>
> This merges -O options given at compile-time into a single
> optimization level to be used for LTO link time (but
> overridden with whatever is specified at LTO link time - unless
> no optimization level is specified there). That is, it
> determines a "default" optimization level used at LTO link time
> (as opposed to the default optimization level zero).
>
> Currently the code merges exact same options as-is and
> mismatching optimization levels based on the maximum value of
> 'optimize' they cause and merging it as -Ooptimize.
> Thus -Og and -Os get merged as -O2, -O and -Ofast get merged as -O3
> and -O and -O1 get merged as -O1.
>
> Specifying any optimization level explicitely at link time
> will override what we came up with above (including explicitely
> specifying -O0).
>
> Comments?
>
> I've tested that it works as expected. Do we want something like
> this for 4.9?
Yes, I do not see much down-sides. Of course I have the grand plans
to make compiler flags to be preserved thorough LTO, but i think you
patch improves things over what we have now.
Honza
>
> Thanks,
> Richard.
>
> 2014-03-04 Richard Biener <rguent...@suse.de>
>
> * lto-wrapper.c (merge_and_complain): Merge compile-time
> optimization levels.
> (run_gcc): And pass it through to the link options.
>
> Index: gcc/lto-wrapper.c
> ===================================================================
> *** gcc/lto-wrapper.c (revision 208305)
> --- gcc/lto-wrapper.c (working copy)
> *************** merge_and_complain (struct cl_decoded_op
> *** 459,464 ****
> --- 459,535 ----
> fatal ("Option %s not used consistently in all LTO input files",
> foption->orig_option_with_args_text);
> break;
> +
> + case OPT_O:
> + case OPT_Ofast:
> + case OPT_Og:
> + case OPT_Os:
> + for (j = 0; j < *decoded_options_count; ++j)
> + if ((*decoded_options)[j].opt_index == OPT_O
> + || (*decoded_options)[j].opt_index == OPT_Ofast
> + || (*decoded_options)[j].opt_index == OPT_Og
> + || (*decoded_options)[j].opt_index == OPT_Os)
> + break;
> + if (j == *decoded_options_count)
> + append_option (decoded_options, decoded_options_count, foption);
> + else if ((*decoded_options)[j].opt_index == foption->opt_index
> + && foption->opt_index != OPT_O)
> + /* Exact same options get merged. */
> + ;
> + else
> + {
> + /* For mismatched option kinds preserve the optimization
> + level only, thus merge it as -On. This also handles
> + merging of same optimization level -On. */
> + int level = 0;
> + switch (foption->opt_index)
> + {
> + case OPT_O:
> + if (foption->arg[0] == '\0')
> + level = MAX (level, 1);
> + else
> + level = MAX (level, atoi (foption->arg));
> + break;
> + case OPT_Ofast:
> + level = MAX (level, 3);
> + break;
> + case OPT_Og:
> + level = MAX (level, 1);
> + break;
> + case OPT_Os:
> + level = MAX (level, 2);
> + break;
> + default:
> + gcc_unreachable ();
> + }
> + switch ((*decoded_options)[j].opt_index)
> + {
> + case OPT_O:
> + if ((*decoded_options)[j].arg[0] == '\0')
> + level = MAX (level, 1);
> + else
> + level = MAX (level, atoi ((*decoded_options)[j].arg));
> + break;
> + case OPT_Ofast:
> + level = MAX (level, 3);
> + break;
> + case OPT_Og:
> + level = MAX (level, 1);
> + break;
> + case OPT_Os:
> + level = MAX (level, 2);
> + break;
> + default:
> + gcc_unreachable ();
> + }
> + (*decoded_options)[j].opt_index = OPT_O;
> + char *tem;
> + asprintf (&tem, "-O%d", level);
> + (*decoded_options)[j].arg = &tem[2];
> + (*decoded_options)[j].canonical_option[0] = tem;
> + (*decoded_options)[j].value = 1;
> + }
> + break;
> }
> }
> }
> *************** run_gcc (unsigned argc, char *argv[])
> *** 610,615 ****
> --- 681,690 ----
> case OPT_fwrapv:
> case OPT_ftrapv:
> case OPT_fstrict_overflow:
> + case OPT_O:
> + case OPT_Ofast:
> + case OPT_Og:
> + case OPT_Os:
> break;
>
> default:
