[llvm] r174479 - Attempt to recover gdb bot after r174445.
Manman Ren
mren at apple.com
Fri Feb 8 15:29:20 PST 2013
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
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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