[llvm] ced1f50 - [X86] IsElementEquivalent - pull out exact matching for same index/op. (#143367)

[via llvm-commits]

Author: Simon Pilgrim
Date: 2025-06-09T15:24:12+01:00
New Revision: ced1f501ce8ec5dce05d577d7d41bc87b7934946

URL: https://github.com/llvm/llvm-project/commit/ced1f501ce8ec5dce05d577d7d41bc87b7934946
DIFF: https://github.com/llvm/llvm-project/commit/ced1f501ce8ec5dce05d577d7d41bc87b7934946.diff

LOG: [X86] IsElementEquivalent - pull out exact matching for same index/op. (#143367)

The types must still be vectors matching MaskSize

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 eafc4acbb1779..244b0f9410b85 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -9790,6 +9790,10 @@ static bool IsElementEquivalent(int MaskSize, SDValue Op, SDValue ExpectedOp,
       (int)ExpectedVT.getVectorNumElements() != MaskSize)
     return false;
 
+  // Exact match.
+  if (Idx == ExpectedIdx && Op == ExpectedOp)
+    return true;
+
   switch (Op.getOpcode()) {
   case ISD::BUILD_VECTOR:
     // If the values are build vectors, we can look through them to find
@@ -9837,8 +9841,7 @@ static bool IsElementEquivalent(int MaskSize, SDValue Op, SDValue ExpectedOp,
       SmallVector<int, 8> Mask;
       DecodeVPERMMask(MaskSize, Op.getConstantOperandVal(1), Mask);
       SDValue Src = Op.getOperand(0);
-      return (Mask[Idx] == Mask[ExpectedIdx]) ||
-             IsElementEquivalent(MaskSize, Src, Src, Mask[Idx],
+      return IsElementEquivalent(MaskSize, Src, Src, Mask[Idx],
                                  Mask[ExpectedIdx]);
     }
     break;