[llvm] [X86][WinEH] Avoid stale RSP after Win64 dynalloca invokes (PR #191616)

[via llvm-commits]

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@@ -4658,7 +4659,8 @@ void SelectionDAGBuilder::visitAlloca(const AllocaInst &I) {
 
   SDValue Ops[] = {
       getRoot(), AllocSize,
-      DAG.getConstant(Alignment ? Alignment->value() : 0, dl, IntPtr)};
+      DAG.getConstant(Alignment ? Alignment->value() : 0, dl, IntPtr),
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taigacon wrote:

I left this as-is since that was already the existing code here. Also, `value_or` would need an `Align`, and the smallest valid `Align` is 1, not 0, so using it here would noticeably change the sentinel semantics.

https://github.com/llvm/llvm-project/pull/191616