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Adds missing TLI check for library simplification of

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* pow(x, 0.5) -> fabs(sqrt(x)) 
* pow(2.0, x) -> exp2(x)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188656 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Kuperstein 2013-08-19 06:55:47 +00:00
parent a0e735ee16
commit 2063637fa7
3 changed files with 31 additions and 3 deletions
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9
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -1133,9 +1133,11 @@ struct PowOpt : public UnsafeFPLibCallOptimization {
Value *Op1 = CI->getArgOperand(0), *Op2 = CI->getArgOperand(1);
if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
if (Op1C->isExactlyValue(1.0)) // pow(1.0, x) -> 1.0
// pow(1.0, x) -> 1.0
if (Op1C->isExactlyValue(1.0))
return Op1C;
if (Op1C->isExactlyValue(2.0)) // pow(2.0, x) -> exp2(x)
// pow(2.0, x) -> exp2(x)
if (Op1C->isExactlyValue(2.0) && TLI->has(LibFunc::exp2))
return EmitUnaryFloatFnCall(Op2, "exp2", B, Callee->getAttributes());
}
@ -1145,7 +1147,8 @@ struct PowOpt : public UnsafeFPLibCallOptimization {
if (Op2C->getValueAPF().isZero()) // pow(x, 0.0) -> 1.0
return ConstantFP::get(CI->getType(), 1.0);
if (Op2C->isExactlyValue(0.5)) {
if (Op2C->isExactlyValue(0.5) &&
TLI->has(LibFunc::sqrt) && TLI->has(LibFunc::fabs)) {
// Expand pow(x, 0.5) to (x == -infinity ? +infinity : fabs(sqrt(x))).
// This is faster than calling pow, and still handles negative zero
// and negative infinity correctly.

13
test/Transforms/InstCombine/pow-1.ll
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@ -151,4 +151,17 @@ define double @test_simplify16(double %x) {
; CHECK-NEXT: ret double [[RECIPROCAL]]
}
declare double @llvm.pow.f64(double %Val, double %Power)
define double @test_simplify17(double %x) {
; CHECK-LABEL: @test_simplify17(
%retval = call double @llvm.pow.f64(double %x, double 0.5)
; CHECK-NEXT: [[SQRT:%[a-z0-9]+]] = call double @sqrt(double %x) [[NUW_RO]]
; CHECK-NEXT: [[FABS:%[a-z0-9]+]] = call double @fabs(double [[SQRT]]) [[NUW_RO]]
; CHECK-NEXT: [[FCMP:%[a-z0-9]+]] = fcmp oeq double %x, 0xFFF0000000000000
; CHECK-NEXT: [[SELECT:%[a-z0-9]+]] = select i1 [[FCMP]], double 0x7FF0000000000000, double [[FABS]]
ret double %retval
; CHECK-NEXT: ret double [[SELECT]]
}
; CHECK: attributes [[NUW_RO]] = { nounwind readonly }

12
test/Transforms/InstCombine/pow-3.ll Normal file
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@ -0,0 +1,12 @@
; Test that the pow won't get simplified to sqrt(fabs) when they are not available.
;
; RUN: opt < %s -disable-simplify-libcalls -instcombine -S | FileCheck %s
declare double @llvm.pow.f64(double %Val, double %Power)
define double @test_simplify_unavailable(double %x) {
; CHECK-LABEL: @test_simplify_unavailable(
%retval = call double @llvm.pow.f64(double %x, double 0.5)
; CHECK-NEXT: call double @llvm.pow.f64(double %x, double 5.000000e-01)
ret double %retval
}