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1b6d733c98
As [1] says, we cannot mix up lock-free and locking atomics for one
object. For example assume atom = (0, 0) initially, if we have a
locking "atomic" xor running on T0 and a lock-free store running on T1
concurrently:
T0 | T1
-----------------------------+-------------------------------------
acquire_lock |
t0 = atom[0] |
/* some CPU cycles */ | atom = (1, 1) /* lock-free atomic */
t1 = atom[1] |
t0 ^= 1 |
t1 ^= 1 |
atom[0] = t0 |
atom[1] = t1 |
release_lock |
we get atom = (0, 1), but the atomicity of xor and store should
guarantee that atom is either (0, 0) or (1, 1).
So, if we want to use a lock-free 16B atomic operation, we need both LSX
and SCQ even if that specific operation only needs one of them. To make
things worse, one may link a TU compiled with -mlsx -mscq and another
without them together, then if we want to use the lock-free 16B atomic
operations in the former, we must make libatomic also use the lock-free
16B atomic operation for the latter so we need to add ifuncs for
libatomic, similar to the discussion about i386 vs. i486 in [1].
Implementing and building the ifuncs currently requires:
- Glibc, because the ifunc resolver interface is libc-specific
- Linux, because the HWCAP bit for LSX is kernel-specific
- A recent enough assembler at build time to recognize sc.q
So the approach here is: only allow 16B lock-free atomic operations in
the compiler if the criteria above is satisfied, and ensure libatomic to
use those lock-free operations on capable hardware (via ifunc unless
both LSX and SCQ are already enabled by the builder) if the compiler
allows 16B lock-free atomic.
[1]: https://gcc.gnu.org/wiki/Atomic/GCCMM/LIbrary
gcc/
* configure.ac (HAVE_AS_16B_ATOMIC): Define if the assembler
supports LSX and sc.q.
* configure: Regenerate.
* config.in: Regenerate.
* config/loongarch/loongarch-opts.h (HAVE_AS_16B_ATOMIC):
Defined to 0 if undefined yet.
* config/loongarch/linux.h (HAVE_IFUNC_FOR_LIBATOMIC_16B):
Define as HAVE_AS_16B_ATOMIC && OPTION_GLIBC.
* config/loongarch/loongarch-protos.h
(loongarch_16b_atomic_lock_free_p): New prototype.
* config/loongarch/loongarch.cc
(loongarch_16b_atomic_lock_free_p): Implement.
* config/loongarch/sync.md (atomic_storeti_lsx): Require
loongarch_16b_atomic_lock_free_p.
(atomic_storeti): Likewise.
(atomic_exchangeti_scq): Likewise.
(atomic_exchangeti): Likewise.
(atomic_compare_and_swapti): Likewise.
(atomic_fetch_<amop_ti_fetch>ti_scq): Likewise.
(atomic_fetch_<amop_ti_fetch>ti): Likewise.
(ALL_SC): Likewise for TImode.
(atomic_storeti_scq): Remove.
libatomic/
* configure.ac (ARCH_LOONGARCH): New AM_CONDITIONAL.
* Makefile.am (IFUNC_OPT): Separate the item from IFUNC_OPTIONS
to allow using multiple options for an ISA variant.
(libatomic_la_LIBADD): Add *_16_1_.lo for LoongArch.
(IFUNC_OPTIONS): Build *_16_1_.lo for LoongArch with -mlsx and
-mscq.
* configure: Regenerate.
* Makefile.in: Regenerate.
* configure.tgt (try_ifunc): Set to yes for LoongArch if the
compiler can produce lock-free 16B atomic with -mlsx -mscq.
* config/loongarch/host-config.h: Implement ifunc selector.
192 lines
6.8 KiB
Makefile
192 lines
6.8 KiB
Makefile
## Copyright (C) 2012-2025 Free Software Foundation, Inc.
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## Contributed by Richard Henderson <rth@redhat.com>.
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##
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## This file is part of the GNU Atomic Library (libatomic).
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##
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## Libatomic is free software; you can redistribute it and/or modify it
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## under the terms of the GNU General Public License as published by
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## the Free Software Foundation; either version 3 of the License, or
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## (at your option) any later version.
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##
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## Libatomic is distributed in the hope that it will be useful, but WITHOUT ANY
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## WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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## FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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## more details.
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##
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## Under Section 7 of GPL version 3, you are granted additional
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## permissions described in the GCC Runtime Library Exception, version
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## 3.1, as published by the Free Software Foundation.
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##
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## You should have received a copy of the GNU General Public License and
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## a copy of the GCC Runtime Library Exception along with this program;
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## see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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## <http://www.gnu.org/licenses/>.
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ACLOCAL_AMFLAGS = -I .. -I ../config
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SUBDIRS = testsuite
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## May be used by toolexeclibdir.
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gcc_version := $(shell @get_gcc_base_ver@ $(top_srcdir)/../gcc/BASE-VER)
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config_path= @config_path@
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search_path = $(addprefix $(top_srcdir)/config/, $(config_path)) \
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$(top_srcdir) $(top_builddir)
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vpath % $(strip $(search_path))
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DEFAULT_INCLUDES = $(addprefix -I, $(search_path))
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AM_CFLAGS = $(XCFLAGS)
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AM_CCASFLAGS = $(XCFLAGS)
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AM_LDFLAGS = $(XLDFLAGS) $(SECTION_LDFLAGS) $(OPT_LDFLAGS)
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toolexeclib_LTLIBRARIES = libatomic.la
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noinst_LTLIBRARIES = libatomic_convenience.la
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if LIBAT_BUILD_VERSIONED_SHLIB
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if LIBAT_BUILD_VERSIONED_SHLIB_GNU
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libatomic_version_script = -Wl,--version-script,$(top_srcdir)/libatomic.map
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libatomic_version_dep = $(top_srcdir)/libatomic.map
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endif
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if LIBAT_BUILD_VERSIONED_SHLIB_SUN
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libatomic_version_script = -Wl,-M,libatomic.map-sun
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libatomic_version_dep = libatomic.map-sun
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libatomic.map-sun : $(top_srcdir)/libatomic.map \
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$(top_srcdir)/../contrib/make_sunver.pl \
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$(libatomic_la_OBJECTS) $(libatomic_la_LIBADD)
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perl $(top_srcdir)/../contrib/make_sunver.pl \
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$(top_srcdir)/libatomic.map \
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$(libatomic_la_OBJECTS) $(libatomic_la_LIBADD) \
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> $@ || (rm -f $@ ; exit 1)
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endif
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else
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libatomic_version_script =
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libatomic_version_dep =
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endif
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libatomic_version_info = -version-info $(libtool_VERSION)
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if ENABLE_DARWIN_AT_RPATH
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libatomic_darwin_rpath = -Wc,-nodefaultrpaths
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libatomic_darwin_rpath += -Wl,-rpath,@loader_path
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endif
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libatomic_la_LDFLAGS = $(libatomic_version_info) $(libatomic_version_script) \
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-Wc,-fno-link-libatomic $(lt_host_flags) $(libatomic_darwin_rpath)
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SIZES = @SIZES@
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if PARTIAL_VXWORKS
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libatomic_la_SOURCES = fenv.c fence.c flag.c
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else
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libatomic_la_SOURCES = gload.c gstore.c gcas.c gexch.c glfree.c lock.c init.c \
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fenv.c fence.c flag.c
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SIZEOBJS = load store cas exch fadd fsub fand fior fxor fnand tas
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EXTRA_libatomic_la_SOURCES = $(addsuffix _n.c,$(SIZEOBJS))
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libatomic_la_DEPENDENCIES = $(libatomic_la_LIBADD) $(libatomic_version_dep)
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## And now our custom target patterns that allow us not to have tons of
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## extra source files hanging about. Unfortunately, the complex relation
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## between source and object filenames doesn't allow us to add an explicit
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## dependency here. Fortunately that doesn't matter since auto-generated
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## dependencies do the job just as well:
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-include $(wildcard $(DEPDIR)/*.Ppo)
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## Naming pattern: base_n_i_.lo
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##
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## N size of data
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## I IFUNC alternative, index beginning at 1.
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##
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## The trailing _ in the output object file name is required to differentiate
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## these objects from those which should be compiled normally. We can only
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## have one stem in the implicit rule.
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empty =
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space = $(empty) $(empty)
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PAT_SPLIT = $(subst _,$(space),$(*F))
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PAT_BASE = $(word 1,$(PAT_SPLIT))
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PAT_N = $(word 2,$(PAT_SPLIT))
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PAT_S = $(word 3,$(PAT_SPLIT))
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IFUNC_DEF = -DIFUNC_ALT=$(PAT_S)
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IFUNC_OPT = $(subst |,$(space),$(word $(PAT_S),$(IFUNC_OPTIONS)))
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@AMDEP_TRUE@M_DEPS = -MT $@ -MD -MP -MF $(DEPDIR)/$(@F).Ppo
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@AMDEP_FALSE@M_DEPS =
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M_SIZE = -DN=$(PAT_N)
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M_IFUNC = $(if $(PAT_S),$(IFUNC_DEF) $(IFUNC_OPT))
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M_FILE = $(PAT_BASE)_n.c
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# The lack of explicit dependency on the source file means that VPATH cannot
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# work properly. Instead, perform this operation by hand. First, collect a
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# list of all .c files in the search path.
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all_c_files := $(foreach dir,$(search_path),$(wildcard $(dir)/*.c))
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# Then sort through them to find the one we want, and select the first.
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M_SRC = $(firstword $(filter %/$(M_FILE), $(all_c_files)))
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%_.lo: Makefile
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$(LTCOMPILE) $(M_DEPS) $(M_SIZE) $(M_IFUNC) -c -o $@ $(M_SRC)
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## Include all of the sizes in the "normal" set of compilation flags.
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libatomic_la_LIBADD = $(foreach s,$(SIZES),$(addsuffix _$(s)_.lo,$(SIZEOBJS)))
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## On a target-specific basis, include alternates to be selected by IFUNC.
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if HAVE_IFUNC
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if ARCH_AARCH64_LINUX
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IFUNC_OPTIONS = -march=armv8-a+lse
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libatomic_la_LIBADD += $(foreach s,$(SIZES),$(addsuffix _$(s)_1_.lo,$(SIZEOBJS)))
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endif
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if ARCH_ARM_LINUX
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IFUNC_OPTIONS = -march=armv7-a+fp -DHAVE_KERNEL64
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libatomic_la_LIBADD += $(foreach s,$(SIZES),$(addsuffix _$(s)_1_.lo,$(SIZEOBJS)))
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libatomic_la_LIBADD += $(addsuffix _8_2_.lo,$(SIZEOBJS))
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libatomic_la_LIBADD += tas_1_2_.lo
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endif
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if ARCH_I386
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IFUNC_OPTIONS = -march=i586
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libatomic_la_LIBADD += $(addsuffix _8_1_.lo,$(SIZEOBJS))
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endif
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if ARCH_X86_64
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IFUNC_OPTIONS = -mcx16 -mcx16
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libatomic_la_LIBADD += $(addsuffix _16_1_.lo,$(SIZEOBJS)) \
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$(addsuffix _16_2_.lo,$(SIZEOBJS))
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endif
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if ARCH_LOONGARCH
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IFUNC_OPTIONS = -mlsx|-mscq
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libatomic_la_LIBADD += $(addsuffix _16_1_.lo,$(SIZEOBJS))
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endif
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endif
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if ARCH_AARCH64_LINUX
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libatomic_la_SOURCES += atomic_16.S
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endif
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endif
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libatomic_convenience_la_SOURCES = $(libatomic_la_SOURCES)
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libatomic_convenience_la_LIBADD = $(libatomic_la_LIBADD)
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# Amend the automake generated all-multi rule to guarantee that all-multi
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# is not run in parallel with the %_.lo rules which generate $(DEPDIR)/*.Ppo
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# makefile fragments to avoid broken *.Ppo getting included into the Makefile
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# when it is reloaded during the build of all-multi.
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all-multi: $(libatomic_la_LIBADD)
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# Copy built libatomic library to $build/gcc so it's easier to locate,
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# similar to libgcc.
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#
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# FIXME: libtool --mode=install also ends up copying libatomic.la in $gcc_objdir,
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# which (somehow) ends up adding $gcc_objdir to RPATH for libraries that get
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# built after libatomic, which makes RPATH insecure. Removing libatomic.la
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# from $gcc_objdir seems to fix the issue.
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gcc_objdir = `pwd`/$(MULTIBUILDTOP)../../gcc/
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all-local: libatomic.la
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$(LIBTOOL) --mode=install $(INSTALL_DATA) libatomic.la $(gcc_objdir)$(MULTISUBDIR)/
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rm $(gcc_objdir)$(MULTISUBDIR)/libatomic.la
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# target overrides
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-include $(tmake_file)
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include $(top_srcdir)/../multilib.am
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