6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-02 07:11:49 +00:00
Code Issues Projects Releases Wiki Activity

Teach InstCombine that (fmul X, -1.0) can be simplified to (fneg X), which LLVM expresses as (fsub -0.0, X).

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199420 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2014-01-16 20:36:42 +00:00
parent a560d155d9
commit a2a8bbb30f
2 changed files with 22 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -426,6 +426,16 @@ Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
return NV;
ConstantFP *C = dyn_cast<ConstantFP>(Op1);
// (fmul X, -1.0) --> (fsub -0.0, X)
if (C && C->isExactlyValue(-1.0)) {
Instruction *RI = BinaryOperator::CreateFSub(
ConstantFP::getNegativeZero(C->getType()),
Op0);
RI->copyFastMathFlags(&I);
return RI;
}
if (C && AllowReassociate && C->getValueAPF().isFiniteNonZero()) {
// Let MDC denote an expression in one of these forms:
// X * C, C/X, X/C, where C is a constant.

12
test/Transforms/InstCombine/fmul.ll
View File

@ -93,3 +93,15 @@ for.body: ; preds = %for.cond
for.end: ; preds = %for.cond
ret void
}
; X * -1.0 => -0.0 - X
define float @test9(float %x) {
%mul = fmul float %x, -1.0
ret float %mul
; CHECK-LABEL: @test9(
; CHECK-NOT: fmul
; CHECK: fsub
}