maintainer-feedback requested: [Bug 258494] lang/erlang lang/erlang-runtime21 lang/erlang-runtime23: clang 13 build breaks dtrace if PGO is enabled
Date: Tue, 14 Sep 2021 08:07:11 UTC
Bugzilla Automation <bugzilla@FreeBSD.org> has asked freebsd-erlang (Nobody) <erlang@FreeBSD.org> for maintainer-feedback: Bug 258494: lang/erlang lang/erlang-runtime21 lang/erlang-runtime23: clang 13 build breaks dtrace if PGO is enabled https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258494 --- Description --- During an exp-run for llvm 13 (see bug 258209), it turned out that lang/erlang and lang/erlang-runtime2[1-3] fail to build with clang 13: http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m 09s/logs/errors/erlang-21.3.8.24_1,4.log http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m 09s/logs/errors/erlang-runtime21-21.3.8.24_1.log http://gohan04.nyi.freebsd.org/data/mainamd64PR258209-default/2021-09-05_20h27m 09s/logs/errors/erlang-runtime23-23.3.4.6.log What appears to happen is that for these versions of erlang, PGO is enabled, and it first builds a PGO-enabled beam.smp: gmake[5]: Entering directory '/wrkdirs/usr/ports/lang/erlang/work/otp-OTP-21.3.8.24/erts/emulator' if utils/gen_git_version amd64-portbld-freebsd14.0/gen_git_version.mk; then touch beam/erl_bif_info.c; fi echo " PROFILE beam.prof.smp" PROFILE beam.prof.smp rm -f obj/amd64-portbld-freebsd14.0/opt/smp/erl*.profraw set -e; LLVM_PROFILE_FILE="obj/amd64-portbld-freebsd14.0/opt/smp/erlc-%m.profraw" \ ERL_FLAGS="-emu_type prof +S 1" erlc -W -DPGO \ -o obj/amd64-portbld-freebsd14.0/opt/smp test/estone_SUITE.erl > obj/amd64-portbld-freebsd14.0/opt/smp/PROFILE_LOG after which it does a test run, and uses llvm-profdata to merge the profiling data into beam_emu_pu.o: llvm-profdata merge -output obj/amd64-portbld-freebsd14.0/opt/smp/default.profdata obj/amd64-portbld-freebsd14.0/opt/smp/*.profraw cc -fprofile-instr-use=obj/amd64-portbld-freebsd14.0/opt/smp/default.profdata -Werror=undef -Werror=implicit -Werror=return-type -O3 -fomit-frame-pointer -pipe -fno-omit-frame-pointer -DMAP_N ORESERVE=0 -fstack-protector-strong -fno-strict-aliasing -I/wrkdirs/usr/ports/lang/erlang/work/otp-OTP-21.3.8.24/erts/amd64-portbld-free bsd14.0 -DHAVE_CONFIG_H -Wall -Wstrict-prototypes -Wmis sing-prototypes -Wdeclaration-after-statement -DUSE_THREADS -D_THREAD_SAFE -D_REENTRANT -DPOSIX_THREADS -Iamd64-portbld-freebsd14.0/opt/smp -Ibeam -Isys/unix -Isys/common -Iamd64-portbld-freebs d14.0 -Ipcre -Ihipe -I../include -I../include/amd64-portbld-freebsd14.0 -I../include/internal -I../include/internal/amd64-portbld-freebsd14.0 -c beam/beam_emu.c -o obj/amd64-portbld-freebsd14.0/o pt/smp/beam_emu_pu.o Later, it runs dtrace over all the collected objects, and this dies: dtrace -G -C -Ibeam \ -s beam/erlang_dtrace.d \ -o obj/amd64-portbld-freebsd14.0/opt/smp/erlang_pu_dtrace.o ... long list of objects ... dtrace: failed to link script beam/erlang_dtrace.d: an error was encountered while processing obj/amd64-portbld-freebsd14.0/opt/smp/beam_emu_pu.o gmake[5]: *** [amd64-portbld-freebsd14.0/Makefile:1005: obj/amd64-portbld-freebsd14.0/opt/smp/erlang_pu_dtrace.o] Error 1 gmake[5]: Leaving directory '/wrkdirs/usr/ports/lang/erlang/work/otp-OTP-21.3.8.24/erts/emulator' Something in beam_emu_pu.o (emitted by clang or llvm 13) is tripping up dtrace, but I have very little knowledge about dtrace so I need help here. :) Now some other erlang runtimes such as lang/erlang-runtime24 *do* build successfully with clang 13, but this is only because upstream disabled the PGO feature, as a side effect of https://github.com/erlang/otp/commit/b165524c732 ("erts: Implement the BeamAsm JIT"): --- a/erts/configure.in +++ b/erts/configure.in ... @@ -704,6 +719,9 @@ else fi fi +dnl Disable pgo for now +USE_PGO=false + AC_SUBST(USE_PGO) AC_SUBST(PROFILE_COMPILER) (This took a *lot* of time to bisect due to erlang's afwul non-linear history... :) So, I'm unsure why upstream disabled this "for now", as it has been disabled for more than a year. We could work around the other erlang failures by also disabling PGO there, or with help from someone knowledgeable about dtrace, try to get to the bottom of why dtrace dies on clang 13 produced PGO object files.