[LLVMdev] -gcolumn-info and PR 14106

Diego Novillo
Wed, 02 Jul 2014 15:37:03 -0000

On Tue, Jul 1, 2014 at 7:56 PM, Alexey Samsonov <vonosmas at gmail.com>
wrote:
>
> On Thu, Jun 26, 2014 at 9:46 AM, Diego Novillo <dnovillo at
google.com> wrote:
>>
>> For -Rpass, and other related uses, I am looking at enabling column
info
>> by default. David pointed me at PR 14106, which seems to be the
original
>> motivation for introducing -gcolumn-info. However, I am finding no
>> differences when using it on this test.  I've tried building
with/without
>> -gcolumn-info and found almost no difference in compile time (+0.4%):
>>
>> $ /usr/bin/time clang -w -fno-builtin -O2 -g -gcolumn-info
test-tgmath2.i
>> 474.38user 2.10system 7:58.00elapsed 99%CPU
>>
>> $ /usr/bin/time clang -w -fno-builtin -O2 -g  test-tgmath2.i
>> 472.63user 2.02system 7:56.11elapsed 99%CPU
>>
>> I'm running clang from trunk @211693.
>>
>> The size of all debug sections (according to readelf) are:
>>
>> - with -g -gcolumn-info: 836,177 bytes
>> - with -g: 826,552 bytes
>>
>> That's a growth of about 1% in debug info size.
>
>
> What about the difference between -gmlt and -gmlt + -gcolumn-info?

Debug info growth is larger in proportion (3%). Total binary size is
roughly the same (~1%). Compile times are identical (7m47s for both).

- with -gmlt -gcolumn-info: 319,792 bytes
- with -gmlt: 310,243 bytes


Diego.