[PATCH] D93243: [FPEnv][AMDGPU] Disable FSUB(-0,X)->FNEG(X) DAGCombine when subnormals are flushed

[Cameron McInally via Phabricator via llvm-commits]

cameron.mcinally added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:13375
+      DenormalMode DenormMode = DAG.getDenormalMode(VT);
+      if (DenormMode == DenormalMode::getIEEE()) {
+        if (SDValue NegN1 =
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arsenm wrote:
> This will also change the behavior on signaling nans, which will no longer quiet
Good catch. 

I'm playing with a change to only allow this transform when NoNaNs are present, but it's breaking a lot of tests across a number of targets. How would you feel about leaving that change to a separate patch? I think this subnormal Diff is a step in the right direction, and doesn't regress from the current behavior.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D93243/new/

https://reviews.llvm.org/D93243