[LLVMdev] -gcolumn-info and PR 14106

[Alexey Samsonov]

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?


>
> These numbers are in line with a comparative build I did of our internal
> codebase. The build included a massive number of C and C++ files. For C
> files, total file size grows by 1% on average. For C++ files the average
> growth is around 0.2%. Build times are unchanged as well.
>
> Does anyone remember any other edge case I may want to try? It seems to me
> that these differences are not really worth the effort of having a flag
> controlling column information.
>
>
> Thanks.  Diego.
>
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>


-- 
Alexey Samsonov
vonosmas at gmail.com
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