[llvm] r183802 - [mips] Add an IR transformation pass that optimizes calls to sqrt.
Akira Hatanaka
ahatanaka at mips.com
Tue Jun 11 15:21:44 PDT 2013
Author: ahatanak
Date: Tue Jun 11 17:21:44 2013
New Revision: 183802
URL: http://llvm.org/viewvc/llvm-project?rev=183802&view=rev
Log:
[mips] Add an IR transformation pass that optimizes calls to sqrt.
The pass emits a call to sqrt that has attribute "read-none". This call will be
converted to an ISD::FSQRT node during DAG construction, which will turn into
a mips native sqrt instruction.
Added:
llvm/trunk/lib/Target/Mips/MipsOptimizeMathLibCalls.cpp
llvm/trunk/test/CodeGen/Mips/optimize-fp-math.ll
Modified:
llvm/trunk/lib/Target/Mips/Mips.h
llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp
Modified: llvm/trunk/lib/Target/Mips/Mips.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/Mips.h?rev=183802&r1=183801&r2=183802&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/Mips.h (original)
+++ llvm/trunk/lib/Target/Mips/Mips.h Tue Jun 11 17:21:44 2013
@@ -28,7 +28,7 @@ namespace llvm {
FunctionPass *createMipsJITCodeEmitterPass(MipsTargetMachine &TM,
JITCodeEmitter &JCE);
FunctionPass *createMipsConstantIslandPass(MipsTargetMachine &tm);
-
+ FunctionPass *createMipsOptimizeMathLibCalls(MipsTargetMachine &TM);
} // end namespace llvm;
#endif
Added: llvm/trunk/lib/Target/Mips/MipsOptimizeMathLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MipsOptimizeMathLibCalls.cpp?rev=183802&view=auto
==============================================================================
--- llvm/trunk/lib/Target/Mips/MipsOptimizeMathLibCalls.cpp (added)
+++ llvm/trunk/lib/Target/Mips/MipsOptimizeMathLibCalls.cpp Tue Jun 11 17:21:44 2013
@@ -0,0 +1,175 @@
+//===---- 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;
+}
Modified: llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp?rev=183802&r1=183801&r2=183802&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp (original)
+++ llvm/trunk/lib/Target/Mips/MipsTargetMachine.cpp Tue Jun 11 17:21:44 2013
@@ -160,6 +160,7 @@ void MipsPassConfig::addIRPasses() {
addPass(createMipsOs16(getMipsTargetMachine()));
if (getMipsSubtarget().inMips16HardFloat())
addPass(createMips16HardFloat(getMipsTargetMachine()));
+ addPass(createMipsOptimizeMathLibCalls(getMipsTargetMachine()));
}
// Install an instruction selector pass using
// the ISelDag to gen Mips code.
Added: llvm/trunk/test/CodeGen/Mips/optimize-fp-math.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/Mips/optimize-fp-math.ll?rev=183802&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/Mips/optimize-fp-math.ll (added)
+++ llvm/trunk/test/CodeGen/Mips/optimize-fp-math.ll Tue Jun 11 17:21:44 2013
@@ -0,0 +1,32 @@
+; RUN: llc -march=mipsel < %s | FileCheck %s -check-prefix=32
+; RUN: llc -march=mips64el -mcpu=mips64 < %s | FileCheck %s -check-prefix=64
+
+; 32: test_sqrtf_float_:
+; 32: sqrt.s $f[[R0:[0-9]+]], $f{{[0-9]+}}
+; 32: c.un.s $f[[R0]], $f[[R0]]
+; 64: test_sqrtf_float_:
+; 64: sqrt.s $f[[R0:[0-9]+]], $f{{[0-9]+}}
+; 64: c.un.s $f[[R0]], $f[[R0]]
+
+define float @test_sqrtf_float_(float %a) {
+entry:
+ %call = tail call float @sqrtf(float %a)
+ ret float %call
+}
+
+declare float @sqrtf(float)
+
+; 32: test_sqrt_double_:
+; 32: sqrt.d $f[[R0:[0-9]+]], $f{{[0-9]+}}
+; 32: c.un.d $f[[R0]], $f[[R0]]
+; 64: test_sqrt_double_:
+; 64: sqrt.d $f[[R0:[0-9]+]], $f{{[0-9]+}}
+; 64: c.un.d $f[[R0]], $f[[R0]]
+
+define double @test_sqrt_double_(double %a) {
+entry:
+ %call = tail call double @sqrt(double %a)
+ ret double %call
+}
+
+declare double @sqrt(double)
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