[llvm] Calculate KnownBits from Metadata correctly for vector loads (PR #128908)

[via llvm-commits]

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@@ -4116,9 +4119,24 @@ SDValue AMDGPUTargetLowering::performShlCombine(SDNode *N,
   SDValue NewShift =
       DAG.getNode(ISD::SHL, SL, TargetType, Lo, ShiftAmt, N->getFlags());
 
-  const SDValue Zero = DAG.getConstant(0, SL, TargetType);
-
-  SDValue Vec = DAG.getBuildVector(TargetVecPairType, SL, {Zero, NewShift});
+  const SDValue Zero = DAG.getConstant(0, SL, TargetScalarType);
+  SDValue Vec;
+
+  if (VT.isVector()) {
+    EVT ConcatType = TargetType.getDoubleNumVectorElementsVT(*DAG.getContext());
+    SmallVector<SDValue, 8> Ops;
+    for (unsigned I = 0, E = TargetType.getVectorNumElements(); I != E; ++I) {
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LU-JOHN wrote:

Will update in separate PR for AMDGPU.

https://github.com/llvm/llvm-project/pull/128908