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a2c6256b2a
The 'Modified' variable should have been removed from SimplifyLibCalls in r177619, but was missed. This commit removes it. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177622 91177308-0d34-0410-b5e6-96231b3b80d8
248 lines
7.6 KiB
C++
248 lines
7.6 KiB
C++
//===- SimplifyLibCalls.cpp - Optimize specific well-known library calls --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a simple pass that applies a variety of small
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// optimizations for calls to specific well-known function calls (e.g. runtime
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// library functions). Any optimization that takes the very simple form
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// "replace call to library function with simpler code that provides the same
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// result" belongs in this file.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "simplify-libcalls"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/StringMap.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Config/config.h" // FIXME: Shouldn't depend on host!
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetLibraryInfo.h"
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#include "llvm/Transforms/Utils/BuildLibCalls.h"
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// Optimizer Base Class
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//===----------------------------------------------------------------------===//
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/// This class is the abstract base class for the set of optimizations that
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/// corresponds to one library call.
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namespace {
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class LibCallOptimization {
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protected:
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Function *Caller;
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const DataLayout *TD;
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const TargetLibraryInfo *TLI;
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LLVMContext* Context;
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public:
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LibCallOptimization() { }
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virtual ~LibCallOptimization() {}
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/// CallOptimizer - This pure virtual method is implemented by base classes to
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/// do various optimizations. If this returns null then no transformation was
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/// performed. If it returns CI, then it transformed the call and CI is to be
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/// deleted. If it returns something else, replace CI with the new value and
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/// delete CI.
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virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B)
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=0;
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Value *OptimizeCall(CallInst *CI, const DataLayout *TD,
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const TargetLibraryInfo *TLI, IRBuilder<> &B) {
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Caller = CI->getParent()->getParent();
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this->TD = TD;
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this->TLI = TLI;
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if (CI->getCalledFunction())
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Context = &CI->getCalledFunction()->getContext();
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// We never change the calling convention.
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if (CI->getCallingConv() != llvm::CallingConv::C)
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return NULL;
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return CallOptimizer(CI->getCalledFunction(), CI, B);
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}
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};
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} // End anonymous namespace.
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//===----------------------------------------------------------------------===//
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// SimplifyLibCalls Pass Implementation
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//===----------------------------------------------------------------------===//
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namespace {
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/// This pass optimizes well known library functions from libc and libm.
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///
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class SimplifyLibCalls : public FunctionPass {
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TargetLibraryInfo *TLI;
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StringMap<LibCallOptimization*> Optimizations;
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public:
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static char ID; // Pass identification
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SimplifyLibCalls() : FunctionPass(ID) {
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initializeSimplifyLibCallsPass(*PassRegistry::getPassRegistry());
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}
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void AddOpt(LibFunc::Func F, LibCallOptimization* Opt);
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void AddOpt(LibFunc::Func F1, LibFunc::Func F2, LibCallOptimization* Opt);
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void InitOptimizations();
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bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<TargetLibraryInfo>();
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}
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};
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} // end anonymous namespace.
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char SimplifyLibCalls::ID = 0;
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INITIALIZE_PASS_BEGIN(SimplifyLibCalls, "simplify-libcalls",
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"Simplify well-known library calls", false, false)
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INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
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INITIALIZE_PASS_END(SimplifyLibCalls, "simplify-libcalls",
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"Simplify well-known library calls", false, false)
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// Public interface to the Simplify LibCalls pass.
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FunctionPass *llvm::createSimplifyLibCallsPass() {
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return new SimplifyLibCalls();
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}
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void SimplifyLibCalls::AddOpt(LibFunc::Func F, LibCallOptimization* Opt) {
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if (TLI->has(F))
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Optimizations[TLI->getName(F)] = Opt;
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}
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void SimplifyLibCalls::AddOpt(LibFunc::Func F1, LibFunc::Func F2,
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LibCallOptimization* Opt) {
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if (TLI->has(F1) && TLI->has(F2))
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Optimizations[TLI->getName(F1)] = Opt;
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}
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/// Optimizations - Populate the Optimizations map with all the optimizations
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/// we know.
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void SimplifyLibCalls::InitOptimizations() {
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}
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/// runOnFunction - Top level algorithm.
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///
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bool SimplifyLibCalls::runOnFunction(Function &F) {
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TLI = &getAnalysis<TargetLibraryInfo>();
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if (Optimizations.empty())
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InitOptimizations();
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const DataLayout *TD = getAnalysisIfAvailable<DataLayout>();
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IRBuilder<> Builder(F.getContext());
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bool Changed = false;
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for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
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// Ignore non-calls.
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CallInst *CI = dyn_cast<CallInst>(I++);
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if (!CI || CI->hasFnAttr(Attribute::NoBuiltin)) continue;
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// Ignore indirect calls and calls to non-external functions.
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Function *Callee = CI->getCalledFunction();
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if (Callee == 0 || !Callee->isDeclaration() ||
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!(Callee->hasExternalLinkage() || Callee->hasDLLImportLinkage()))
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continue;
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// Ignore unknown calls.
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LibCallOptimization *LCO = Optimizations.lookup(Callee->getName());
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if (!LCO) continue;
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// Set the builder to the instruction after the call.
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Builder.SetInsertPoint(BB, I);
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// Use debug location of CI for all new instructions.
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Builder.SetCurrentDebugLocation(CI->getDebugLoc());
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// Try to optimize this call.
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Value *Result = LCO->OptimizeCall(CI, TD, TLI, Builder);
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if (Result == 0) continue;
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DEBUG(dbgs() << "SimplifyLibCalls simplified: " << *CI;
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dbgs() << " into: " << *Result << "\n");
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// Something changed!
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Changed = true;
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// Inspect the instruction after the call (which was potentially just
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// added) next.
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I = CI; ++I;
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if (CI != Result && !CI->use_empty()) {
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CI->replaceAllUsesWith(Result);
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if (!Result->hasName())
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Result->takeName(CI);
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}
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CI->eraseFromParent();
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}
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}
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return Changed;
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}
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// TODO:
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// Additional cases that we need to add to this file:
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//
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// cbrt:
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// * cbrt(expN(X)) -> expN(x/3)
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// * cbrt(sqrt(x)) -> pow(x,1/6)
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// * cbrt(sqrt(x)) -> pow(x,1/9)
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//
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// exp, expf, expl:
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// * exp(log(x)) -> x
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//
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// log, logf, logl:
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// * log(exp(x)) -> x
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// * log(x**y) -> y*log(x)
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// * log(exp(y)) -> y*log(e)
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// * log(exp2(y)) -> y*log(2)
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// * log(exp10(y)) -> y*log(10)
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// * log(sqrt(x)) -> 0.5*log(x)
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// * log(pow(x,y)) -> y*log(x)
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//
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// lround, lroundf, lroundl:
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// * lround(cnst) -> cnst'
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//
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// pow, powf, powl:
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// * pow(exp(x),y) -> exp(x*y)
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// * pow(sqrt(x),y) -> pow(x,y*0.5)
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// * pow(pow(x,y),z)-> pow(x,y*z)
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//
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// round, roundf, roundl:
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// * round(cnst) -> cnst'
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//
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// signbit:
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// * signbit(cnst) -> cnst'
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// * signbit(nncst) -> 0 (if pstv is a non-negative constant)
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//
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// sqrt, sqrtf, sqrtl:
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// * sqrt(expN(x)) -> expN(x*0.5)
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// * sqrt(Nroot(x)) -> pow(x,1/(2*N))
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// * sqrt(pow(x,y)) -> pow(|x|,y*0.5)
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//
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// strchr:
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// * strchr(p, 0) -> strlen(p)
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// tan, tanf, tanl:
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// * tan(atan(x)) -> x
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//
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// trunc, truncf, truncl:
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// * trunc(cnst) -> cnst'
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//
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//
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