[llvm] [X86][AVX] Fix handling of out-of-bounds shift amounts in AVX2 vector shift nodes (PR #84426)

[via llvm-commits]

================
@@ -47291,6 +47291,16 @@ static SDValue combineShiftRightArithmetic(SDNode *N, SelectionDAG &DAG,
   if (SDValue V = combineShiftToPMULH(N, DAG, Subtarget))
     return V;
 
+  APInt ShiftAmt;
+  SDNode *UMinNode = N1.getNode();
+  if (UMinNode->getOpcode() == ISD::UMIN &&
+      ISD::isConstantSplatVector(UMinNode->getOperand(1).getNode(), ShiftAmt) &&
+      ShiftAmt == VT.getScalarSizeInBits() - 1) {
+    SDValue ShrAmtVal = UMinNode->getOperand(0);
+    SDLoc DL(N);
+    return DAG.getNode(N->getOpcode(), DL, N->getVTList(), N0, ShrAmtVal);
----------------
SahilPatidar wrote:

Okay, here is the modified code:
```cpp
if (supportedVectorShiftWithImm(VT, Subtarget, ISD::SRA) &&
      UMinNode->getOpcode() == ISD::UMIN &&
      ISD::isConstantSplatVector(UMinNode->getOperand(1).getNode(), ShiftAmt) &&
      ShiftAmt == VT.getScalarSizeInBits() - 1) {
    SDValue ShrAmtVal = UMinNode->getOperand(0);
    SDLoc DL(N);
    return DAG.getNode(X86ISD::VSRAV, DL, N->getVTList(), N0, ShrAmtVal);
  }
```
With this code, it still crashes.

https://github.com/llvm/llvm-project/pull/84426