[llvm] [X86] getFauxShuffleMask - OR(BITCAST(SHUFFLE()),BITCAST(SHUFFLE())) patterns should return bitcasted source values (PR #134993)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-x86

Author: Simon Pilgrim (RKSimon)

<details>
<summary>Changes</summary>

Noticed while investigating #<!-- -->133947 regressions - if we peek through bitcasts we can lose track of oneuse/combined nodes in shuffle combining

Currently the same codegen as combineX86ShufflesRecursively still peeks through the bitcasts itself, but we will soon handle this consistently as another part of #<!-- -->133947

---
Full diff: https://github.com/llvm/llvm-project/pull/134993.diff


1 Files Affected:

- (modified) llvm/lib/Target/X86/X86ISelLowering.cpp (+2-2) 


``````````diff
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 47ac1ee571269..53bed634c3cc6 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6155,8 +6155,8 @@ static bool getFauxShuffleMask(SDValue N, const APInt &DemandedElts,
       else
         return false;
     }
-    Ops.push_back(N0);
-    Ops.push_back(N1);
+    Ops.push_back(N.getOperand(0));
+    Ops.push_back(N.getOperand(1));
     return true;
   }
   case ISD::CONCAT_VECTORS: {

``````````

</details>


https://github.com/llvm/llvm-project/pull/134993