[llvm] [SelectionDAG] Fix incorrect fold condition in foldSetCCWithFunnelShift. (PR #137637)

[Simon Pilgrim via llvm-commits]

================
@@ -4462,7 +4462,11 @@ static SDValue foldSetCCWithFunnelShift(EVT VT, SDValue N0, SDValue N1,
 
   unsigned BitWidth = N0.getScalarValueSizeInBits();
   auto *ShAmtC = isConstOrConstSplat(N0.getOperand(2));
-  if (!ShAmtC || ShAmtC->getAPIntValue().uge(BitWidth))
+  if (!ShAmtC)
+    return SDValue();
+
+  APInt AmtVal = ShAmtC->getAPIntValue();
+  if (AmtVal.uge(BitWidth) || AmtVal.isZero())
     return SDValue();
----------------
RKSimon wrote:

Why not:
```cpp
uint64_t AmtVal = ShAmtC->getAPIntValue().urem(BitWidth);
if (AmtVal == 0)
  return SDValue();
```

https://github.com/llvm/llvm-project/pull/137637