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

[David Blaikie]

On Wed, Mar 26, 2014 at 12:59 PM, Timur Iskhodzhanov
<timurrrr at google.com> wrote:
> Sorry, I now understand the phrasing is weird.
>
> I've added support for
> a) generating DI for functions without lexical scopes (see the testcase
> where a function immediately tailcalls)
> b) not crashing if it turned out there is in fact no DI for a given function
>
> Does that make sense now?

Ah, OK.

It might've been nice to have this as two separate patches.

The test case for (a) could use some explanatory comments (and
possibly an explanatory name - you can mention the PR somewhere in
there, but it's sort of difficult to work with if that's the /only/
explanation given so you have to consult the PR to understand what's
being tested)

>
>
> 2014-03-26 19:28 GMT+04:00 David Blaikie <dblaikie at gmail.com>:
>
>> On Wed, Mar 26, 2014 at 2:50 AM, Timur Iskhodzhanov <timurrrr at google.com>
>> wrote:
>> > Author: timurrrr
>> > Date: Wed Mar 26 04:50:36 2014
>> > New Revision: 204790
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=204790&view=rev
>> > Log:
>> > Fix PR19239 - Add support for generating debug info for functions
>> > without lexical scopes and/or debug info at all
>>
>> I don't really understand this change from the code involved (perhaps
>> when I get to the tests it'll make more sense) but what kind of debug
>> info (since this is in WinCode I assume we're talking about COFF and
>> we only support line tables there, right?) can you produce for a
>> function with no debug info? All you have is a function name... which
>> you'd already have (except inlining?) without emitting any debug
>> info/line tables.
>>
>> So is that what this is - the ability to ascribe non-debug-built
>> functions inlined into other functions by name, even if you don't have
>> line/file information for the functions or any of their instructions?
>> (do we keep track of that through inlining? I would've assumed the
>> debug intrinsics/per-instruction debug info was the only thing that
>> told us inlined instructions came from another function)
>>
>> >
>> > Modified:
>> >     llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>> >     llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.h
>> >
>> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>> > URL:
>> > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp?rev=204790&r1=204789&r2=204790&view=diff
>> >
>> > ==============================================================================
>> > --- llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp
>> > (original)
>> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.cpp Wed Mar
>> > 26 04:50:36 2014
>> > @@ -131,9 +131,12 @@ void WinCodeViewLineTables::emitDebugInf
>> >    // For each function there is a separate subsection
>> >    // which holds the PC to file:line table.
>> >    const MCSymbol *Fn = Asm->getSymbol(GV);
>> > -  const FunctionInfo &FI = FnDebugInfo[GV];
>> >    assert(Fn);
>> > -  assert(FI.Instrs.size() > 0);
>> > +
>> > +  const FunctionInfo &FI = FnDebugInfo[GV];
>> > +  if (FI.Instrs.empty())
>> > +    return;
>> > +  assert(FI.End && "Don't know where the function ends?");
>> >
>> >    // PCs/Instructions are grouped into segments sharing the same
>> > filename.
>> >    // Pre-calculate the lengths (in instructions) of these segments and
>> > store
>> > @@ -264,12 +267,6 @@ void WinCodeViewLineTables::beginFunctio
>> >    if (!Asm || !Asm->MMI->hasDebugInfo())
>> >      return;
>> >
>> > -  // 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;
>> >  }
>> >
>> >
>> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.h
>> > URL:
>> > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.h?rev=204790&r1=204789&r2=204790&view=diff
>> >
>> > ==============================================================================
>> > --- llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.h (original)
>> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/WinCodeViewLineTables.h Wed Mar 26
>> > 04:50:36 2014
>> > @@ -32,13 +32,13 @@ namespace llvm {
>> >  class WinCodeViewLineTables : public AsmPrinterHandler {
>> >    AsmPrinter *Asm;
>> >    DebugLoc PrevInstLoc;
>> > -  LexicalScopes LScopes;
>> >
>> >    // For each function, store a vector of labels to its instructions,
>> > as well as
>> >    // to the end of the function.
>> >    struct FunctionInfo {
>> >      SmallVector<MCSymbol *, 10> Instrs;
>> >      MCSymbol *End;
>> > +    FunctionInfo() : End(0) {}
>> >    } *CurFn;
>> >
>> >    typedef DenseMap<const Function *, FunctionInfo> FnDebugInfoTy;
>> >
>> >
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>
>