zsrkmyn marked an inline comment as done.
zsrkmyn added inline comments.
================
Comment at: clang/lib/CodeGen/CodeGenModule.cpp:3002
false);
llvm::Constant *Resolver = GetOrCreateLLVMFunction(
MangledName + ".resolver", ResolverType, GlobalDecl{},
----------------
zsrkmyn wrote:
> erichkeane wrote:
> > zsrkmyn wrote:
> > > 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.
> > The crash message is complaining it isn't external/weak. However, WeakODR
> > should count, right? Can you look into it a bit more to see what it thinks
> > is broken?
> No, actually I've tried it earlier with the example I mentioned in my last
> comment, but WeakODR still makes compiler complaining. I think it's
> `foo.resolver` that cannot be declared with as WeakODR/LinkOnceODR without
> definition. But I'm really not familiar with these rules.
According to the `Verifier::visitGlobalValue()` in Verify.cpp, an declaration
can only be `ExternalLinkage` or `ExternalWeakLinkage`. So I still believe we
cannot set the resolver to `LinkOnceODRLinkage/WeakODRLinkage` here, as they
are declared but not defined when we only have `cpu_specified` but no
`cpu_dispatch` in a TU as the example above.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D67058/new/
https://reviews.llvm.org/D67058
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