[PATCH] D73978: [WIP][FPEnv] Don't transform FSUB(-0.0,X)->FNEG(X) when flushing denormals

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp:2997-3015
   // -0.0 - X --> fneg
   Type *Ty = I.getType();
   if (isa<Constant>(I.getOperand(0)) &&
       I.getOperand(0) == ConstantFP::getZeroValueForNegation(Ty)) {
     SDValue Op2 = getValue(I.getOperand(1));
-    setValue(&I, DAG.getNode(ISD::FNEG, getCurSDLoc(),
-                             Op2.getValueType(), Op2));
-    return;
+    EVT VT =  Op2.getValueType();
+
----------------
arsenm wrote:
> Why does SelectionDAGBuilder bother doing this fold at all? It should just directly translate the fsub?
I think this should be just ripped out in a separate patch. The same problem seems to have been copied to IRTranslator, which should also be removed


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D73978/new/

https://reviews.llvm.org/D73978