InstCombine: fold fcmp (fneg x), (fneg y) -> fcmp x, y

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128627 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 14 insertions, 0 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 6743885cd4..cb434bda57 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2855,6 +2855,11 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
       }
   }
 
+  // fcmp (fneg x), (fneg y) -> fcmp x, y
+  Value *X, *Y;
+  if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
+    return new FCmpInst(I.getPredicate(), X, Y);
+
   // fcmp (fpext x), (fpext y) -> fcmp x, y
   if (FPExtInst *LHSExt = dyn_cast<FPExtInst>(Op0))
     if (FPExtInst *RHSExt = dyn_cast<FPExtInst>(Op1))
diff --git a/test/Transforms/InstCombine/fcmp.ll b/test/Transforms/InstCombine/fcmp.ll
index f869a18992..66607ea001 100644
--- a/test/Transforms/InstCombine/fcmp.ll
+++ b/test/Transforms/InstCombine/fcmp.ll
@@ -40,3 +40,12 @@ define i1 @test5(float %a) nounwind {
 ; CHECK: @test5
 ; CHECK-NEXT: fcmp olt float %a, -1.0
 }
+
+define i1 @test6(float %x, float %y) nounwind {
+  %neg1 = fsub float -0.000000e+00, %x
+  %neg2 = fsub float -0.000000e+00, %y
+  %cmp = fcmp ogt float %neg1, %neg2
+  ret i1 %cmp
+; CHECK: @test6
+; CHECK-NEXT: fcmp ogt float %x, %y
+}