[InstCombine] canonicalize negated operand of fdiv

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@367146 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index cc753ce05313ef8363fa42489c445a571e55db69..30861bfe6c58fb9130232363a4d216af41190adb 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -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.

diff --git a/test/Transforms/InstCombine/fdiv.ll b/test/Transforms/InstCombine/fdiv.ll
index 62ef758d9e38877837de86233f09726a6db93929..1cc505283054679f04ed0fa0682c6c201b7cbff7 100644 (file)
--- a/test/Transforms/InstCombine/fdiv.ll
+++ b/test/Transforms/InstCombine/fdiv.ll
@@ -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
 }
-