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When InstCombine tries to fold away (fsub x, (fneg y)) into (fadd x, y), it is

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also worthwhile for it to look through FP extensions and truncations, whose
application commutes with fneg.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187249 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2013-07-26 21:40:29 +00:00
parent d063a326b2
commit 0c326f07ca
2 changed files with 25 additions and 1 deletions
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14
lib/Transforms/InstCombine/InstCombineAddSub.cpp
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@ -1528,9 +1528,21 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
if (Instruction *NV = FoldOpIntoSelect(I, SI))
return NV;
// If this is a 'B = x-(-A)', change to B = x+A...
// If this is a 'B = x-(-A)', change to B = x+A, potentially looking
// through FP extensions/truncations along the way.
if (Value *V = dyn_castFNegVal(Op1))
return BinaryOperator::CreateFAdd(Op0, V);
if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) {
if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) {
Value *NewTrunc = Builder->CreateFPTrunc(V, I.getType());
return BinaryOperator::CreateFAdd(Op0, NewTrunc);
}
} else if (FPExtInst *FPEI = dyn_cast<FPExtInst>(Op1)) {
if (Value *V = dyn_castFNegVal(FPEI->getOperand(0))) {
Value *NewTrunc = Builder->CreateFPExt(V, I.getType());
return BinaryOperator::CreateFAdd(Op0, NewTrunc);
}
}
if (I.hasUnsafeAlgebra()) {
if (Value *V = FAddCombine(Builder).simplify(&I))

12
test/Transforms/InstCombine/fneg-ext.ll Normal file
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@ -0,0 +1,12 @@
; RUN: opt -instcombine -S < %s | FileCheck %s
; CHECK: test1
define double @test1(float %a, double %b) nounwind readnone ssp uwtable {
; CHECK-NOT: fsub
; CHECK: fpext
; CHECK: fadd
%1 = fsub float -0.000000e+00, %a
%2 = fpext float %1 to double
%3 = fsub double %b, %2
ret double %3
}