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

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.

llvm-svn: 217286
This commit is contained in:
Sanjay Patel 2014-09-05 22:26:22 +00:00
parent 47a8a83dc3
commit 75cc90eddc
2 changed files with 25 additions and 2 deletions
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4
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -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
llvm/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
}