[InstSimplify] Restore fsub 0.0, (fsub 0.0, X) ==> X optzn

I accidentally removed this in r262212 but there was no test coverage to
detect it.

llvm-svn: 262215

2 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index aca19de4f17..bb0a275f947 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -839,7 +839,7 @@ static Value *SimplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags FMF,
     return X;
 
   // fsub 0.0, (fsub 0.0, X) ==> X if signed zeros are ignored.
-  if (FMF.noSignedZeros() && match(Op0, m_NegZero()) &&
+  if (FMF.noSignedZeros() && match(Op0, m_AnyZero()) &&
       match(Op1, m_FSub(m_AnyZero(), m_Value(X))))
     return X;
 
diff --git a/llvm/test/Transforms/InstSimplify/fast-math.ll b/llvm/test/Transforms/InstSimplify/fast-math.ll
index 90532fa5db8..c499af33f52 100644
--- a/llvm/test/Transforms/InstSimplify/fast-math.ll
+++ b/llvm/test/Transforms/InstSimplify/fast-math.ll
@@ -91,6 +91,16 @@ define float @fsub_x_x(float %a) {
   ret float %ret
 }
 
+; fsub nsz 0.0, (fsub 0.0, X) ==> X
+; CHECK-LABEL: @fsub_0_0_x(
+define float @fsub_0_0_x(float %a) {
+  %t1 = fsub float 0.0, %a
+  %ret = fsub nsz float 0.0, %t1
+
+; CHECK: ret float %a
+  ret float %ret
+}
+
 ; fadd nsz X, 0 ==> X
 ; CHECK-LABEL: @nofold_fadd_x_0(
 define float @nofold_fadd_x_0(float %a) {