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

[Matt Arsenault via llvm-commits]

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@@ -116,6 +116,9 @@ class X86MachineFunctionInfo : public MachineFunctionInfo {
   unsigned ArgumentStackSize = 0;
   /// NumLocalDynamics - Number of local-dynamic TLS accesses.
   unsigned NumLocalDynamics = 0;
+  /// On x86_64-windows-msvc dynalloca functions, stores the rounded stable
+  /// outgoing call-frame size inferred from ADJCALLSTACKDOWN64/UP64 pseudos.
+  unsigned Win64MSVCDynAllocaCallFrameSize = 0;
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arsenm wrote:

The yaml definitions have a way to specify the default value, which is not printed with -simplify-mir. The remaining problem is -simplify-mir should be the default, and it's not 

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