takuto.ikuta added a comment.
Ping?
This patch reduced obj size largely, and I expect this makes distributed build
(like goma) faster by reducing data transferred on network.
================
Comment at: clang/lib/Driver/ToolChains/Clang.cpp:5244
+ false))
+ CmdArgs.push_back("-fvisibility-inlines-hidden");
+
----------------
takuto.ikuta wrote:
> rnk wrote:
> > takuto.ikuta wrote:
> > > hans wrote:
> > > > takuto.ikuta wrote:
> > > > > hans wrote:
> > > > > > Huh, does this actually affect whether functions get dllexported or
> > > > > > not?
> > > > > Sorry, what you want to ask?
> > > > >
> > > > > This will used to not add dllexport attr in L5690 of SemaDeclCXX.cpp.
> > > > >
> > > > Oops, I didn't see that. I'm glad to see this is looking so simple :-)
> > > >
> > > > Actually, I don't think we should the same flag name for this, since
> > > > "hidden" is an ELF concept, not a COFF one, just that we should match
> > > > the behaviour of the flag.
> > > >
> > > > Hmm, or do people use -fvisibility-inlines-hidden on MinGW or
> > > > something? Where does the hidden-dllimport.cpp file come from?
> > > >
> > > > Also, is it the case that -fvisibility-inlines-hidden just ignores the
> > > > problem of static local variables? If that's the case we can probably
> > > > do it too, we just have to be sure, and document it eventually.
> > > >
> > > I confirmed that -fvisibility-inlines-hidden treats local static var
> > > correctly in linux.
> > > So I'm trying to export inline functions if it has local static variables.
> > This sounds like it would be really hard in general, since you can hide
> > static locals almost anywhere:
> > ```
> > struct Foo {
> > static int foo() {
> > return ([]() { static int x; return ++x; })();
> > }
> > };
> > ```
> > Can we reuse the RecursiveASTVisitor @hans added to check if we can emit
> > dllimport inline functions as available_externally definitions? I think it
> > will find exactly the circumstances we are looking for, i.e. export all the
> > things that cannot be emitted inline in other DLLs.
> Actually, StmtVisitor added dll export attribute to local static variable in
> lambda function. And static variables seems exported.
>
> But I found other issue in current implementation, some cxx method decls
> passed to emitting function before local static variable checker adds dll
> export attributes. In such case local static variables are not exported and
> link failure happens.
>
> So let me try to use DLLImportFunctionVisitor in
> CodeGenModule::shouldEmitFunction for exported function instead of
> processing/checking dll attribute around SemaDeclCXX.
I think avoiding dll export is better to be done before we reached around
CodeGenModule. Also removing dll attribute later made it difficult to pass
tests.
https://reviews.llvm.org/D51340
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