[llvm] edc22c6 - [X86] getFauxShuffleMask - only handle VTRUNC nodes with matching src/dst sizes (#134161)

[via llvm-commits]

Author: Simon Pilgrim
Date: 2025-04-03T09:42:27+01:00
New Revision: edc22c64e527171041876f26a491bb1d03d905d5

URL: https://github.com/llvm/llvm-project/commit/edc22c64e527171041876f26a491bb1d03d905d5
DIFF: https://github.com/llvm/llvm-project/commit/edc22c64e527171041876f26a491bb1d03d905d5.diff

LOG: [X86] getFauxShuffleMask - only handle VTRUNC nodes with matching src/dst sizes (#134161)

Cleanup work for #133947 - we need to handle VTRUNC nodes with large
source vectors directly to allow us to widen the size of the shuffle
combine

We currently discard these results in combineX86ShufflesRecursively
anyhow as we don't allow inputs from getTargetShuffleInputs to be larger
than the shuffle value type

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 8e6a891444bf1..aea80120a0481 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6413,9 +6413,7 @@ static bool getFauxShuffleMask(SDValue N, const APInt &DemandedElts,
   case X86ISD::VTRUNC: {
     SDValue Src = N.getOperand(0);
     EVT SrcVT = Src.getValueType();
-    // Truncated source must be a simple vector.
-    if (!SrcVT.isSimple() || (SrcVT.getSizeInBits() % 128) != 0 ||
-        (SrcVT.getScalarSizeInBits() % 8) != 0)
+    if (SrcVT.getSizeInBits() != NumSizeInBits)
       return false;
     unsigned NumSrcElts = SrcVT.getVectorNumElements();
     unsigned NumBitsPerSrcElt = SrcVT.getScalarSizeInBits();