[llvm-branch-commits] [llvm] 3900ec6 - [X86] combineX86ShufflesRecursively - remove old FIXME comment. NFC.

[Simon Pilgrim via llvm-branch-commits]

Author: Simon Pilgrim
Date: 2020-12-02T16:29:38Z
New Revision: 3900ec6f0538368e6bb6ce6743e7e5e0ef13f895

URL: https://github.com/llvm/llvm-project/commit/3900ec6f0538368e6bb6ce6743e7e5e0ef13f895
DIFF: https://github.com/llvm/llvm-project/commit/3900ec6f0538368e6bb6ce6743e7e5e0ef13f895.diff

LOG: [X86] combineX86ShufflesRecursively - remove old FIXME comment. NFC.

Its unlikely an undef element in a zero vector will be any use, and SimplifyDemandedVectorElts now calls combineX86ShufflesRecursively so its unlikely we actually have a dependency on these specific elements.

Added: 
    

Modified: 
    llvm/lib/Target/X86/X86ISelLowering.cpp

Removed: 
    


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diff  --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index eefd7219ae3f..1a822c086b6a 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -36248,10 +36248,6 @@ static SDValue combineX86ShufflesRecursively(
   // Handle the all undef/zero cases early.
   if (all_of(Mask, [](int Idx) { return Idx == SM_SentinelUndef; }))
     return DAG.getUNDEF(Root.getValueType());
-
-  // TODO - should we handle the mixed zero/undef case as well? Just returning
-  // a zero mask will lose information on undef elements possibly reducing
-  // future combine possibilities.
   if (all_of(Mask, [](int Idx) { return Idx < 0; }))
     return getZeroVector(Root.getSimpleValueType(), Subtarget, DAG,
                          SDLoc(Root));