[PATCH] D67058: [clang][CodeGen] Add alias for cpu_dispatch function with IFunc & Fix resolver linkage type

[Sr.Zhang via Phabricator via cfe-commits]

zsrkmyn added inline comments.


================
Comment at: clang/lib/CodeGen/CodeGenModule.cpp:3002
         false);
     llvm::Constant *Resolver = GetOrCreateLLVMFunction(
         MangledName + ".resolver", ResolverType, GlobalDecl{},
----------------
erichkeane wrote:
> This Resolver should have the same linkage as below.
Actually, I wanted to set linkage here at the first time, but failed. When compiling code with cpu_specific but no cpu_dispatch, we cannot set it as LinkOnceODR or WeakODR. E.g.:

```
$ cat specific_only.c
__declspec(cpu_specific(pentium_iii))
int foo(void) { return 0; }
int usage() { return foo(); }

$ clang -fdeclspec specific_only.c                                                 
Global is external, but doesn't have external or weak linkage!                                                                
i32 ()* ()* @foo.resolver                                                                                                     
fatal error: error in backend: Broken module found, compilation aborted!   
```

This is found by lit test test/CodeGen/attr-cpuspecific.c, in which 'SingleVersion()' doesn't have a cpu_dispatch declaration.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67058/new/

https://reviews.llvm.org/D67058