Ping.
Thanks,
Kyrill
> On 21 Jul 2026, at 17:28, Kyrylo Tkachov <[email protected]> wrote:
>
> From: Kyrylo Tkachov <[email protected]>
>
> The stage 2 and stage 3 object comparison runs one command per object in a
> serial shell loop. Everything after it waits while an otherwise idle machine
> compares thousands of objects.
>
> Generate one make target per object and run the comparisons through $(MAKE),
> so they share the original jobserver. Keep the generated makefile and result
> shards invocation-specific, clean them on normal and signal exits, and sort
> the shards before creating the traditional .bad_compare diagnostic. Files in
> the exclusion list still only warn. Comparator statuses other than zero or
> one now report an operational error instead of being treated as equal.
>
> The tail-based fallback for cmp implementations without byte skipping used
> fixed temporary names. Give those files process-specific names, clean them
> with a trap, and preserve the same status contract for tail failures and
> signals.
>
> On highly parallel AArch64 and x86_64 systems this reduces comparison wall
> time by about 95%.
>
> ChangeLog:
>
> * Makefile.tpl ([+compare-target+]): Run object comparisons through an
> invocation-specific parallel sub-make. Collect sorted failure shards
> and clean temporary state on exit.
> * Makefile.in: Regenerate.
> * configure: Regenerate.
>
> config/ChangeLog:
>
> * acx.m4 (ACX_PROG_CMP_IGNORE_INITIAL): Use process-specific temporary
> files and clean them on exit. Diagnose tail failures as errors.
>
> Signed-off-by: Kyrylo Tkachov <[email protected]>
> ---
> Makefile.in | 116 ++++++++++++++++++++++++++++++++++++--------------
> Makefile.tpl | 58 ++++++++++++++++++-------
> config/acx.m4 | 11 ++++-
> configure | 11 ++++-
> 4 files changed, 146 insertions(+), 50 deletions(-)
>
> diff --git a/Makefile.in b/Makefile.in
> index f34142cc077..5cca69c3f52 100644
> --- a/Makefile.in
> +++ b/Makefile.in
> @@ -66022,6 +66022,9 @@ do-clean: clean-stage3
> # only possibility, but now it conflicts with no-bootstrap rules
> @if gcc-bootstrap
>
> +# Run the comparisons in parallel through a generated sub-makefile under
> +# the jobserver. Each failing recipe writes a separate result shard that
> +# is collected after the sub-make finishes.
> compare:
> @r=`${PWD_COMMAND}`; export r; \
> s=`cd $(srcdir); ${PWD_COMMAND}`; export s; \
> @@ -66030,29 +66033,52 @@ compare:
> exit 0; \
> fi; \
> : $(MAKE); $(stage); \
> - rm -f .bad_compare; \
> + compare_id=$$$$; \
> + bad_compare=.bad_compare.$$compare_id; export bad_compare; \
> + compare_makefile=compare.$$compare_id.mk; \
> + trap 'st=$$?; rm -f "$$compare_makefile" "$$bad_compare" \
> + "$$bad_compare".*; trap - 0; exit $$st' 0; \
> + trap 'exit 1' 1 2 3 15; \
> echo Comparing stages 2 and 3; \
> sed=`echo stage3 | sed 's,^stage,,;s,.,.,g'`; \
> files=`find stage3-* -name "*$(objext)" -print | \
> sed -n s,^stage$$sed-,,p`; \
> - for file in $${files} ${extra-compare}; do \
> - f1=$$r/stage2-$$file; f2=$$r/stage3-$$file; \
> - if test ! -f $$f1; then continue; fi; \
> - $(do-compare) > /dev/null 2>&1; \
> - if test $$? -eq 1; then \
> - case $$file in \
> - @compare_exclusions@) \
> - echo warning: $$file differs ;; \
> - *) \
> - echo $$file differs >> .bad_compare ;; \
> - esac; \
> - fi; \
> - done; \
> - if [ -f .bad_compare ]; then \
> + cmp_raw='$(do-compare)'; \
> + { \
> + echo 'all:'; \
> + echo '.PHONY: all FORCE'; \
> + echo 'FORCE:'; \
> + printf 'compare/%%: FORCE ; @'; \
> + printf 'f1=$$$$r/stage2-$$*; '; \
> + printf 'f2=$$$$r/stage3-$$*; '; \
> + printf '%s' "$$cmp_raw" | sed 's,\$$,$$$$,g'; \
> + printf ' > /dev/null 2>&1; st=$$$$?; '; \
> + printf 'if test $$$$st -eq 1; then '; \
> + printf 'case $$* in '; \
> + printf '@compare_exclusions@) echo warning: $$* differs ;; '; \
> + printf '*) echo $$* differs >> "$$$$bad_compare.$$$$$$$$" ;; '; \
> + printf 'esac; '; \
> + printf 'elif test $$$$st -ne 0; then '; \
> + printf 'echo "$$* compare: error status $$$$st" '; \
> + printf '>> "$$$$bad_compare.$$$$$$$$"; fi\n'; \
> + for file in $${files} ${extra-compare}; do \
> + if test ! -f $$r/stage2-$$file; then continue; fi; \
> + echo "all: compare/$$file"; \
> + done; \
> + } > "$$compare_makefile"; \
> + $(MAKE) -s -f "$$compare_makefile" all; compare_status=$$?; \
> + if test $$compare_status -ne 0; then \
> + exit $$compare_status; \
> + fi; \
> + set -- "$$bad_compare".*; \
> + if test -f "$$1"; then \
> echo "Bootstrap comparison failure!"; \
> - cat .bad_compare; \
> + LC_ALL=C sort "$$bad_compare".* > "$$bad_compare" || exit 1; \
> + cat "$$bad_compare"; \
> + mv -f "$$bad_compare" .bad_compare; \
> exit 1; \
> else \
> + rm -f .bad_compare; \
> echo Comparison successful.; \
> fi; \
> $(STAMP) compare
> @@ -66456,6 +66482,9 @@ do-clean: clean-stage4
> # only possibility, but now it conflicts with no-bootstrap rules
> @if gcc-bootstrap
>
> +# Run the comparisons in parallel through a generated sub-makefile under
> +# the jobserver. Each failing recipe writes a separate result shard that
> +# is collected after the sub-make finishes.
> compare3:
> @r=`${PWD_COMMAND}`; export r; \
> s=`cd $(srcdir); ${PWD_COMMAND}`; export s; \
> @@ -66464,29 +66493,52 @@ compare3:
> exit 0; \
> fi; \
> : $(MAKE); $(stage); \
> - rm -f .bad_compare; \
> + compare_id=$$$$; \
> + bad_compare=.bad_compare.$$compare_id; export bad_compare; \
> + compare_makefile=compare3.$$compare_id.mk; \
> + trap 'st=$$?; rm -f "$$compare_makefile" "$$bad_compare" \
> + "$$bad_compare".*; trap - 0; exit $$st' 0; \
> + trap 'exit 1' 1 2 3 15; \
> echo Comparing stages 3 and 4; \
> sed=`echo stage4 | sed 's,^stage,,;s,.,.,g'`; \
> files=`find stage4-* -name "*$(objext)" -print | \
> sed -n s,^stage$$sed-,,p`; \
> - for file in $${files} ${extra-compare}; do \
> - f1=$$r/stage3-$$file; f2=$$r/stage4-$$file; \
> - if test ! -f $$f1; then continue; fi; \
> - $(do-compare3) > /dev/null 2>&1; \
> - if test $$? -eq 1; then \
> - case $$file in \
> - @compare_exclusions@) \
> - echo warning: $$file differs ;; \
> - *) \
> - echo $$file differs >> .bad_compare ;; \
> - esac; \
> - fi; \
> - done; \
> - if [ -f .bad_compare ]; then \
> + cmp_raw='$(do-compare3)'; \
> + { \
> + echo 'all:'; \
> + echo '.PHONY: all FORCE'; \
> + echo 'FORCE:'; \
> + printf 'compare3/%%: FORCE ; @'; \
> + printf 'f1=$$$$r/stage3-$$*; '; \
> + printf 'f2=$$$$r/stage4-$$*; '; \
> + printf '%s' "$$cmp_raw" | sed 's,\$$,$$$$,g'; \
> + printf ' > /dev/null 2>&1; st=$$$$?; '; \
> + printf 'if test $$$$st -eq 1; then '; \
> + printf 'case $$* in '; \
> + printf '@compare_exclusions@) echo warning: $$* differs ;; '; \
> + printf '*) echo $$* differs >> "$$$$bad_compare.$$$$$$$$" ;; '; \
> + printf 'esac; '; \
> + printf 'elif test $$$$st -ne 0; then '; \
> + printf 'echo "$$* compare: error status $$$$st" '; \
> + printf '>> "$$$$bad_compare.$$$$$$$$"; fi\n'; \
> + for file in $${files} ${extra-compare}; do \
> + if test ! -f $$r/stage3-$$file; then continue; fi; \
> + echo "all: compare3/$$file"; \
> + done; \
> + } > "$$compare_makefile"; \
> + $(MAKE) -s -f "$$compare_makefile" all; compare_status=$$?; \
> + if test $$compare_status -ne 0; then \
> + exit $$compare_status; \
> + fi; \
> + set -- "$$bad_compare".*; \
> + if test -f "$$1"; then \
> echo "Bootstrap comparison failure!"; \
> - cat .bad_compare; \
> + LC_ALL=C sort "$$bad_compare".* > "$$bad_compare" || exit 1; \
> + cat "$$bad_compare"; \
> + mv -f "$$bad_compare" .bad_compare; \
> exit 1; \
> else \
> + rm -f .bad_compare; \
> echo Comparison successful.; \
> fi; \
> $(STAMP) compare3
> diff --git a/Makefile.tpl b/Makefile.tpl
> index 5891b67b697..98bd03e9a33 100644
> --- a/Makefile.tpl
> +++ b/Makefile.tpl
> @@ -1821,6 +1821,9 @@ do-clean: clean-stage[+id+]
> # only possibility, but now it conflicts with no-bootstrap rules
> @if gcc-bootstrap
> [+ IF compare-target +]
> +# Run the comparisons in parallel through a generated sub-makefile under
> +# the jobserver. Each failing recipe writes a separate result shard that
> +# is collected after the sub-make finishes.
> [+compare-target+]:
> @r=`${PWD_COMMAND}`; export r; \
> s=`cd $(srcdir); ${PWD_COMMAND}`; export s; \
> @@ -1829,29 +1832,52 @@ do-clean: clean-stage[+id+]
> exit 0; \
> fi; \
> : $(MAKE); $(stage); \
> - rm -f .bad_compare; \
> + compare_id=$$$$; \
> + bad_compare=.bad_compare.$$compare_id; export bad_compare; \
> + compare_makefile=[+compare-target+].$$compare_id.mk; \
> + trap 'st=$$?; rm -f "$$compare_makefile" "$$bad_compare" \
> + "$$bad_compare".*; trap - 0; exit $$st' 0; \
> + trap 'exit 1' 1 2 3 15; \
> echo Comparing stages [+prev+] and [+id+]; \
> sed=`echo stage[+id+] | sed 's,^stage,,;s,.,.,g'`; \
> files=`find stage[+id+]-* -name "*$(objext)" -print | \
> sed -n s,^stage$$sed-,,p`; \
> - for file in $${files} ${extra-compare}; do \
> - f1=$$r/stage[+prev+]-$$file; f2=$$r/stage[+id+]-$$file; \
> - if test ! -f $$f1; then continue; fi; \
> - $(do-[+compare-target+]) > /dev/null 2>&1; \
> - if test $$? -eq 1; then \
> - case $$file in \
> - @compare_exclusions@) \
> - echo warning: $$file differs ;; \
> - *) \
> - echo $$file differs >> .bad_compare ;; \
> - esac; \
> - fi; \
> - done; \
> - if [ -f .bad_compare ]; then \
> + cmp_raw='$(do-[+compare-target+])'; \
> + { \
> + echo 'all:'; \
> + echo '.PHONY: all FORCE'; \
> + echo 'FORCE:'; \
> + printf '[+compare-target+]/%%: FORCE ; @'; \
> + printf 'f1=$$$$r/stage[+prev+]-$$*; '; \
> + printf 'f2=$$$$r/stage[+id+]-$$*; '; \
> + printf '%s' "$$cmp_raw" | sed 's,\$$,$$$$,g'; \
> + printf ' > /dev/null 2>&1; st=$$$$?; '; \
> + printf 'if test $$$$st -eq 1; then '; \
> + printf 'case $$* in '; \
> + printf '@compare_exclusions@) echo warning: $$* differs ;; '; \
> + printf '*) echo $$* differs >> "$$$$bad_compare.$$$$$$$$" ;; '; \
> + printf 'esac; '; \
> + printf 'elif test $$$$st -ne 0; then '; \
> + printf 'echo "$$* compare: error status $$$$st" '; \
> + printf '>> "$$$$bad_compare.$$$$$$$$"; fi\n'; \
> + for file in $${files} ${extra-compare}; do \
> + if test ! -f $$r/stage[+prev+]-$$file; then continue; fi; \
> + echo "all: [+compare-target+]/$$file"; \
> + done; \
> + } > "$$compare_makefile"; \
> + $(MAKE) -s -f "$$compare_makefile" all; compare_status=$$?; \
> + if test $$compare_status -ne 0; then \
> + exit $$compare_status; \
> + fi; \
> + set -- "$$bad_compare".*; \
> + if test -f "$$1"; then \
> echo "Bootstrap comparison failure!"; \
> - cat .bad_compare; \
> + LC_ALL=C sort "$$bad_compare".* > "$$bad_compare" || exit 1; \
> + cat "$$bad_compare"; \
> + mv -f "$$bad_compare" .bad_compare; \
> exit 1; \
> else \
> + rm -f .bad_compare; \
> echo Comparison successful.; \
> fi; \
> $(STAMP) [+compare-target+][+ IF prev +]
> diff --git a/config/acx.m4 b/config/acx.m4
> index ef5468bdd35..5547cbeb9b8 100644
> --- a/config/acx.m4
> +++ b/config/acx.m4
> @@ -477,7 +477,16 @@ AC_DEFUN([ACX_PROG_CMP_IGNORE_INITIAL],
> [AC_CACHE_CHECK([how to compare bootstrapped objects], gcc_cv_prog_cmp_skip,
> [ echo abfoo >t1
> echo cdfoo >t2
> - gcc_cv_prog_cmp_skip='tail -c +17 $$f1 > tmp-foo1; tail -c +17 $$f2 >
> tmp-foo2; cmp tmp-foo1 tmp-foo2'
> + gcc_cv_prog_cmp_skip='(trap "st=\$$?; rm -f tmp-foo1.$$$$ '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tmp-foo2.$$$$; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'trap - 0; exit \$$st" 0; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'trap "exit 2" 1 2 3 15; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tail -c +17 $$f1 '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'> tmp-foo1.$$$$ || exit 2; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tail -c +17 $$f2 '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'> tmp-foo2.$$$$ || exit 2; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'cmp tmp-foo1.$$$$ '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tmp-foo2.$$$$)'
> if cmp t1 t2 2 2 > /dev/null 2>&1; then
> if cmp t1 t2 1 1 > /dev/null 2>&1; then
> :
> diff --git a/configure b/configure
> index ad490083741..4db0edbdccd 100755
> --- a/configure
> +++ b/configure
> @@ -6123,7 +6123,16 @@ if ${gcc_cv_prog_cmp_skip+:} false; then :
> else
> echo abfoo >t1
> echo cdfoo >t2
> - gcc_cv_prog_cmp_skip='tail -c +17 $$f1 > tmp-foo1; tail -c +17 $$f2 >
> tmp-foo2; cmp tmp-foo1 tmp-foo2'
> + gcc_cv_prog_cmp_skip='(trap "st=\$$?; rm -f tmp-foo1.$$$$ '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tmp-foo2.$$$$; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'trap - 0; exit \$$st" 0; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'trap "exit 2" 1 2 3 15; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tail -c +17 $$f1 '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'> tmp-foo1.$$$$ || exit 2; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tail -c +17 $$f2 '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'> tmp-foo2.$$$$ || exit 2; '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'cmp tmp-foo1.$$$$ '
> + gcc_cv_prog_cmp_skip="$gcc_cv_prog_cmp_skip"'tmp-foo2.$$$$)'
> if cmp t1 t2 2 2 > /dev/null 2>&1; then
> if cmp t1 t2 1 1 > /dev/null 2>&1; then
> :
> --
> 2.50.1 (Apple Git-155)
>
