[PATCH] D89986: [AIX] do not emit visibility attribute into IR when there is -mignore-xcoff-visibility

[Sean Fertile via Phabricator via cfe-commits]

sfertile added inline comments.


================
Comment at: clang/lib/CodeGen/BackendUtil.cpp:520
   Options.DataSections = CodeGenOpts.DataSections;
-  Options.IgnoreXCOFFVisibility = CodeGenOpts.IgnoreXCOFFVisibility;
   Options.UniqueSectionNames = CodeGenOpts.UniqueSectionNames;
----------------
DiggerLin wrote:
> sfertile wrote:
> > DiggerLin wrote:
> > > jasonliu wrote:
> > > > DiggerLin wrote:
> > > > > DiggerLin wrote:
> > > > > > jasonliu wrote:
> > > > > > > DiggerLin wrote:
> > > > > > > > jasonliu wrote:
> > > > > > > > > DiggerLin wrote:
> > > > > > > > > > jasonliu wrote:
> > > > > > > > > > > Instead of just removing this line, should this get replaced with the new LangOpts option?
> > > > > > > > > > I do not think we need a CodeGenOp of ignore-xcoff-visibility in clang, we only need the LangOpt of the ignore-xcoff-visilbity to control whether we will  generate the visibility in the IR,  when the LangOpt of ignore-xcoff-visibility do not generate the visibility attribute of GV in the IR. it do not need CodeGenOp of ignore-xcoff-visibility any more for the clang .
> > > > > > > > > > 
> > > > > > > > > > we have still CodeGen ignore-xcoff-visibility op in  llc.
> > > > > > > > > We removed the visibility from IR level with this patch. But there is also visibility settings coming from CodeGen part of clang, which needs to get ignore when we are doing the code gen in llc. So I think you still need to set the options correct for llc.
> > > > > > > > yes we have the set the options correct for llc in the code.
> > > > > > > > 
> > > > > > > > in the source file llvm/lib/CodeGen/CommandFlags.cpp, we have (in the patch https://reviews.llvm.org/D87451 add new option -mignore-xcoff-visibility) , the function
> > > > > > > > TargetOptions codegen::InitTargetOptionsFromCodeGenFlags() {
> > > > > > > > ....
> > > > > > > > Options.IgnoreXCOFFVisibility = getIgnoreXCOFFVisibility(); 
> > > > > > > > ...}
> > > > > > > > 
> > > > > > > What I'm saying is... 
> > > > > > > I think we need a line like this:
> > > > > > > `Options.IgnoreXCOFFVisibility = LangOpts.IgnoreXCOFFVisibility;`
> > > > > > > so that when you invoke clang, backend would get the correct setting as well. 
> > > > > > I do not think so, from the clang FE, we do not generated the visibility in the IR. so there is no need these line.
> > > > > or we can say that because we do not set the hidden visibility into the GlobalValue , so we do not need the 
> > > > > Options.IgnoreXCOFFVisibility = LangOpts.IgnoreXCOFFVisibility;
> > > > I think I mentioned this before, we could have extra visibility settings in clang/lib/CodeGen that's not depending on the existing visibility setting in the IR. (You could search for `setVisibility` there.) That was the reason we did it in llc first. 
> > > I will add Options.IgnoreXCOFFVisibility = LangOpts.IgnoreXCOFFVisibility;  here.
> > > I think I mentioned this before, we could have extra visibility settings in clang/lib/CodeGen that's not depending on the existing visibility setting in the IR. (You could search for setVisibility there.) That was the reason we did it in llc first.
> > 
> >  A lot of these are in places we wouldn't encounter with AIX, like for Objective-C code gen. But are others like [[ https://github.com/llvm/llvm-project/blob/b03ea054db1bcf9452b3a70e21d3372b6e58759a/clang/lib/CodeGen/ItaniumCXXABI.cpp#L2507 | this]]  an issue? Should they be addressed in this patch?
> after I added the Options.IgnoreXCOFFVisibility = LangOpts.IgnoreXCOFFVisibility , even there is  GV->setVisibility(llvm::GlobalValue::HiddenVisibility);  it do not effect our output.
> 
> there is following code in the function void PPCAIXAsmPrinter::emitLinkage(const GlobalValue *GV,
>                                    MCSymbol *GVSym) const
> {
>  ..... 
>   if (!TM.getIgnoreXCOFFVisibility()) {
>     switch (GV->getVisibility()) {
> 
>     // TODO: "exported" and "internal" Visibility needs to go here.
>     case GlobalValue::DefaultVisibility:
>       break;
>     case GlobalValue::HiddenVisibility:
>       VisibilityAttr = MAI->getHiddenVisibilityAttr();
>       break;
>     case GlobalValue::ProtectedVisibility:
>       VisibilityAttr = MAI->getProtectedVisibilityAttr();
>       break;
>     }
>   }
> 
> ...
> }
> it do not effect our output.
It can if we set the GlobalValue to be dso_local though ... that is the whole point of this patch.


================
Comment at: clang/test/CodeGen/aix-visibility-inlines-hidden.cpp:1
+// REQUIRES: powerpc-registered-target
+
----------------
DiggerLin wrote:
> jasonliu wrote:
> > sfertile wrote:
> > > Shouldn't need this requires either.
> > Do you need this line?
> there is a comment in https://reviews.llvm.org/D87451   " Hello. I added a power-pc REQUIRES clause to the new clang test here in a15bd0bfc20c2b2955c59450a67b6e8efe89c708. Hope that looks OK."
> 
> please  see the 
> https://reviews.llvm.org/rGa15bd0bfc20c2b2955c59450a67b6e8efe89c708
Look at the run steps in the test when that was added. eg:

```
// RUN: %clang_cc1 -triple powerpc-unknown-aix -o - -x c++ -S  %s  |\
// RUN:   FileCheck --check-prefix=IGNOREVISIBILITY-ASM %s

```

You are producing **assembly** output for a powerpc target. If you don't compile the powerpc backend then you will get a message along the lines of 
`error: unable to create target: 'No available targets are compatible with triple "powerpc-unknown-aix"'`

But now you have cleaned up the test to only produce IR. That doesn't require a powerpc code generator to run the test, so we can remove the dependency (in both this test and the other).


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D89986/new/

https://reviews.llvm.org/D89986