) { + NoSignedWrap = true; + return Val; + } + + // If Scale is zero then it does not divide Val. + if (Scale.isMinValue()) + return nullptr; + + // Look through chains of multiplications, searching for a constant that is + // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4 + // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by + // a factor of 4 will produce X*(Y*2). The principle of operation is to bore + // down from Val: + // + // Val = M1 * X || Analysis starts here and works down + // M1 = M2 * Y || Doesn't descend into terms with more + // M2 = Z * 4 \/ than one use + // + // Then to modify a term at the bottom: + // + // Val = M1 * X + // M1 = Z * Y || Replaced M2 with Z + // + // Then to work back up correcting nsw flags. + + // Op - the term we are currently analyzing. Starts at Val then drills down. + // Replaced with its descaled value before exiting from the drill down loop. + Value *Op = Val; + + // Parent - initially null, but after drilling down notes where Op came from. + // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the + // 0'th operand of Val. + std::pair<Instruction*, unsigned> Parent; + + // Set if the transform requires a descaling at deeper levels that doesn't + // overflow. + bool RequireNoSignedWrap = false; + + // Log base 2 of the scale. Negative if not a power of 2. + int32_t logScale = Scale.exactLogBase2(); + + for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down + + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) { + // If Op is a constant divisible by Scale then descale to the quotient. + APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth. + APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder); + if (!Remainder.isMinValue()) + // Not divisible by Scale. + return nullptr; + // Replace with the quotient in the parent. + Op = ConstantInt::get(CI->getType(), Quotient); + NoSignedWrap = true; + break; + } + + if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) { + + if (BO->getOpcode() == Instruction::Mul) { + // Multiplication. + NoSignedWrap = BO->hasNoSignedWrap(); + if (RequireNoSignedWrap && !NoSignedWrap) + return nullptr; + + // There are three cases for multiplication: multiplication by exactly + // the scale, multiplication by a constant different to the scale, and + // multiplication by something else. + Value *LHS = BO->getOperand(0); + Value *RHS = BO->getOperand(1); + + if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { + // Multiplication by a constant. + if (CI->getValue() == Scale) { + // Multiplication by exactly the scale, replace the multiplication + // by its left-hand side in the parent. + Op = LHS; + break; + } + + // Otherwise drill down into the constant. + if (!Op->hasOneUse()) + return nullptr; + + Parent = std::make_pair(BO, 1); + continue; + } + + // Multiplication by something else. Drill down into the left-hand side + // since that's where the reassociate pass puts the good stuff. + if (!Op->hasOneUse()) + return nullptr; + + Parent = std::make_pair(BO, 0); + continue; + } + + if (logScale > 0 && BO->getOpcode() == Instruction::Shl && + isa<ConstantInt>(BO->getOperand(1))) { + // Multiplication by a power of 2. + NoSignedWrap = BO->hasNoSignedWrap(); + if (RequireNoSignedWrap && !NoSignedWrap) + return nullptr; + + Value *LHS = BO->getOperand(0); + int32_t Amt = cast<ConstantInt>(BO->getOperand(1))-> + getLimitedValue(Scale.getBitWidth()); + // Op = LHS << Amt. + + if (Amt == logScale) { + // Multiplication by exactly the scale, replace the multiplication + // by its left-hand side in the parent. + Op = LHS; + break; + } + if (Amt < logScale || !Op->hasOneUse()) + return nullptr; + + // Multiplication by more than the scale. Reduce the multiplying amount + // by the scale in the parent. + Parent = std::make_pair(BO, 1); + Op = ConstantInt::get(BO->getType(), Amt - logScale); + break; + } + } + + if (!Op->hasOneUse()) + return nullptr; + + if (CastInst *Cast = dyn_cast<CastInst>(Op)) { + if (Cast->getOpcode() == Instruction::SExt) { + // Op is sign-extended from a smaller type, descale in the smaller type. + unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); + APInt SmallScale = Scale.trunc(SmallSize); + // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to + // descale Op as (sext Y) * Scale. In order to have + // sext (Y * SmallScale) = (sext Y) * Scale + // some conditions need to hold however: SmallScale must sign-extend to + // Scale and the multiplication Y * SmallScale should not overflow. + if (SmallScale.sext(Scale.getBitWidth()) != Scale) + // SmallScale does not sign-extend to Scale. + return nullptr; + assert(SmallScale.exactLogBase2() == logScale); + // Require that Y * SmallScale must not overflow. + RequireNoSignedWrap = true; + + // Drill down through the cast. + Parent = std::make_pair(Cast, 0); + Scale = SmallScale; + continue; + } + + if (Cast->getOpcode() == Instruction::Trunc) { + // Op is truncated from a larger type, descale in the larger type. + // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then + // trunc (Y * sext Scale) = (trunc Y) * Scale + // always holds. However (trunc Y) * Scale may overflow even if + // trunc (Y * sext Scale) does not, so nsw flags need to be cleared + // from this point up in the expression (see later). + if (RequireNoSignedWrap) + return nullptr; + + // Drill down through the cast. + unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); + Parent = std::make_pair(Cast, 0); + Scale = Scale.sext(LargeSize); + if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits()) + logScale = -1; + assert(Scale.exactLogBase2() == logScale); + continue; + } + } + + // Unsupported expression, bail out. + return nullptr; + } + + // If Op is zero then Val = Op * Scale. + if (match(Op, m_Zero())) { + NoSignedWrap = true; + return Op; + } + + // We know that we can successfully descale, so from here on we can safely + // modify the IR. Op holds the descaled version of the deepest term in the + // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known + // not to overflow. + + if (!Parent.first) + // The expression only had one term. + return Op; + + // Rewrite the parent using the descaled version of its operand. + assert(Parent.first->hasOneUse() && "Drilled down when more than one use!"); + assert(Op != Parent.first->getOperand(Parent.second) && + "Descaling was a no-op?"); + Parent.first->setOperand(Parent.second, Op); + Worklist.Add(Parent.first); + + // Now work back up the expression correcting nsw flags. The logic is based + // on the following observation: if X * Y is known not to overflow as a signed + // multiplication, and Y is replaced by a value Z with smaller absolute value, + // then X * Z will not overflow as a signed multiplication either. As we work + // our way up, having NoSignedWrap 'true' means that the descaled value at the + // current level has strictly smaller absolute value than the original. + Instruction *Ancestor = Parent.first; + do { + if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) { + // If the multiplication wasn't nsw then we can't say anything about the + // value of the descaled multiplication, and we have to clear nsw flags + // from this point on up. + bool OpNoSignedWrap = BO->hasNoSignedWrap(); + NoSignedWrap &= OpNoSignedWrap; + if (NoSignedWrap != OpNoSignedWrap) { + BO->setHasNoSignedWrap(NoSignedWrap); + Worklist.Add(Ancestor); + } + } else if (Ancestor->getOpcode() == Instruction::Trunc) { + // The fact that the descaled input to the trunc has smaller absolute + // value than the original input doesn't tell us anything useful about + // the absolute values of the truncations. + NoSignedWrap = false; + } + assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) && + "Failed to keep proper track of nsw flags while drilling down?"); + + if (Ancestor == Val) + // Got to the top, all done! + return Val; + + // Move up one level in the expression. + assert(Ancestor->hasOneUse() && "Drilled down when more than one use!"); + Ancestor = Ancestor->user_back(); + } while (1); +} + +/// \brief Creates node of binary operation with the same attributes as the +/// specified one but with other operands. +static Value *CreateBinOpAsGiven(BinaryOperator &Inst, Value *LHS, Value *RHS, + InstCombiner::BuilderTy *B) { + Value *BO = B->CreateBinOp(Inst.getOpcode(), LHS, RHS); + // If LHS and RHS are constant, BO won't be a binary operator. + if (BinaryOperator *NewBO = dyn_cast<BinaryOperator>(BO)) + NewBO->copyIRFlags(&Inst); + return BO; +} + +/// \brief Makes transformation of binary operation specific for vector types. +/// \param Inst Binary operator to transform. +/// \return Pointer to node that must replace the original binary operator, or +/// null pointer if no transformation was made. +Value *InstCombiner::SimplifyVectorOp(BinaryOperator &Inst) { + if (!Inst.getType()->isVectorTy()) return nullptr; + + // It may not be safe to reorder shuffles and things like div, urem, etc. + // because we may trap when executing those ops on unknown vector elements. + // See PR20059. + if (!isSafeToSpeculativelyExecute(&Inst)) + return nullptr; + + unsigned VWidth = cast<VectorType>(Inst.getType())->getNumElements(); + Value *LHS = Inst.getOperand(0), *RHS = Inst.getOperand(1); + assert(cast<VectorType>(LHS->getType())->getNumElements() == VWidth); + assert(cast<VectorType>(RHS->getType())->getNumElements() == VWidth); + + // If both arguments of binary operation are shuffles, which use the same + // mask and shuffle within a single vector, it is worthwhile to move the + // shuffle after binary operation: + // Op(shuffle(v1, m), shuffle(v2, m)) -> shuffle(Op(v1, v2), m) + if (isa<ShuffleVectorInst>(LHS) && isa<ShuffleVectorInst>(RHS)) { + ShuffleVectorInst *LShuf = cast<ShuffleVectorInst>(LHS); + ShuffleVectorInst *RShuf = cast<ShuffleVectorInst>(RHS); + if (isa<UndefValue>(LShuf->getOperand(1)) && + isa<UndefValue>(RShuf->getOperand(1)) && + LShuf->getOperand(0)->getType() == RShuf->getOperand(0)->getType() && + LShuf->getMask() == RShuf->getMask()) { + Value *NewBO = CreateBinOpAsGiven(Inst, LShuf->getOperand(0), + RShuf->getOperand(0), Builder); + return Builder->CreateShuffleVector(NewBO, + UndefValue::get(NewBO->getType()), LShuf->getMask()); + } + } + + // If one argument is a shuffle within one vector, the other is a constant, + // try moving the shuffle after the binary operation. + ShuffleVectorInst *Shuffle = nullptr; + Constant *C1 = nullptr; + if (isa<ShuffleVectorInst>(LHS)) Shuffle = cast<ShuffleVectorInst>(LHS); + if (isa<ShuffleVectorInst>(RHS)) Shuffle = cast<ShuffleVectorInst>(RHS); + if (isa<Constant>(LHS)) C1 = cast<Constant>(LHS); + if (isa<Constant>(RHS)) C1 = cast<Constant>(RHS); + if (Shuffle && C1 && + (isa<ConstantVector>(C1) || isa<ConstantDataVector>(C1)) && + isa<UndefValue>(Shuffle->getOperand(1)) && + Shuffle->getType() == Shuffle->getOperand(0)->getType()) { + SmallVector<int, 16> ShMask = Shuffle->getShuffleMask(); + // Find constant C2 that has property: + // shuffle(C2, ShMask) = C1 + // If such constant does not exist (example: ShMask=<0,0> and C1=<1,2>) + // reorder is not possible. + SmallVector<Constant*, 16> C2M(VWidth, + UndefValue::get(C1->getType()->getScalarType())); + bool MayChange = true; + for (unsigned I = 0; I < VWidth; ++I) { + if (ShMask[I] >= 0) { + assert(ShMask[I] < (int)VWidth); + if (!isa<UndefValue>(C2M[ShMask[I]])) { + MayChange = false; + break; + } + C2M[ShMask[I]] = C1->getAggregateElement(I); + } + } + if (MayChange) { + Constant *C2 = ConstantVector::get(C2M); + Value *NewLHS = isa<Constant>(LHS) ? C2 : Shuffle->getOperand(0); + Value *NewRHS = isa<Constant>(LHS) ? Shuffle->getOperand(0) : C2; + Value *NewBO = CreateBinOpAsGiven(Inst, NewLHS, NewRHS, Builder); + return Builder->CreateShuffleVector(NewBO, + UndefValue::get(Inst.getType()), Shuffle->getMask()); + } + } + + return nullptr; +} + +Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { + SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); + + if (Value *V = SimplifyGEPInst(Ops, DL, TLI, DT, AC)) + return ReplaceInstUsesWith(GEP, V); + + Value *PtrOp = GEP.getOperand(0); + + // Eliminate unneeded casts for indices, and replace indices which displace + // by multiples of a zero size type with zero. + bool MadeChange = false; + Type *IntPtrTy = + DL.getIntPtrType(GEP.getPointerOperandType()->getScalarType()); + + gep_type_iterator GTI = gep_type_begin(GEP); + for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); I != E; + ++I, ++GTI) { + // Skip indices into struct types. + SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI); + if (!SeqTy) + continue; + + // Index type should have the same width as IntPtr + Type *IndexTy = (*I)->getType(); + Type *NewIndexType = IndexTy->isVectorTy() ? + VectorType::get(IntPtrTy, IndexTy->getVectorNumElements()) : IntPtrTy; + + // If the element type has zero size then any index over it is equivalent + // to an index of zero, so replace it with zero if it is not zero already. + if (SeqTy->getElementType()->isSized() && + DL.getTypeAllocSize(SeqTy->getElementType()) == 0) + if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { + *I = Constant::getNullValue(NewIndexType); + MadeChange = true; + } + + if (IndexTy != NewIndexType) { + // If we are using a wider index than needed for this platform, shrink + // it to what we need. If narrower, sign-extend it to what we need. + // This explicit cast can make subsequent optimizations more obvious. + *I = Builder->CreateIntCast(*I, NewIndexType, true); + MadeChange = true; + } + } + if (MadeChange) + return &GEP; + + // Check to see if the inputs to the PHI node are getelementptr instructions. + if (PHINode *PN = dyn_cast<PHINode>(PtrOp)) { + GetElementPtrInst *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0)); + if (!Op1) + return nullptr; + + // Don't fold a GEP into itself through a PHI node. This can only happen + // through the back-edge of a loop. Folding a GEP into itself means that + // the value of the previous iteration needs to be stored in the meantime, + // thus requiring an additional register variable to be live, but not + // actually achieving anything (the GEP still needs to be executed once per + // loop iteration). + if (Op1 == &GEP) + return nullptr; + + signed DI = -1; + + for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) { + GetElementPtrInst *Op2 = dyn_cast<GetElementPtrInst>(*I); + if (!Op2 || Op1->getNumOperands() != Op2->getNumOperands()) + return nullptr; + + // As for Op1 above, don't try to fold a GEP into itself. + if (Op2 == &GEP) + return nullptr; + + // Keep track of the type as we walk the GEP. + Type *CurTy = Op1->getOperand(0)->getType()->getScalarType(); + + for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) { + if (Op1->getOperand(J)->getType() != Op2->getOperand(J)->getType()) + return nullptr; + + if (Op1->getOperand(J) != Op2->getOperand(J)) { + if (DI == -1) { + // We have not seen any differences yet in the GEPs feeding the + // PHI yet, so we record this one if it is allowed to be a + // variable. + + // The first two arguments can vary for any GEP, the rest have to be + // static for struct slots + if (J > 1 && CurTy->isStructTy()) + return nullptr; + + DI = J; + } else { + // The GEP is different by more than one input. While this could be + // extended to support GEPs that vary by more than one variable it + // doesn't make sense since it greatly increases the complexity and + // would result in an R+R+R addressing mode which no backend + // directly supports and would need to be broken into several + // simpler instructions anyway. + return nullptr; + } + } + + // Sink down a layer of the type for the next iteration. + if (J > 0) { + if (CompositeType *CT = dyn_cast<CompositeType>(CurTy)) { + CurTy = CT->getTypeAtIndex(Op1->getOperand(J)); + } else { + CurTy = nullptr; + } + } + } + } + + // If not all GEPs are identical we'll have to create a new PHI node. + // Check that the old PHI node has only one use so that it will get + // removed. + if (DI != -1 && !PN->hasOneUse()) + return nullptr; + + GetElementPtrInst *NewGEP = cast<GetElementPtrInst>(Op1->clone()); + if (DI == -1) { + // All the GEPs feeding the PHI are identical. Clone one down into our + // BB so that it can be merged with the current GEP. + GEP.getParent()->getInstList().insert( + GEP.getParent()->getFirstInsertionPt(), NewGEP); + } else { + // All the GEPs feeding the PHI differ at a single offset. Clone a GEP + // into the current block so it can be merged, and create a new PHI to + // set that index. + PHINode *NewPN; + { + IRBuilderBase::InsertPointGuard Guard(*Builder); + Builder->SetInsertPoint(PN); + NewPN = Builder->CreatePHI(Op1->getOperand(DI)->getType(), + PN->getNumOperands()); + } + + for (auto &I : PN->operands()) + NewPN->addIncoming(cast<GEPOperator>(I)->getOperand(DI), + PN->getIncomingBlock(I)); + + NewGEP->setOperand(DI, NewPN); + GEP.getParent()->getInstList().insert( + GEP.getParent()->getFirstInsertionPt(), NewGEP); + NewGEP->setOperand(DI, NewPN); + } + + GEP.setOperand(0, NewGEP); + PtrOp = NewGEP; + } + + // Combine Indices - If the source pointer to this getelementptr instruction + // is a getelementptr instruction, combine the indices of the two + // getelementptr instructions into a single instruction. + // + if (GEPOperator *Src = dyn_cast<GEPOperator>(PtrOp)) { + if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src)) + return nullptr; + + // Note that if our source is a gep chain itself then we wait for that + // chain to be resolved before we perform this transformation. This + // avoids us creating a TON of code in some cases. + if (GEPOperator *SrcGEP = + dyn_cast<GEPOperator>(Src->getOperand(0))) + if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP)) + return nullptr; // Wait until our source is folded to completion. + + SmallVector<Value*, 8> Indices; + + // Find out whether the last index in the source GEP is a sequential idx. + bool EndsWithSequential = false; + for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src); + I != E; ++I) + EndsWithSequential = !(*I)->isStructTy(); + + // Can we combine the two pointer arithmetics offsets? + if (EndsWithSequential) { + // Replace: gep (gep %P, long B), long A, ... + // With: T = long A+B; gep %P, T, ... + // + Value *Sum; + Value *SO1 = Src->getOperand(Src->getNumOperands()-1); + Value *GO1 = GEP.getOperand(1); + if (SO1 == Constant::getNullValue(SO1->getType())) { + Sum = GO1; + } else if (GO1 == Constant::getNullValue(GO1->getType())) { + Sum = SO1; + } else { + // If they aren't the same type, then the input hasn't been processed + // by the loop above yet (which canonicalizes sequential index types to + // intptr_t). Just avoid transforming this until the input has been + // normalized. + if (SO1->getType() != GO1->getType()) + return nullptr; + // Only do the combine when GO1 and SO1 are both constants. Only in + // this case, we are sure the cost after the merge is never more than + // that before the merge. + if (!isa<Constant>(GO1) || !isa<Constant>(SO1)) + return nullptr; + Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum"); + } + + // Update the GEP in place if possible. + if (Src->getNumOperands() == 2) { + GEP.setOperand(0, Src->getOperand(0)); + GEP.setOperand(1, Sum); + return &GEP; + } + Indices.append(Src->op_begin()+1, Src->op_end()-1); + Indices.push_back(Sum); + Indices.append(GEP.op_begin()+2, GEP.op_end()); + } else if (isa<Constant>(*GEP.idx_begin()) && + cast<Constant>(*GEP.idx_begin())->isNullValue() && + Src->getNumOperands() != 1) { + // Otherwise we can do the fold if the first index of the GEP is a zero + Indices.append(Src->op_begin()+1, Src->op_end()); + Indices.append(GEP.idx_begin()+1, GEP.idx_end()); + } + + if (!Indices.empty()) + return GEP.isInBounds() && Src->isInBounds() + ? GetElementPtrInst::CreateInBounds( + Src->getSourceElementType(), Src->getOperand(0), Indices, + GEP.getName()) + : GetElementPtrInst::Create(Src->getSourceElementType(), + Src->getOperand(0), Indices, + GEP.getName()); + } + + if (GEP.getNumIndices() == 1) { + unsigned AS = GEP.getPointerAddressSpace(); + if (GEP.getOperand(1)->getType()->getScalarSizeInBits() == + DL.getPointerSizeInBits(AS)) { + Type *PtrTy = GEP.getPointerOperandType(); + Type *Ty = PtrTy->getPointerElementType(); + uint64_t TyAllocSize = DL.getTypeAllocSize(Ty); + + bool Matched = false; + uint64_t C; + Value *V = nullptr; + if (TyAllocSize == 1) { + V = GEP.getOperand(1); + Matched = true; + } else if (match(GEP.getOperand(1), + m_AShr(m_Value(V), m_ConstantInt(C)))) { + if (TyAllocSize == 1ULL << C) + Matched = true; + } else if (match(GEP.getOperand(1), + m_SDiv(m_Value(V), m_ConstantInt(C)))) { + if (TyAllocSize == C) + Matched = true; + } + + if (Matched) { + // Canonicalize (gep i8* X, -(ptrtoint Y)) + // to (inttoptr (sub (ptrtoint X), (ptrtoint Y))) + // The GEP pattern is emitted by the SCEV expander for certain kinds of + // pointer arithmetic. + if (match(V, m_Neg(m_PtrToInt(m_Value())))) { + Operator *Index = cast<Operator>(V); + Value *PtrToInt = Builder->CreatePtrToInt(PtrOp, Index->getType()); + Value *NewSub = Builder->CreateSub(PtrToInt, Index->getOperand(1)); + return CastInst::Create(Instruction::IntToPtr, NewSub, GEP.getType()); + } + // Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X)) + // to (bitcast Y) + Value *Y; + if (match(V, m_Sub(m_PtrToInt(m_Value(Y)), + m_PtrToInt(m_Specific(GEP.getOperand(0)))))) { + return CastInst::CreatePointerBitCastOrAddrSpaceCast(Y, + GEP.getType()); + } + } + } + } + + // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). + Value *StrippedPtr = PtrOp->stripPointerCasts(); + PointerType *StrippedPtrTy = dyn_cast<PointerType>(StrippedPtr->getType()); + + // We do not handle pointer-vector geps here. + if (!StrippedPtrTy) + return nullptr; + + if (StrippedPtr != PtrOp) { + bool HasZeroPointerIndex = false; + if (ConstantInt *C = dyn_cast<ConstantInt>(GEP.getOperand(1))) + HasZeroPointerIndex = C->isZero(); + + // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... + // into : GEP [10 x i8]* X, i32 0, ... + // + // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ... + // into : GEP i8* X, ... + // + // This occurs when the program declares an array extern like "int X[];" + if (HasZeroPointerIndex) { + PointerType *CPTy = cast<PointerType>(PtrOp->getType()); + if (ArrayType *CATy = + dyn_cast<ArrayType>(CPTy->getElementType())) { + // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ? + if (CATy->getElementType() == StrippedPtrTy->getElementType()) { + // -> GEP i8* X, ... + SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end()); + GetElementPtrInst *Res = GetElementPtrInst::Create( + StrippedPtrTy->getElementType(), StrippedPtr, Idx, GEP.getName()); + Res->setIsInBounds(GEP.isInBounds()); + if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace()) + return Res; + // Insert Res, and create an addrspacecast. + // e.g., + // GEP (addrspacecast i8 addrspace(1)* X to [0 x i8]*), i32 0, ... + // -> + // %0 = GEP i8 addrspace(1)* X, ... + // addrspacecast i8 addrspace(1)* %0 to i8* + return new AddrSpaceCastInst(Builder->Insert(Res), GEP.getType()); + } + + if (ArrayType *XATy = + dyn_cast<ArrayType>(StrippedPtrTy->getElementType())){ + // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ? + if (CATy->getElementType() == XATy->getElementType()) { + // -> GEP [10 x i8]* X, i32 0, ... + // At this point, we know that the cast source type is a pointer + // to an array of the same type as the destination pointer + // array. Because the array type is never stepped over (there + // is a leading zero) we can fold the cast into this GEP. + if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace()) { + GEP.setOperand(0, StrippedPtr); + GEP.setSourceElementType(XATy); + return &GEP; + } + // Cannot replace the base pointer directly because StrippedPtr's + // address space is different. Instead, create a new GEP followed by + // an addrspacecast. + // e.g., + // GEP (addrspacecast [10 x i8] addrspace(1)* X to [0 x i8]*), + // i32 0, ... + // -> + // %0 = GEP [10 x i8] addrspace(1)* X, ... + // addrspacecast i8 addrspace(1)* %0 to i8* + SmallVector<Value*, 8> Idx(GEP.idx_begin(), GEP.idx_end()); + Value *NewGEP = GEP.isInBounds() + ? Builder->CreateInBoundsGEP( + nullptr, StrippedPtr, Idx, GEP.getName()) + : Builder->CreateGEP(nullptr, StrippedPtr, Idx, + GEP.getName()); + return new AddrSpaceCastInst(NewGEP, GEP.getType()); + } + } + } + } else if (GEP.getNumOperands() == 2) { + // Transform things like: + // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V + // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast + Type *SrcElTy = StrippedPtrTy->getElementType(); + Type *ResElTy = PtrOp->getType()->getPointerElementType(); + if (SrcElTy->isArrayTy() && + DL.getTypeAllocSize(SrcElTy->getArrayElementType()) == + DL.getTypeAllocSize(ResElTy)) { + Type *IdxType = DL.getIntPtrType(GEP.getType()); + Value *Idx[2] = { Constant::getNullValue(IdxType), GEP.getOperand(1) }; + Value *NewGEP = + GEP.isInBounds() + ? Builder->CreateInBoundsGEP(nullptr, StrippedPtr, Idx, + GEP.getName()) + : Builder->CreateGEP(nullptr, StrippedPtr, Idx, GEP.getName()); + + // V and GEP are both pointer types --> BitCast + return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, + GEP.getType()); + } + + // Transform things like: + // %V = mul i64 %N, 4 + // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V + // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast + if (ResElTy->isSized() && SrcElTy->isSized()) { + // Check that changing the type amounts to dividing the index by a scale + // factor. + uint64_t ResSize = DL.getTypeAllocSize(ResElTy); + uint64_t SrcSize = DL.getTypeAllocSize(SrcElTy); + if (ResSize && SrcSize % ResSize == 0) { + Value *Idx = GEP.getOperand(1); + unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); + uint64_t Scale = SrcSize / ResSize; + + // Earlier transforms ensure that the index has type IntPtrType, which + // considerably simplifies the logic by eliminating implicit casts. + assert(Idx->getType() == DL.getIntPtrType(GEP.getType()) && + "Index not cast to pointer width?"); + + bool NSW; + if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { + // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. + // If the multiplication NewIdx * Scale may overflow then the new + // GEP may not be "inbounds". + Value *NewGEP = + GEP.isInBounds() && NSW + ? Builder->CreateInBoundsGEP(nullptr, StrippedPtr, NewIdx, + GEP.getName()) + : Builder->CreateGEP(nullptr, StrippedPtr, NewIdx, + GEP.getName()); + + // The NewGEP must be pointer typed, so must the old one -> BitCast + return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, + GEP.getType()); + } + } + } + + // Similarly, transform things like: + // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp + // (where tmp = 8*tmp2) into: + // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast + if (ResElTy->isSized() && SrcElTy->isSized() && SrcElTy->isArrayTy()) { + // Check that changing to the array element type amounts to dividing the + // index by a scale factor. + uint64_t ResSize = DL.getTypeAllocSize(ResElTy); + uint64_t ArrayEltSize = + DL.getTypeAllocSize(SrcElTy->getArrayElementType()); + if (ResSize && ArrayEltSize % ResSize == 0) { + Value *Idx = GEP.getOperand(1); + unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); + uint64_t Scale = ArrayEltSize / ResSize; + + // Earlier transforms ensure that the index has type IntPtrType, which + // considerably simplifies the logic by eliminating implicit casts. + assert(Idx->getType() == DL.getIntPtrType(GEP.getType()) && + "Index not cast to pointer width?"); + + bool NSW; + if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { + // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. + // If the multiplication NewIdx * Scale may overflow then the new + // GEP may not be "inbounds". + Value *Off[2] = { + Constant::getNullValue(DL.getIntPtrType(GEP.getType())), + NewIdx}; + + Value *NewGEP = GEP.isInBounds() && NSW + ? Builder->CreateInBoundsGEP( + SrcElTy, StrippedPtr, Off, GEP.getName()) + : Builder->CreateGEP(SrcElTy, StrippedPtr, Off, + GEP.getName()); + // The NewGEP must be pointer typed, so must the old one -> BitCast + return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, + GEP.getType()); + } + } + } + } + } + + // addrspacecast between types is canonicalized as a bitcast, then an + // addrspacecast. To take advantage of the below bitcast + struct GEP, look + // through the addrspacecast. + if (AddrSpaceCastInst *ASC = dyn_cast<AddrSpaceCastInst>(PtrOp)) { + // X = bitcast A addrspace(1)* to B addrspace(1)* + // Y = addrspacecast A addrspace(1)* to B addrspace(2)* + // Z = gep Y, <...constant indices...> + // Into an addrspacecasted GEP of the struct. + if (BitCastInst *BC = dyn_cast<BitCastInst>(ASC->getOperand(0))) + PtrOp = BC; + } + + /// See if we can simplify: + /// X = bitcast A* to B* + /// Y = gep X, <...constant indices...> + /// into a gep of the original struct. This is important for SROA and alias + /// analysis of unions. If "A" is also a bitcast, wait for A/X to be merged. + if (BitCastInst *BCI = dyn_cast<BitCastInst>(PtrOp)) { + Value *Operand = BCI->getOperand(0); + PointerType *OpType = cast<PointerType>(Operand->getType()); + unsigned OffsetBits = DL.getPointerTypeSizeInBits(GEP.getType()); + APInt Offset(OffsetBits, 0); + if (!isa<BitCastInst>(Operand) && + GEP.accumulateConstantOffset(DL, Offset)) { + + // If this GEP instruction doesn't move the pointer, just replace the GEP + // with a bitcast of the real input to the dest type. + if (!Offset) { + // If the bitcast is of an allocation, and the allocation will be + // converted to match the type of the cast, don't touch this. + if (isa<AllocaInst>(Operand) || isAllocationFn(Operand, TLI)) { + // See if the bitcast simplifies, if so, don't nuke this GEP yet. + if (Instruction *I = visitBitCast(*BCI)) { + if (I != BCI) { + I->takeName(BCI); + BCI->getParent()->getInstList().insert(BCI->getIterator(), I); + ReplaceInstUsesWith(*BCI, I); + } + return &GEP; + } + } + + if (Operand->getType()->getPointerAddressSpace() != GEP.getAddressSpace()) + return new AddrSpaceCastInst(Operand, GEP.getType()); + return new BitCastInst(Operand, GEP.getType()); + } + + // Otherwise, if the offset is non-zero, we need to find out if there is a + // field at Offset in 'A's type. If so, we can pull the cast through the + // GEP. + SmallVector<Value*, 8> NewIndices; + if (FindElementAtOffset(OpType, Offset.getSExtValue(), NewIndices)) { + Value *NGEP = + GEP.isInBounds() + ? Builder->CreateInBoundsGEP(nullptr, Operand, NewIndices) + : Builder->CreateGEP(nullptr, Operand, NewIndices); + + if (NGEP->getType() == GEP.getType()) + return ReplaceInstUsesWith(GEP, NGEP); + NGEP->takeName(&GEP); + + if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace()) + return new AddrSpaceCastInst(NGEP, GEP.getType()); + return new BitCastInst(NGEP, GEP.getType()); + } + } + } + + return nullptr; +} + +static bool +isAllocSiteRemovable(Instruction *AI, SmallVectorImpl<WeakVH> &Users, + const TargetLibraryInfo *TLI) { + SmallVector<Instruction*, 4> Worklist; + Worklist.push_back(AI); + + do { + Instruction *PI = Worklist.pop_back_val(); + for (User *U : PI->users()) { + Instruction *I = cast<Instruction>(U); + switch (I->getOpcode()) { + default: + // Give up the moment we see something we can't handle. + return false; + + case Instruction::BitCast: + case Instruction::GetElementPtr: + Users.emplace_back(I); + Worklist.push_back(I); + continue; + + case Instruction::ICmp: { + ICmpInst *ICI = cast<ICmpInst>(I); + // We can fold eq/ne comparisons with null to false/true, respectively. + if (!ICI->isEquality() || !isa<ConstantPointerNull>(ICI->getOperand(1))) + return false; + Users.emplace_back(I); + continue; + } + + case Instruction::Call: + // Ignore no-op and store intrinsics. + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { + switch (II->getIntrinsicID()) { + default: + return false; + + case Intrinsic::memmove: + case Intrinsic::memcpy: + case Intrinsic::memset: { + MemIntrinsic *MI = cast<MemIntrinsic>(II); + if (MI->isVolatile() || MI->getRawDest() != PI) + return false; + } + // fall through + case Intrinsic::dbg_declare: + case Intrinsic::dbg_value: + case Intrinsic::invariant_start: + case Intrinsic::invariant_end: + case Intrinsic::lifetime_start: + case Intrinsic::lifetime_end: + case Intrinsic::objectsize: + Users.emplace_back(I); + continue; + } + } + + if (isFreeCall(I, TLI)) { + Users.emplace_back(I); + continue; + } + return false; + + case Instruction::Store: { + StoreInst *SI = cast<StoreInst>(I); + if (SI->isVolatile() || SI->getPointerOperand() != PI) + return false; + Users.emplace_back(I); + continue; + } + } + llvm_unreachable("missing a return?"); + } + } while (!Worklist.empty()); + return true; +} + +Instruction *InstCombiner::visitAllocSite(Instruction &MI) { + // If we have a malloc call which is only used in any amount of comparisons + // to null and free calls, delete the calls and replace the comparisons with + // true or false as appropriate. + SmallVector<WeakVH, 64> Users; + if (isAllocSiteRemovable(&MI, Users, TLI)) { + for (unsigned i = 0, e = Users.size(); i != e; ++i) { + Instruction *I = cast_or_null<Instruction>(&*Users[i]); + if (!I) continue; + + if (ICmpInst *C = dyn_cast<ICmpInst>(I)) { + ReplaceInstUsesWith(*C, + ConstantInt::get(Type::getInt1Ty(C->getContext()), + C->isFalseWhenEqual())); + } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I)) { + ReplaceInstUsesWith(*I, UndefValue::get(I->getType())); + } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { + if (II->getIntrinsicID() == Intrinsic::objectsize) { + ConstantInt *CI = cast<ConstantInt>(II->getArgOperand(1)); + uint64_t DontKnow = CI->isZero() ? -1ULL : 0; + ReplaceInstUsesWith(*I, ConstantInt::get(I->getType(), DontKnow)); + } + } + EraseInstFromFunction(*I); + } + + if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) { + // Replace invoke with a NOP intrinsic to maintain the original CFG + Module *M = II->getModule(); + Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing); + InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(), + None, "", II->getParent()); + } + return EraseInstFromFunction(MI); + } + return nullptr; +} + +/// \brief Move the call to free before a NULL test. +/// +/// Check if this free is accessed after its argument has been test +/// against NULL (property 0). +/// If yes, it is legal to move this call in its predecessor block. +/// +/// The move is performed only if the block containing the call to free +/// will be removed, i.e.: +/// 1. it has only one predecessor P, and P has two successors +/// 2. it contains the call and an unconditional branch +/// 3. its successor is the same as its predecessor's successor +/// +/// The profitability is out-of concern here and this function should +/// be called only if the caller knows this transformation would be +/// profitable (e.g., for code size). +static Instruction * +tryToMoveFreeBeforeNullTest(CallInst &FI) { + Value *Op = FI.getArgOperand(0); + BasicBlock *FreeInstrBB = FI.getParent(); + BasicBlock *PredBB = FreeInstrBB->getSinglePredecessor(); + + // Validate part of constraint #1: Only one predecessor + // FIXME: We can extend the number of predecessor, but in that case, we + // would duplicate the call to free in each predecessor and it may + // not be profitable even for code size. + if (!PredBB) + return nullptr; + + // Validate constraint #2: Does this block contains only the call to + // free and an unconditional branch? + // FIXME: We could check if we can speculate everything in the + // predecessor block + if (FreeInstrBB->size() != 2) + return nullptr; + BasicBlock *SuccBB; + if (!match(FreeInstrBB->getTerminator(), m_UnconditionalBr(SuccBB))) + return nullptr; + + // Validate the rest of constraint #1 by matching on the pred branch. + TerminatorInst *TI = PredBB->getTerminator(); + BasicBlock *TrueBB, *FalseBB; + ICmpInst::Predicate Pred; + if (!match(TI, m_Br(m_ICmp(Pred, m_Specific(Op), m_Zero()), TrueBB, FalseBB))) + return nullptr; + if (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE) + return nullptr; + + // Validate constraint #3: Ensure the null case just falls through. + if (SuccBB != (Pred == ICmpInst::ICMP_EQ ? TrueBB : FalseBB)) + return nullptr; + assert(FreeInstrBB == (Pred == ICmpInst::ICMP_EQ ? FalseBB : TrueBB) && + "Broken CFG: missing edge from predecessor to successor"); + + FI.moveBefore(TI); + return &FI; +} + + +Instruction *InstCombiner::visitFree(CallInst &FI) { + Value *Op = FI.getArgOperand(0); + + // free undef -> unreachable. + if (isa<UndefValue>(Op)) { + // Insert a new store to null because we cannot modify the CFG here. + Builder->CreateStore(ConstantInt::getTrue(FI.getContext()), + UndefValue::get(Type::getInt1PtrTy(FI.getContext()))); + return EraseInstFromFunction(FI); + } + + // If we have 'free null' delete the instruction. This can happen in stl code + // when lots of inlining happens. + if (isa<ConstantPointerNull>(Op)) + return EraseInstFromFunction(FI); + + // If we optimize for code size, try to move the call to free before the null + // test so that simplify cfg can remove the empty block and dead code + // elimination the branch. I.e., helps to turn something like: + // if (foo) free(foo); + // into + // free(foo); + if (MinimizeSize) + if (Instruction *I = tryToMoveFreeBeforeNullTest(FI)) + return I; + + return nullptr; +} + +Instruction *InstCombiner::visitReturnInst(ReturnInst &RI) { + if (RI.getNumOperands() == 0) // ret void + return nullptr; + + Value *ResultOp = RI.getOperand(0); + Type *VTy = ResultOp->getType(); + if (!VTy->isIntegerTy()) + return nullptr; + + // There might be assume intrinsics dominating this return that completely + // determine the value. If so, constant fold it. + unsigned BitWidth = VTy->getPrimitiveSizeInBits(); + APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); + computeKnownBits(ResultOp, KnownZero, KnownOne, 0, &RI); + if ((KnownZero|KnownOne).isAllOnesValue()) + RI.setOperand(0, Constant::getIntegerValue(VTy, KnownOne)); + + return nullptr; +} + +Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { + // Change br (not X), label True, label False to: br X, label False, True + Value *X = nullptr; + BasicBlock *TrueDest; + BasicBlock *FalseDest; + if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) && + !isa<Constant>(X)) { + // Swap Destinations and condition... + BI.setCondition(X); + BI.swapSuccessors(); + return &BI; + } + + // If the condition is irrelevant, remove the use so that other + // transforms on the condition become more effective. + if (BI.isConditional() && + BI.getSuccessor(0) == BI.getSuccessor(1) && + !isa<UndefValue>(BI.getCondition())) { + BI.setCondition(UndefValue::get(BI.getCondition()->getType())); + return &BI; + } + + // Canonicalize fcmp_one -> fcmp_oeq + FCmpInst::Predicate FPred; Value *Y; + if (match(&BI, m_Br(m_FCmp(FPred, m_Value(X), m_Value(Y)), + TrueDest, FalseDest)) && + BI.getCondition()->hasOneUse()) + if (FPred == FCmpInst::FCMP_ONE || FPred == FCmpInst::FCMP_OLE || + FPred == FCmpInst::FCMP_OGE) { + FCmpInst *Cond = cast<FCmpInst>(BI.getCondition()); + Cond->setPredicate(FCmpInst::getInversePredicate(FPred)); + + // Swap Destinations and condition. + BI.swapSuccessors(); + Worklist.Add(Cond); + return &BI; + } + + // Canonicalize icmp_ne -> icmp_eq + ICmpInst::Predicate IPred; + if (match(&BI, m_Br(m_ICmp(IPred, m_Value(X), m_Value(Y)), + TrueDest, FalseDest)) && + BI.getCondition()->hasOneUse()) + if (IPred == ICmpInst::ICMP_NE || IPred == ICmpInst::ICMP_ULE || + IPred == ICmpInst::ICMP_SLE || IPred == ICmpInst::ICMP_UGE || + IPred == ICmpInst::ICMP_SGE) { + ICmpInst *Cond = cast<ICmpInst>(BI.getCondition()); + Cond->setPredicate(ICmpInst::getInversePredicate(IPred)); + // Swap Destinations and condition. + BI.swapSuccessors(); + Worklist.Add(Cond); + return &BI; + } + + return nullptr; +} + +Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { + Value *Cond = SI.getCondition(); + unsigned BitWidth = cast<IntegerType>(Cond->getType())->getBitWidth(); + APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); + computeKnownBits(Cond, KnownZero, KnownOne, 0, &SI); + unsigned LeadingKnownZeros = KnownZero.countLeadingOnes(); + unsigned LeadingKnownOnes = KnownOne.countLeadingOnes(); + + // Compute the number of leading bits we can ignore. + for (auto &C : SI.cases()) { + LeadingKnownZeros = std::min( + LeadingKnownZeros, C.getCaseValue()->getValue().countLeadingZeros()); + LeadingKnownOnes = std::min( + LeadingKnownOnes, C.getCaseValue()->getValue().countLeadingOnes()); + } + + unsigned NewWidth = BitWidth - std::max(LeadingKnownZeros, LeadingKnownOnes); + + // Truncate the condition operand if the new type is equal to or larger than + // the largest legal integer type. We need to be conservative here since + // x86 generates redundant zero-extension instructions if the operand is + // truncated to i8 or i16. + bool TruncCond = false; + if (NewWidth > 0 && BitWidth > NewWidth && + NewWidth >= DL.getLargestLegalIntTypeSize()) { + TruncCond = true; + IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth); + Builder->SetInsertPoint(&SI); + Value *NewCond = Builder->CreateTrunc(SI.getCondition(), Ty, "trunc"); + SI.setCondition(NewCond); + + for (auto &C : SI.cases()) + static_cast<SwitchInst::CaseIt *>(&C)->setValue(ConstantInt::get( + SI.getContext(), C.getCaseValue()->getValue().trunc(NewWidth))); + } + + if (Instruction *I = dyn_cast<Instruction>(Cond)) { + if (I->getOpcode() == Instruction::Add) + if (ConstantInt *AddRHS = dyn_cast<ConstantInt>(I->getOperand(1))) { + // change 'switch (X+4) case 1:' into 'switch (X) case -3' + // Skip the first item since that's the default case. + for (SwitchInst::CaseIt i = SI.case_begin(), e = SI.case_end(); + i != e; ++i) { + ConstantInt* CaseVal = i.getCaseValue(); + Constant *LHS = CaseVal; + if (TruncCond) + LHS = LeadingKnownZeros + ? ConstantExpr::getZExt(CaseVal, Cond->getType()) + : ConstantExpr::getSExt(CaseVal, Cond->getType()); + Constant* NewCaseVal = ConstantExpr::getSub(LHS, AddRHS); + assert(isa<ConstantInt>(NewCaseVal) && + "Result of expression should be constant"); + i.setValue(cast<ConstantInt>(NewCaseVal)); + } + SI.setCondition(I->getOperand(0)); + Worklist.Add(I); + return &SI; + } + } + + return TruncCond ? &SI : nullptr; +} + +Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { + Value *Agg = EV.getAggregateOperand(); + + if (!EV.hasIndices()) + return ReplaceInstUsesWith(EV, Agg); + + if (Value *V = + SimplifyExtractValueInst(Agg, EV.getIndices(), DL, TLI, DT, AC)) + return ReplaceInstUsesWith(EV, V); + + if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) { + // We're extracting from an insertvalue instruction, compare the indices + const unsigned *exti, *exte, *insi, *inse; + for (exti = EV.idx_begin(), insi = IV->idx_begin(), + exte = EV.idx_end(), inse = IV->idx_end(); + exti != exte && insi != inse; + ++exti, ++insi) { + if (*insi != *exti) + // The insert and extract both reference distinctly different elements. + // This means the extract is not influenced by the insert, and we can + // replace the aggregate operand of the extract with the aggregate + // operand of the insert. i.e., replace + // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 + // %E = extractvalue { i32, { i32 } } %I, 0 + // with + // %E = extractvalue { i32, { i32 } } %A, 0 + return ExtractValueInst::Create(IV->getAggregateOperand(), + EV.getIndices()); + } + if (exti == exte && insi == inse) + // Both iterators are at the end: Index lists are identical. Replace + // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 + // %C = extractvalue { i32, { i32 } } %B, 1, 0 + // with "i32 42" + return ReplaceInstUsesWith(EV, IV->getInsertedValueOperand()); + if (exti == exte) { + // The extract list is a prefix of the insert list. i.e. replace + // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 + // %E = extractvalue { i32, { i32 } } %I, 1 + // with + // %X = extractvalue { i32, { i32 } } %A, 1 + // %E = insertvalue { i32 } %X, i32 42, 0 + // by switching the order of the insert and extract (though the + // insertvalue should be left in, since it may have other uses). + Value *NewEV = Builder->CreateExtractValue(IV->getAggregateOperand(), + EV.getIndices()); + return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), + makeArrayRef(insi, inse)); + } + if (insi == inse) + // The insert list is a prefix of the extract list + // We can simply remove the common indices from the extract and make it + // operate on the inserted value instead of the insertvalue result. + // i.e., replace + // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 + // %E = extractvalue { i32, { i32 } } %I, 1, 0 + // with + // %E extractvalue { i32 } { i32 42 }, 0 + return ExtractValueInst::Create(IV->getInsertedValueOperand(), + makeArrayRef(exti, exte)); + } + if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) { + // We're extracting from an intrinsic, see if we're the only user, which + // allows us to simplify multiple result intrinsics to simpler things that + // just get one value. + if (II->hasOneUse()) { + // Check if we're grabbing the overflow bit or the result of a 'with + // overflow' intrinsic. If it's the latter we can remove the intrinsic + // and replace it with a traditional binary instruction. + switch (II->getIntrinsicID()) { + case Intrinsic::uadd_with_overflow: + case Intrinsic::sadd_with_overflow: + if (*EV.idx_begin() == 0) { // Normal result. + Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); + ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); + EraseInstFromFunction(*II); + return BinaryOperator::CreateAdd(LHS, RHS); + } + + // If the normal result of the add is dead, and the RHS is a constant, + // we can transform this into a range comparison. + // overflow = uadd a, -4 --> overflow = icmp ugt a, 3 + if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow) + if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1))) + return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0), + ConstantExpr::getNot(CI)); + break; + case Intrinsic::usub_with_overflow: + case Intrinsic::ssub_with_overflow: + if (*EV.idx_begin() == 0) { // Normal result. + Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); + ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); + EraseInstFromFunction(*II); + return BinaryOperator::CreateSub(LHS, RHS); + } + break; + case Intrinsic::umul_with_overflow: + case Intrinsic::smul_with_overflow: + if (*EV.idx_begin() == 0) { // Normal result. + Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); + ReplaceInstUsesWith(*II, UndefValue::get(II->getType())); + EraseInstFromFunction(*II); + return BinaryOperator::CreateMul(LHS, RHS); + } + break; + default: + break; + } + } + } + if (LoadInst *L = dyn_cast<LoadInst>(Agg)) + // If the (non-volatile) load only has one use, we can rewrite this to a + // load from a GEP. This reduces the size of the load. If a load is used + // only by extractvalue instructions then this either must have been + // optimized before, or it is a struct with padding, in which case we + // don't want to do the transformation as it loses padding knowledge. + if (L->isSimple() && L->hasOneUse()) { + // extractvalue has integer indices, getelementptr has Value*s. Convert. + SmallVector<Value*, 4> Indices; + // Prefix an i32 0 since we need the first element. + Indices.push_back(Builder->getInt32(0)); + for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end(); + I != E; ++I) + Indices.push_back(Builder->getInt32(*I)); + + // We need to insert these at the location of the old load, not at that of + // the extractvalue. + Builder->SetInsertPoint(L); + Value *GEP = Builder->CreateInBoundsGEP(L->getType(), + L->getPointerOperand(), Indices); + // Returning the load directly will cause the main loop to insert it in + // the wrong spot, so use ReplaceInstUsesWith(). + return ReplaceInstUsesWith(EV, Builder->CreateLoad(GEP)); + } + // We could simplify extracts from other values. Note that nested extracts may + // already be simplified implicitly by the above: extract (extract (insert) ) + // will be translated into extract ( insert ( extract ) ) first and then just + // the value inserted, if appropriate. Similarly for extracts from single-use + // loads: extract (extract (load)) will be translated to extract (load (gep)) + // and if again single-use then via load (gep (gep)) to load (gep). + // However, double extracts from e.g. function arguments or return values + // aren't handled yet. + return nullptr; +} + +/// Return 'true' if the given typeinfo will match anything. +static bool isCatchAll(EHPersonality Personality, Constant *TypeInfo) { + switch (Personality) { + case EHPersonality::GNU_C: + // The GCC C EH personality only exists to support cleanups, so it's not + // clear what the semantics of catch clauses are. + return false; + case EHPersonality::Unknown: + return false; + case EHPersonality::GNU_Ada: + // While __gnat_all_others_value will match any Ada exception, it doesn't + // match foreign exceptions (or didn't, before gcc-4.7). + return false; + case EHPersonality::GNU_CXX: + case EHPersonality::GNU_ObjC: + case EHPersonality::MSVC_X86SEH: + case EHPersonality::MSVC_Win64SEH: + case EHPersonality::MSVC_CXX: + case EHPersonality::CoreCLR: + return TypeInfo->isNullValue(); + } + llvm_unreachable("invalid enum"); +} + +static bool shorter_filter(const Value *LHS, const Value *RHS) { + return + cast<ArrayType>(LHS->getType())->getNumElements() + < + cast<ArrayType>(RHS->getType())->getNumElements(); +} + +Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) { + // The logic here should be correct for any real-world personality function. + // However if that turns out not to be true, the offending logic can always + // be conditioned on the personality function, like the catch-all logic is. + EHPersonality Personality = + classifyEHPersonality(LI.getParent()->getParent()->getPersonalityFn()); + + // Simplify the list of clauses, eg by removing repeated catch clauses + // (these are often created by inlining). + bool MakeNewInstruction = false; // If true, recreate using the following: + SmallVector<Constant *, 16> NewClauses; // - Clauses for the new instruction; + bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup. + + SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already. + for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) { + bool isLastClause = i + 1 == e; + if (LI.isCatch(i)) { + // A catch clause. + Constant *CatchClause = LI.getClause(i); + Constant *TypeInfo = CatchClause->stripPointerCasts(); + + // If we already saw this clause, there is no point in having a second + // copy of it. + if (AlreadyCaught.insert(TypeInfo).second) { + // This catch clause was not already seen. + NewClauses.push_back(CatchClause); + } else { + // Repeated catch clause - drop the redundant copy. + MakeNewInstruction = true; + } + + // If this is a catch-all then there is no point in keeping any following + // clauses or marking the landingpad as having a cleanup. + if (isCatchAll(Personality, TypeInfo)) { + if (!isLastClause) + MakeNewInstruction = true; + CleanupFlag = false; + break; + } + } else { + // A filter clause. If any of the filter elements were already caught + // then they can be dropped from the filter. It is tempting to try to + // exploit the filter further by saying that any typeinfo that does not + // occur in the filter can't be caught later (and thus can be dropped). + // However this would be wrong, since typeinfos can match without being + // equal (for example if one represents a C++ class, and the other some + // class derived from it). + assert(LI.isFilter(i) && "Unsupported landingpad clause!"); + Constant *FilterClause = LI.getClause(i); + ArrayType *FilterType = cast<ArrayType>(FilterClause->getType()); + unsigned NumTypeInfos = FilterType->getNumElements(); + + // An empty filter catches everything, so there is no point in keeping any + // following clauses or marking the landingpad as having a cleanup. By + // dealing with this case here the following code is made a bit simpler. + if (!NumTypeInfos) { + NewClauses.push_back(FilterClause); + if (!isLastClause) + MakeNewInstruction = true; + CleanupFlag = false; + break; + } + + bool MakeNewFilter = false; // If true, make a new filter. + SmallVector<Constant *, 16> NewFilterElts; // New elements. + if (isa<ConstantAggregateZero>(FilterClause)) { + // Not an empty filter - it contains at least one null typeinfo. + assert(NumTypeInfos > 0 && "Should have handled empty filter already!"); + Constant *TypeInfo = + Constant::getNullValue(FilterType->getElementType()); + // If this typeinfo is a catch-all then the filter can never match. + if (isCatchAll(Personality, TypeInfo)) { + // Throw the filter away. + MakeNewInstruction = true; + continue; + } + + // There is no point in having multiple copies of this typeinfo, so + // discard all but the first copy if there is more than one. + NewFilterElts.push_back(TypeInfo); + if (NumTypeInfos > 1) + MakeNewFilter = true; + } else { + ConstantArray *Filter = cast<ConstantArray>(FilterClause); + SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements. + NewFilterElts.reserve(NumTypeInfos); + + // Remove any filter elements that were already caught or that already + // occurred in the filter. While there, see if any of the elements are + // catch-alls. If so, the filter can be discarded. + bool SawCatchAll = false; + for (unsigned j = 0; j != NumTypeInfos; ++j) { + Constant *Elt = Filter->getOperand(j); + Constant *TypeInfo = Elt->stripPointerCasts(); + if (isCatchAll(Personality, TypeInfo)) { + // This element is a catch-all. Bail out, noting this fact. + SawCatchAll = true; + break; + } + + // Even if we've seen a type in a catch clause, we don't want to + // remove it from the filter. An unexpected type handler may be + // set up for a call site which throws an exception of the same + // type caught. In order for the exception thrown by the unexpected + // handler to propogate correctly, the filter must be correctly + // described for the call site. + // + // Example: + // + // void unexpected() { throw 1;} + // void foo() throw (int) { + // std::set_unexpected(unexpected); + // try { + // throw 2.0; + // } catch (int i) {} + // } + + // There is no point in having multiple copies of the same typeinfo in + // a filter, so only add it if we didn't already. + if (SeenInFilter.insert(TypeInfo).second) + NewFilterElts.push_back(cast<Constant>(Elt)); + } + // A filter containing a catch-all cannot match anything by definition. + if (SawCatchAll) { + // Throw the filter away. + MakeNewInstruction = true; + continue; + } + + // If we dropped something from the filter, make a new one. + if (NewFilterElts.size() < NumTypeInfos) + MakeNewFilter = true; + } + if (MakeNewFilter) { + FilterType = ArrayType::get(FilterType->getElementType(), + NewFilterElts.size()); + FilterClause = ConstantArray::get(FilterType, NewFilterElts); + MakeNewInstruction = true; + } + + NewClauses.push_back(FilterClause); + + // If the new filter is empty then it will catch everything so there is + // no point in keeping any following clauses or marking the landingpad + // as having a cleanup. The case of the original filter being empty was + // already handled above. + if (MakeNewFilter && !NewFilterElts.size()) { + assert(MakeNewInstruction && "New filter but not a new instruction!"); + CleanupFlag = false; + break; + } + } + } + + // If several filters occur in a row then reorder them so that the shortest + // filters come first (those with the smallest number of elements). This is + // advantageous because shorter filters are more likely to match, speeding up + // unwinding, but mostly because it increases the effectiveness of the other + // filter optimizations below. + for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) { + unsigned j; + // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters. + for (j = i; j != e; ++j) + if (!isa<ArrayType>(NewClauses[j]->getType())) + break; + + // Check whether the filters are already sorted by length. We need to know + // if sorting them is actually going to do anything so that we only make a + // new landingpad instruction if it does. + for (unsigned k = i; k + 1 < j; ++k) + if (shorter_filter(NewClauses[k+1], NewClauses[k])) { + // Not sorted, so sort the filters now. Doing an unstable sort would be + // correct too but reordering filters pointlessly might confuse users. + std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j, + shorter_filter); + MakeNewInstruction = true; + break; + } + + // Look for the next batch of filters. + i = j + 1; + } + + // If typeinfos matched if and only if equal, then the elements of a filter L + // that occurs later than a filter F could be replaced by the intersection of + // the elements of F and L. In reality two typeinfos can match without being + // equal (for example if one represents a C++ class, and the other some class + // derived from it) so it would be wrong to perform this transform in general. + // However the transform is correct and useful if F is a subset of L. In that + // case L can be replaced by F, and thus removed altogether since repeating a + // filter is pointless. So here we look at all pairs of filters F and L where + // L follows F in the list of clauses, and remove L if every element of F is + // an element of L. This can occur when inlining C++ functions with exception + // specifications. + for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) { + // Examine each filter in turn. + Value *Filter = NewClauses[i]; + ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType()); + if (!FTy) + // Not a filter - skip it. + continue; + unsigned FElts = FTy->getNumElements(); + // Examine each filter following this one. Doing this backwards means that + // we don't have to worry about filters disappearing under us when removed. + for (unsigned j = NewClauses.size() - 1; j != i; --j) { + Value *LFilter = NewClauses[j]; + ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType()); + if (!LTy) + // Not a filter - skip it. + continue; + // If Filter is a subset of LFilter, i.e. every element of Filter is also + // an element of LFilter, then discard LFilter. + SmallVectorImpl<Constant *>::iterator J = NewClauses.begin() + j; + // If Filter is empty then it is a subset of LFilter. + if (!FElts) { + // Discard LFilter. + NewClauses.erase(J); + MakeNewInstruction = true; + // Move on to the next filter. + continue; + } + unsigned LElts = LTy->getNumElements(); + // If Filter is longer than LFilter then it cannot be a subset of it. + if (FElts > LElts) + // Move on to the next filter. + continue; + // At this point we know that LFilter has at least one element. + if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros. + // Filter is a subset of LFilter iff Filter contains only zeros (as we + // already know that Filter is not longer than LFilter). + if (isa<ConstantAggregateZero>(Filter)) { + assert(FElts <= LElts && "Should have handled this case earlier!"); + // Discard LFilter. + NewClauses.erase(J); + MakeNewInstruction = true; + } + // Move on to the next filter. + continue; + } + ConstantArray *LArray = cast<ConstantArray>(LFilter); + if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros. + // Since Filter is non-empty and contains only zeros, it is a subset of + // LFilter iff LFilter contains a zero. + assert(FElts > 0 && "Should have eliminated the empty filter earlier!"); + for (unsigned l = 0; l != LElts; ++l) + if (LArray->getOperand(l)->isNullValue()) { + // LFilter contains a zero - discard it. + NewClauses.erase(J); + MakeNewInstruction = true; + break; + } + // Move on to the next filter. + continue; + } + // At this point we know that both filters are ConstantArrays. Loop over + // operands to see whether every element of Filter is also an element of + // LFilter. Since filters tend to be short this is probably faster than + // using a method that scales nicely. + ConstantArray *FArray = cast<ConstantArray>(Filter); + bool AllFound = true; + for (unsigned f = 0; f != FElts; ++f) { + Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts(); + AllFound = false; + for (unsigned l = 0; l != LElts; ++l) { + Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts(); + if (LTypeInfo == FTypeInfo) { + AllFound = true; + break; + } + } + if (!AllFound) + break; + } + if (AllFound) { + // Discard LFilter. + NewClauses.erase(J); + MakeNewInstruction = true; + } + // Move on to the next filter. + } + } + + // If we changed any of the clauses, replace the old landingpad instruction + // with a new one. + if (MakeNewInstruction) { + LandingPadInst *NLI = LandingPadInst::Create(LI.getType(), + NewClauses.size()); + for (unsigned i = 0, e = NewClauses.size(); i != e; ++i) + NLI->addClause(NewClauses[i]); + // A landing pad with no clauses must have the cleanup flag set. It is + // theoretically possible, though highly unlikely, that we eliminated all + // clauses. If so, force the cleanup flag to true. + if (NewClauses.empty()) + CleanupFlag = true; + NLI->setCleanup(CleanupFlag); + return NLI; + } + + // Even if none of the clauses changed, we may nonetheless have understood + // that the cleanup flag is pointless. Clear it if so. + if (LI.isCleanup() != CleanupFlag) { + assert(!CleanupFlag && "Adding a cleanup, not removing one?!"); + LI.setCleanup(CleanupFlag); + return &LI; + } + + return nullptr; +} + +/// Try to move the specified instruction from its current block into the +/// beginning of DestBlock, which can only happen if it's safe to move the +/// instruction past all of the instructions between it and the end of its +/// block. +static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { + assert(I->hasOneUse() && "Invariants didn't hold!"); + + // Cannot move control-flow-involving, volatile loads, vaarg, etc. + if (isa<PHINode>(I) || I->isEHPad() || I->mayHaveSideEffects() || + isa<TerminatorInst>(I)) + return false; + + // Do not sink alloca instructions out of the entry block. + if (isa<AllocaInst>(I) && I->getParent() == + &DestBlock->getParent()->getEntryBlock()) + return false; + + // Do not sink convergent call instructions. + if (auto *CI = dyn_cast<CallInst>(I)) { + if (CI->isConvergent()) + return false; + } + + // We can only sink load instructions if there is nothing between the load and + // the end of block that could change the value. + if (I->mayReadFromMemory()) { + for (BasicBlock::iterator Scan = I->getIterator(), + E = I->getParent()->end(); + Scan != E; ++Scan) + if (Scan->mayWriteToMemory()) + return false; + } + + BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt(); + I->moveBefore(&*InsertPos); + ++NumSunkInst; + return true; +} + +bool InstCombiner::run() { + while (!Worklist.isEmpty()) { + Instruction *I = Worklist.RemoveOne(); + if (I == nullptr) continue; // skip null values. + + // Check to see if we can DCE the instruction. + if (isInstructionTriviallyDead(I, TLI)) { + DEBUG(dbgs() << "IC: DCE: " << *I << '\n'); + EraseInstFromFunction(*I); + ++NumDeadInst; + MadeIRChange = true; + continue; + } + + // Instruction isn't dead, see if we can constant propagate it. + if (!I->use_empty() && + (I->getNumOperands() == 0 || isa<Constant>(I->getOperand(0)))) { + if (Constant *C = ConstantFoldInstruction(I, DL, TLI)) { + DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " << *I << '\n'); + + // Add operands to the worklist. + ReplaceInstUsesWith(*I, C); + ++NumConstProp; + EraseInstFromFunction(*I); + MadeIRChange = true; + continue; + } + } + + // In general, it is possible for computeKnownBits to determine all bits in a + // value even when the operands are not all constants. + if (!I->use_empty() && I->getType()->isIntegerTy()) { + unsigned BitWidth = I->getType()->getScalarSizeInBits(); + APInt KnownZero(BitWidth, 0); + APInt KnownOne(BitWidth, 0); + computeKnownBits(I, KnownZero, KnownOne, /*Depth*/0, I); + if ((KnownZero | KnownOne).isAllOnesValue()) { + Constant *C = ConstantInt::get(I->getContext(), KnownOne); + DEBUG(dbgs() << "IC: ConstFold (all bits known) to: " << *C << + " from: " << *I << '\n'); + + // Add operands to the worklist. + ReplaceInstUsesWith(*I, C); + ++NumConstProp; + EraseInstFromFunction(*I); + MadeIRChange = true; + continue; + } + } + + // See if we can trivially sink this instruction to a successor basic block. + if (I->hasOneUse()) { + BasicBlock *BB = I->getParent(); + Instruction *UserInst = cast<Instruction>(*I->user_begin()); + BasicBlock *UserParent; + + // Get the block the use occurs in. + if (PHINode *PN = dyn_cast<PHINode>(UserInst)) + UserParent = PN->getIncomingBlock(*I->use_begin()); + else + UserParent = UserInst->getParent(); + + if (UserParent != BB) { + bool UserIsSuccessor = false; + // See if the user is one of our successors. + for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) + if (*SI == UserParent) { + UserIsSuccessor = true; + break; + } + + // If the user is one of our immediate successors, and if that successor + // only has us as a predecessors (we'd have to split the critical edge + // otherwise), we can keep going. + if (UserIsSuccessor && UserParent->getSinglePredecessor()) { + // Okay, the CFG is simple enough, try to sink this instruction. + if (TryToSinkInstruction(I, UserParent)) { + MadeIRChange = true; + // We'll add uses of the sunk instruction below, but since sinking + // can expose opportunities for it's *operands* add them to the + // worklist + for (Use &U : I->operands()) + if (Instruction *OpI = dyn_cast<Instruction>(U.get())) + Worklist.Add(OpI); + } + } + } + } + + // Now that we have an instruction, try combining it to simplify it. + Builder->SetInsertPoint(I); + Builder->SetCurrentDebugLocation(I->getDebugLoc()); + +#ifndef NDEBUG + std::string OrigI; +#endif + DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); + DEBUG(dbgs() << "IC: Visiting: " << OrigI << '\n'); + + if (Instruction *Result = visit(*I)) { + ++NumCombined; + // Should we replace the old instruction with a new one? + if (Result != I) { + DEBUG(dbgs() << "IC: Old = " << *I << '\n' + << " New = " << *Result << '\n'); + + if (I->getDebugLoc()) + Result->setDebugLoc(I->getDebugLoc()); + // Everything uses the new instruction now. + I->replaceAllUsesWith(Result); + + // Move the name to the new instruction first. + Result->takeName(I); + + // Push the new instruction and any users onto the worklist. + Worklist.Add(Result); + Worklist.AddUsersToWorkList(*Result); + + // Insert the new instruction into the basic block... + BasicBlock *InstParent = I->getParent(); + BasicBlock::iterator InsertPos = I->getIterator(); + + // If we replace a PHI with something that isn't a PHI, fix up the + // insertion point. + if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos)) + InsertPos = InstParent->getFirstInsertionPt(); + + InstParent->getInstList().insert(InsertPos, Result); + + EraseInstFromFunction(*I); + } else { +#ifndef NDEBUG + DEBUG(dbgs() << "IC: Mod = " << OrigI << '\n' + << " New = " << *I << '\n'); +#endif + + // If the instruction was modified, it's possible that it is now dead. + // if so, remove it. + if (isInstructionTriviallyDead(I, TLI)) { + EraseInstFromFunction(*I); + } else { + Worklist.Add(I); + Worklist.AddUsersToWorkList(*I); + } + } + MadeIRChange = true; + } + } + + Worklist.Zap(); + return MadeIRChange; +} + +/// Walk the function in depth-first order, adding all reachable code to the +/// worklist. +/// +/// This has a couple of tricks to make the code faster and more powerful. In +/// particular, we constant fold and DCE instructions as we go, to avoid adding +/// them to the worklist (this significantly speeds up instcombine on code where +/// many instructions are dead or constant). Additionally, if we find a branch +/// whose condition is a known constant, we only visit the reachable successors. +/// +static bool AddReachableCodeToWorklist(BasicBlock *BB, const DataLayout &DL, + SmallPtrSetImpl<BasicBlock *> &Visited, + InstCombineWorklist &ICWorklist, + const TargetLibraryInfo *TLI) { + bool MadeIRChange = false; + SmallVector<BasicBlock*, 256> Worklist; + Worklist.push_back(BB); + + SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; + DenseMap<ConstantExpr*, Constant*> FoldedConstants; + + do { + BB = Worklist.pop_back_val(); + + // We have now visited this block! If we've already been here, ignore it. + if (!Visited.insert(BB).second) + continue; + + for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { + Instruction *Inst = &*BBI++; + + // DCE instruction if trivially dead. + if (isInstructionTriviallyDead(Inst, TLI)) { + ++NumDeadInst; + DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n'); + Inst->eraseFromParent(); + continue; + } + + // ConstantProp instruction if trivially constant. + if (!Inst->use_empty() && + (Inst->getNumOperands() == 0 || isa<Constant>(Inst->getOperand(0)))) + if (Constant *C = ConstantFoldInstruction(Inst, DL, TLI)) { + DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " + << *Inst << '\n'); + Inst->replaceAllUsesWith(C); + ++NumConstProp; + Inst->eraseFromParent(); + continue; + } + + // See if we can constant fold its operands. + for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end(); i != e; + ++i) { + ConstantExpr *CE = dyn_cast<ConstantExpr>(i); + if (CE == nullptr) + continue; + + Constant *&FoldRes = FoldedConstants[CE]; + if (!FoldRes) + FoldRes = ConstantFoldConstantExpression(CE, DL, TLI); + if (!FoldRes) + FoldRes = CE; + + if (FoldRes != CE) { + *i = FoldRes; + MadeIRChange = true; + } + } + + InstrsForInstCombineWorklist.push_back(Inst); + } + + // Recursively visit successors. If this is a branch or switch on a + // constant, only visit the reachable successor. + TerminatorInst *TI = BB->getTerminator(); + if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { + if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) { + bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue(); + BasicBlock *ReachableBB = BI->getSuccessor(!CondVal); + Worklist.push_back(ReachableBB); + continue; + } + } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { + if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) { + // See if this is an explicit destination. + for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); + i != e; ++i) + if (i.getCaseValue() == Cond) { + BasicBlock *ReachableBB = i.getCaseSuccessor(); + Worklist.push_back(ReachableBB); + continue; + } + + // Otherwise it is the default destination. + Worklist.push_back(SI->getDefaultDest()); + continue; + } + } + + for (BasicBlock *SuccBB : TI->successors()) + Worklist.push_back(SuccBB); + } while (!Worklist.empty()); + + // Once we've found all of the instructions to add to instcombine's worklist, + // add them in reverse order. This way instcombine will visit from the top + // of the function down. This jives well with the way that it adds all uses + // of instructions to the worklist after doing a transformation, thus avoiding + // some N^2 behavior in pathological cases. + ICWorklist.AddInitialGroup(InstrsForInstCombineWorklist); + + return MadeIRChange; +} + +/// \brief Populate the IC worklist from a function, and prune any dead basic +/// blocks discovered in the process. +/// +/// This also does basic constant propagation and other forward fixing to make +/// the combiner itself run much faster. +static bool prepareICWorklistFromFunction(Function &F, const DataLayout &DL, + TargetLibraryInfo *TLI, + InstCombineWorklist &ICWorklist) { + bool MadeIRChange = false; + + // Do a depth-first traversal of the function, populate the worklist with + // the reachable instructions. Ignore blocks that are not reachable. Keep + // track of which blocks we visit. + SmallPtrSet<BasicBlock *, 64> Visited; + MadeIRChange |= + AddReachableCodeToWorklist(&F.front(), DL, Visited, ICWorklist, TLI); + + // Do a quick scan over the function. If we find any blocks that are + // unreachable, remove any instructions inside of them. This prevents + // the instcombine code from having to deal with some bad special cases. + for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { + if (Visited.count(&*BB)) + continue; + + // Delete the instructions backwards, as it has a reduced likelihood of + // having to update as many def-use and use-def chains. + Instruction *EndInst = BB->getTerminator(); // Last not to be deleted. + while (EndInst != BB->begin()) { + // Delete the next to last instruction. + Instruction *Inst = &*--EndInst->getIterator(); + if (!Inst->use_empty() && !Inst->getType()->isTokenTy()) + Inst->replaceAllUsesWith(UndefValue::get(Inst->getType())); + if (Inst->isEHPad() || Inst->getType()->isTokenTy()) { + EndInst = Inst; + continue; + } + if (!isa<DbgInfoIntrinsic>(Inst)) { + ++NumDeadInst; + MadeIRChange = true; + } + Inst->eraseFromParent(); + } + } + + return MadeIRChange; +} + +static bool +combineInstructionsOverFunction(Function &F, InstCombineWorklist &Worklist, + AliasAnalysis *AA, AssumptionCache &AC, + TargetLibraryInfo &TLI, DominatorTree &DT, + LoopInfo *LI = nullptr) { + auto &DL = F.getParent()->getDataLayout(); + + /// Builder - This is an IRBuilder that automatically inserts new + /// instructions into the worklist when they are created. + IRBuilder<true, TargetFolder, InstCombineIRInserter> Builder( + F.getContext(), TargetFolder(DL), InstCombineIRInserter(Worklist, &AC)); + + // Lower dbg.declare intrinsics otherwise their value may be clobbered + // by instcombiner. + bool DbgDeclaresChanged = LowerDbgDeclare(F); + + // Iterate while there is work to do. + int Iteration = 0; + for (;;) { + ++Iteration; + DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " + << F.getName() << "\n"); + + bool Changed = false; + if (prepareICWorklistFromFunction(F, DL, &TLI, Worklist)) + Changed = true; + + InstCombiner IC(Worklist, &Builder, F.optForMinSize(), + AA, &AC, &TLI, &DT, DL, LI); + if (IC.run()) + Changed = true; + + if (!Changed) + break; + } + + return DbgDeclaresChanged || Iteration > 1; +} + +PreservedAnalyses InstCombinePass::run(Function &F, + AnalysisManager<Function> *AM) { + auto &AC = AM->getResult<AssumptionAnalysis>(F); + auto &DT = AM->getResult<DominatorTreeAnalysis>(F); + auto &TLI = AM->getResult<TargetLibraryAnalysis>(F); + + auto *LI = AM->getCachedResult<LoopAnalysis>(F); + + // FIXME: The AliasAnalysis is not yet supported in the new pass manager + if (!combineInstructionsOverFunction(F, Worklist, nullptr, AC, TLI, DT, LI)) + // No changes, all analyses are preserved. + return PreservedAnalyses::all(); + + // Mark all the analyses that instcombine updates as preserved. + // FIXME: Need a way to preserve CFG analyses here! + PreservedAnalyses PA; + PA.preserve<DominatorTreeAnalysis>(); + return PA; +} + +namespace { +/// \brief The legacy pass manager's instcombine pass. +/// +/// This is a basic whole-function wrapper around the instcombine utility. It +/// will try to combine all instructions in the function. +class InstructionCombiningPass : public FunctionPass { + InstCombineWorklist Worklist; + +public: + static char ID; // Pass identification, replacement for typeid + + InstructionCombiningPass() : FunctionPass(ID) { + initializeInstructionCombiningPassPass(*PassRegistry::getPassRegistry()); + } + + void getAnalysisUsage(AnalysisUsage &AU) const override; + bool runOnFunction(Function &F) override; +}; +} + +void InstructionCombiningPass::getAnalysisUsage(AnalysisUsage &AU) const { + AU.setPreservesCFG(); + AU.addRequired<AAResultsWrapperPass>(); + AU.addRequired<AssumptionCacheTracker>(); + AU.addRequired<TargetLibraryInfoWrapperPass>(); + AU.addRequired<DominatorTreeWrapperPass>(); + AU.addPreserved<DominatorTreeWrapperPass>(); + AU.addPreserved<GlobalsAAWrapperPass>(); +} + +bool InstructionCombiningPass::runOnFunction(Function &F) { + if (skipOptnoneFunction(F)) + return false; + + // Required analyses. + auto AA = &getAnalysis<AAResultsWrapperPass>().getAAResults(); + auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); + auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); + auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); + + // Optional analyses. + auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>(); + auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr; + + return combineInstructionsOverFunction(F, Worklist, AA, AC, TLI, DT, LI); +} + +char InstructionCombiningPass::ID = 0; +INITIALIZE_PASS_BEGIN(InstructionCombiningPass, "instcombine", + "Combine redundant instructions", false, false) +INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) +INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) +INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass) +INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass) +INITIALIZE_PASS_END(InstructionCombiningPass, "instcombine", + "Combine redundant instructions", false, false) + +// Initialization Routines +void llvm::initializeInstCombine(PassRegistry &Registry) { + initializeInstructionCombiningPassPass(Registry); +} + +void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { + initializeInstructionCombiningPassPass(*unwrap(R)); +} + +FunctionPass *llvm::createInstructionCombiningPass() { + return new InstructionCombiningPass(); +} |
