InstCombine: fdiv -x, -y -> fdiv x, y

llvm-svn: 291611

Author: arsenm

llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -1443,6 +1443,16 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
     }
   }
 
+  Value *LHS;
+  Value *RHS;
+
+  // -x / -y -> x / y
+  if (match(Op0, m_FNeg(m_Value(LHS))) && match(Op1, m_FNeg(m_Value(RHS)))) {
+    I.setOperand(0, LHS);
+    I.setOperand(1, RHS);
+    return &I;
+  }
+
   return nullptr;
 }
 

llvm/test/Transforms/InstCombine/fdiv.ll

@@ -49,3 +49,21 @@ define float @test6(float %x, float %y, float %z) nounwind readnone ssp {
 ; CHECK-NEXT: fmul fast
 ; CHECK-NEXT: fdiv fast
 }
+
+; CHECK-LABEL @fdiv_fneg_fneg(
+; CHECK: %div = fdiv float %x, %y
+define float @fdiv_fneg_fneg(float %x, float %y) {
+  %x.fneg = fsub float -0.0, %x
+  %y.fneg = fsub float -0.0, %y
+  %div = fdiv float %x.fneg, %y.fneg
+  ret float %div
+}
+
+; CHECK-LABEL @fdiv_fneg_fneg_fast(
+; CHECK: %div = fdiv fast float %x, %y
+define float @fdiv_fneg_fneg_fast(float %x, float %y) {
+  %x.fneg = fsub float -0.0, %x
+  %y.fneg = fsub float -0.0, %y
+  %div = fdiv fast float %x.fneg, %y.fneg
+  ret float %div
+}