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[InstSimplify] fold fsub+fsub with common operand 

llvm-svn: 339171
This commit is contained in:
Sanjay Patel 2018-08-07 20:14:27 +00:00
parent 1662647995
commit f7a8fb2dee
2 changed files with 7 additions and 6 deletions
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5
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -4396,6 +4396,11 @@ static Value *SimplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags FMF,
if (FMF.noNaNs() && Op0 == Op1)
return Constant::getNullValue(Op0->getType());
// Y - (Y - X) --> X
if (FMF.noSignedZeros() && FMF.allowReassoc() &&
match(Op1, m_FSub(m_Specific(Op0), m_Value(X))))
return X;
return nullptr;
}

8
llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
View File

@ -737,9 +737,7 @@ define float @maxnum_x_y_maxnum_z(float %x, float %y, float %z) {
define float @fsub_fsub_common_op(float %x, float %y) {
; CHECK-LABEL: @fsub_fsub_common_op(
; CHECK-NEXT: [[S:%.*]] = fsub float [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = fsub reassoc nsz float [[Y]], [[S]]
; CHECK-NEXT: ret float [[R]]
; CHECK-NEXT: ret float [[X:%.*]]
;
%s = fsub float %y, %x
%r = fsub reassoc nsz float %y, %s
@ -748,9 +746,7 @@ define float @fsub_fsub_common_op(float %x, float %y) {
define <2 x float> @fsub_fsub_common_op_vec(<2 x float> %x, <2 x float> %y) {
; CHECK-LABEL: @fsub_fsub_common_op_vec(
; CHECK-NEXT: [[S:%.*]] = fsub <2 x float> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = fsub reassoc nsz <2 x float> [[Y]], [[S]]
; CHECK-NEXT: ret <2 x float> [[R]]
; CHECK-NEXT: ret <2 x float> [[X:%.*]]
;
%s = fsub <2 x float> %y, %x
%r = fsub reassoc nsz <2 x float> %y, %s