[llvm] r267226 - Update discriminator assignment algorithm in clang assembler.

[Dehao Chen via llvm-commits]

Thanks for the pointer, patch sent:

http://reviews.llvm.org/D19522

Dehao

On Mon, Apr 25, 2016 at 5:13 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
> On Mon, Apr 25, 2016 at 11:03 AM, Dehao Chen <dehao at google.com> wrote:
>>
>> I have a test x86 assembly in the internal bug database. But I'm not sure
>> how to write a test for MCDwarf as its output is object file. Could you
>> point me to an example?
>
>
> Tests in llvm's test/DebugInfo generally check debug info of all kinds,
> including the line table (check previous commits to the discriminators for
> specific examples, or just search test/DebugInfo for discriminator and I'm
> sure you'll find a few)
>
> Basically we test by writing assembly or LLVM IR, generating an object,
> dwarfdumping the result and checking the dump shows what we want.
>
> - Dave
>
>>
>>
>> Thanks,
>> Dehao
>>
>> On Mon, Apr 25, 2016 at 10:56 AM, David Blaikie <dblaikie at gmail.com>
>> wrote:
>>>
>>> Test case?
>>>
>>> On Fri, Apr 22, 2016 at 2:31 PM, Dehao Chen via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>>>
>>>> Author: dehao
>>>> Date: Fri Apr 22 16:31:18 2016
>>>> New Revision: 267226
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=267226&view=rev
>>>> Log:
>>>> Update discriminator assignment algorithm in clang assembler.
>>>>
>>>> Summary: The clang assembler assumes that the discriminator remains the
>>>> same when there is source line change. The correct behavior is that when
>>>> there is line change, discriminator will automatically reset to 0.
>>>>
>>>> Reviewers: dnovillo, davidxl, echristo
>>>>
>>>> Subscribers: echristo, llvm-commits
>>>>
>>>> Differential Revision: http://reviews.llvm.org/D19436
>>>>
>>>> Modified:
>>>>     llvm/trunk/lib/MC/MCDwarf.cpp
>>>>
>>>> Modified: llvm/trunk/lib/MC/MCDwarf.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/MC/MCDwarf.cpp?rev=267226&r1=267225&r2=267226&view=diff
>>>>
>>>> ==============================================================================
>>>> --- llvm/trunk/lib/MC/MCDwarf.cpp (original)
>>>> +++ llvm/trunk/lib/MC/MCDwarf.cpp Fri Apr 22 16:31:18 2016
>>>> @@ -112,6 +112,12 @@ EmitDwarfLineTable(MCObjectStreamer *MCO
>>>>              ie = LineEntries.end();
>>>>         it != ie; ++it) {
>>>>
>>>> +    int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
>>>> +
>>>> +    // Discriminator will be cleared if there is line change.
>>>> +    if (LineDelta != 0)
>>>> +      Discriminator = 0;
>>>> +
>>>>      if (FileNum != it->getFileNum()) {
>>>>        FileNum = it->getFileNum();
>>>>        MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
>>>> @@ -146,7 +152,6 @@ EmitDwarfLineTable(MCObjectStreamer *MCO
>>>>      if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
>>>>        MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
>>>>
>>>> -    int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
>>>>      MCSymbol *Label = it->getLabel();
>>>>
>>>>      // At this point we want to emit/create the sequence to encode the
>>>> delta in
>>>>
>>>>
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>>>
>>>
>>
>