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Diffstat (limited to 'contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp')
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1 files changed, 1662 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp new file mode 100644 index 0000000..37123d0 --- /dev/null +++ b/contrib/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp @@ -0,0 +1,1662 @@ +//===- 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. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "instcombine" +#include "llvm/Transforms/Scalar.h" +#include "InstCombine.h" +#include "llvm/IntrinsicInst.h" +#include "llvm/Analysis/ConstantFolding.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/MemoryBuiltins.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Transforms/Utils/Local.h" +#include "llvm/Support/CFG.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Support/PatternMatch.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm-c/Initialization.h" +#include <algorithm> +#include <climits> +using namespace llvm; +using namespace llvm::PatternMatch; + +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"); + +// Initialization Routines +void llvm::initializeInstCombine(PassRegistry &Registry) { + initializeInstCombinerPass(Registry); +} + +void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { + initializeInstCombine(*unwrap(R)); +} + +char InstCombiner::ID = 0; +INITIALIZE_PASS(InstCombiner, "instcombine", + "Combine redundant instructions", false, false) + +void InstCombiner::getAnalysisUsage(AnalysisUsage &AU) const { + AU.addPreservedID(LCSSAID); + AU.setPreservesCFG(); +} + + +/// ShouldChangeType - 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(const Type *From, const Type *To) const { + assert(From->isIntegerTy() && To->isIntegerTy()); + + // If we don't have TD, we don't know if the source/dest are legal. + if (!TD) return false; + + unsigned FromWidth = From->getPrimitiveSizeInBits(); + unsigned ToWidth = To->getPrimitiveSizeInBits(); + bool FromLegal = TD->isLegalInteger(FromWidth); + bool ToLegal = TD->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; +} + + +/// SimplifyAssociativeOrCommutative - This performs a few simplifications for +/// operators which 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, TD)) { + // 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. + I.clearSubclassOptionalData(); + 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, TD)) { + // 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. + I.clearSubclassOptionalData(); + 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, TD)) { + // 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. + I.clearSubclassOptionalData(); + 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, TD)) { + // 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. + I.clearSubclassOptionalData(); + 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); + Instruction *New = BinaryOperator::Create(Opcode, A, B, Op1->getName(), + &I); + Worklist.Add(New); + I.setOperand(0, New); + I.setOperand(1, Folded); + // Conservatively clear the optional flags, since they may not be + // preserved by the reassociation. + I.clearSubclassOptionalData(); + Changed = true; + continue; + } + } + + // No further simplifications. + return Changed; + } while (1); +} + +/// LeftDistributesOverRight - 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; + } + } +} + +/// RightDistributesOverLeft - 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); + // 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; +} + +/// SimplifyUsingDistributiveLaws - 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); + Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); // op + + // Factorization. + if (Op0 && Op1 && Op0->getOpcode() == Op1->getOpcode()) { + // The instruction has the form "(A op' B) op (C op' D)". Try to factorize + // a common term. + Value *A = Op0->getOperand(0), *B = Op0->getOperand(1); + Value *C = Op1->getOperand(0), *D = Op1->getOperand(1); + Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' + + // 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. + Value *V = SimplifyBinOp(TopLevelOpcode, B, D, TD); + // 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 && Op0->hasOneUse() && Op1->hasOneUse()) + V = Builder->CreateBinOp(TopLevelOpcode, B, D, Op1->getName()); + if (V) { + ++NumFactor; + V = Builder->CreateBinOp(InnerOpcode, A, V); + V->takeName(&I); + return V; + } + } + + // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? + if (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. + Value *V = SimplifyBinOp(TopLevelOpcode, A, C, TD); + // 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 && Op0->hasOneUse() && Op1->hasOneUse()) + V = Builder->CreateBinOp(TopLevelOpcode, A, C, Op0->getName()); + if (V) { + ++NumFactor; + V = Builder->CreateBinOp(InnerOpcode, V, B); + V->takeName(&I); + 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, TD)) + if (Value *R = SimplifyBinOp(TopLevelOpcode, B, C, TD)) { + // 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, TD)) + 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, TD)) + if (Value *R = SimplifyBinOp(TopLevelOpcode, A, C, TD)) { + // 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, TD)) + return V; + // Otherwise, create a new instruction. + A = Builder->CreateBinOp(InnerOpcode, L, R); + A->takeName(&I); + return A; + } + } + + return 0; +} + +// dyn_castNegVal - 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 (ConstantVector *C = dyn_cast<ConstantVector>(V)) + if (C->getType()->getElementType()->isIntegerTy()) + return ConstantExpr::getNeg(C); + + return 0; +} + +// dyn_castFNegVal - 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) const { + if (BinaryOperator::isFNeg(V)) + 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 (ConstantVector *C = dyn_cast<ConstantVector>(V)) + if (C->getType()->getElementType()->isFloatingPointTy()) + return ConstantExpr::getFNeg(C); + + return 0; +} + +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)) + return IC->Builder->CreateBinOp(BO->getOpcode(), Op0, Op1, + SO->getName()+".op"); + 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!"); +} + +// FoldOpIntoSelect - 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 0; + 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 0; + + // 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)) { + const VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); + const VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); + + // Verify that either both or neither are vectors. + if ((SrcTy == NULL) != (DestTy == NULL)) return 0; + // If vectors, verify that they have the same number of elements. + if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) + return 0; + } + + Value *SelectTrueVal = FoldOperationIntoSelectOperand(Op, TV, this); + Value *SelectFalseVal = FoldOperationIntoSelectOperand(Op, FV, this); + + return SelectInst::Create(SI->getCondition(), + SelectTrueVal, SelectFalseVal); + } + return 0; +} + + +/// FoldOpIntoPhi - 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 0; + + // 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 (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); + UI != E; ++UI) { + Instruction *User = cast<Instruction>(*UI); + if (User != &I && !I.isIdenticalTo(User)) + return 0; + } + // 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 = 0; + 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 0; // Itself a phi. + if (NonConstBB) return 0; // 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 0; + + // 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 (NonConstBB == I.getParent()) + return 0; + } + + // 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 one some other paths (e.g. inside a loop). Only + // do this if the pred block is unconditionally branching into the phi block. + if (NonConstBB != 0) { + BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); + if (!BI || !BI->isUnconditional()) return 0; + } + + // Okay, we can do the transformation: create the new PHI node. + PHINode *NewPN = PHINode::Create(I.getType(), ""); + NewPN->reserveOperandSpace(PN->getNumOperands()/2); + InsertNewInstBefore(NewPN, *PN); + NewPN->takeName(PN); + + // If we are going to have to insert a new computation, do so right before the + // predecessors 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 = 0; + if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) + 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 = 0; + 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 = 0; + 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); + const 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 (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); + UI != E; ) { + Instruction *User = cast<Instruction>(*UI++); + if (User == &I) continue; + ReplaceInstUsesWith(*User, NewPN); + EraseInstFromFunction(*User); + } + return ReplaceInstUsesWith(I, NewPN); +} + +/// FindElementAtOffset - Given a type and a constant offset, determine whether +/// or not there is a sequence of GEP indices into the type that will land us at +/// the specified offset. If so, fill them into NewIndices and return the +/// resultant element type, otherwise return null. +const Type *InstCombiner::FindElementAtOffset(const Type *Ty, int64_t Offset, + SmallVectorImpl<Value*> &NewIndices) { + if (!TD) return 0; + if (!Ty->isSized()) return 0; + + // 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}] + const Type *IntPtrTy = TD->getIntPtrType(Ty->getContext()); + int64_t FirstIdx = 0; + if (int64_t TySize = TD->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) >= TD->getTypeSizeInBits(Ty)) + return 0; + + if (const StructType *STy = dyn_cast<StructType>(Ty)) { + const StructLayout *SL = TD->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 (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) { + uint64_t EltSize = TD->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 0; + } + } + + return Ty; +} + + + +Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { + SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); + + if (Value *V = SimplifyGEPInst(&Ops[0], Ops.size(), TD)) + 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. + if (TD) { + bool MadeChange = false; + const Type *IntPtrTy = TD->getIntPtrType(GEP.getContext()); + + 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. + const SequentialType *SeqTy = dyn_cast<SequentialType>(*GTI); + if (!SeqTy) continue; + + // 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() && + TD->getTypeAllocSize(SeqTy->getElementType()) == 0) + if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { + *I = Constant::getNullValue(IntPtrTy); + MadeChange = true; + } + + if ((*I)->getType() != IntPtrTy) { + // 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, IntPtrTy, true); + MadeChange = true; + } + } + if (MadeChange) return &GEP; + } + + // 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)) { + // Note that if our source is a gep chain itself that 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 (GetElementPtrInst *SrcGEP = + dyn_cast<GetElementPtrInst>(Src->getOperand(0))) + if (SrcGEP->getNumOperands() == 2) + return 0; // 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 0; + 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->getOperand(0), Indices.begin(), + Indices.end(), GEP.getName()) : + GetElementPtrInst::Create(Src->getOperand(0), Indices.begin(), + Indices.end(), GEP.getName()); + } + + // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). + Value *StrippedPtr = PtrOp->stripPointerCasts(); + if (StrippedPtr != PtrOp) { + const PointerType *StrippedPtrTy =cast<PointerType>(StrippedPtr->getType()); + + 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) { + const PointerType *CPTy = cast<PointerType>(PtrOp->getType()); + if (const 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(StrippedPtr, Idx.begin(), + Idx.end(), GEP.getName()); + Res->setIsInBounds(GEP.isInBounds()); + return Res; + } + + if (const 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. + GEP.setOperand(0, StrippedPtr); + return &GEP; + } + } + } + } 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 + const Type *SrcElTy = StrippedPtrTy->getElementType(); + const Type *ResElTy=cast<PointerType>(PtrOp->getType())->getElementType(); + if (TD && SrcElTy->isArrayTy() && + TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()) == + TD->getTypeAllocSize(ResElTy)) { + Value *Idx[2]; + Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); + Idx[1] = GEP.getOperand(1); + Value *NewGEP = GEP.isInBounds() ? + Builder->CreateInBoundsGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()) : + Builder->CreateGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()); + // V and GEP are both pointer types --> BitCast + return new BitCastInst(NewGEP, GEP.getType()); + } + + // 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 (TD && SrcElTy->isArrayTy() && ResElTy->isIntegerTy(8)) { + uint64_t ArrayEltSize = + TD->getTypeAllocSize(cast<ArrayType>(SrcElTy)->getElementType()); + + // Check to see if "tmp" is a scale by a multiple of ArrayEltSize. We + // allow either a mul, shift, or constant here. + Value *NewIdx = 0; + ConstantInt *Scale = 0; + if (ArrayEltSize == 1) { + NewIdx = GEP.getOperand(1); + Scale = ConstantInt::get(cast<IntegerType>(NewIdx->getType()), 1); + } else if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP.getOperand(1))) { + NewIdx = ConstantInt::get(CI->getType(), 1); + Scale = CI; + } else if (Instruction *Inst =dyn_cast<Instruction>(GEP.getOperand(1))){ + if (Inst->getOpcode() == Instruction::Shl && + isa<ConstantInt>(Inst->getOperand(1))) { + ConstantInt *ShAmt = cast<ConstantInt>(Inst->getOperand(1)); + uint32_t ShAmtVal = ShAmt->getLimitedValue(64); + Scale = ConstantInt::get(cast<IntegerType>(Inst->getType()), + 1ULL << ShAmtVal); + NewIdx = Inst->getOperand(0); + } else if (Inst->getOpcode() == Instruction::Mul && + isa<ConstantInt>(Inst->getOperand(1))) { + Scale = cast<ConstantInt>(Inst->getOperand(1)); + NewIdx = Inst->getOperand(0); + } + } + + // If the index will be to exactly the right offset with the scale taken + // out, perform the transformation. Note, we don't know whether Scale is + // signed or not. We'll use unsigned version of division/modulo + // operation after making sure Scale doesn't have the sign bit set. + if (ArrayEltSize && Scale && Scale->getSExtValue() >= 0LL && + Scale->getZExtValue() % ArrayEltSize == 0) { + Scale = ConstantInt::get(Scale->getType(), + Scale->getZExtValue() / ArrayEltSize); + if (Scale->getZExtValue() != 1) { + Constant *C = ConstantExpr::getIntegerCast(Scale, NewIdx->getType(), + false /*ZExt*/); + NewIdx = Builder->CreateMul(NewIdx, C, "idxscale"); + } + + // Insert the new GEP instruction. + Value *Idx[2]; + Idx[0] = Constant::getNullValue(Type::getInt32Ty(GEP.getContext())); + Idx[1] = NewIdx; + Value *NewGEP = GEP.isInBounds() ? + Builder->CreateInBoundsGEP(StrippedPtr, Idx, Idx + 2,GEP.getName()): + Builder->CreateGEP(StrippedPtr, Idx, Idx + 2, GEP.getName()); + // The NewGEP must be pointer typed, so must the old one -> BitCast + return new BitCastInst(NewGEP, GEP.getType()); + } + } + } + } + + /// 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)) { + if (TD && + !isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices()) { + // Determine how much the GEP moves the pointer. We are guaranteed to get + // a constant back from EmitGEPOffset. + ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(&GEP)); + int64_t Offset = OffsetV->getSExtValue(); + + // 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 == 0) { + // 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>(BCI->getOperand(0)) || + isMalloc(BCI->getOperand(0))) { + // 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, I); + ReplaceInstUsesWith(*BCI, I); + } + return &GEP; + } + } + return new BitCastInst(BCI->getOperand(0), 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; + const Type *InTy = + cast<PointerType>(BCI->getOperand(0)->getType())->getElementType(); + if (FindElementAtOffset(InTy, Offset, NewIndices)) { + Value *NGEP = GEP.isInBounds() ? + Builder->CreateInBoundsGEP(BCI->getOperand(0), NewIndices.begin(), + NewIndices.end()) : + Builder->CreateGEP(BCI->getOperand(0), NewIndices.begin(), + NewIndices.end()); + + if (NGEP->getType() == GEP.getType()) + return ReplaceInstUsesWith(GEP, NGEP); + NGEP->takeName(&GEP); + return new BitCastInst(NGEP, GEP.getType()); + } + } + } + + return 0; +} + + + +static bool IsOnlyNullComparedAndFreed(const Value &V) { + for (Value::const_use_iterator UI = V.use_begin(), UE = V.use_end(); + UI != UE; ++UI) { + const User *U = *UI; + if (isFreeCall(U)) + continue; + if (const ICmpInst *ICI = dyn_cast<ICmpInst>(U)) + if (ICI->isEquality() && isa<ConstantPointerNull>(ICI->getOperand(1))) + continue; + return false; + } + return true; +} + +Instruction *InstCombiner::visitMalloc(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. + if (IsOnlyNullComparedAndFreed(MI)) { + for (Value::use_iterator UI = MI.use_begin(), UE = MI.use_end(); + UI != UE;) { + // We can assume that every remaining use is a free call or an icmp eq/ne + // to null, so the cast is safe. + Instruction *I = cast<Instruction>(*UI); + + // Early increment here, as we're about to get rid of the user. + ++UI; + + if (isFreeCall(I)) { + EraseInstFromFunction(*cast<CallInst>(I)); + continue; + } + // Again, the cast is safe. + ICmpInst *C = cast<ICmpInst>(I); + ReplaceInstUsesWith(*C, ConstantInt::get(Type::getInt1Ty(C->getContext()), + C->isFalseWhenEqual())); + EraseInstFromFunction(*C); + } + return EraseInstFromFunction(MI); + } + return 0; +} + + + +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. + new StoreInst(ConstantInt::getTrue(FI.getContext()), + UndefValue::get(Type::getInt1PtrTy(FI.getContext())), &FI); + 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); + + return 0; +} + + + +Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { + // Change br (not X), label True, label False to: br X, label False, True + Value *X = 0; + 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.setSuccessor(0, FalseDest); + BI.setSuccessor(1, TrueDest); + return &BI; + } + + // Cannonicalize 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.setSuccessor(0, FalseDest); + BI.setSuccessor(1, TrueDest); + Worklist.Add(Cond); + return &BI; + } + + // Cannonicalize 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.setSuccessor(0, FalseDest); + BI.setSuccessor(1, TrueDest); + Worklist.Add(Cond); + return &BI; + } + + return 0; +} + +Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { + Value *Cond = SI.getCondition(); + 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' + for (unsigned i = 2, e = SI.getNumOperands(); i != e; i += 2) + SI.setOperand(i, + ConstantExpr::getSub(cast<Constant>(SI.getOperand(i)), + AddRHS)); + SI.setOperand(0, I->getOperand(0)); + Worklist.Add(I); + return &SI; + } + } + return 0; +} + +Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { + Value *Agg = EV.getAggregateOperand(); + + if (!EV.hasIndices()) + return ReplaceInstUsesWith(EV, Agg); + + if (Constant *C = dyn_cast<Constant>(Agg)) { + if (isa<UndefValue>(C)) + return ReplaceInstUsesWith(EV, UndefValue::get(EV.getType())); + + if (isa<ConstantAggregateZero>(C)) + return ReplaceInstUsesWith(EV, Constant::getNullValue(EV.getType())); + + if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) { + // Extract the element indexed by the first index out of the constant + Value *V = C->getOperand(*EV.idx_begin()); + if (EV.getNumIndices() > 1) + // Extract the remaining indices out of the constant indexed by the + // first index + return ExtractValueInst::Create(V, EV.idx_begin() + 1, EV.idx_end()); + else + return ReplaceInstUsesWith(EV, V); + } + return 0; // Can't handle other constants + } + 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.idx_begin(), EV.idx_end()); + } + 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.idx_begin(), EV.idx_end()); + return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), + 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(), + 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); + II->replaceAllUsesWith(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); + II->replaceAllUsesWith(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); + II->replaceAllUsesWith(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. + // FIXME: If a load is used only by extractvalue instructions then this + // could be done regardless of having multiple uses. + if (!L->isVolatile() && 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->getParent(), L); + Value *GEP = Builder->CreateInBoundsGEP(L->getPointerOperand(), + Indices.begin(), Indices.end()); + // 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 0; +} + + + + +/// TryToSinkInstruction - 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->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; + + // 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, E = I->getParent()->end(); + Scan != E; ++Scan) + if (Scan->mayWriteToMemory()) + return false; + } + + BasicBlock::iterator InsertPos = DestBlock->getFirstNonPHI(); + + I->moveBefore(InsertPos); + ++NumSunkInst; + return true; +} + + +/// AddReachableCodeToWorklist - 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, + SmallPtrSet<BasicBlock*, 64> &Visited, + InstCombiner &IC, + const TargetData *TD) { + bool MadeIRChange = false; + SmallVector<BasicBlock*, 256> Worklist; + Worklist.push_back(BB); + + SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; + SmallPtrSet<ConstantExpr*, 64> 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)) continue; + + for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { + Instruction *Inst = BBI++; + + // DCE instruction if trivially dead. + if (isInstructionTriviallyDead(Inst)) { + ++NumDeadInst; + DEBUG(errs() << "IC: DCE: " << *Inst << '\n'); + Inst->eraseFromParent(); + continue; + } + + // ConstantProp instruction if trivially constant. + if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0))) + if (Constant *C = ConstantFoldInstruction(Inst, TD)) { + DEBUG(errs() << "IC: ConstFold to: " << *C << " from: " + << *Inst << '\n'); + Inst->replaceAllUsesWith(C); + ++NumConstProp; + Inst->eraseFromParent(); + continue; + } + + if (TD) { + // 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 == 0) continue; + + // If we already folded this constant, don't try again. + if (!FoldedConstants.insert(CE)) + continue; + + Constant *NewC = ConstantFoldConstantExpression(CE, TD); + if (NewC && NewC != CE) { + *i = NewC; + 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 (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) + if (SI->getCaseValue(i) == Cond) { + BasicBlock *ReachableBB = SI->getSuccessor(i); + Worklist.push_back(ReachableBB); + continue; + } + + // Otherwise it is the default destination. + Worklist.push_back(SI->getSuccessor(0)); + continue; + } + } + + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + Worklist.push_back(TI->getSuccessor(i)); + } 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. + IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0], + InstrsForInstCombineWorklist.size()); + + return MadeIRChange; +} + +bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) { + MadeIRChange = false; + + DEBUG(errs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " + << F.getNameStr() << "\n"); + + { + // 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.begin(), Visited, *this, TD); + + // 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)) { + Instruction *Term = BB->getTerminator(); + while (Term != BB->begin()) { // Remove instrs bottom-up + BasicBlock::iterator I = Term; --I; + + DEBUG(errs() << "IC: DCE: " << *I << '\n'); + // A debug intrinsic shouldn't force another iteration if we weren't + // going to do one without it. + if (!isa<DbgInfoIntrinsic>(I)) { + ++NumDeadInst; + MadeIRChange = true; + } + + // If I is not void type then replaceAllUsesWith undef. + // This allows ValueHandlers and custom metadata to adjust itself. + if (!I->getType()->isVoidTy()) + I->replaceAllUsesWith(UndefValue::get(I->getType())); + I->eraseFromParent(); + } + } + } + + while (!Worklist.isEmpty()) { + Instruction *I = Worklist.RemoveOne(); + if (I == 0) continue; // skip null values. + + // Check to see if we can DCE the instruction. + if (isInstructionTriviallyDead(I)) { + DEBUG(errs() << "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() && isa<Constant>(I->getOperand(0))) + if (Constant *C = ConstantFoldInstruction(I, TD)) { + DEBUG(errs() << "IC: ConstFold 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->use_back()); + BasicBlock *UserParent; + + // Get the block the use occurs in. + if (PHINode *PN = dyn_cast<PHINode>(UserInst)) + UserParent = PN->getIncomingBlock(I->use_begin().getUse()); + 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. + MadeIRChange |= TryToSinkInstruction(I, UserParent); + } + } + + // Now that we have an instruction, try combining it to simplify it. + Builder->SetInsertPoint(I->getParent(), I); + +#ifndef NDEBUG + std::string OrigI; +#endif + DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); + DEBUG(errs() << "IC: Visiting: " << OrigI << '\n'); + + if (Instruction *Result = visit(*I)) { + ++NumCombined; + // Should we replace the old instruction with a new one? + if (Result != I) { + DEBUG(errs() << "IC: Old = " << *I << '\n' + << " New = " << *Result << '\n'); + + Result->setDebugLoc(I->getDebugLoc()); + // Everything uses the new instruction now. + I->replaceAllUsesWith(Result); + + // Push the new instruction and any users onto the worklist. + Worklist.Add(Result); + Worklist.AddUsersToWorkList(*Result); + + // Move the name to the new instruction first. + Result->takeName(I); + + // Insert the new instruction into the basic block... + BasicBlock *InstParent = I->getParent(); + BasicBlock::iterator InsertPos = I; + + if (!isa<PHINode>(Result)) // If combining a PHI, don't insert + while (isa<PHINode>(InsertPos)) // middle of a block of PHIs. + ++InsertPos; + + InstParent->getInstList().insert(InsertPos, Result); + + EraseInstFromFunction(*I); + } else { +#ifndef NDEBUG + DEBUG(errs() << "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)) { + EraseInstFromFunction(*I); + } else { + Worklist.Add(I); + Worklist.AddUsersToWorkList(*I); + } + } + MadeIRChange = true; + } + } + + Worklist.Zap(); + return MadeIRChange; +} + + +bool InstCombiner::runOnFunction(Function &F) { + MustPreserveLCSSA = mustPreserveAnalysisID(LCSSAID); + TD = getAnalysisIfAvailable<TargetData>(); + + + /// Builder - This is an IRBuilder that automatically inserts new + /// instructions into the worklist when they are created. + IRBuilder<true, TargetFolder, InstCombineIRInserter> + TheBuilder(F.getContext(), TargetFolder(TD), + InstCombineIRInserter(Worklist)); + Builder = &TheBuilder; + + bool EverMadeChange = false; + + // Iterate while there is work to do. + unsigned Iteration = 0; + while (DoOneIteration(F, Iteration++)) + EverMadeChange = true; + + Builder = 0; + return EverMadeChange; +} + +FunctionPass *llvm::createInstructionCombiningPass() { + return new InstCombiner(); +} |
