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Re: [google/4_8] Disable -g/-gmlt during LIPO instrumentation


I don't quite understand here. We use the profile-generate memory
consumption to estimate the profile use memory consumption.
we still have -g/-gmlt in profile-use compilation. Will this change
effectively under estimate the memory use in the use phrase?

-Rong

On Fri, Sep 27, 2013 at 11:50 AM, Teresa Johnson <tejohnson@google.com> wrote:
> David and Rong,
>
> The following patch will disable -g/-gmlt when instrumenting for LIPO
> since they will affect the recorded ggc_memory used in the module
> grouping decision. Added -fripa-allow-debug to override this behavior.
>
> Passes regression tests and simple tests on the new functionality.
>
> Ok for google/4_8?
>
> Teresa
>
> 2013-09-27  Teresa Johnson  <tejohnson@google.com>
>
>         * opts.c (finish_options): Suppress -g/-gmlt when we are
>         building for LIPO instrumention.
>         * common.opt (fripa-allow-debug): New option.
>
> Index: opts.c
> ===================================================================
> --- opts.c      (revision 202976)
> +++ opts.c      (working copy)
> @@ -799,7 +799,7 @@ finish_options (struct gcc_options *opts, struct g
>  #endif
>        if (!opts->x_flag_fat_lto_objects && !HAVE_LTO_PLUGIN)
>          error_at (loc, "-fno-fat-lto-objects are supported only with
> linker plugin.");
> -}
> +    }
>    if ((opts->x_flag_lto_partition_balanced != 0) +
> (opts->x_flag_lto_partition_1to1 != 0)
>         + (opts->x_flag_lto_partition_none != 0) >= 1)
>      {
> @@ -852,6 +852,26 @@ finish_options (struct gcc_options *opts, struct g
>    /* Turn on -ffunction-sections when -freorder-functions=* is used.  */
>    if (opts->x_flag_reorder_functions > 1)
>      opts->x_flag_function_sections = 1;
> +
> +  /* LIPO module grouping depends on the memory consumed by the profile-gen
> +     parsing phase, recorded in a per-module ggc_memory field of the module
> +     info struct. This will be higher when debug generation is on via
> +     -g/-gmlt, which causes the FE to generate debug structures that will
> +     increase the ggc_total_memory. This could in theory cause the module
> +     groups to be slightly more conservative. Disable -g/-gmlt under
> +     -fripa -fprofile-generate, but provide an option to override this
> +     in case we actually need to debug an instrumented binary.  */
> +  if (opts->x_profile_arc_flag
> +      && opts->x_flag_dyn_ipa
> +      && opts->x_debug_info_level != DINFO_LEVEL_NONE
> +      && !opts->x_flag_dyn_ipa_allow_debug)
> +    {
> +      inform (loc,
> +             "Debug generation via -g option disabled under -fripa "
> +              "-fprofile-generate (use -fripa-allow-debug to override)");
> +      set_debug_level (NO_DEBUG, DEFAULT_GDB_EXTENSIONS, "0", opts, opts_set,
> +                       loc);
> +    }
>  }
>
>  #define LEFT_COLUMN    27
> Index: common.opt
> ===================================================================
> --- common.opt  (revision 202976)
> +++ common.opt  (working copy)
> @@ -1155,6 +1155,10 @@ fripa
>  Common Report Var(flag_dyn_ipa)
>  Perform Dynamic Inter-Procedural Analysis.
>
> +fripa-allow-debug
> +Common Report Var(flag_dyn_ipa_allow_debug) Init(0)
> +Allow -g enablement for -fripa -fprofile-generate compiles.
> +
>  fripa-disallow-asm-modules
>  Common Report Var(flag_ripa_disallow_asm_modules)
>  Don't import an auxiliary module if it contains asm statements
>
> --
> Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413


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