[lld] r267020 - [LTO] Discard names for values that are not global by default.

[Rafael Espíndola via llvm-commits]

I like Peter's idea: Lets keep local names only when using -save-temps.

Cheers,
Rafael


On 21 April 2016 at 14:32, Teresa Johnson <tejohnson at google.com> wrote:

>
>
> On Thu, Apr 21, 2016 at 11:18 AM, Davide Italiano <davide at freebsd.org>
> wrote:
>
>> On Thu, Apr 21, 2016 at 10:57 AM, Peter Collingbourne <peter at pcc.me.uk>
>> wrote:
>> >
>> >
>> > On Thu, Apr 21, 2016 at 10:46 AM, Davide Italiano via llvm-commits
>> > <llvm-commits at lists.llvm.org> wrote:
>> >>
>> >> Author: davide
>> >> Date: Thu Apr 21 12:46:38 2016
>> >> New Revision: 267020
>> >>
>> >> URL: http://llvm.org/viewvc/llvm-project?rev=267020&view=rev
>> >> Log:
>> >> [LTO] Discard names for values that are not global by default.
>> >>
>> >> Rafael reported on the mailing list that this reduces peak memory
>> >> usage while linking llvm-as by 15%. It makes sense to make it
>> >> the default, and introduce an inverse knob -lto-no-discard-value-names
>> >> for those who want to restore the old behavior.
>> >>
>> >> Modified:
>> >>     lld/trunk/ELF/Driver.cpp
>> >>     lld/trunk/ELF/Options.td
>> >>     lld/trunk/test/ELF/lto/discard-value-names.ll
>> >>     lld/trunk/test/ELF/lto/type-merge2.ll
>> >>
>> >> Modified: lld/trunk/ELF/Driver.cpp
>> >> URL:
>> >>
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=267020&r1=267019&r2=267020&view=diff
>> >>
>> >>
>> ==============================================================================
>> >> --- lld/trunk/ELF/Driver.cpp (original)
>> >> +++ lld/trunk/ELF/Driver.cpp Thu Apr 21 12:46:38 2016
>> >> @@ -289,7 +289,7 @@ void LinkerDriver::readConfigs(opt::Inpu
>> >>    Config->Demangle = !Args.hasArg(OPT_no_demangle);
>> >>    Config->DisableVerify = Args.hasArg(OPT_disable_verify);
>> >>    Config->DiscardAll = Args.hasArg(OPT_discard_all);
>> >> -  Config->DiscardValueNames =
>> Args.hasArg(OPT_lto_discard_value_names);
>> >> +  Config->DiscardValueNames =
>> >> !Args.hasArg(OPT_lto_no_discard_value_names);
>> >>    Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
>> >>    Config->DiscardNone = Args.hasArg(OPT_discard_none);
>> >>    Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
>> >>
>> >> Modified: lld/trunk/ELF/Options.td
>> >> URL:
>> >>
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Options.td?rev=267020&r1=267019&r2=267020&view=diff
>> >>
>> >>
>> ==============================================================================
>> >> --- lld/trunk/ELF/Options.td (original)
>> >> +++ lld/trunk/ELF/Options.td Thu Apr 21 12:46:38 2016
>> >> @@ -238,7 +238,7 @@ def G : Separate<["-"], "G">;
>> >>  def alias_version_script_version_script : Joined<["--"],
>> >> "version-script=">, Alias<version_script>;
>> >>
>> >>  // LTO-related options.
>> >> -def lto_discard_value_names : Flag<["-"], "lto-discard-value-names">;
>> >> +def lto_no_discard_value_names : Flag<["-"],
>> >> "lto-no-discard-value-names">;
>> >
>> >
>> > We probably don't want to name flags "-l(something)", as that would
>> conflict
>> > with the -l flag. Can you please rename this "--lto-..."?
>> >
>> > (That is, if we want a flag for this at all. Have you considered gating
>> this
>> > behavior behind -save-temps instead?)
>> >
>>
>> I'm fine with one less flag (and using -save-temps), but I'm cc:ing
>> the other people involved to hear if they agree.
>>
>
> Interesting idea. When I added this to gold-plugin yesterday morning I
> also had to add a no- variant so that certain tests would keep working. If
> lld goes the route of using -save-temps we should consider doing the same
> for gold-plugin for consistency and flag reduction.
>
> Teresa
>
>
>>
>> --
>> Davide
>>
>> "There are no solved problems; there are only problems that are more
>> or less solved" -- Henri Poincare
>>
>
>
>
> --
> Teresa Johnson |  Software Engineer |  tejohnson at google.com |
> 408-460-2413
>
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