[PATCH] D90901: [DAGCombiner] Don't fold ((fma (fneg X), Y, (fneg Z)) to fneg (fma X, Y, Z))

[Jim Lin via Phabricator via llvm-commits]

Jim created this revision.
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In the special case, X = -1,  Y = 0 and Z = 0 that (-(-1))*0+(-0)=0 is not equal to -(-1*0+0)=-0.
So it is a incorrect transform.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D90901

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13374,12 +13374,6 @@
     }
   }
 
-  // fold ((fma (fneg X), Y, (fneg Z)) -> fneg (fma X, Y, Z))
-  // fold ((fma X, (fneg Y), (fneg Z)) -> fneg (fma X, Y, Z))
-  if (!TLI.isFNegFree(VT))
-    if (SDValue Neg = TLI.getCheaperNegatedExpression(
-            SDValue(N, 0), DAG, LegalOperations, ForCodeSize))
-      return DAG.getNode(ISD::FNEG, DL, VT, Neg);
   return SDValue();
 }
 


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