[clang] [X86] Add regcall4 attribute to make a specific function respect regc… (PR #69628)

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@@ -9347,6 +9352,7 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
   case ParsedAttr::AT_ThisCall:
   case ParsedAttr::AT_Pascal:
   case ParsedAttr::AT_RegCall:
+  //case ParsedAttr::AT_RegCall4:
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yubingex007-a11y wrote:

@mikerice1969 hi, if i uncomment here, and delete L9648-9650, regcall4 won't be added into Decl because hasDeclarator(D) is true:
```
static void handleCallConvAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (hasDeclarator(D)) return;
```

do you know why this happened?

https://github.com/llvm/llvm-project/pull/69628