All my findings are documented in the GCC help mailing list thread here: https://gcc.gnu.org/pipermail/gcc-help/2021-May/140334.html In summary, GCC arm LTO assumes that all objects being linked have been built with the same kinds of arch and tune flags. This is not necessarily the case. In my case, I was building a project that set -mtune=arm946e-s for its object files, but the thumb newlib libc was not built with any mtune parameter. This causes an ICE during an lto1 pass. Reproducible: Always Steps to Reproduce: 1. Prepare an ARM cross compiler (arm-none-eabi) with crossdev 2. Follow the reduced example from the GCC bug report (in the URL) For convenience, here's the reduced reproduction example from the bug report (with slight modifications, tested so I could run this on my own system): arm-none-eabi-gcc -O -c -march=armv5te -flto t1.c arm-none-eabi-gcc -O -c -mcpu=arm946e-s -flto main.c arm-none-eabi-gcc -flto -o main main.o t1.o Where t1.c is int f() { return 1;} and main.c is int f(void); int main() { return f(); } Actual Results: lto1: internal compiler error: Segmentation fault Expected Results: Success building the example I may file an additional bug report, because the toolchain.eclass makes it impossible to build a cross-compilation toolchain with debugging symbols enabled (there's a check that if is_crosscompile is set then it forcibly sets *FLAGS to "-O2 -pipe"). After hacking the eclass I was able to build the cross-compiler with debugging symbols which then let me actually debug the problem, as I described in the gcc-help mailing list. For completeness, here's my own emerge --info: # emerge --info Portage 3.0.18 (python 3.8.10-final-0, default/linux/amd64/17.1/desktop/plasma, gcc-11.1.0, glibc-2.33, 5.12.2-gentoo x86_64) ================================================================= System uname: Linux-5.12.2-gentoo-x86_64-Intel-R-_Core-TM-_i7-3770K_CPU_@_3.50GHz-with-glibc2.2.5 KiB Mem: 16350004 total, 513880 free KiB Swap: 16776192 total, 11709688 free Timestamp of repository gentoo: Tue, 25 May 2021 05:20:07 +0000 Head commit of repository gentoo: 1f26aaf339afd3e7f313e6cac938856f119845b0 sh bash 5.1_p8 ld GNU ld (Gentoo 2.36.1 p3) 2.36.1 distcc 3.4 x86_64-pc-linux-gnu [disabled] ccache version 4.3 [disabled] app-shells/bash: 5.1_p8::gentoo dev-java/java-config: 2.3.1::gentoo dev-lang/perl: 5.32.1::gentoo dev-lang/python: 2.7.18_p10::gentoo, 3.7.10_p3::gentoo, 3.8.10_p1::gentoo, 3.9.5_p1::gentoo, 3.10.0_beta1::gentoo dev-lang/rust: 1.52.1::gentoo dev-util/ccache: 4.3::gentoo dev-util/cmake: 3.20.2::gentoo dev-util/pkgconfig: 0.29.2::gentoo sys-apps/baselayout: 2.7-r2::gentoo sys-apps/openrc: 0.43.3::gentoo sys-apps/sandbox: 2.24::gentoo sys-devel/autoconf: 2.13-r1::gentoo, 2.69-r5::gentoo sys-devel/automake: 1.16.3-r1::gentoo sys-devel/binutils: 2.36.1-r1::gentoo sys-devel/gcc: 10.3.0::gentoo, 11.1.0::gentoo sys-devel/gcc-config: 2.4::gentoo sys-devel/libtool: 2.4.6-r6::gentoo sys-devel/make: 4.3::gentoo sys-kernel/linux-headers: 5.12::gentoo (virtual/os-headers) sys-libs/glibc: 2.33::gentoo Repositories: gentoo location: /var/db/repos/gentoo sync-type: git sync-uri: git://github.com/gentoo-mirror/gentoo priority: -1000 sync-git-verify-commit-signature: true Local_Overlay location: /var/db/repos/local masters: gentoo eclass-overrides: gentoo Local_Overlay crossdev location: /var/db/repos/crossdev masters: gentoo eclass-overrides: gentoo crossdev brother-overlay location: /var/lib/layman/brother-overlay masters: gentoo priority: 50 guru location: /var/lib/layman/guru sync-type: laymansync sync-uri: https://anongit.gentoo.org/git/repo/proj/guru.git masters: gentoo priority: 50 ACCEPT_KEYWORDS="amd64 ~amd64" ACCEPT_LICENSE="@FREE" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /opt/brother/scanner/brscan4/brsanenetdevice4.cfg /usr/lib64/libreoffice/program/sofficerc /usr/share/config /usr/share/gnupg/qualified.txt" CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c" CXXFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" DISTDIR="/var/cache/distfiles" ENV_UNSET="CARGO_HOME DBUS_SESSION_BUS_ADDRESS DISPLAY GOBIN GOPATH PERL5LIB PERL5OPT PERLPREFIX PERL_CORE PERL_MB_OPT PERL_MM_OPT XAUTHORITY XDG_CACHE_HOME XDG_CONFIG_HOME XDG_DATA_HOME XDG_RUNTIME_DIR" FCFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" FEATURES="assume-digests binpkg-docompress binpkg-dostrip binpkg-logs binpkg-multi-instance clean-logs config-protect-if-modified distlocks ebuild-locks fixlafiles ipc-sandbox merge-sync multilib-strict network-sandbox news parallel-fetch pid-sandbox preserve-libs protect-owned qa-unresolved-soname-deps sandbox sfperms split-log strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr" FFLAGS="-march=ivybridge -pipe -fomit-frame-pointer -O3 -flto" GENTOO_MIRRORS="http://distfiles.gentoo.org" LANG="en_US.utf8" LDFLAGS="-Wl,-O1 -Wl,--as-needed" LINGUAS="en es" MAKEOPTS="-j9" PKGDIR="/var/cache/binpkgs" PORTAGE_CONFIGROOT="/" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git" PORTAGE_TMPDIR="/tmp" USE="=-ppp X a52 aac acl acpi activities alsa amd64 avx bash-completion berkdb bluetooth branding bzip2 cairo cdda cdr cli crypt cups dbus declarative dri dts dvd dvdr elogind emboss encode exif flac fortran gdbm gif gpm gtk gui iconv icu ipv6 jpeg kde kipi kwallet lcms libglvnd libnotify libtirpc lm-sensors lto mad mmx mng mp3 mp4 mpeg mtp multilib ncurses nls nptl nvidia ogg opengl openmp pam pango pcre pdf phonon plasma png policykit ppds pulseaudio qml qt qt5 readline sdl seccomp semantic-desktop spell split-usr sse sse2 sse3 sse4 ssl startup-notification svg tcpd tiff truetype udev udisks unicode upower usb vdpau vorbis widgets wxwidgets x264 xattr xcb xml xv xvid zeroconf zlib" ABI_X86="64" ADA_TARGET="gnat_2018" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="karbon sheets words" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="mmx mmxext sse sse2 aes avx f16c pclmul popcnt rdrand sse3 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock greis isync itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 timing tsip tripmate tnt ublox ubx" GRUB_PLATFORMS="efi-64 emu" INPUT_DEVICES="evdev roccat_tyon" KERNEL="linux" L10N="en es" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LLVM_TARGETS="AArch64 ARM RISCV WebAssembly" LUA_SINGLE_TARGET="lua5-1" LUA_TARGETS="lua5-1" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php7-3 php7-4" POSTGRES_TARGETS="postgres10 postgres11" PYTHON_SINGLE_TARGET="python3_8" PYTHON_TARGETS="python3_8" RUBY_TARGETS="ruby27 ruby30" SANE_BACKENDS="test" USERLAND="GNU" VIDEO_CARDS="nvidia" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq proto steal rawnat logmark ipmark dhcpmac delude chaos account" Unset: CC, CPPFLAGS, CTARGET, CXX, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LC_ALL, PORTAGE_BINHOST, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, RUSTFLAGS
Richard filed an upstream bug as: https://gcc.gnu.org/PR100767 We'll wait an upstream fix.
Upstream has committed a (tentative?) fix. I tested the upstream patch via user patches, and it does get rid of the ICE (although I'm running into what might very well be a different bug with undefined references to libc.a symbols).
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=f0adcd768cd9ceea562a91795774f2453e2da9b9 commit f0adcd768cd9ceea562a91795774f2453e2da9b9 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-05-29 09:22:33 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-05-29 09:22:33 +0000 11.1.0: backport PR100767: fix ICE on arm -flto march mix Reported-by: Gabriel Marcano Bug: https://bugs.gentoo.org/792291 Bug: https://gcc.gnu.org/PR100767 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> 11.1.0/gentoo/30_all_arm-lto-ICE-march-mix.patch | 153 +++++++++++++++++++++++ 11.1.0/gentoo/README.history | 1 + 2 files changed, 154 insertions(+)
The patch will be included in next gentoo's patchset tut (usually takes a few weeks). Meanwhile you can check if it helps by dropping path to /etc/portage/patches/sys-devel/gcc:11/ Patch itself: https://gitweb.gentoo.org/proj/gcc-patches.git/tree/11.1.0/gentoo/30_all_arm-lto-ICE-march-mix.patch
Yep, that's pretty much what I did to test the upstream patch, and I can confirm the LTO ICE is gone. There appears to be an ld.bfd bug also that causes undefined references to show up when LTO is enabled, but that's not an ICE so it's unrelated to this bug report. Thanks for the prompt reponse!
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/proj/gcc-patches.git/commit/?id=9d40799e2ef69d8650dd59325c0e84b902258b00 commit 9d40799e2ef69d8650dd59325c0e84b902258b00 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-06-10 07:28:54 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-06-10 07:28:54 +0000 11.1.0: cut 2 patchset Five new patches: + 27_all_msp430-f2c.patch: fix build on 16-bit targets + 28_all_ctor-union-PR100489.patch: fix ICE on some c++ initializers + 29_all_perfect-implicit-PR100644.patch: fix move deletion (fireofx build) + 30_all_arm-lto-ICE-march-mix.patch: fix LTO ICE on arm -march=/-mtune mix + 31_all_ICE-tsubst-PR100102.patch: Bug: https://gcc.gnu.org/PR100361 Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Bug: https://gcc.gnu.org/PR100644 Bug: https://bugs.gentoo.org/792705 Bug: https://gcc.gnu.org/PR100767 Bug: https://bugs.gentoo.org/792291 Bug: https://bugs.gentoo.org/794775 Bug: https://gcc.gnu.org/PR100102 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> 11.1.0/gentoo/README.history | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
The bug has been referenced in the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=b250f4243abd49acdd459751ae1e55c995bf9818 commit b250f4243abd49acdd459751ae1e55c995bf9818 Author: Sergei Trofimovich <slyfox@gentoo.org> AuthorDate: 2021-06-10 07:39:30 +0000 Commit: Sergei Trofimovich <slyfox@gentoo.org> CommitDate: 2021-06-10 07:50:31 +0000 sys-devel/gcc: 11.1.0: cut 2 patchset Five new patches: + 27_all_msp430-f2c.patch: fix build on 16-bit targets + 28_all_ctor-union-PR100489.patch: fix ICE on some c++ initializers + 29_all_perfect-implicit-PR100644.patch: fix move deletion (fireofx build) + 30_all_arm-lto-ICE-march-mix.patch: fix LTO ICE on arm -march=/-mtune mix + 31_all_ICE-tsubst-PR100102.patch: fix ICE in c++ tempate substitution Bug: https://gcc.gnu.org/PR100361 Bug: https://bugs.gentoo.org/788829 Bug: https://gcc.gnu.org/PR100489 Bug: https://gcc.gnu.org/PR100644 Bug: https://bugs.gentoo.org/792705 Bug: https://gcc.gnu.org/PR100767 Bug: https://bugs.gentoo.org/792291 Bug: https://bugs.gentoo.org/794775 Bug: https://gcc.gnu.org/PR100102 Package-Manager: Portage-3.0.19, Repoman-3.0.3 Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org> sys-devel/gcc/Manifest | 1 + sys-devel/gcc/gcc-11.1.0-r1.ebuild | 21 +++++++++++++++++++++ 2 files changed, 22 insertions(+)
Should be fixed in gcc-11.1.0-r1.
