[llvm] x86: fix musttail sibcall miscompilation (PR #168956)

[Folkert de Vries via llvm-commits]

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@@ -18,13 +18,15 @@ define dso_local x86_thiscallcc void @methodWithVtorDisp_thunk(ptr %0, ptr inall
 ; CHECK-LABEL: methodWithVtorDisp_thunk:
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    pushl %esi
+; CHECK-NEXT:    subl $20, %esp
 ; CHECK-NEXT:    movl %ecx, %esi
 ; CHECK-NEXT:    subl -4(%ecx), %esi
 ; CHECK-NEXT:    pushl {{[0-9]+}}(%esp)
 ; CHECK-NEXT:    pushl $_methodWithVtorDisp_thunk
 ; CHECK-NEXT:    calll ___cyg_profile_func_exit
 ; CHECK-NEXT:    addl $8, %esp
 ; CHECK-NEXT:    movl %esi, %ecx
+; CHECK-NEXT:    addl $20, %esp
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folkertdev wrote:

I'm not entirely sure what causes this yet, it looks harmless but is a bit unfortunate.

https://github.com/llvm/llvm-project/pull/168956