Re: [PATCH] Fix bootstrap miscompare with LTO bootstrap (PR85571)

[Richard Biener <rguenther at suse dot de>]

On Wed, 2 May 2018, Richard Biener wrote:

> 
> The following fixes the LTO part of the -f[no-]checking miscompare issue.
> I introduce a compare-lto script similar to compare-debug where I strip
> the LTO option section and re-compare.  I have no easy way to test
> the nonplugin path and at least for targets using simple-object to
> wrap all LTO sections into one native sections we can't strip the
> option section anyway so this just disables compare for those.
> 
> As a followup I'd like to add support to add extra files to compare
> and for LTO bootstrap we'd like to compare cc1plus$(exeext) and 
> lto1$(exeext) - maybe I can come up with a pattern that works everywhere
> but I guess this would be a start.  But then for this we need PR85574
> to be fixed first.
> 
> LTO bootstrapped on x86_64-unknown-linux-gnu.
> 
> OK for trunk?

Ping.

Richard.

> Thanks,
> Richard.
> 
> 2018-05-02  Richard Biener  <rguenther@suse.de>
> 
> 	PR bootstrap/85571
> 	config/
> 	* bootstrap-lto-noplugin.mk: Disable compare.
> 	* bootstrap-lto.mk: Supply contrib/compare-lto for do-compare.
> 
> 	contrib/
> 	* compare-lto: New script derived from compare-debug.
> 
> Index: config/bootstrap-lto-noplugin.mk
> ===================================================================
> --- config/bootstrap-lto-noplugin.mk	(revision 259829)
> +++ config/bootstrap-lto-noplugin.mk	(working copy)
> @@ -6,3 +6,4 @@ STAGE3_CFLAGS += -flto=jobserver -frando
>  STAGEprofile_CFLAGS += -flto=jobserver -frandom-seed=1
>  STAGEtrain_CFLAGS += -flto=jobserver -frandom-seed=1
>  STAGEfeedback_CFLAGS += -flto=jobserver -frandom-seed=1
> +do-compare = /bin/true
> Index: config/bootstrap-lto.mk
> ===================================================================
> --- config/bootstrap-lto.mk	(revision 259829)
> +++ config/bootstrap-lto.mk	(working copy)
> @@ -13,3 +13,5 @@ LTO_RANLIB = $$r/$(HOST_SUBDIR)/prev-gcc
>  LTO_EXPORTS = AR="$(LTO_AR)"; export AR; \
>  	      RANLIB="$(LTO_RANLIB)"; export RANLIB;
>  LTO_FLAGS_TO_PASS = AR="$(LTO_AR)" RANLIB="$(LTO_RANLIB)"
> +
> +do-compare = $(SHELL) $(srcdir)/contrib/compare-lto $$f1 $$f2
> Index: contrib/compare-lto
> ===================================================================
> --- contrib/compare-lto	(nonexistent)
> +++ contrib/compare-lto	(working copy)
> @@ -0,0 +1,111 @@
> +#! /bin/sh
> +
> +# Compare copies of two given object files.
> +
> +# Copyright (C) 2007, 2008, 2009, 2010, 2012 Free Software Foundation
> +# Originally by Alexandre Oliva <aoliva@redhat.com>
> +# Modified for LTO bootstrap by Richard Biener <rguenther@suse.de>
> +
> +# This file is part of GCC.
> +
> +# GCC is free software; you can redistribute it and/or modify it under
> +# the terms of the GNU General Public License as published by the Free
> +# Software Foundation; either version 3, or (at your option) any later
> +# version.
> +
> +# GCC is distributed in the hope that it will be useful, but WITHOUT
> +# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
> +# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
> +# License for more details.
> +
> +# You should have received a copy of the GNU General Public License
> +# along with GCC; see the file COPYING3.  If not see
> +# <http://www.gnu.org/licenses/>.
> +
> +rm='rm -f'
> +
> +case $1 in
> +-p | --preserve)
> +  rm='echo preserving'
> +  shift
> +  ;;
> +esac
> +
> +if test $# != 2; then
> +  echo 'usage: compare-lto file1.o file2.o' >&2
> +  exit 1
> +fi
> +
> +if test ! -f "$1"; then
> +  echo "$1" does not exist >&2
> +  exit 1
> +fi
> +
> +if test ! -f "$2"; then
> +  echo "$2" does not exist >&2
> +  exit 1
> +fi
> +
> +suf1=stripped
> +while test -f "$1.$suf1"; do
> +  suf1=$suf1.
> +done
> +
> +suf2=stripped
> +while test -f "$2.$suf2"; do
> +  suf2=$suf2.
> +done
> +
> +trap 'rm -f "$1.$suf1" "$2.$suf2"' 0 1 2 15
> +
> +if cmp "$1" "$2"; then
> +  status=0
> +else
> +  status=1
> +
> +  cmd=
> +  for t in objdump readelf eu-readelf; do
> +    if ($t --help) 2>&1 | grep ' --\[*section-\]*headers' > /dev/null; then
> +      cmd=$t
> +      break
> +    fi
> +  done
> +
> +  # If there are LTO option sections, try to strip them off.
> +  if test "x$cmd" = "x" ||
> +     $cmd --section-headers "$1" | grep '.gnu.lto_.opts' > /dev/null ||
> +     $cmd --section-headers "$2" | grep '.gnu.lto_.opts' > /dev/null ; then
> +
> +    echo stripping off LTO option section, then retrying >&2
> +
> +    seclist=".gnu.lto_.opts"
> +    rsopts=`for sec in $seclist; do echo " --remove-section $sec"; done`
> +
> +    if (objcopy -v) 2>&1 | grep ' --remove-section' > /dev/null; then
> +      objcopy $rsopts "$1" "$1.$suf1"
> +      objcopy $rsopts "$2" "$2.$suf2"
> +    elif (strip --help) 2>&1 | grep ' --remove-section' > /dev/null; then
> +      cp "$1" "$1.$suf1"
> +      strip $rsopts "$1.$suf1"
> +
> +      cp "$2" "$2.$suf2"
> +      strip $rsopts "$2.$suf2"
> +    else
> +      echo failed to strip off LTO option section >&2
> +    fi
> +
> +    trap 'rm -f "$1.$suf1" "$2.$suf2"' 0 1 2 15
> +
> +    if cmp "$1.$suf1" "$2.$suf2"; then
> +      status=0
> +    else
> +      status=1
> +    fi
> +  fi
> +fi
> +
> +$rm "$1.$suf1" "$2.$suf2"
> +
> +trap "exit $status; exit" 0 1 2 15
> +
> +exit $status
> 
> Property changes on: contrib/compare-lto
> ___________________________________________________________________
> Added: svn:executable
> ## -0,0 +1 ##
> +*
> \ No newline at end of property
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)