[llvm] [WebAssembly] Combine shuffle and signed extend to extend_high (PR #179166)

[via llvm-commits]

================
@@ -2289,13 +2289,17 @@ WebAssemblyTargetLowering::LowerSIGN_EXTEND_INREG(SDValue Op,
 
 static SDValue GetExtendHigh(SDValue Op, unsigned UserOpc, EVT VT,
                              SelectionDAG &DAG) {
-  if (Op.getOpcode() != ISD::VECTOR_SHUFFLE)
+  SDValue Source = Op;
+  if (Source.getOpcode() == ISD::BITCAST)
+    Source = Source.getOperand(0);
----------------
valadaptive wrote:

I think you can use the `peekThroughBitcasts` helper here?

https://github.com/llvm/llvm-project/pull/179166