[PATCH] D28237: InstCombine: fdiv -x, -y -> fdiv x, y

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added a subscriber: llvm-commits.
Herald added a subscriber: wdng.

https://reviews.llvm.org/D28237

Files:
  lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  test/Transforms/InstCombine/fdiv.ll


Index: test/Transforms/InstCombine/fdiv.ll
===================================================================
--- test/Transforms/InstCombine/fdiv.ll
+++ test/Transforms/InstCombine/fdiv.ll
@@ -49,3 +49,21 @@
 ; 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
+}
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1443,6 +1443,16 @@
     }
   }
 
+  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;
 }
 


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