llvm dev - Dec 2019 - aarch64 do not generate debug info for tls var

Hi Devs,

consider below testcase
$cat test.c
__thread int mtls=1;
void foo(){
mtls++;
}

it emits this debug info for mtls

0x0000002a:   DW_TAG_variable
                DW_AT_name      ("mtls")
                DW_AT_type      (0x00000035 "int")
                DW_AT_external  (true)
                DW_AT_decl_file ("test.c")
                DW_AT_decl_line (1)

which does not contain DW_AT_Location.

Currently, aarch64 does not emit DW_AT_Location for TLS variables.
I could see at this line, it says some restriction in aarch64 elf abi.
https://github.com/llvm-mirror/llvm/blob/master/lib/Target/AArch64/AArch64TargetObjectFile.cpp#L24

I would like to know community thoughts on this and is there any other way
to tackle this, or we simply can not debug TLS variables for this
architecture?


./Kamlesh
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What does GCC do?

On Mon, Dec 9, 2019 at 10:25 PM kamlesh kumar via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi Devs,
>
> consider below testcase
> $cat test.c
> __thread int mtls=1;
> void foo(){
> mtls++;
> }
>
> it emits this debug info for mtls
>
> 0x0000002a:   DW_TAG_variable
>                 DW_AT_name      ("mtls")
>                 DW_AT_type      (0x00000035 "int")
>                 DW_AT_external  (true)
>                 DW_AT_decl_file ("test.c")
>                 DW_AT_decl_line (1)
>
> which does not contain DW_AT_Location.
>
> Currently, aarch64 does not emit DW_AT_Location for TLS variables.
> I could see at this line, it says some restriction in aarch64 elf abi.
>
>
https://github.com/llvm-mirror/llvm/blob/master/lib/Target/AArch64/AArch64TargetObjectFile.cpp#L24
>
> I would like to know community thoughts on this and is there any other way
> to tackle this, or we simply can not debug TLS variables for this
> architecture?
>
>
> ./Kamlesh
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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GCC's behavior matches LLVM.
so should we leave it?

On Tue, Dec 10, 2019 at 12:54 PM David Blaikie <dblaikie at gmail.com>
wrote:
> What does GCC do?
>
> On Mon, Dec 9, 2019 at 10:25 PM kamlesh kumar via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi Devs,
>>
>> consider below testcase
>> $cat test.c
>> __thread int mtls=1;
>> void foo(){
>> mtls++;
>> }
>>
>> it emits this debug info for mtls
>>
>> 0x0000002a:   DW_TAG_variable
>>                 DW_AT_name      ("mtls")
>>                 DW_AT_type      (0x00000035 "int")
>>                 DW_AT_external  (true)
>>                 DW_AT_decl_file ("test.c")
>>                 DW_AT_decl_line (1)
>>
>> which does not contain DW_AT_Location.
>>
>> Currently, aarch64 does not emit DW_AT_Location for TLS variables.
>> I could see at this line, it says some restriction in aarch64 elf abi.
>>
>>
https://github.com/llvm-mirror/llvm/blob/master/lib/Target/AArch64/AArch64TargetObjectFile.cpp#L24
>>
>> I would like to know community thoughts on this and is there any other
>> way to tackle this, or we simply can not debug TLS variables for this
>> architecture?
>>
>>
>> ./Kamlesh
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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