[llvm] r204790 - Fix PR19239 - Add support for generating debug info for functions without lexical scopes and/or debug info at all

[Eric Christopher]

On Tue, Apr 1, 2014 at 10:02 AM, Eric Christopher <echristo at gmail.com> wrote:
> On Tue, Apr 1, 2014 at 3:07 AM, Timur Iskhodzhanov <timurrrr at google.com> wrote:
>> 2014-04-01 4:12 GMT+04:00 Eric Christopher <echristo at gmail.com>:
>>>> -  // Grab the lexical scopes for the function, if we don't have any of those
>>>> -  // then we're not going to be able to do anything.
>>>> -  LScopes.initialize(*MF);
>>>> -  if (LScopes.empty())
>>>> -    return;
>>>> -
>>>>    const Function *GV = MF->getFunction();
>>>>    assert(FnDebugInfo.count(GV) == false);
>>>>    VisitedFunctions.push_back(GV);
>>>> @@ -311,13 +308,12 @@ void WinCodeViewLineTables::endFunction(
>>>>    if (!Asm || !CurFn)  // We haven't created any debug info for this function.
>>>>      return;
>>>>
>>>> -  if (CurFn->Instrs.empty())
>>>> -    llvm_unreachable("Can this ever happen?");
>>>> -
>>>> -  // Define end label for subprogram.
>>>> -  MCSymbol *FunctionEndSym = Asm->OutStreamer.getContext().CreateTempSymbol();
>>>> -  Asm->OutStreamer.EmitLabel(FunctionEndSym);
>>>> -  CurFn->End = FunctionEndSym;
>>>> +  if (!CurFn->Instrs.empty()) {
>>>> +    // Define end label for subprogram.
>>>> +    MCSymbol *FunctionEndSym = Asm->OutStreamer.getContext().CreateTempSymbol();
>>>> +    Asm->OutStreamer.EmitLabel(FunctionEndSym);
>>>> +    CurFn->End = FunctionEndSym;
>>>> +  }
>>>>    CurFn = 0;
>>>>  }
>>>
>>> This part doesn't really make sense. You're saying that without any
>>> scope we can still generate a line table entry for this?
>>
>> Yes - I think we can get some minimal required information even if
>> there's no lexical scope.
>>
>>> What's the information contained within and how did it get line information on there?
>>> I might be missing something though.
>>
>> The MI's seem to have DebugLoc available, the IR instructions seem to
>> have some minimal debug metadata too.
>
> Then there should be a lexical scope, can you show where it's not?
>

In other words, if there's debug information in the IR, but no lexical
scopes then that's a bug in the lexical scope code :)

-eric

> -eric
>
>>
>>> I'm not sure what kind of code this is supposed to be catching (and I looked at the testcases :)
>>
>> One of the other problems is that we discuss this on a number of
>> commits and some stuff and comments already got fixed, improved, etc.
>>
>> Please see the attached patch that contains all the changes I did and
>> tests for them.