[clang] [llvm] Arm64EC entry/exit thunks, consolidated. (PR #79067)

[Fangrui Song via cfe-commits]

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@@ -44,7 +44,11 @@ define void @varargs_caller() nounwind {
 ; CHECK-NEXT:    stp xzr, x30, [sp, #24] // 8-byte Folded Spill
 ; CHECK-NEXT:    stp x9, x8, [sp]
 ; CHECK-NEXT:    str xzr, [sp, #16]
-; CHECK-NEXT:    bl varargs_callee
+; CHECK-NEXT:    .weak_anti_dep varargs_callee
+; CHECK-NEXT:  .set varargs_callee, "#varargs_callee"@WEAKREF
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MaskRay wrote:

Is it intended to create a MCSymbolRef with specifier `VK_WEAKREF`?

.weakref is an (essentially) ELF-specific feature for weak alias https://sourceware.org/binutils/docs/as.html#Weakref 
https://sourceware.org/pipermail/binutils/2005-October/044471.html

https://github.com/llvm/llvm-project/pull/79067