Re: RFA: Enhance information recorded by -frecord-gcc-switches

[Richard Biener <richard dot guenther at gmail dot com>]

On Thu, Jun 8, 2017 at 11:21 AM, Nick Clifton <nickc@redhat.com> wrote:
> Hi Guys,
>
>   The -frecord-gcc-switches option records the gcc command line.  It
>   does not however expand options like -O2 into the optimizations that
>   this enables.  Thus if a user wants to know if a specific optimization
>   was used when creating an object file, (or library or executable),
>   they will have to reverse engineer the compilation process.  Which may
>   or may not be possible.
>
>   The attached patch is a proposal to address this problem by making
>   -frecord-gcc-switches also record all the enabled options.  This does
>   make object files bigger, but this cannot be helped.  The enhancement
>   is not enabled by default however, instead a second command line
>   option must be used.  In a possibly contentious move I chose to reuse
>   the -fverbose-asm option, rather than creating a new one.  I did this
>   because a) it simplifies the patch, b) we have more than enough switch
>   recording options already, c) it does not conflict with the current
>   use of -fverbose-asm and d) it ties in nicely with the name of the
>   option.
>
>   Tested, with no regressions on an x86_64-pc-linux-gnu target, and
>   built for a variety of other targets.
>
>   OK to apply ?

I think individually enabled passes by -On are not really useful information
as you generally cannot replace -On by a set of other switches on the
command-line.

Richard.

> Cheers
>   Nick
>
> gcc/ChangeLog
> 2017-06-08  Nick Clifton  <nickc@redhat.com>
>
>         * varasm.c (dump_enabled_to_asm_out_file): New function.  Prints
>         enabled options to the asm_out_file.
>         (elf_record_gcc_switches): If verbose-asm is set then also dump
>         all enabled options to the asm file.
>         * toplec.c (print_switch_values): Convert from static to global.
>         * doc/invoke.texi (-fverbose-asm): Mention its effect on the
>         -frecord-gcc-switches option.
>         (-frecord-gcc-switches): Refactor the description and add details
>         of how -fverbose-asm modifies its behaviour.
>