Location via proxy:   [ UP ]  
[Report a bug]   [Manage cookies]                
Skip to content

Commit 78c09bd

Browse files
committed
jit: Use -mno-outline-atomics for bitcode on ARM.
If the executable's .o files were produced by a compiler (probably gcc) not using -moutline-atomics, and the corresponding .bc files were produced by clang using -moutline-atomics (probably by default), then the generated bitcode functions would have the target attribute "+outline-atomics", and could fail at runtime when inlined. If the target ISA at bitcode generation time was armv8-a (the most conservative aarch64 target, no LSE), then LLVM IR atomic instructions would generate calls to functions in libgcc.a or libclang_rt.*.a that switch between LL/SC and faster LSE instructions depending on a runtime AT_HWCAP check. Since the corresponding .o files didn't need those functions, they wouldn't have been included in the executable, and resolution would fail. At least Debian and Ubuntu are known to ship gcc and clang compilers that target armv8-a but differ on the use of outline atomics by default. Fix, by suppressing the outline atomics attribute in bitcode explicitly. Inline LL/SC instructions will be generated for atomic operations in bitcode built for armv8-a. Only configure scripts are adjusted for now, because the meson build system doesn't generate bitcode yet. This doesn't seem to be a new phenomenon, so real cases of functions using atomics that are inlined by JIT must be rare in the wild given how long it took for a bug report to arrive. The reported case could be reduced to: postgres=# set jit_inline_above_cost = 0; SET postgres=# set jit_above_cost = 0; SET postgres=# select pg_last_wal_receive_lsn(); WARNING: failed to resolve name __aarch64_swp4_acq_rel FATAL: fatal llvm error: Program used external function '__aarch64_swp4_acq_rel' which could not be resolved! The change doesn't affect non-ARM systems or later target ISAs. Back-patch to all supported releases. Reported-by: Alexander Kozhemyakin <a.kozhemyakin@postgrespro.ru> Discussion: https://postgr.es/m/18610-37bf303f904fede3%40postgresql.org
1 parent c06e71d commit 78c09bd

File tree

2 files changed

+112
-0
lines changed

2 files changed

+112
-0
lines changed

configure

+105
Original file line numberDiff line numberDiff line change
@@ -7283,6 +7283,111 @@ if test x"$pgac_cv_prog_CLANGXX_cxxflags__fexcess_precision_standard" = x"yes";
72837283
fi
72847284

72857285

7286+
# Ideally bitcode should perhaps match $CC's use, or not, of outline atomic
7287+
# functions, but for now we err on the side of suppressing them in bitcode,
7288+
# because we can't assume they're available at runtime. This affects aarch64
7289+
# builds using the basic armv8-a ISA without LSE support.
7290+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CLANG} supports -mno-outline-atomics, for BITCODE_CFLAGS" >&5
7291+
$as_echo_n "checking whether ${CLANG} supports -mno-outline-atomics, for BITCODE_CFLAGS... " >&6; }
7292+
if ${pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics+:} false; then :
7293+
$as_echo_n "(cached) " >&6
7294+
else
7295+
pgac_save_CXXFLAGS=$CXXFLAGS
7296+
pgac_save_CXX=$CXX
7297+
CXX=${CLANG}
7298+
CXXFLAGS="${BITCODE_CFLAGS} -mno-outline-atomics"
7299+
ac_save_cxx_werror_flag=$ac_cxx_werror_flag
7300+
ac_cxx_werror_flag=yes
7301+
ac_ext=cpp
7302+
ac_cpp='$CXXCPP $CPPFLAGS'
7303+
ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
7304+
ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
7305+
ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
7306+
7307+
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
7308+
/* end confdefs.h. */
7309+
7310+
int
7311+
main ()
7312+
{
7313+
7314+
;
7315+
return 0;
7316+
}
7317+
_ACEOF
7318+
if ac_fn_cxx_try_compile "$LINENO"; then :
7319+
pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics=yes
7320+
else
7321+
pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics=no
7322+
fi
7323+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
7324+
ac_ext=c
7325+
ac_cpp='$CPP $CPPFLAGS'
7326+
ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
7327+
ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
7328+
ac_compiler_gnu=$ac_cv_c_compiler_gnu
7329+
7330+
ac_cxx_werror_flag=$ac_save_cxx_werror_flag
7331+
CXXFLAGS="$pgac_save_CXXFLAGS"
7332+
CXX="$pgac_save_CXX"
7333+
fi
7334+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics" >&5
7335+
$as_echo "$pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics" >&6; }
7336+
if test x"$pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics" = x"yes"; then
7337+
BITCODE_CFLAGS="${BITCODE_CFLAGS} -mno-outline-atomics"
7338+
fi
7339+
7340+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CLANG} supports -mno-outline-atomics, for BITCODE_CXXFLAGS" >&5
7341+
$as_echo_n "checking whether ${CLANG} supports -mno-outline-atomics, for BITCODE_CXXFLAGS... " >&6; }
7342+
if ${pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics+:} false; then :
7343+
$as_echo_n "(cached) " >&6
7344+
else
7345+
pgac_save_CXXFLAGS=$CXXFLAGS
7346+
pgac_save_CXX=$CXX
7347+
CXX=${CLANG}
7348+
CXXFLAGS="${BITCODE_CXXFLAGS} -mno-outline-atomics"
7349+
ac_save_cxx_werror_flag=$ac_cxx_werror_flag
7350+
ac_cxx_werror_flag=yes
7351+
ac_ext=cpp
7352+
ac_cpp='$CXXCPP $CPPFLAGS'
7353+
ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
7354+
ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
7355+
ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
7356+
7357+
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
7358+
/* end confdefs.h. */
7359+
7360+
int
7361+
main ()
7362+
{
7363+
7364+
;
7365+
return 0;
7366+
}
7367+
_ACEOF
7368+
if ac_fn_cxx_try_compile "$LINENO"; then :
7369+
pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics=yes
7370+
else
7371+
pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics=no
7372+
fi
7373+
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
7374+
ac_ext=c
7375+
ac_cpp='$CPP $CPPFLAGS'
7376+
ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
7377+
ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
7378+
ac_compiler_gnu=$ac_cv_c_compiler_gnu
7379+
7380+
ac_cxx_werror_flag=$ac_save_cxx_werror_flag
7381+
CXXFLAGS="$pgac_save_CXXFLAGS"
7382+
CXX="$pgac_save_CXX"
7383+
fi
7384+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics" >&5
7385+
$as_echo "$pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics" >&6; }
7386+
if test x"$pgac_cv_prog_CLANG_cxxflags__mno_outline_atomics" = x"yes"; then
7387+
BITCODE_CXXFLAGS="${BITCODE_CXXFLAGS} -mno-outline-atomics"
7388+
fi
7389+
7390+
72867391
NOT_THE_CFLAGS=""
72877392
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CLANG} supports -Wunused-command-line-argument, for NOT_THE_CFLAGS" >&5
72887393
$as_echo_n "checking whether ${CLANG} supports -Wunused-command-line-argument, for NOT_THE_CFLAGS... " >&6; }

configure.ac

+7
Original file line numberDiff line numberDiff line change
@@ -633,6 +633,13 @@ if test "$with_llvm" = yes ; then
633633
PGAC_PROG_VARCC_VARFLAGS_OPT(CLANG, BITCODE_CFLAGS, [-fexcess-precision=standard])
634634
PGAC_PROG_VARCXX_VARFLAGS_OPT(CLANGXX, BITCODE_CXXFLAGS, [-fexcess-precision=standard])
635635

636+
# Ideally bitcode should perhaps match $CC's use, or not, of outline atomic
637+
# functions, but for now we err on the side of suppressing them in bitcode,
638+
# because we can't assume they're available at runtime. This affects aarch64
639+
# builds using the basic armv8-a ISA without LSE support.
640+
PGAC_PROG_VARCXX_VARFLAGS_OPT(CLANG, BITCODE_CFLAGS, [-mno-outline-atomics])
641+
PGAC_PROG_VARCXX_VARFLAGS_OPT(CLANG, BITCODE_CXXFLAGS, [-mno-outline-atomics])
642+
636643
NOT_THE_CFLAGS=""
637644
PGAC_PROG_VARCC_VARFLAGS_OPT(CLANG, NOT_THE_CFLAGS, [-Wunused-command-line-argument])
638645
if test -n "$NOT_THE_CFLAGS"; then

0 commit comments

Comments
 (0)