[llvm] r219717 - Optimize away fabs() calls when input is squared (known positive).
Sanjay Patel
spatel at rotateright.com
Tue Oct 14 13:43:12 PDT 2014
Author: spatel
Date: Tue Oct 14 15:43:11 2014
New Revision: 219717
URL: http://llvm.org/viewvc/llvm-project?rev=219717&view=rev
Log:
Optimize away fabs() calls when input is squared (known positive).
Eliminate library calls and intrinsic calls to fabs when the input
is a squared value.
Note that no unsafe-math / fast-math assumptions are needed for
this optimization.
Differential Revision: http://reviews.llvm.org/D5777
Added:
llvm/trunk/test/Transforms/InstCombine/fabs.ll
Modified:
llvm/trunk/include/llvm/Transforms/Utils/SimplifyLibCalls.h
llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
Modified: llvm/trunk/include/llvm/Transforms/Utils/SimplifyLibCalls.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/SimplifyLibCalls.h?rev=219717&r1=219716&r2=219717&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/SimplifyLibCalls.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/SimplifyLibCalls.h Tue Oct 14 15:43:11 2014
@@ -92,6 +92,7 @@ private:
Value *optimizeCos(CallInst *CI, IRBuilder<> &B);
Value *optimizePow(CallInst *CI, IRBuilder<> &B);
Value *optimizeExp2(CallInst *CI, IRBuilder<> &B);
+ Value *optimizeFabs(CallInst *CI, IRBuilder<> &B);
Value *optimizeSinCosPi(CallInst *CI, IRBuilder<> &B);
// Integer Library Call Optimizations
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp?rev=219717&r1=219716&r2=219717&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp Tue Oct 14 15:43:11 2014
@@ -1230,6 +1230,30 @@ Value *LibCallSimplifier::optimizeExp2(C
return Ret;
}
+Value *LibCallSimplifier::optimizeFabs(CallInst *CI, IRBuilder<> &B) {
+ Function *Callee = CI->getCalledFunction();
+
+ Value *Ret = nullptr;
+ if (Callee->getName() == "fabs" && TLI->has(LibFunc::fabsf)) {
+ Ret = optimizeUnaryDoubleFP(CI, B, false);
+ }
+
+ FunctionType *FT = Callee->getFunctionType();
+ // Make sure this has 1 argument of FP type which matches the result type.
+ if (FT->getNumParams() != 1 || FT->getReturnType() != FT->getParamType(0) ||
+ !FT->getParamType(0)->isFloatingPointTy())
+ return Ret;
+
+ Value *Op = CI->getArgOperand(0);
+ if (Instruction *I = dyn_cast<Instruction>(Op)) {
+ // Fold fabs(x * x) -> x * x; any squared FP value must already be positive.
+ if (I->getOpcode() == Instruction::FMul)
+ if (I->getOperand(0) == I->getOperand(1))
+ return Op;
+ }
+ return Ret;
+}
+
static bool isTrigLibCall(CallInst *CI);
static void insertSinCosCall(IRBuilder<> &B, Function *OrigCallee, Value *Arg,
bool UseFloat, Value *&Sin, Value *&Cos,
@@ -1893,6 +1917,8 @@ Value *LibCallSimplifier::optimizeCall(C
return optimizePow(CI, Builder);
case Intrinsic::exp2:
return optimizeExp2(CI, Builder);
+ case Intrinsic::fabs:
+ return optimizeFabs(CI, Builder);
default:
return nullptr;
}
@@ -1965,6 +1991,10 @@ Value *LibCallSimplifier::optimizeCall(C
case LibFunc::exp2:
case LibFunc::exp2f:
return optimizeExp2(CI, Builder);
+ case LibFunc::fabsf:
+ case LibFunc::fabs:
+ case LibFunc::fabsl:
+ return optimizeFabs(CI, Builder);
case LibFunc::ffs:
case LibFunc::ffsl:
case LibFunc::ffsll:
@@ -1999,7 +2029,6 @@ Value *LibCallSimplifier::optimizeCall(C
case LibFunc::fputc:
return optimizeErrorReporting(CI, Builder, 1);
case LibFunc::ceil:
- case LibFunc::fabs:
case LibFunc::floor:
case LibFunc::rint:
case LibFunc::round:
Added: llvm/trunk/test/Transforms/InstCombine/fabs.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fabs.ll?rev=219717&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fabs.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/fabs.ll Tue Oct 14 15:43:11 2014
@@ -0,0 +1,100 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; Make sure all library calls are eliminated when the input is known positive.
+
+declare float @fabsf(float)
+declare double @fabs(double)
+declare fp128 @fabsl(fp128)
+
+define float @square_fabs_call_f32(float %x) {
+ %mul = fmul float %x, %x
+ %fabsf = tail call float @fabsf(float %mul)
+ ret float %fabsf
+
+; CHECK-LABEL: square_fabs_call_f32(
+; CHECK-NEXT: %mul = fmul float %x, %x
+; CHECK-NEXT: ret float %mul
+}
+
+define double @square_fabs_call_f64(double %x) {
+ %mul = fmul double %x, %x
+ %fabs = tail call double @fabs(double %mul)
+ ret double %fabs
+
+; CHECK-LABEL: square_fabs_call_f64(
+; CHECK-NEXT: %mul = fmul double %x, %x
+; CHECK-NEXT: ret double %mul
+}
+
+define fp128 @square_fabs_call_f128(fp128 %x) {
+ %mul = fmul fp128 %x, %x
+ %fabsl = tail call fp128 @fabsl(fp128 %mul)
+ ret fp128 %fabsl
+
+; CHECK-LABEL: square_fabs_call_f128(
+; CHECK-NEXT: %mul = fmul fp128 %x, %x
+; CHECK-NEXT: ret fp128 %mul
+}
+
+; Make sure all intrinsic calls are eliminated when the input is known positive.
+
+declare float @llvm.fabs.f32(float)
+declare double @llvm.fabs.f64(double)
+declare fp128 @llvm.fabs.f128(fp128)
+
+define float @square_fabs_intrinsic_f32(float %x) {
+ %mul = fmul float %x, %x
+ %fabsf = tail call float @llvm.fabs.f32(float %mul)
+ ret float %fabsf
+
+; CHECK-LABEL: square_fabs_intrinsic_f32(
+; CHECK-NEXT: %mul = fmul float %x, %x
+; CHECK-NEXT: ret float %mul
+}
+
+define double @square_fabs_intrinsic_f64(double %x) {
+ %mul = fmul double %x, %x
+ %fabs = tail call double @llvm.fabs.f64(double %mul)
+ ret double %fabs
+
+; CHECK-LABEL: square_fabs_intrinsic_f64(
+; CHECK-NEXT: %mul = fmul double %x, %x
+; CHECK-NEXT: ret double %mul
+}
+
+define fp128 @square_fabs_intrinsic_f128(fp128 %x) {
+ %mul = fmul fp128 %x, %x
+ %fabsl = tail call fp128 @llvm.fabs.f128(fp128 %mul)
+ ret fp128 %fabsl
+
+; CHECK-LABEL: square_fabs_intrinsic_f128(
+; CHECK-NEXT: %mul = fmul fp128 %x, %x
+; CHECK-NEXT: ret fp128 %mul
+}
+
+; Shrinking a library call to a smaller type should not be inhibited by nor inhibit the square optimization.
+
+define float @square_fabs_shrink_call1(float %x) {
+ %ext = fpext float %x to double
+ %sq = fmul double %ext, %ext
+ %fabs = call double @fabs(double %sq)
+ %trunc = fptrunc double %fabs to float
+ ret float %trunc
+
+; CHECK-LABEL: square_fabs_shrink_call1(
+; CHECK-NEXT: %trunc = fmul float %x, %x
+; CHECK-NEXT: ret float %trunc
+}
+
+define float @square_fabs_shrink_call2(float %x) {
+ %sq = fmul float %x, %x
+ %ext = fpext float %sq to double
+ %fabs = call double @fabs(double %ext)
+ %trunc = fptrunc double %fabs to float
+ ret float %trunc
+
+; CHECK-LABEL: square_fabs_shrink_call2(
+; CHECK-NEXT: %sq = fmul float %x, %x
+; CHECK-NEXT: ret float %sq
+}
+
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