Re: [RFC][PATCH] Stabilize a few qsort comparison functions

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

Am 2018-06-12 um 23:49 schrieb Jeff Law:
> On 02/07/2018 09:58 AM, Franz Sirl wrote:
> > Hi,
> >
> > this is the result of an attempt to minimize the differences between the
> > compile results of a Linux-based and a Cygwin64-based powerpc-eabi cross
> > toolchain.
> > The method used was:
> >
> >      - find the -fverbose-asm assembler files that differ
> >      - compile that file again on both platforms with
> >         -O2 -g3 -fdump-tree-all-all -fdump-rtl-all -fdump-noaddr
> >      - look for the first dump file with differences and check that pass
> >        for qsort's
> >      - stabilize the compare functions
> >
> > With some help on IRC to better understand the passes and some serious
> > debugging of GCC I came up with this patch. On the tested codebase the
> > differences in the assembler sources are now down to 0.
> > If the various pass maintainers have better ideas on how to stabilize
> > the compare functions, I'll be happy to verify them on the codebase.
> > For the SRA patch I already have an alternate version with an additional
> > ID member.
> >
> > Comments?
> >
> > Bootstrapped on linux-x86_64, no testsuite regressions.
> >
> > Franz Sirl
> >
> >
> > 2018-02-07  Franz Sirl <franz.sirl-kernel@lauterbach.com>
> >
> >      * ira-build.c (object_range_compare_func): Stabilize sort.
> >      * tree-sra.c (compare_access_positions): Likewise.
> >      * varasm.c (output_object_block_compare): Likewise.
> >      * tree-ssa-loop-ivopts.c (group_compare_offset): Likewise.
> >      (struct iv_common_cand): New member.
> >      (record_common_cand): Initialize new member.
> >      (common_cand_cmp): Use new member to stabilize sort.
> >      * tree-vrp.c (struct assert_locus): New member.
> >      (register_new_assert_for): Initialize new member.
> >      (compare_assert_loc): Use new member to stabilize sort.
> This looks pretty reasonable.   I don't think you've contributed much
> recently, do you still have write access to the repository?

Hi Jeff,

after Alexander Monakov's gcc_qsort changes, this patch is not necessary 
anymore. I've verified that with a backport (the 2 patches r260216 and 
r260222 applied cleanly) of gcc_qsort to the gcc-8-branch. The resulting 
powerpc-eabi crosscompilers produce no more unexpected differences 
between a Linux and a Cygwin host.
Tested (same like with my patch) by comparing the -fverbose-asm assembly 
output on a complete rebuild of the software here.
So, unless someone thinks one of the changes makes sense anyway, this 
patch is obsolete.

On the repository write access, yes, I don't have one anymore. But 
before reactivating that I need to do the legal paperwork, because 
unless before when GCC was a strictly private pet project for me, it now 
is work related. I already got permission from my company for that, just 
need to find some spare time to start the legal stuff.

Franz