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

[Teresa Johnson via llvm-commits]

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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