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

[Timur Iskhodzhanov]

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?


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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>
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