[llvm] r174479 - Attempt to recover gdb bot after r174445.
Manman Ren
mren at apple.com
Fri Feb 8 15:35:45 PST 2013
On Feb 8, 2013, at 3:31 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Fri, Feb 8, 2013 at 3:29 PM, Manman Ren <mren at apple.com> wrote:
>>
>> On Feb 8, 2013, at 3:21 PM, David Blaikie <dblaikie at gmail.com> wrote:
>>
>>> On Fri, Feb 8, 2013 at 3:14 PM, Manman Ren <mren at apple.com> wrote:
>>>>
>>>> On Feb 8, 2013, at 11:41 AM, David Blaikie <dblaikie at gmail.com> wrote:
>>>>
>>>>> On Tue, Feb 5, 2013 at 4:59 PM, Manman Ren <mren at apple.com> wrote:
>>>>>> Author: mren
>>>>>> Date: Tue Feb 5 18:59:41 2013
>>>>>> New Revision: 174479
>>>>>>
>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=174479&view=rev
>>>>>> Log:
>>>>>> Attempt to recover gdb bot after r174445.
>>>>>>
>>>>>> Failure: undefined symbol 'Lline_table_start0'.
>>>>>> Root-cause: we use a symbol subtraction to calculate at_stmt_list, but
>>>>>> the line table entries are not dumped in the assembly.
>>>>>> Fix: use zero instead of a symbol subtraction for Compile Unit 0.
>>>>>
>>>>> This seems to not have completely fixed problems of this kind. I
>>>>> discovered more breakage in DragonEgg. Any attempt to build with debug
>>>>> info in DragonEgg is currently broken due to the original change, even
>>>>> after this fix.
>>>>>
>>>>> You can reproduce this without dragonegg:
>>>>>
>>>>> $ echo "int main() { }" | clang -x c++ -g -S - -o hello.s && clang hello.s
>>>>
>>>> This simple example worked for me with source up to r174431.
>>>
>>> It works for me when I revert r174479 + r174445, fails for me with ToT.
>> Works for me without any local change:
>> Maybe it is because our ld version.
>> I got another email from Duncan, there the version of ld is: GNU ld (GNU Binutils for Debian) 2.20.1-system.20100303
>
> I'm not sure how it'd be an ld version issue - when I look at the
> assembly produced by the above command I see a reference to the
> .Lline_table_start0 symbol in the debug info & no other mention of it.
> Seems pretty clearly something that would not be able to be linked...
>
> does your hello.s from the above command not contain any mention of
> line_table_start0?
No, my hello.s does not have line_table_start0.
I asked Chad to try, and it worked for him too.
The email from Duncan is about a more complicated case, so there it is maybe a linker issue.
Thanks,
Manman
>
>>
>> Thanks,
>> Manman
>>
>>>
>>>> With r174479, we are not using line_table_start0 in at_stmt_list, so it should be okay if we don't emit the line table entries in MCAsmStreamer.
>>>
>>> It's not clear to me - have you tried? So far as I can see, with ToT,
>>> that repro fails to link with the aforementioned linker error. Are you
>>> not seeing that behavior?
>>>
>>>> I noticed that using -disable-dot-loc will dump the line table entries.
>>>
>>> Right - because we emit the line table if we don't emit .loc
>>> directives. If we do emit .loc directives then we skip the line table
>>> because we figure the linker can figure it out based on the .loc
>>> directives.
>>>
>>> - David
>>>
>>>>
>>>> Thanks,
>>>> Manman
>>>>
>>>>> /tmp/hello-5jpGIX.o:(.debug_info+0x1e): undefined reference to
>>>>> `.Lline_table_start0'
>>>>>
>>>>> Essentially: the assembly code emitted by clang -g is currently
>>>>> unusable due to this undefined reference
>>>>>
>>>>> Eric pointed out that MCAsmStreamer.cpp:1420 - where we don't emit the
>>>>> line table if we expect the .loc directives to be sufficient for the
>>>>> assembler to create the line table itself. Since we don't emit the
>>>>> line table we don't emit the extra special line_table_start symbol
>>>>> that's being used in the debug info. (this is paraphrased from Eric's
>>>>> comments based on my rather shallow understanding of the issues)
>>>>>
>>>>> - David
>>>>>
>>>>>>
>>>>>> Modified:
>>>>>> llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>>>>>> llvm/trunk/test/CodeGen/ARM/2011-01-19-MergedGlobalDbg.ll
>>>>>> llvm/trunk/test/CodeGen/ARM/2011-08-02-MergedGlobalDbg.ll
>>>>>> llvm/trunk/test/CodeGen/X86/2011-01-24-DbgValue-Before-Use.ll
>>>>>> llvm/trunk/test/CodeGen/X86/dbg-value-location.ll
>>>>>> llvm/trunk/test/DebugInfo/X86/stringpool.ll
>>>>>>
>>>>>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=174479&r1=174478&r2=174479&view=diff
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
>>>>>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Tue Feb 5 18:59:41 2013
>>>>>> @@ -674,6 +674,8 @@ CompileUnit *DwarfDebug::constructCompil
>>>>>> if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
>>>>>> NewCU->addLabel(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4,
>>>>>> LineTableStartSym);
>>>>>> + else if (NewCU->getUniqueID() == 0)
>>>>>> + NewCU->addUInt(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4, 0);
>>>>>> else
>>>>>> NewCU->addDelta(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4,
>>>>>> LineTableStartSym, Asm->GetTempSymbol("section_line"));
>>>>>>
>>>>>> Modified: llvm/trunk/test/CodeGen/ARM/2011-01-19-MergedGlobalDbg.ll
>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/2011-01-19-MergedGlobalDbg.ll?rev=174479&r1=174478&r2=174479&view=diff
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/CodeGen/ARM/2011-01-19-MergedGlobalDbg.ll (original)
>>>>>> +++ llvm/trunk/test/CodeGen/ARM/2011-01-19-MergedGlobalDbg.ll Tue Feb 5 18:59:41 2013
>>>>>> @@ -17,7 +17,7 @@ target triple = "thumbv7-apple-darwin10"
>>>>>> ; DW_OP_constu
>>>>>> ; offset
>>>>>>
>>>>>> -;CHECK: .long Lset7
>>>>>> +;CHECK: .long Lset6
>>>>>> ;CHECK-NEXT: @ DW_AT_type
>>>>>> ;CHECK-NEXT: @ DW_AT_decl_file
>>>>>> ;CHECK-NEXT: @ DW_AT_decl_line
>>>>>>
>>>>>> Modified: llvm/trunk/test/CodeGen/ARM/2011-08-02-MergedGlobalDbg.ll
>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/ARM/2011-08-02-MergedGlobalDbg.ll?rev=174479&r1=174478&r2=174479&view=diff
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/CodeGen/ARM/2011-08-02-MergedGlobalDbg.ll (original)
>>>>>> +++ llvm/trunk/test/CodeGen/ARM/2011-08-02-MergedGlobalDbg.ll Tue Feb 5 18:59:41 2013
>>>>>> @@ -8,7 +8,7 @@
>>>>>> ; DW_OP_constu
>>>>>> ; offset
>>>>>>
>>>>>> -;CHECK: .long Lset34
>>>>>> +;CHECK: .long Lset33
>>>>>> ;CHECK-NEXT: @ DW_AT_type
>>>>>> ;CHECK-NEXT: @ DW_AT_decl_file
>>>>>> ;CHECK-NEXT: @ DW_AT_decl_line
>>>>>>
>>>>>> Modified: llvm/trunk/test/CodeGen/X86/2011-01-24-DbgValue-Before-Use.ll
>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/2011-01-24-DbgValue-Before-Use.ll?rev=174479&r1=174478&r2=174479&view=diff
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/CodeGen/X86/2011-01-24-DbgValue-Before-Use.ll (original)
>>>>>> +++ llvm/trunk/test/CodeGen/X86/2011-01-24-DbgValue-Before-Use.ll Tue Feb 5 18:59:41 2013
>>>>>> @@ -4,7 +4,7 @@ target datalayout = "e-p:64:64:64-i1:8:8
>>>>>> target triple = "x86_64-apple-darwin10.0.0"
>>>>>>
>>>>>> ; Check debug info for variable z_s
>>>>>> -;CHECK: .long Lset14
>>>>>> +;CHECK: .long Lset13
>>>>>> ;CHECK-NEXT: ## DW_AT_decl_file
>>>>>> ;CHECK-NEXT: ## DW_AT_decl_line
>>>>>> ;CHECK-NEXT: ## DW_AT_type
>>>>>>
>>>>>> Modified: llvm/trunk/test/CodeGen/X86/dbg-value-location.ll
>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/dbg-value-location.ll?rev=174479&r1=174478&r2=174479&view=diff
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/CodeGen/X86/dbg-value-location.ll (original)
>>>>>> +++ llvm/trunk/test/CodeGen/X86/dbg-value-location.ll Tue Feb 5 18:59:41 2013
>>>>>> @@ -4,7 +4,7 @@ target datalayout = "e-p:64:64:64-i1:8:8
>>>>>> target triple = "x86_64-apple-darwin10.0.0"
>>>>>> ;Radar 8950491
>>>>>>
>>>>>> -;CHECK: .long Lset6
>>>>>> +;CHECK: .long Lset5
>>>>>> ;CHECK-NEXT: ## DW_AT_decl_file
>>>>>> ;CHECK-NEXT: ## DW_AT_decl_line
>>>>>> ;CHECK-NEXT: ## DW_AT_type
>>>>>>
>>>>>> Modified: llvm/trunk/test/DebugInfo/X86/stringpool.ll
>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/stringpool.ll?rev=174479&r1=174478&r2=174479&view=diff
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/DebugInfo/X86/stringpool.ll (original)
>>>>>> +++ llvm/trunk/test/DebugInfo/X86/stringpool.ll Tue Feb 5 18:59:41 2013
>>>>>> @@ -23,8 +23,8 @@
>>>>>> ; LINUX-NEXT: .quad yyyy
>>>>>>
>>>>>> ; Verify that we refer to 'yyyy' without a relocation.
>>>>>> -; DARWIN: Lset6 = Linfo_string3-Linfo_string ## DW_AT_name
>>>>>> -; DARWIN-NEXT: .long Lset6
>>>>>> +; DARWIN: Lset5 = Linfo_string3-Linfo_string ## DW_AT_name
>>>>>> +; DARWIN-NEXT: .long Lset5
>>>>>> ; DARWIN-NEXT: .long 39 ## DW_AT_type
>>>>>> ; DARWIN-NEXT: .byte 1 ## DW_AT_external
>>>>>> ; DARWIN-NEXT: .byte 1 ## DW_AT_decl_file
>>>>>>
>>>>>>
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>>
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