[cfe-commits] [PATCH] "-gline-tables-only" flag for Clang

[Alexey Samsonov]

Hi!

On Thu, Apr 26, 2012 at 12:44 AM, Eric Christopher <echristo at apple.com>wrote:

>
> On Apr 25, 2012, at 4:51 AM, Alexey Samsonov <samsonov at google.com> wrote:
>
> > Hi, cfe-commits!
> >
> > This patch adds a new Clang compiler flag "-gline-tables-only". It
> should reduce the amount of emitted debug information:
> > 1) DIEs in .debug_info should only have types DW_TAG_compile_unit,
> DW_TAG_subprogram, DW_TAG_inlined_subroutine (for opt builds),
> DW_TAG_lexical_block.
> > 2) .debug_str should only contain function names
> > 3) No debug data for types/namespaces/variables should be emitted.
> > 4) The data in .debug_line should be enough to produce valid stack
> traces with function names and line numbers.
> >
> > This flag can reduce the size of the binary by some factor, but still
> allow to obtain valid stack traces (both for debug and opt builds, and for
> inlined functions).
> > Results of measurements on SPEC CPU 2006 benchmarks (for Clang r155349):
> >
> > binary size increase factor for:
> > "-O0 -g": average - 2x, max - 5.85x
> > "-O0 -gline-tables-only": average - 1.2x, max - 1.44x
> > "-O2 -g": average - 3.45x, max - 11x
> > "-O2 -gline-tables-only": average - 1.47x, max - 2.76x
> >
> > Similar patch exists for gcc but is not yet in trunk
> > (See this patch at
> http://old.nabble.com/-patch--Add-new--gmlt-option-for-min.-debug-info-with-line-tables-(issue4440072)-td31482851.html
> > or http://codereview.appspot.com/4440072). gcc patch is used in Google
> for about 2 years already.
> >
> > You can review the Clang patch at:
> http://codereview.appspot.com/6112056/
>
> So two requests:
>
> a) Please do turn it into an enum and refactor the current uses before as
> a separate patch.
>
b) I think the fixme should be fixed first. Also, no need to put your name
> next to a fixme.
>

Sending the revised (modulo r155697) patch. Please take a look.

Codereview: http://codereview.appspot.com/6112056/#ps9001

-- 
Alexey Samsonov, MSK
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