These machine-dependent inline string functions have never been on by
default, and even if they were a good idea at the time they were
introduced, they haven't really been touched in ten to fifteen years
and probably aren't a good idea on current-gen processors. Current
thinking is that this class of optimization is best left to the
compiler.
* bits/string.h, string/bits/string.h
* sysdeps/aarch64/bits/string.h
* sysdeps/m68k/m680x0/m68020/bits/string.h
* sysdeps/s390/bits/string.h, sysdeps/sparc/bits/string.h
* sysdeps/x86/bits/string.h: Delete file.
* string/string.h: Don't include bits/string.h.
* string/bits/string3.h: Rename to bits/string_fortified.h.
No need to undef various symbols that the removed headers
might have defined as macros.
* string/Makefile (headers): Remove bits/string.h, change
bits/string3.h to bits/string_fortified.h.
* string/string-inlines.c: Update commentary. Remove definitions
of various macros that nothing looks at anymore. Don't directly
include bits/string.h. Set _STRING_INLINE_unaligned here, based on
compiler-predefined macros.
* string/strncat.c: If STRNCAT is not defined, or STRNCAT_PRIMARY
_is_ defined, provide internal hidden alias __strncat.
* include/string.h: Declare internal hidden alias __strncat.
Only forward __stpcpy to __builtin_stpcpy if __NO_STRING_INLINES is
not defined.
* include/bits/string3.h: Rename to bits/string_fortified.h,
update to match above.
* sysdeps/i386/string-inlines.c: Define compat symbols for
everything formerly defined by sysdeps/x86/bits/string.h.
Make existing definitions into compat symbols as well.
Remove some no-longer-necessary messing around with macros.
* sysdeps/powerpc/powerpc32/power4/multiarch/mempcpy.c
* sysdeps/powerpc/powerpc64/multiarch/mempcpy.c
* sysdeps/powerpc/powerpc64/multiarch/stpcpy.c
* sysdeps/s390/multiarch/mempcpy.c
No need to define _HAVE_STRING_ARCH_mempcpy.
Do define __NO_STRING_INLINES and NO_MEMPCPY_STPCPY_REDIRECT.
* sysdeps/i386/i686/multiarch/strncat-c.c
* sysdeps/s390/multiarch/strncat-c.c
* sysdeps/x86_64/multiarch/strncat-c.c
Define STRNCAT_PRIMARY. Don't change definition of libc_hidden_def.
This patch optimizes the generic spinlock code.
The type pthread_spinlock_t is a typedef to volatile int on all archs.
Passing a volatile pointer to the atomic macros which are not mapped to the
C11 atomic builtins can lead to extra stores and loads to stack if such
a macro creates a temporary variable by using "__typeof (*(mem)) tmp;".
Thus, those macros which are used by spinlock code - atomic_exchange_acquire,
atomic_load_relaxed, atomic_compare_exchange_weak - have to be adjusted.
According to the comment from Szabolcs Nagy, the type of a cast expression is
unqualified (see http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_423.htm):
__typeof ((__typeof (*(mem)) *(mem)) tmp;
Thus from spinlock perspective the variable tmp is of type int instead of
type volatile int. This patch adjusts those macros in include/atomic.h.
With this construct GCC >= 5 omits the extra stores and loads.
The atomic macros are replaced by the C11 like atomic macros and thus
the code is aligned to it. The pthread_spin_unlock implementation is now
using release memory order instead of sequentially consistent memory order.
The issue with passed volatile int pointers applies to the C11 like atomic
macros as well as the ones used before.
I've added a glibc_likely hint to the first atomic exchange in
pthread_spin_lock in order to return immediately to the caller if the lock is
free. Without the hint, there is an additional jump if the lock is free.
I've added the atomic_spin_nop macro within the loop of plain reads.
The plain reads are also realized by C11 like atomic_load_relaxed macro.
The new define ATOMIC_EXCHANGE_USES_CAS determines if the first try to acquire
the spinlock in pthread_spin_lock or pthread_spin_trylock is an exchange
or a CAS. This is defined in atomic-machine.h for all architectures.
The define SPIN_LOCK_READS_BETWEEN_CMPXCHG is now removed.
There is no technical reason for throwing in a CAS every now and then,
and so far we have no evidence that it can improve performance.
If that would be the case, we have to adjust other spin-waiting loops
elsewhere, too! Using a CAS loop without plain reads is not a good idea
on many targets and wasn't used by one. Thus there is now no option to
do so.
Architectures are now using the generic spinlock automatically if they
do not provide an own implementation. Thus the pthread_spin_lock.c files
in sysdeps folder are deleted.
ChangeLog:
* NEWS: Mention new spinlock implementation.
* include/atomic.h:
(__atomic_val_bysize): Cast type to omit volatile qualifier.
(atomic_exchange_acq): Likewise.
(atomic_load_relaxed): Likewise.
(ATOMIC_EXCHANGE_USES_CAS): Check definition.
* nptl/pthread_spin_init.c (pthread_spin_init):
Use atomic_store_relaxed.
* nptl/pthread_spin_lock.c (pthread_spin_lock):
Use C11-like atomic macros.
* nptl/pthread_spin_trylock.c (pthread_spin_trylock):
Likewise.
* nptl/pthread_spin_unlock.c (pthread_spin_unlock):
Use atomic_store_release.
* sysdeps/aarch64/nptl/pthread_spin_lock.c: Delete File.
* sysdeps/arm/nptl/pthread_spin_lock.c: Likewise.
* sysdeps/hppa/nptl/pthread_spin_lock.c: Likewise.
* sysdeps/m68k/nptl/pthread_spin_lock.c: Likewise.
* sysdeps/microblaze/nptl/pthread_spin_lock.c: Likewise.
* sysdeps/mips/nptl/pthread_spin_lock.c: Likewise.
* sysdeps/nios2/nptl/pthread_spin_lock.c: Likewise.
* sysdeps/aarch64/atomic-machine.h (ATOMIC_EXCHANGE_USES_CAS): Define.
* sysdeps/alpha/atomic-machine.h: Likewise.
* sysdeps/arm/atomic-machine.h: Likewise.
* sysdeps/i386/atomic-machine.h: Likewise.
* sysdeps/ia64/atomic-machine.h: Likewise.
* sysdeps/m68k/coldfire/atomic-machine.h: Likewise.
* sysdeps/m68k/m680x0/m68020/atomic-machine.h: Likewise.
* sysdeps/microblaze/atomic-machine.h: Likewise.
* sysdeps/mips/atomic-machine.h: Likewise.
* sysdeps/powerpc/powerpc32/atomic-machine.h: Likewise.
* sysdeps/powerpc/powerpc64/atomic-machine.h: Likewise.
* sysdeps/s390/atomic-machine.h: Likewise.
* sysdeps/sparc/sparc32/atomic-machine.h: Likewise.
* sysdeps/sparc/sparc32/sparcv9/atomic-machine.h: Likewise.
* sysdeps/sparc/sparc64/atomic-machine.h: Likewise.
* sysdeps/tile/tilegx/atomic-machine.h: Likewise.
* sysdeps/tile/tilepro/atomic-machine.h: Likewise.
* sysdeps/unix/sysv/linux/hppa/atomic-machine.h: Likewise.
* sysdeps/unix/sysv/linux/m68k/coldfire/atomic-machine.h: Likewise.
* sysdeps/unix/sysv/linux/nios2/atomic-machine.h: Likewise.
* sysdeps/unix/sysv/linux/sh/atomic-machine.h: Likewise.
* sysdeps/x86_64/atomic-machine.h: Likewise.
As discussed in
https://sourceware.org/ml/libc-alpha/2015-10/msg00403.html
the setting of _STRING_ARCH_unaligned currently controls the external
GLIBC ABI as well as selecting the use of unaligned accesses withing
GLIBC.
Since _STRING_ARCH_unaligned was recently changed for AArch64, this
would potentially break the ABI in GLIBC 2.23, so split the uses and add
_STRING_INLINE_unaligned to select the string ABI. This setting must be
fixed for each target, while _STRING_ARCH_unaligned may be changed from
release to release. _STRING_ARCH_unaligned is used unconditionally in
glibc. But <bits/string.h>, which defines _STRING_ARCH_unaligned, isn't
included with -Os. Since _STRING_ARCH_unaligned is internal to glibc and
may change between glibc releases, it should be made private to glibc.
_STRING_ARCH_unaligned should defined in the new string_private.h heade
file which is included unconditionally from internal <string.h> for glibc
build.
[BZ #19462]
* bits/string.h (_STRING_ARCH_unaligned): Renamed to ...
(_STRING_INLINE_unaligned): This.
* include/string.h: Include <string_private.h>.
* string/bits/string2.h: Replace _STRING_ARCH_unaligned with
_STRING_INLINE_unaligned.
* sysdeps/aarch64/bits/string.h (_STRING_ARCH_unaligned): Removed.
(_STRING_INLINE_unaligned): New.
* sysdeps/aarch64/string_private.h: New file.
* sysdeps/generic/string_private.h: Likewise.
* sysdeps/m68k/m680x0/m68020/string_private.h: Likewise.
* sysdeps/s390/string_private.h: Likewise.
* sysdeps/x86/string_private.h: Likewise.
* sysdeps/m68k/m680x0/m68020/bits/string.h
(_STRING_ARCH_unaligned): Renamed to ...
(_STRING_INLINE_unaligned): This.
* sysdeps/s390/bits/string.h (_STRING_ARCH_unaligned): Renamed
to ...
(_STRING_INLINE_unaligned): This.
* sysdeps/sparc/bits/string.h (_STRING_ARCH_unaligned): Renamed
to ...
(_STRING_INLINE_unaligned): This.
* sysdeps/x86/bits/string.h (_STRING_ARCH_unaligned): Renamed
to ...
(_STRING_INLINE_unaligned): This.
It was noted in
<https://sourceware.org/ml/libc-alpha/2012-09/msg00305.html> that the
bits/*.h naming scheme should only be used for installed headers.
This patch renames bits/atomic.h to atomic-machine.h to follow that
convention.
This is the only change in this series that needs to change the
filename rather than simply removing a directory level (because both
atomic.h and bits/atomic.h exist at present).
Tested for x86_64 (testsuite, and that installed stripped shared
libraries are unchanged by the patch).
[BZ #14912]
* sysdeps/aarch64/bits/atomic.h: Move to ...
* sysdeps/aarch64/atomic-machine.h: ...here.
(_AARCH64_BITS_ATOMIC_H): Rename macro to
_AARCH64_ATOMIC_MACHINE_H.
* sysdeps/alpha/bits/atomic.h: Move to ...
* sysdeps/alpha/atomic-machine.h: ...here.
* sysdeps/arm/bits/atomic.h: Move to ...
* sysdeps/arm/atomic-machine.h: ...here. Update comments.
* bits/atomic.h: Move to ...
* sysdeps/generic/atomic-machine.h: ...here.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/i386/bits/atomic.h: Move to ...
* sysdeps/i386/atomic-machine.h: ...here.
* sysdeps/ia64/bits/atomic.h: Move to ...
* sysdeps/ia64/atomic-machine.h: ...here.
* sysdeps/m68k/coldfire/bits/atomic.h: Move to ...
* sysdeps/m68k/coldfire/atomic-machine.h: ...here.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/m68k/m680x0/m68020/bits/atomic.h: Move to ...
* sysdeps/m68k/m680x0/m68020/atomic-machine.h: ...here.
* sysdeps/microblaze/bits/atomic.h: Move to ...
* sysdeps/microblaze/atomic-machine.h: ...here.
* sysdeps/mips/bits/atomic.h: Move to ...
* sysdeps/mips/atomic-machine.h: ...here.
(_MIPS_BITS_ATOMIC_H): Rename macro to _MIPS_ATOMIC_MACHINE_H.
* sysdeps/powerpc/bits/atomic.h: Move to ...
* sysdeps/powerpc/atomic-machine.h: ...here. Update comments.
* sysdeps/powerpc/powerpc32/bits/atomic.h: Move to ...
* sysdeps/powerpc/powerpc32/atomic-machine.h: ...here. Update
comments. Include <atomic-machine.h> instead of <bits/atomic.h>.
* sysdeps/powerpc/powerpc64/bits/atomic.h: Move to ...
* sysdeps/powerpc/powerpc64/atomic-machine.h: ...here. Include
<atomic-machine.h> instead of <bits/atomic.h>.
* sysdeps/s390/bits/atomic.h: Move to ...
* sysdeps/s390/atomic-machine.h: ...here.
* sysdeps/sparc/sparc32/bits/atomic.h: Move to ...
* sysdeps/sparc/sparc32/atomic-machine.h: ...here.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/sparc/sparc32/sparcv9/bits/atomic.h: Move to ...
* sysdeps/sparc/sparc32/sparcv9/atomic-machine.h: ...here.
* sysdeps/sparc/sparc64/bits/atomic.h: Move to ...
* sysdeps/sparc/sparc64/atomic-machine.h: ...here.
* sysdeps/tile/bits/atomic.h: Move to ...
* sysdeps/tile/atomic-machine.h: ...here.
* sysdeps/tile/tilegx/bits/atomic.h: Move to ...
* sysdeps/tile/tilegx/atomic-machine.h: ...here. Include
<sysdeps/tile/atomic-machine.h> instead of
<sysdeps/tile/bits/atomic.h>.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/tile/tilepro/bits/atomic.h: Move to ...
* sysdeps/tile/tilepro/atomic-machine.h: ...here. Include
<sysdeps/tile/atomic-machine.h> instead of
<sysdeps/tile/bits/atomic.h>.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/unix/sysv/linux/arm/bits/atomic.h: Move to ...
* sysdeps/unix/sysv/linux/arm/atomic-machine.h: ...here. Include
<sysdeps/arm/atomic-machine.h> instead of
<sysdeps/arm/bits/atomic.h>.
* sysdeps/unix/sysv/linux/hppa/bits/atomic.h: Move to ...
* sysdeps/unix/sysv/linux/hppa/atomic-machine.h: ...here.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/unix/sysv/linux/m68k/coldfire/bits/atomic.h: Move to ...
* sysdeps/unix/sysv/linux/m68k/coldfire/atomic-machine.h: ...here.
(_BITS_ATOMIC_H): Rename macro to _ATOMIC_MACHINE_H.
* sysdeps/unix/sysv/linux/nios2/bits/atomic.h: Move to ...
* sysdeps/unix/sysv/linux/nios2/atomic-machine.h: ...here.
(_NIOS2_BITS_ATOMIC_H): Rename macro to _NIOS2_ATOMIC_MACHINE_H.
* sysdeps/unix/sysv/linux/sh/bits/atomic.h: Move to ...
* sysdeps/unix/sysv/linux/sh/atomic-machine.h: ...here.
* sysdeps/x86_64/bits/atomic.h: Move to ...
* sysdeps/x86_64/atomic-machine.h: ...here.
* include/atomic.h: Include <atomic-machine.h> instead of
<bits/atomic.h>.
This sets __HAVE_64B_ATOMICS if provided. It also sets
USE_ATOMIC_COMPILER_BUILTINS to true if the existing atomic ops use the
__atomic* builtins (aarch64, mips partially) or if this has been
tested (x86_64); otherwise, this is set to false so that C11 atomics will
be based on the existing atomic operations.
