[Bug 258494] lang/erlang lang/erlang-runtime21 lang/erlang-runtime23: clang 13 build breaks dtrace if PGO is enabled

From: <bugzilla-noreply_at_freebsd.org>
Date: Sun, 03 Oct 2021 10:20:27 UTC

--- Comment #3 from commit-hook@FreeBSD.org ---
A commit in branch main references this bug:


commit 9ce64e91907aaa43fc43a7b2faaae5bf99faaa56
Author:     Dimitry Andric <dim@FreeBSD.org>
AuthorDate: 2021-10-02 14:52:35 +0000
Commit:     Dimitry Andric <dim@FreeBSD.org>
CommitDate: 2021-10-03 10:13:35 +0000

    lang/(erlang(-runtime2[13])?): work around dtrace failures with clang 13

    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
    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 >

    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
-Werror=undef -Werror=implicit -Werror=return-type   -O3 -fomit-frame-pointer
-pipe  -fno-omit-frame-pointer -DMAP_NORESERVE=0 -fstack-protector-strong
   -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

    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
      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

    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

    +dnl Disable pgo for now

    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

 lang/erlang-runtime21/Makefile | 7 ++++++-
 lang/erlang-runtime23/Makefile | 7 ++++++-
 lang/erlang/Makefile           | 7 ++++++-
 3 files changed, 18 insertions(+), 3 deletions(-)

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