1//===---- MipsOptimizeMathLibCalls.cpp - Optimize math lib calls. ----===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This pass does an IR transformation which enables the backend to emit native 11// math instructions. 12// 13//===----------------------------------------------------------------------===// 14 15#include "MipsTargetMachine.h" 16#include "llvm/IR/IRBuilder.h" 17#include "llvm/IR/Intrinsics.h" 18#include "llvm/Pass.h" 19#include "llvm/Support/CommandLine.h" 20#include "llvm/Target/TargetLibraryInfo.h" 21#include "llvm/Transforms/Utils/BasicBlockUtils.h" 22 23using namespace llvm; 24 25static cl::opt<bool> DisableOpt("disable-mips-math-optimization", 26 cl::init(false), 27 cl::desc("MIPS: Disable math lib call " 28 "optimization."), cl::Hidden); 29 30namespace { 31 class MipsOptimizeMathLibCalls : public FunctionPass { 32 public: 33 static char ID; 34 35 MipsOptimizeMathLibCalls(MipsTargetMachine &TM_) : 36 FunctionPass(ID), TM(TM_) {} 37 38 virtual const char *getPassName() const { 39 return "MIPS: Optimize calls to math library functions."; 40 } 41 42 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 43 44 virtual bool runOnFunction(Function &F); 45 46 private: 47 /// Optimize calls to sqrt. 48 bool optimizeSQRT(CallInst *Call, Function *CalledFunc, 49 BasicBlock &CurrBB, 50 Function::iterator &BB); 51 52 const TargetMachine &TM; 53 }; 54 55 char MipsOptimizeMathLibCalls::ID = 0; 56} 57 58FunctionPass *llvm::createMipsOptimizeMathLibCalls(MipsTargetMachine &TM) { 59 return new MipsOptimizeMathLibCalls(TM); 60} 61 62void MipsOptimizeMathLibCalls::getAnalysisUsage(AnalysisUsage &AU) const { 63 AU.addRequired<TargetLibraryInfo>(); 64 FunctionPass::getAnalysisUsage(AU); 65} 66 67bool MipsOptimizeMathLibCalls::runOnFunction(Function &F) { 68 if (DisableOpt) 69 return false; 70 71 const MipsSubtarget &Subtarget = TM.getSubtarget<MipsSubtarget>(); 72 73 if (Subtarget.inMips16Mode()) 74 return false; 75 76 bool Changed = false; 77 Function::iterator CurrBB; 78 const TargetLibraryInfo *LibInfo = &getAnalysis<TargetLibraryInfo>(); 79 80 for (Function::iterator BB = F.begin(), BE = F.end(); BB != BE;) { 81 CurrBB = BB++; 82 83 for (BasicBlock::iterator II = CurrBB->begin(), IE = CurrBB->end(); 84 II != IE; ++II) { 85 CallInst *Call = dyn_cast<CallInst>(&*II); 86 Function *CalledFunc; 87 88 if (!Call || !(CalledFunc = Call->getCalledFunction())) 89 continue; 90 91 LibFunc::Func LibFunc; 92 Attribute A = CalledFunc->getAttributes() 93 .getAttribute(AttributeSet::FunctionIndex, "use-soft-float"); 94 95 // Skip if function has "use-soft-float" attribute. 96 if ((A.isStringAttribute() && (A.getValueAsString() == "true")) || 97 TM.Options.UseSoftFloat) 98 continue; 99 100 // Skip if function either has local linkage or is not a known library 101 // function. 102 if (CalledFunc->hasLocalLinkage() || !CalledFunc->hasName() || 103 !LibInfo->getLibFunc(CalledFunc->getName(), LibFunc)) 104 continue; 105 106 switch (LibFunc) { 107 case LibFunc::sqrtf: 108 case LibFunc::sqrt: 109 if (optimizeSQRT(Call, CalledFunc, *CurrBB, BB)) 110 break; 111 continue; 112 default: 113 continue; 114 } 115 116 Changed = true; 117 break; 118 } 119 } 120 121 return Changed; 122} 123 124bool MipsOptimizeMathLibCalls::optimizeSQRT(CallInst *Call, 125 Function *CalledFunc, 126 BasicBlock &CurrBB, 127 Function::iterator &BB) { 128 // There is no need to change the IR, since backend will emit sqrt 129 // instruction if the call has already been marked read-only. 130 if (Call->onlyReadsMemory()) 131 return false; 132 133 // Do the following transformation: 134 // 135 // (before) 136 // dst = sqrt(src) 137 // 138 // (after) 139 // v0 = sqrt_noreadmem(src) # native sqrt instruction. 140 // if (v0 is a NaN) 141 // v1 = sqrt(src) # library call. 142 // dst = phi(v0, v1) 143 // 144 145 // Move all instructions following Call to newly created block JoinBB. 146 // Create phi and replace all uses. 147 BasicBlock *JoinBB = llvm::SplitBlock(&CurrBB, Call->getNextNode(), this); 148 IRBuilder<> Builder(JoinBB, JoinBB->begin()); 149 PHINode *Phi = Builder.CreatePHI(Call->getType(), 2); 150 Call->replaceAllUsesWith(Phi); 151 152 // Create basic block LibCallBB and insert a call to library function sqrt. 153 BasicBlock *LibCallBB = BasicBlock::Create(CurrBB.getContext(), "call.sqrt", 154 CurrBB.getParent(), JoinBB); 155 Builder.SetInsertPoint(LibCallBB); 156 Instruction *LibCall = Call->clone(); 157 Builder.Insert(LibCall); 158 Builder.CreateBr(JoinBB); 159 160 // Add attribute "readnone" so that backend can use a native sqrt instruction 161 // for this call. Insert a FP compare instruction and a conditional branch 162 // at the end of CurrBB. 163 Call->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone); 164 CurrBB.getTerminator()->eraseFromParent(); 165 Builder.SetInsertPoint(&CurrBB); 166 Value *FCmp = Builder.CreateFCmpOEQ(Call, Call); 167 Builder.CreateCondBr(FCmp, JoinBB, LibCallBB); 168 169 // Add phi operands. 170 Phi->addIncoming(Call, &CurrBB); 171 Phi->addIncoming(LibCall, LibCallBB); 172 173 BB = JoinBB; 174 return true; 175} 176