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+//===-- LibCallsShrinkWrap.cpp ----------------------------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass shrink-wraps a call to function if the result is not used.
+// The call can set errno but is otherwise side effect free. For example:
+// sqrt(val);
+// is transformed to
+// if (val < 0)
+// sqrt(val);
+// Even if the result of library call is not being used, the compiler cannot
+// safely delete the call because the function can set errno on error
+// conditions.
+// Note in many functions, the error condition solely depends on the incoming
+// parameter. In this optimization, we can generate the condition can lead to
+// the errno to shrink-wrap the call. Since the chances of hitting the error
+// condition is low, the runtime call is effectively eliminated.
+//
+// These partially dead calls are usually results of C++ abstraction penalty
+// exposed by inlining.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/LibCallsShrinkWrap.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/Pass.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "libcalls-shrinkwrap"
+
+STATISTIC(NumWrappedOneCond, "Number of One-Condition Wrappers Inserted");
+STATISTIC(NumWrappedTwoCond, "Number of Two-Condition Wrappers Inserted");
+
+static cl::opt<bool> LibCallsShrinkWrapDoDomainError(
+ "libcalls-shrinkwrap-domain-error", cl::init(true), cl::Hidden,
+ cl::desc("Perform shrink-wrap on lib calls with domain errors"));
+static cl::opt<bool> LibCallsShrinkWrapDoRangeError(
+ "libcalls-shrinkwrap-range-error", cl::init(true), cl::Hidden,
+ cl::desc("Perform shrink-wrap on lib calls with range errors"));
+static cl::opt<bool> LibCallsShrinkWrapDoPoleError(
+ "libcalls-shrinkwrap-pole-error", cl::init(true), cl::Hidden,
+ cl::desc("Perform shrink-wrap on lib calls with pole errors"));
+
+namespace {
+class LibCallsShrinkWrapLegacyPass : public FunctionPass {
+public:
+ static char ID; // Pass identification, replacement for typeid
+ explicit LibCallsShrinkWrapLegacyPass() : FunctionPass(ID) {
+ initializeLibCallsShrinkWrapLegacyPassPass(
+ *PassRegistry::getPassRegistry());
+ }
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
+ bool runOnFunction(Function &F) override;
+};
+}
+
+char LibCallsShrinkWrapLegacyPass::ID = 0;
+INITIALIZE_PASS_BEGIN(LibCallsShrinkWrapLegacyPass, "libcalls-shrinkwrap",
+ "Conditionally eliminate dead library calls", false,
+ false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(LibCallsShrinkWrapLegacyPass, "libcalls-shrinkwrap",
+ "Conditionally eliminate dead library calls", false, false)
+
+namespace {
+class LibCallsShrinkWrap : public InstVisitor<LibCallsShrinkWrap> {
+public:
+ LibCallsShrinkWrap(const TargetLibraryInfo &TLI) : TLI(TLI), Changed(false){};
+ bool isChanged() const { return Changed; }
+ void visitCallInst(CallInst &CI) { checkCandidate(CI); }
+ void perform() {
+ for (auto &CI : WorkList) {
+ DEBUG(dbgs() << "CDCE calls: " << CI->getCalledFunction()->getName()
+ << "\n");
+ if (perform(CI)) {
+ Changed = true;
+ DEBUG(dbgs() << "Transformed\n");
+ }
+ }
+ }
+
+private:
+ bool perform(CallInst *CI);
+ void checkCandidate(CallInst &CI);
+ void shrinkWrapCI(CallInst *CI, Value *Cond);
+ bool performCallDomainErrorOnly(CallInst *CI, const LibFunc::Func &Func);
+ bool performCallErrors(CallInst *CI, const LibFunc::Func &Func);
+ bool performCallRangeErrorOnly(CallInst *CI, const LibFunc::Func &Func);
+ Value *generateOneRangeCond(CallInst *CI, const LibFunc::Func &Func);
+ Value *generateTwoRangeCond(CallInst *CI, const LibFunc::Func &Func);
+ Value *generateCondForPow(CallInst *CI, const LibFunc::Func &Func);
+
+ // Create an OR of two conditions.
+ Value *createOrCond(CallInst *CI, CmpInst::Predicate Cmp, float Val,
+ CmpInst::Predicate Cmp2, float Val2) {
+ IRBuilder<> BBBuilder(CI);
+ Value *Arg = CI->getArgOperand(0);
+ auto Cond2 = createCond(BBBuilder, Arg, Cmp2, Val2);
+ auto Cond1 = createCond(BBBuilder, Arg, Cmp, Val);
+ return BBBuilder.CreateOr(Cond1, Cond2);
+ }
+
+ // Create a single condition using IRBuilder.
+ Value *createCond(IRBuilder<> &BBBuilder, Value *Arg, CmpInst::Predicate Cmp,
+ float Val) {
+ Constant *V = ConstantFP::get(BBBuilder.getContext(), APFloat(Val));
+ if (!Arg->getType()->isFloatTy())
+ V = ConstantExpr::getFPExtend(V, Arg->getType());
+ return BBBuilder.CreateFCmp(Cmp, Arg, V);
+ }
+
+ // Create a single condition.
+ Value *createCond(CallInst *CI, CmpInst::Predicate Cmp, float Val) {
+ IRBuilder<> BBBuilder(CI);
+ Value *Arg = CI->getArgOperand(0);
+ return createCond(BBBuilder, Arg, Cmp, Val);
+ }
+
+ const TargetLibraryInfo &TLI;
+ SmallVector<CallInst *, 16> WorkList;
+ bool Changed;
+};
+} // end anonymous namespace
+
+// Perform the transformation to calls with errno set by domain error.
+bool LibCallsShrinkWrap::performCallDomainErrorOnly(CallInst *CI,
+ const LibFunc::Func &Func) {
+ Value *Cond = nullptr;
+
+ switch (Func) {
+ case LibFunc::acos: // DomainError: (x < -1 || x > 1)
+ case LibFunc::acosf: // Same as acos
+ case LibFunc::acosl: // Same as acos
+ case LibFunc::asin: // DomainError: (x < -1 || x > 1)
+ case LibFunc::asinf: // Same as asin
+ case LibFunc::asinl: // Same as asin
+ {
+ ++NumWrappedTwoCond;
+ Cond = createOrCond(CI, CmpInst::FCMP_OLT, -1.0f, CmpInst::FCMP_OGT, 1.0f);
+ break;
+ }
+ case LibFunc::cos: // DomainError: (x == +inf || x == -inf)
+ case LibFunc::cosf: // Same as cos
+ case LibFunc::cosl: // Same as cos
+ case LibFunc::sin: // DomainError: (x == +inf || x == -inf)
+ case LibFunc::sinf: // Same as sin
+ case LibFunc::sinl: // Same as sin
+ {
+ ++NumWrappedTwoCond;
+ Cond = createOrCond(CI, CmpInst::FCMP_OEQ, INFINITY, CmpInst::FCMP_OEQ,
+ -INFINITY);
+ break;
+ }
+ case LibFunc::acosh: // DomainError: (x < 1)
+ case LibFunc::acoshf: // Same as acosh
+ case LibFunc::acoshl: // Same as acosh
+ {
+ ++NumWrappedOneCond;
+ Cond = createCond(CI, CmpInst::FCMP_OLT, 1.0f);
+ break;
+ }
+ case LibFunc::sqrt: // DomainError: (x < 0)
+ case LibFunc::sqrtf: // Same as sqrt
+ case LibFunc::sqrtl: // Same as sqrt
+ {
+ ++NumWrappedOneCond;
+ Cond = createCond(CI, CmpInst::FCMP_OLT, 0.0f);
+ break;
+ }
+ default:
+ return false;
+ }
+ shrinkWrapCI(CI, Cond);
+ return true;
+}
+
+// Perform the transformation to calls with errno set by range error.
+bool LibCallsShrinkWrap::performCallRangeErrorOnly(CallInst *CI,
+ const LibFunc::Func &Func) {
+ Value *Cond = nullptr;
+
+ switch (Func) {
+ case LibFunc::cosh:
+ case LibFunc::coshf:
+ case LibFunc::coshl:
+ case LibFunc::exp:
+ case LibFunc::expf:
+ case LibFunc::expl:
+ case LibFunc::exp10:
+ case LibFunc::exp10f:
+ case LibFunc::exp10l:
+ case LibFunc::exp2:
+ case LibFunc::exp2f:
+ case LibFunc::exp2l:
+ case LibFunc::sinh:
+ case LibFunc::sinhf:
+ case LibFunc::sinhl: {
+ Cond = generateTwoRangeCond(CI, Func);
+ break;
+ }
+ case LibFunc::expm1: // RangeError: (709, inf)
+ case LibFunc::expm1f: // RangeError: (88, inf)
+ case LibFunc::expm1l: // RangeError: (11356, inf)
+ {
+ Cond = generateOneRangeCond(CI, Func);
+ break;
+ }
+ default:
+ return false;
+ }
+ shrinkWrapCI(CI, Cond);
+ return true;
+}
+
+// Perform the transformation to calls with errno set by combination of errors.
+bool LibCallsShrinkWrap::performCallErrors(CallInst *CI,
+ const LibFunc::Func &Func) {
+ Value *Cond = nullptr;
+
+ switch (Func) {
+ case LibFunc::atanh: // DomainError: (x < -1 || x > 1)
+ // PoleError: (x == -1 || x == 1)
+ // Overall Cond: (x <= -1 || x >= 1)
+ case LibFunc::atanhf: // Same as atanh
+ case LibFunc::atanhl: // Same as atanh
+ {
+ if (!LibCallsShrinkWrapDoDomainError || !LibCallsShrinkWrapDoPoleError)
+ return false;
+ ++NumWrappedTwoCond;
+ Cond = createOrCond(CI, CmpInst::FCMP_OLE, -1.0f, CmpInst::FCMP_OGE, 1.0f);
+ break;
+ }
+ case LibFunc::log: // DomainError: (x < 0)
+ // PoleError: (x == 0)
+ // Overall Cond: (x <= 0)
+ case LibFunc::logf: // Same as log
+ case LibFunc::logl: // Same as log
+ case LibFunc::log10: // Same as log
+ case LibFunc::log10f: // Same as log
+ case LibFunc::log10l: // Same as log
+ case LibFunc::log2: // Same as log
+ case LibFunc::log2f: // Same as log
+ case LibFunc::log2l: // Same as log
+ case LibFunc::logb: // Same as log
+ case LibFunc::logbf: // Same as log
+ case LibFunc::logbl: // Same as log
+ {
+ if (!LibCallsShrinkWrapDoDomainError || !LibCallsShrinkWrapDoPoleError)
+ return false;
+ ++NumWrappedOneCond;
+ Cond = createCond(CI, CmpInst::FCMP_OLE, 0.0f);
+ break;
+ }
+ case LibFunc::log1p: // DomainError: (x < -1)
+ // PoleError: (x == -1)
+ // Overall Cond: (x <= -1)
+ case LibFunc::log1pf: // Same as log1p
+ case LibFunc::log1pl: // Same as log1p
+ {
+ if (!LibCallsShrinkWrapDoDomainError || !LibCallsShrinkWrapDoPoleError)
+ return false;
+ ++NumWrappedOneCond;
+ Cond = createCond(CI, CmpInst::FCMP_OLE, -1.0f);
+ break;
+ }
+ case LibFunc::pow: // DomainError: x < 0 and y is noninteger
+ // PoleError: x == 0 and y < 0
+ // RangeError: overflow or underflow
+ case LibFunc::powf:
+ case LibFunc::powl: {
+ if (!LibCallsShrinkWrapDoDomainError || !LibCallsShrinkWrapDoPoleError ||
+ !LibCallsShrinkWrapDoRangeError)
+ return false;
+ Cond = generateCondForPow(CI, Func);
+ if (Cond == nullptr)
+ return false;
+ break;
+ }
+ default:
+ return false;
+ }
+ assert(Cond && "performCallErrors should not see an empty condition");
+ shrinkWrapCI(CI, Cond);
+ return true;
+}
+
+// Checks if CI is a candidate for shrinkwrapping and put it into work list if
+// true.
+void LibCallsShrinkWrap::checkCandidate(CallInst &CI) {
+ if (CI.isNoBuiltin())
+ return;
+ // A possible improvement is to handle the calls with the return value being
+ // used. If there is API for fast libcall implementation without setting
+ // errno, we can use the same framework to direct/wrap the call to the fast
+ // API in the error free path, and leave the original call in the slow path.
+ if (!CI.use_empty())
+ return;
+
+ LibFunc::Func Func;
+ Function *Callee = CI.getCalledFunction();
+ if (!Callee)
+ return;
+ if (!TLI.getLibFunc(*Callee, Func) || !TLI.has(Func))
+ return;
+
+ if (CI.getNumArgOperands() == 0)
+ return;
+ // TODO: Handle long double in other formats.
+ Type *ArgType = CI.getArgOperand(0)->getType();
+ if (!(ArgType->isFloatTy() || ArgType->isDoubleTy() ||
+ ArgType->isX86_FP80Ty()))
+ return;
+
+ WorkList.push_back(&CI);
+}
+
+// Generate the upper bound condition for RangeError.
+Value *LibCallsShrinkWrap::generateOneRangeCond(CallInst *CI,
+ const LibFunc::Func &Func) {
+ float UpperBound;
+ switch (Func) {
+ case LibFunc::expm1: // RangeError: (709, inf)
+ UpperBound = 709.0f;
+ break;
+ case LibFunc::expm1f: // RangeError: (88, inf)
+ UpperBound = 88.0f;
+ break;
+ case LibFunc::expm1l: // RangeError: (11356, inf)
+ UpperBound = 11356.0f;
+ break;
+ default:
+ llvm_unreachable("Should be reach here");
+ }
+
+ ++NumWrappedOneCond;
+ return createCond(CI, CmpInst::FCMP_OGT, UpperBound);
+}
+
+// Generate the lower and upper bound condition for RangeError.
+Value *LibCallsShrinkWrap::generateTwoRangeCond(CallInst *CI,
+ const LibFunc::Func &Func) {
+ float UpperBound, LowerBound;
+ switch (Func) {
+ case LibFunc::cosh: // RangeError: (x < -710 || x > 710)
+ case LibFunc::sinh: // Same as cosh
+ LowerBound = -710.0f;
+ UpperBound = 710.0f;
+ break;
+ case LibFunc::coshf: // RangeError: (x < -89 || x > 89)
+ case LibFunc::sinhf: // Same as coshf
+ LowerBound = -89.0f;
+ UpperBound = 89.0f;
+ break;
+ case LibFunc::coshl: // RangeError: (x < -11357 || x > 11357)
+ case LibFunc::sinhl: // Same as coshl
+ LowerBound = -11357.0f;
+ UpperBound = 11357.0f;
+ break;
+ case LibFunc::exp: // RangeError: (x < -745 || x > 709)
+ LowerBound = -745.0f;
+ UpperBound = 709.0f;
+ break;
+ case LibFunc::expf: // RangeError: (x < -103 || x > 88)
+ LowerBound = -103.0f;
+ UpperBound = 88.0f;
+ break;
+ case LibFunc::expl: // RangeError: (x < -11399 || x > 11356)
+ LowerBound = -11399.0f;
+ UpperBound = 11356.0f;
+ break;
+ case LibFunc::exp10: // RangeError: (x < -323 || x > 308)
+ LowerBound = -323.0f;
+ UpperBound = 308.0f;
+ break;
+ case LibFunc::exp10f: // RangeError: (x < -45 || x > 38)
+ LowerBound = -45.0f;
+ UpperBound = 38.0f;
+ break;
+ case LibFunc::exp10l: // RangeError: (x < -4950 || x > 4932)
+ LowerBound = -4950.0f;
+ UpperBound = 4932.0f;
+ break;
+ case LibFunc::exp2: // RangeError: (x < -1074 || x > 1023)
+ LowerBound = -1074.0f;
+ UpperBound = 1023.0f;
+ break;
+ case LibFunc::exp2f: // RangeError: (x < -149 || x > 127)
+ LowerBound = -149.0f;
+ UpperBound = 127.0f;
+ break;
+ case LibFunc::exp2l: // RangeError: (x < -16445 || x > 11383)
+ LowerBound = -16445.0f;
+ UpperBound = 11383.0f;
+ break;
+ default:
+ llvm_unreachable("Should be reach here");
+ }
+
+ ++NumWrappedTwoCond;
+ return createOrCond(CI, CmpInst::FCMP_OGT, UpperBound, CmpInst::FCMP_OLT,
+ LowerBound);
+}
+
+// For pow(x,y), We only handle the following cases:
+// (1) x is a constant && (x >= 1) && (x < MaxUInt8)
+// Cond is: (y > 127)
+// (2) x is a value coming from an integer type.
+// (2.1) if x's bit_size == 8
+// Cond: (x <= 0 || y > 128)
+// (2.2) if x's bit_size is 16
+// Cond: (x <= 0 || y > 64)
+// (2.3) if x's bit_size is 32
+// Cond: (x <= 0 || y > 32)
+// Support for powl(x,y) and powf(x,y) are TBD.
+//
+// Note that condition can be more conservative than the actual condition
+// (i.e. we might invoke the calls that will not set the errno.).
+//
+Value *LibCallsShrinkWrap::generateCondForPow(CallInst *CI,
+ const LibFunc::Func &Func) {
+ // FIXME: LibFunc::powf and powl TBD.
+ if (Func != LibFunc::pow) {
+ DEBUG(dbgs() << "Not handled powf() and powl()\n");
+ return nullptr;
+ }
+
+ Value *Base = CI->getArgOperand(0);
+ Value *Exp = CI->getArgOperand(1);
+ IRBuilder<> BBBuilder(CI);
+
+ // Constant Base case.
+ if (ConstantFP *CF = dyn_cast<ConstantFP>(Base)) {
+ double D = CF->getValueAPF().convertToDouble();
+ if (D < 1.0f || D > APInt::getMaxValue(8).getZExtValue()) {
+ DEBUG(dbgs() << "Not handled pow(): constant base out of range\n");
+ return nullptr;
+ }
+
+ ++NumWrappedOneCond;
+ Constant *V = ConstantFP::get(CI->getContext(), APFloat(127.0f));
+ if (!Exp->getType()->isFloatTy())
+ V = ConstantExpr::getFPExtend(V, Exp->getType());
+ return BBBuilder.CreateFCmp(CmpInst::FCMP_OGT, Exp, V);
+ }
+
+ // If the Base value coming from an integer type.
+ Instruction *I = dyn_cast<Instruction>(Base);
+ if (!I) {
+ DEBUG(dbgs() << "Not handled pow(): FP type base\n");
+ return nullptr;
+ }
+ unsigned Opcode = I->getOpcode();
+ if (Opcode == Instruction::UIToFP || Opcode == Instruction::SIToFP) {
+ unsigned BW = I->getOperand(0)->getType()->getPrimitiveSizeInBits();
+ float UpperV = 0.0f;
+ if (BW == 8)
+ UpperV = 128.0f;
+ else if (BW == 16)
+ UpperV = 64.0f;
+ else if (BW == 32)
+ UpperV = 32.0f;
+ else {
+ DEBUG(dbgs() << "Not handled pow(): type too wide\n");
+ return nullptr;
+ }
+
+ ++NumWrappedTwoCond;
+ Constant *V = ConstantFP::get(CI->getContext(), APFloat(UpperV));
+ Constant *V0 = ConstantFP::get(CI->getContext(), APFloat(0.0f));
+ if (!Exp->getType()->isFloatTy())
+ V = ConstantExpr::getFPExtend(V, Exp->getType());
+ if (!Base->getType()->isFloatTy())
+ V0 = ConstantExpr::getFPExtend(V0, Exp->getType());
+
+ Value *Cond = BBBuilder.CreateFCmp(CmpInst::FCMP_OGT, Exp, V);
+ Value *Cond0 = BBBuilder.CreateFCmp(CmpInst::FCMP_OLE, Base, V0);
+ return BBBuilder.CreateOr(Cond0, Cond);
+ }
+ DEBUG(dbgs() << "Not handled pow(): base not from integer convert\n");
+ return nullptr;
+}
+
+// Wrap conditions that can potentially generate errno to the library call.
+void LibCallsShrinkWrap::shrinkWrapCI(CallInst *CI, Value *Cond) {
+ assert(Cond != nullptr && "hrinkWrapCI is not expecting an empty call inst");
+ MDNode *BranchWeights =
+ MDBuilder(CI->getContext()).createBranchWeights(1, 2000);
+ TerminatorInst *NewInst =
+ SplitBlockAndInsertIfThen(Cond, CI, false, BranchWeights);
+ BasicBlock *CallBB = NewInst->getParent();
+ CallBB->setName("cdce.call");
+ CallBB->getSingleSuccessor()->setName("cdce.end");
+ CI->removeFromParent();
+ CallBB->getInstList().insert(CallBB->getFirstInsertionPt(), CI);
+ DEBUG(dbgs() << "== Basic Block After ==");
+ DEBUG(dbgs() << *CallBB->getSinglePredecessor() << *CallBB
+ << *CallBB->getSingleSuccessor() << "\n");
+}
+
+// Perform the transformation to a single candidate.
+bool LibCallsShrinkWrap::perform(CallInst *CI) {
+ LibFunc::Func Func;
+ Function *Callee = CI->getCalledFunction();
+ assert(Callee && "perform() should apply to a non-empty callee");
+ TLI.getLibFunc(*Callee, Func);
+ assert(Func && "perform() is not expecting an empty function");
+
+ if (LibCallsShrinkWrapDoDomainError && performCallDomainErrorOnly(CI, Func))
+ return true;
+
+ if (LibCallsShrinkWrapDoRangeError && performCallRangeErrorOnly(CI, Func))
+ return true;
+
+ return performCallErrors(CI, Func);
+}
+
+void LibCallsShrinkWrapLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addPreserved<GlobalsAAWrapperPass>();
+ AU.addRequired<TargetLibraryInfoWrapperPass>();
+}
+
+static bool runImpl(Function &F, const TargetLibraryInfo &TLI) {
+ if (F.hasFnAttribute(Attribute::OptimizeForSize))
+ return false;
+ LibCallsShrinkWrap CCDCE(TLI);
+ CCDCE.visit(F);
+ CCDCE.perform();
+ return CCDCE.isChanged();
+}
+
+bool LibCallsShrinkWrapLegacyPass::runOnFunction(Function &F) {
+ auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+ return runImpl(F, TLI);
+}
+
+namespace llvm {
+char &LibCallsShrinkWrapPassID = LibCallsShrinkWrapLegacyPass::ID;
+
+// Public interface to LibCallsShrinkWrap pass.
+FunctionPass *createLibCallsShrinkWrapPass() {
+ return new LibCallsShrinkWrapLegacyPass();
+}
+
+PreservedAnalyses LibCallsShrinkWrapPass::run(Function &F,
+ FunctionAnalysisManager &FAM) {
+ auto &TLI = FAM.getResult<TargetLibraryAnalysis>(F);
+ bool Changed = runImpl(F, TLI);
+ if (!Changed)
+ return PreservedAnalyses::all();
+ auto PA = PreservedAnalyses();
+ PA.preserve<GlobalsAA>();
+ return PA;
+}
+}
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