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[InstCombine] canonicalize negated operand of fdiv

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This is a transform that we use with fmul, so use
it for fdiv too for consistency.

llvm-svn: 367146
This commit is contained in:
Sanjay Patel 2019-07-26 19:56:59 +00:00
parent be61bc9411
commit 0c15846ea8
2 changed files with 14 additions and 5 deletions
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10
lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -1234,6 +1234,16 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
return &I;
}
// Sink negation: -X / Y --> -(X / Y)
// But don't transform constant expressions because there's an inverse fold.
if (match(Op0, m_OneUse(m_FNeg(m_Value(X)))) && !isa<ConstantExpr>(Op0))
return BinaryOperator::CreateFNegFMF(Builder.CreateFDivFMF(X, Op1, &I), &I);
// Sink negation: Y / -X --> -(Y / X)
// But don't transform constant expressions because there's an inverse fold.
if (match(Op1, m_OneUse(m_FNeg(m_Value(X)))) && !isa<ConstantExpr>(Op1))
return BinaryOperator::CreateFNegFMF(Builder.CreateFDivFMF(Op0, X, &I), &I);
// X / (X * Y) --> 1.0 / Y
// Reassociate to (X / X -> 1.0) is legal when NaNs are not allowed.
// We can ignore the possibility that X is infinity because INF/INF is NaN.

9
test/Transforms/InstCombine/fdiv.ll
View File

@ -501,8 +501,8 @@ define <2 x float> @div_constant_dividend3(<2 x float> %x) {
define double @fdiv_fneg1(double %x, double %y) {
; CHECK-LABEL: @fdiv_fneg1(
; CHECK-NEXT: [[NEG:%.*]] = fsub double -0.000000e+00, [[X:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = fdiv double [[NEG]], [[Y:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = fdiv double [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = fsub double -0.000000e+00, [[TMP1]]
; CHECK-NEXT: ret double [[DIV]]
;
%neg = fsub double -0.0, %x
@ -512,8 +512,8 @@ define double @fdiv_fneg1(double %x, double %y) {
define <2 x float> @fdiv_fneg2(<2 x float> %x, <2 x float> %y) {
; CHECK-LABEL: @fdiv_fneg2(
; CHECK-NEXT: [[NEG:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[X:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = fdiv <2 x float> [[Y:%.*]], [[NEG]]
; CHECK-NEXT: [[TMP1:%.*]] = fdiv <2 x float> [[Y:%.*]], [[X:%.*]]
; CHECK-NEXT: [[DIV:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[TMP1]]
; CHECK-NEXT: ret <2 x float> [[DIV]]
;
%neg = fsub <2 x float> <float -0.0, float -0.0>, %x
@ -533,4 +533,3 @@ define float @fdiv_fneg1_extra_use(float %x, float %y) {
%div = fdiv float %neg, %y
ret float %div
}