During an exp-run for llvm 13 (see bug 258209), it turned out that
lang/erlang and lang/erlang-runtime2[13] fail to build with clang 13.
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_NORESERVE=0 -fstack-protector-strong -fno-strict-aliasing -I/wrkdirs/usr/ports/lang/erlang/work/otp-OTP-21.3.8.24/erts/amd64-portbld-freebsd14.0 -DHAVE_CONFIG_H -Wall -Wstrict-prototypes -Wmissing-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-freebsd14.0 -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/opt/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)
I am unsure why upstream disabled this "for now", as it has been
disabled for more than a year. So, for now, work around the dtrace
failures by disabling PGO using the configure flag --disable-pgo, when
building with clang >= 13.
PR: 258494
Approved by: maintainer timeout (2 weeks)
MFH: 2021Q4
9ce64e9190