-//===---- MipsOptimizeMathLibCalls.cpp - Optimize math lib calls. ----===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This pass does an IR transformation which enables the backend to emit native
-// math instructions.
-//
-//===----------------------------------------------------------------------===//
-
-#include "MipsTargetMachine.h"
-#include "llvm/IR/IRBuilder.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Target/TargetLibraryInfo.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-
-using namespace llvm;
-
-static cl::opt<bool> DisableOpt("disable-mips-math-optimization",
- cl::init(false),
- cl::desc("MIPS: Disable math lib call "
- "optimization."), cl::Hidden);
-
-namespace {
- class MipsOptimizeMathLibCalls : public FunctionPass {
- public:
- static char ID;
-
- MipsOptimizeMathLibCalls(MipsTargetMachine &TM_) :
- FunctionPass(ID), TM(TM_) {}
-
- virtual const char *getPassName() const {
- return "MIPS: Optimize calls to math library functions.";
- }
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
-
- virtual bool runOnFunction(Function &F);
-
- private:
- /// Optimize calls to sqrt.
- bool optimizeSQRT(CallInst *Call, Function *CalledFunc,
- BasicBlock &CurrBB,
- Function::iterator &BB);
-
- const TargetMachine &TM;
- };
-
- char MipsOptimizeMathLibCalls::ID = 0;
-}
-
-FunctionPass *llvm::createMipsOptimizeMathLibCalls(MipsTargetMachine &TM) {
- return new MipsOptimizeMathLibCalls(TM);
-}
-
-void MipsOptimizeMathLibCalls::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<TargetLibraryInfo>();
- FunctionPass::getAnalysisUsage(AU);
-}
-
-bool MipsOptimizeMathLibCalls::runOnFunction(Function &F) {
- if (DisableOpt)
- return false;
-
- const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>();
-
- if (Subtarget.inMips16Mode())
- return false;
-
- bool Changed = false;
- Function::iterator CurrBB;
- const TargetLibraryInfo *LibInfo = &getAnalysis<TargetLibraryInfo>();
-
- for (Function::iterator BB = F.begin(), BE = F.end(); BB != BE;) {
- CurrBB = BB++;
-
- for (BasicBlock::iterator II = CurrBB->begin(), IE = CurrBB->end();
- II != IE; ++II) {
- CallInst *Call = dyn_cast<CallInst>(&*II);
- Function *CalledFunc;
-
- if (!Call || !(CalledFunc = Call->getCalledFunction()))
- continue;
-
- LibFunc::Func LibFunc;
- Attribute A = CalledFunc->getAttributes()
- .getAttribute(AttributeSet::FunctionIndex, "use-soft-float");
-
- // Skip if function has "use-soft-float" attribute.
- if ((A.isStringAttribute() && (A.getValueAsString() == "true")) ||
- TM.Options.UseSoftFloat)
- continue;
-
- // Skip if function either has local linkage or is not a known library
- // function.
- if (CalledFunc->hasLocalLinkage() || !CalledFunc->hasName() ||
- !LibInfo->getLibFunc(CalledFunc->getName(), LibFunc))
- continue;
-
- switch (LibFunc) {
- case LibFunc::sqrtf:
- case LibFunc::sqrt:
- if (optimizeSQRT(Call, CalledFunc, *CurrBB, BB))
- break;
- continue;
- default:
- continue;
- }
-
- Changed = true;
- break;
- }
- }
-
- return Changed;
-}
-
-bool MipsOptimizeMathLibCalls::optimizeSQRT(CallInst *Call,
- Function *CalledFunc,
- BasicBlock &CurrBB,
- Function::iterator &BB) {
- // There is no need to change the IR, since backend will emit sqrt
- // instruction if the call has already been marked read-only.
- if (Call->onlyReadsMemory())
- return false;
-
- // Do the following transformation:
- //
- // (before)
- // dst = sqrt(src)
- //
- // (after)
- // v0 = sqrt_noreadmem(src) # native sqrt instruction.
- // if (v0 is a NaN)
- // v1 = sqrt(src) # library call.
- // dst = phi(v0, v1)
- //
-
- // Move all instructions following Call to newly created block JoinBB.
- // Create phi and replace all uses.
- BasicBlock *JoinBB = llvm::SplitBlock(&CurrBB, Call->getNextNode(), this);
- IRBuilder<> Builder(JoinBB, JoinBB->begin());
- PHINode *Phi = Builder.CreatePHI(Call->getType(), 2);
- Call->replaceAllUsesWith(Phi);
-
- // Create basic block LibCallBB and insert a call to library function sqrt.
- BasicBlock *LibCallBB = BasicBlock::Create(CurrBB.getContext(), "call.sqrt",
- CurrBB.getParent(), JoinBB);
- Builder.SetInsertPoint(LibCallBB);
- Instruction *LibCall = Call->clone();
- Builder.Insert(LibCall);
- Builder.CreateBr(JoinBB);
-
- // Add attribute "readnone" so that backend can use a native sqrt instruction
- // for this call. Insert a FP compare instruction and a conditional branch
- // at the end of CurrBB.
- Call->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
- CurrBB.getTerminator()->eraseFromParent();
- Builder.SetInsertPoint(&CurrBB);
- Value *FCmp = Builder.CreateFCmpOEQ(Call, Call);
- Builder.CreateCondBr(FCmp, JoinBB, LibCallBB);
-
- // Add phi operands.
- Phi->addIncoming(Call, &CurrBB);
- Phi->addIncoming(LibCall, LibCallBB);
-
- BB = JoinBB;
- return true;
-}