[llvm] r233562 - Verifier: Loosen r233559 check for 'function:' field in MDSubprogram

[Duncan P. N. Exon Smith]

> On 2015-Mar-30, at 10:52, David Blaikie <dblaikie at gmail.com> wrote:
> 
> 
> 
> On Mon, Mar 30, 2015 at 10:47 AM, David Blaikie <dblaikie at gmail.com> wrote:
> 
> 
> On Mon, Mar 30, 2015 at 10:45 AM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
> 
> > On 2015-Mar-30, at 10:39, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> >
> > On Mon, Mar 30, 2015 at 10:04 AM, Duncan P. N. Exon Smith <dexonsmith at apple.com> wrote:
> > Author: dexonsmith
> > Date: Mon Mar 30 12:04:06 2015
> > New Revision: 233562
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=233562&view=rev
> > Log:
> > Verifier: Loosen r233559 check for 'function:' field in MDSubprogram
> >
> > Stop worrying about what the `function:` field is in `MDSubprogram`,
> > since it could be a bitcast [1].  Just check its type and leave it at
> > that.
> >
> > [1]: http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_build/3540/
> >
> > Is this an acceptable thing? How does this arise? Could we have a small test case demonstrating it? (and/or demonstrating how it comes about?)
> 
> I think it's from function merging, so we needed bitcasts from one
> function type to the other.
> 
> Once your opaque pointer type work is complete, those bitcasts won't
> be necessary, so we can check that it's pointing at a `Function`.
> 
> Maybe I can use `stripPointerCasts()` to do that even now?
> 
> My concern is that since the function type has changed, we probably shouldn't be describing it in the debug info anymore - if the debugger tries to call it, it'll be using the function type described in the debug info which will no longer match the implementation... that seems... bad.
> 
> FWIW ArgPromo and DAE are both setup to null out the llvm::Function pointers in this case - so as to ensure debug info no longer describes the function in such a way that a debugger might try to call it or print its arguments, etc. (there's no way in DWARF to describe the original type while telling the debugger to call the function in a different way (omitting arguments, etc) and we haven't taught LLVM about how to omit the location of certain variables, I don't think - maybe that bit just works?)
> 
> so I'm not sure which optimizations are creating this bitcast & not nulling out the MDSubprogram's llvm::Function* - but I /think/ whenever that is happening, it's a bug.
> 

(Just saw this follow-up.)

I think the new `Function`s are compatible, so the bitcast is fine.  (I
guess respond to my other mail if you disagree.)

> - David
>  
> 
> 
> - David
>  
> 
> >
> >
> >
> > Modified:
> >     llvm/trunk/lib/IR/Verifier.cpp
> >
> > Modified: llvm/trunk/lib/IR/Verifier.cpp
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=233562&r1=233561&r2=233562&view=diff
> > ==============================================================================
> > --- llvm/trunk/lib/IR/Verifier.cpp (original)
> > +++ llvm/trunk/lib/IR/Verifier.cpp Mon Mar 30 12:04:06 2015
> > @@ -846,9 +846,8 @@ void Verifier::visitMDSubprogram(const M
> >      auto *FMD = dyn_cast<ConstantAsMetadata>(RawF);
> >      auto *F = FMD ? FMD->getValue() : nullptr;
> >      auto *FT = F ? dyn_cast<PointerType>(F->getType()) : nullptr;
> > -    Assert(F && (isa<Function>(F) || isa<ConstantPointerNull>(F)) && FT &&
> > -               isa<FunctionType>(FT->getElementType()),
> > -           "invalid function", &N, F);
> > +    Assert(F && FT && isa<FunctionType>(FT->getElementType()),
> > +           "invalid function", &N, F, FT);
> >    }
> >    if (N.getRawTemplateParams()) {
> >      auto *Params = dyn_cast<MDTuple>(N.getRawTemplateParams());
> >
> >
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