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Allow vector fsub ops with constants to get the same optimizations as scalars.

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This problem is bigger than just fsub, but this is the minimum fix to solve
fneg for PR20556 ( http://llvm.org/bugs/show_bug.cgi?id=20556 ), and we solve
zero subtraction with the same change.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217286 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2014-09-05 22:26:22 +00:00
parent e8b19acded
commit 52af82df95
2 changed files with 25 additions and 2 deletions
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4
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -6754,8 +6754,8 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
SDValue DAGCombiner::visitFSUB(SDNode *N) {
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(N0);
ConstantFPSDNode *N1CFP = dyn_cast<ConstantFPSDNode>(N1);
ConstantFPSDNode *N0CFP = isConstOrConstSplatFP(N0);
ConstantFPSDNode *N1CFP = isConstOrConstSplatFP(N1);
EVT VT = N->getValueType(0);
SDLoc dl(N);
const TargetOptions &Options = DAG.getTarget().Options;

23
test/CodeGen/X86/vec_unsafe-fp-math.ll Normal file
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@ -0,0 +1,23 @@
; RUN: llc < %s -enable-unsafe-fp-math -mtriple=x86_64-unknown-unknown -mcpu=corei7 | FileCheck %s
; Make sure that vectors get the same benefits as scalars when using unsafe-fp-math.
; Subtracting zero is free.
define <4 x float> @vec_fsub_zero(<4 x float> %x) {
; CHECK-LABEL: vec_fsub_zero:
; CHECK-NOT: subps
; CHECK-NOT: xorps
; CHECK: retq
%sub = fsub <4 x float> %x, zeroinitializer
ret <4 x float> %sub
}
; Negating doesn't require subtraction.
define <4 x float> @vec_fneg(<4 x float> %x) {
; CHECK-LABEL: vec_fneg:
; CHECK: xorps {{.*}}LCP{{.*}}, %xmm0
; CHECK-NOT: subps
; CHECK-NEXT: retq
%sub = fsub <4 x float> zeroinitializer, %x
ret <4 x float> %sub
}