[libunwind] [libunwind] [SEH] Set NonVolatileRegisters before calling a personality function (PR #137951)

[Jacek Caban via cfe-commits]

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@@ -212,6 +212,11 @@ __libunwind_seh_personality(int version, _Unwind_Action state,
   ms_exc.ExceptionInformation[2] = state;
   DISPATCHER_CONTEXT *disp_ctx =
       __unw_seh_get_disp_ctx((unw_cursor_t *)context);
+#if defined(__aarch64__)
+  disp_ctx->NonVolatileRegisters = (PBYTE)&disp_ctx->ContextRecord->X19;
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cjacek wrote:

I'm not very familiar with this, but from what I can tell based on reading the Wine source (which itself isn't guaranteed to be entirely correct), that seems roughly right. `DISPATCHER_CONTEXT_NONVOLREG_ARM64` is allocated on the stack along with `DISPATCHER_CONTEXT` (which libunwind stores in the cursor). It's populated from the context at the beginning of unwinding step.

https://github.com/llvm/llvm-project/pull/137951