[PATCH] D62013: [InstSimplify] Add unary fneg to `fsub 0.0, (fneg X) ==> X` transform

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally updated this revision to Diff 199878.
cameron.mcinally added a comment.

Address reviews...


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62013/new/

https://reviews.llvm.org/D62013

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstSimplify/fast-math.ll


Index: llvm/test/Transforms/InstSimplify/fast-math.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/fast-math.ll
+++ llvm/test/Transforms/InstSimplify/fast-math.ll
@@ -219,9 +219,7 @@
 ; fsub nsz 0.0, (fneg X) ==> X
 define float @fneg_x(float %a) {
 ; CHECK-LABEL: @fneg_x(
-; CHECK-NEXT:    [[T1:%.*]] = fneg float [[A:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = fsub nsz float 0.000000e+00, [[T1]]
-; CHECK-NEXT:    ret float [[RET]]
+; CHECK-NEXT:    ret float [[A:%.*]]
 ;
   %t1 = fneg float %a
   %ret = fsub nsz float 0.0, %t1
@@ -239,9 +237,7 @@
 
 define <2 x float> @fneg_x_vec_undef1(<2 x float> %a) {
 ; CHECK-LABEL: @fneg_x_vec_undef1(
-; CHECK-NEXT:    [[T1:%.*]] = fneg <2 x float> [[A:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = fsub nsz <2 x float> <float 0.000000e+00, float undef>, [[T1]]
-; CHECK-NEXT:    ret <2 x float> [[RET]]
+; CHECK-NEXT:    ret <2 x float> [[A:%.*]]
 ;
   %t1 = fneg <2 x float> %a
   %ret = fsub nsz <2 x float> <float 0.0, float undef>, %t1
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4400,8 +4400,10 @@
     return X;
 
   // fsub 0.0, (fsub 0.0, X) ==> X if signed zeros are ignored.
+  // fsub 0.0, (fneg X) ==> X if signed zeros are ignored.
   if (FMF.noSignedZeros() && match(Op0, m_AnyZeroFP()) &&
-      match(Op1, m_FSub(m_AnyZeroFP(), m_Value(X))))
+      (match(Op1, m_FSub(m_AnyZeroFP(), m_Value(X))) ||
+       match(Op1, m_FNeg(m_Value(X)))))
     return X;
 
   // fsub nnan x, x ==> 0.0


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