https://github.com/python/cpython/commit/2fdccb3f88603cb72d311ca304ab7fcf9df12d00 commit: 2fdccb3f88603cb72d311ca304ab7fcf9df12d00 branch: 3.14 author: Miss Islington (bot) <[email protected]> committer: vstinner <[email protected]> date: 2026-04-16T17:46:06Z summary:
[3.14] gh-148535: Don't use gcc -fprofile-update=atomic flag on i686 (GH-148554) (#148655) gh-148535: Don't use gcc -fprofile-update=atomic flag on i686 (GH-148554) The -fprofile-update=atomic flag was added to fix a random GCC internal error on PGO build (gh-145801) caused by corruption of profile data (.gcda files). The problem is that it makes the PGO build way slower (up to 47x slower) on i686. Since the GCC internal error was not seen on i686 so far, don't use -fprofile-update=atomic on i686. (cherry picked from commit 2faceeec5c0fb06498a9654d429180ac4610c65a) Co-authored-by: Victor Stinner <[email protected]> files: A Misc/NEWS.d/next/Build/2026-04-14-15-20-29.gh-issue-148535.JjKiaa.rst M configure M configure.ac diff --git a/Misc/NEWS.d/next/Build/2026-04-14-15-20-29.gh-issue-148535.JjKiaa.rst b/Misc/NEWS.d/next/Build/2026-04-14-15-20-29.gh-issue-148535.JjKiaa.rst new file mode 100644 index 00000000000000..39f37acb14e098 --- /dev/null +++ b/Misc/NEWS.d/next/Build/2026-04-14-15-20-29.gh-issue-148535.JjKiaa.rst @@ -0,0 +1,6 @@ +No longer use the ``gcc -fprofile-update=atomic`` flag on i686. The flag has +been added to fix a random GCC internal error on PGO build (:gh:`145801`) +caused by corruption of profile data (.gcda files). The problem is that it +makes the PGO build way slower (up to 47x slower) on i686. Since the GCC +internal error was not seen on i686 so far, don't use +``-fprofile-update=atomic`` on i686 anymore. Patch by Victor Stinner. diff --git a/configure b/configure index 1cc1d2a2a54dd4..30590a397f8bc0 100755 --- a/configure +++ b/configure @@ -9050,7 +9050,57 @@ case "$ac_cv_cc_name" in fi ;; gcc) - { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fprofile-update=atomic" >&5 + # Check for 32-bit x86 ISA + { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for i686" >&5 +printf %s "checking for i686... " >&6; } +if test ${ac_cv_i686+y} +then : + printf %s "(cached) " >&6 +else case e in #( + e) + cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ + + + #ifdef __i386__ + # error "i386" + #endif + +int +main (void) +{ + + ; + return 0; +} + +_ACEOF +if ac_fn_c_try_compile "$LINENO" +then : + ac_cv_i686=no +else case e in #( + e) ac_cv_i686=yes ;; +esac +fi +rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext + ;; +esac +fi +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $ac_cv_i686" >&5 +printf "%s\n" "$ac_cv_i686" >&6; } + + PGO_PROF_GEN_FLAG="-fprofile-generate" + + # Use -fprofile-update=atomic to fix a random GCC internal error on PGO + # build (gh-145801) caused by corruption of profile data (.gcda files). + # + # gh-148535: On i686, using -fprofile-update=atomic makes the PGO build + # way slower (up to 47x slower). So far, the GCC internal error on PGO + # build was not seen on i686, so don't use this flag on i686. + if test "x$ac_cv_i686" = xno +then : + + { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fprofile-update=atomic" >&5 printf %s "checking whether C compiler accepts -fprofile-update=atomic... " >&6; } if test ${ax_cv_check_cflags___fprofile_update_atomic+y} then : @@ -9085,10 +9135,13 @@ fi printf "%s\n" "$ax_cv_check_cflags___fprofile_update_atomic" >&6; } if test "x$ax_cv_check_cflags___fprofile_update_atomic" = xyes then : - PGO_PROF_GEN_FLAG="-fprofile-generate -fprofile-update=atomic" + PGO_PROF_GEN_FLAG="$PGO_PROF_GEN_FLAG -fprofile-update=atomic" else case e in #( - e) PGO_PROF_GEN_FLAG="-fprofile-generate" ;; + e) : ;; esac +fi + + fi PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction" diff --git a/configure.ac b/configure.ac index 21cef7a98181b6..87c0ead45a61da 100644 --- a/configure.ac +++ b/configure.ac @@ -2072,10 +2072,32 @@ case "$ac_cv_cc_name" in fi ;; gcc) - AX_CHECK_COMPILE_FLAG( - [-fprofile-update=atomic], - [PGO_PROF_GEN_FLAG="-fprofile-generate -fprofile-update=atomic"], - [PGO_PROF_GEN_FLAG="-fprofile-generate"]) + # Check for 32-bit x86 ISA + AC_CACHE_CHECK([for i686], [ac_cv_i686], [ + AC_COMPILE_IFELSE([ + AC_LANG_PROGRAM([ + #ifdef __i386__ + # error "i386" + #endif + ], []) + ],[ac_cv_i686=no],[ac_cv_i686=yes]) + ]) + + PGO_PROF_GEN_FLAG="-fprofile-generate" + + # Use -fprofile-update=atomic to fix a random GCC internal error on PGO + # build (gh-145801) caused by corruption of profile data (.gcda files). + # + # gh-148535: On i686, using -fprofile-update=atomic makes the PGO build + # way slower (up to 47x slower). So far, the GCC internal error on PGO + # build was not seen on i686, so don't use this flag on i686. + AS_VAR_IF([ac_cv_i686], [no], [ + AX_CHECK_COMPILE_FLAG( + [-fprofile-update=atomic], + [PGO_PROF_GEN_FLAG="$PGO_PROF_GEN_FLAG -fprofile-update=atomic"], + []) + ]) + PGO_PROF_USE_FLAG="-fprofile-use -fprofile-correction" LLVM_PROF_MERGER="true" LLVM_PROF_FILE="" _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
