mirror of git://sourceware.org/git/glibc.git
d7e4c642ef
This patch optimizes both __lll_lock_wait_private and __lll_lock_wait by issuing only one lll_futex_wait. Since it is defined as an inlined syscall and inlined syscalls are defined using inlined assembly the compiler usually can not see both calls are equal and optimize accordingly. On aarch64 the resulting binary is change from: 0000000000000060 <__lll_lock_wait>: 60: 2a0103e5 mov w5, w1 64: b9400001 ldr w1, [x0] 68: aa0003e4 mov x4, x0 6c: 7100083f cmp w1, #0x2 70: 540000e1 b.ne 8c <__lll_lock_wait+0x2c> // b.any 74: 521900a1 eor w1, w5, #0x80 78: d2800042 mov x2, #0x2 // #2 7c: 93407c21 sxtw x1, w1 80: d2800003 mov x3, #0x0 // #0 84: d2800c48 mov x8, #0x62 // #98 88: d4000001 svc #0x0 8c: 521900a5 eor w5, w5, #0x80 90: 52800046 mov w6, #0x2 // #2 94: 93407ca5 sxtw x5, w5 98: 14000008 b b8 <__lll_lock_wait+0x58> 9c: d503201f nop a0: aa0403e0 mov x0, x4 a4: aa0503e1 mov x1, x5 a8: d2800042 mov x2, #0x2 // #2 ac: d2800003 mov x3, #0x0 // #0 b0: d2800c48 mov x8, #0x62 // #98 b4: d4000001 svc #0x0 b8: 885ffc80 ldaxr w0, [x4] bc: 88017c86 stxr w1, w6, [x4] c0: 35ffffc1 cbnz w1, b8 <__lll_lock_wait+0x58> c4: 35fffee0 cbnz w0, a0 <__lll_lock_wait+0x40> c8: d65f03c0 ret To: 0000000000000048 <__lll_lock_wait>: 48: aa0003e4 mov x4, x0 4c: 2a0103e5 mov w5, w1 50: b9400000 ldr w0, [x0] 54: 7100081f cmp w0, #0x2 58: 540000c0 b.eq 70 <__lll_lock_wait+0x28> // b.none 5c: 52800041 mov w1, #0x2 // #2 60: 885ffc80 ldaxr w0, [x4] 64: 88027c81 stxr w2, w1, [x4] 68: 35ffffc2 cbnz w2, 60 <__lll_lock_wait+0x18> 6c: 34000120 cbz w0, 90 <__lll_lock_wait+0x48> 70: 521900a1 eor w1, w5, #0x80 74: aa0403e0 mov x0, x4 78: 93407c21 sxtw x1, w1 7c: d2800042 mov x2, #0x2 // #2 80: d2800003 mov x3, #0x0 // #0 84: d2800c48 mov x8, #0x62 // #98 88: d4000001 svc #0x0 8c: 17fffff4 b 5c <__lll_lock_wait+0x14> 90: d65f03c0 ret I see similar changes on powerpc and other architectures. It also aligns with x86_64 implementation by adding the systemtap probes. Checker on aarch64-linux-gnu. * nptl/lowlevellock.c (__lll_lock_wait, __lll_lock_wait_private): Optimize futex call and add systemtap probe. |
||
|---|---|---|
| ChangeLog.old | ||
| argp | ||
| assert | ||
| benchtests | ||
| bits | ||
| catgets | ||
| conform | ||
| crypt | ||
| csu | ||
| ctype | ||
| debug | ||
| dirent | ||
| dlfcn | ||
| elf | ||
| gmon | ||
| gnulib | ||
| grp | ||
| gshadow | ||
| hesiod | ||
| htl | ||
| hurd | ||
| iconv | ||
| iconvdata | ||
| include | ||
| inet | ||
| intl | ||
| io | ||
| libio | ||
| locale | ||
| localedata | ||
| login | ||
| mach | ||
| malloc | ||
| manual | ||
| math | ||
| mathvec | ||
| misc | ||
| nis | ||
| nptl | ||
| nptl_db | ||
| nscd | ||
| nss | ||
| po | ||
| posix | ||
| pwd | ||
| resolv | ||
| resource | ||
| rt | ||
| scripts | ||
| setjmp | ||
| shadow | ||
| signal | ||
| socket | ||
| soft-fp | ||
| stdio-common | ||
| stdlib | ||
| string | ||
| sunrpc | ||
| support | ||
| sysdeps | ||
| sysvipc | ||
| termios | ||
| time | ||
| timezone | ||
| wcsmbs | ||
| wctype | ||
| .gitattributes | ||
| .gitignore | ||
| COPYING | ||
| COPYING.LIB | ||
| ChangeLog | ||
| INSTALL | ||
| LICENSES | ||
| MAINTAINERS | ||
| Makeconfig | ||
| Makefile | ||
| Makefile.in | ||
| Makerules | ||
| NEWS | ||
| README | ||
| Rules | ||
| abi-tags | ||
| aclocal.m4 | ||
| config.h.in | ||
| config.make.in | ||
| configure | ||
| configure.ac | ||
| extra-lib.mk | ||
| gen-locales.mk | ||
| libc-abis | ||
| libof-iterator.mk | ||
| o-iterator.mk | ||
| shlib-versions | ||
| test-skeleton.c | ||
| version.h | ||
README
This directory contains the sources of the GNU C Library. See the file "version.h" for what release version you have. The GNU C Library is the standard system C library for all GNU systems, and is an important part of what makes up a GNU system. It provides the system API for all programs written in C and C-compatible languages such as C++ and Objective C; the runtime facilities of other programming languages use the C library to access the underlying operating system. In GNU/Linux systems, the C library works with the Linux kernel to implement the operating system behavior seen by user applications. In GNU/Hurd systems, it works with a microkernel and Hurd servers. The GNU C Library implements much of the POSIX.1 functionality in the GNU/Hurd system, using configurations i[4567]86-*-gnu. When working with Linux kernels, this version of the GNU C Library requires Linux kernel version 3.2 or later. Also note that the shared version of the libgcc_s library must be installed for the pthread library to work correctly. The GNU C Library supports these configurations for using Linux kernels: aarch64*-*-linux-gnu alpha*-*-linux-gnu arm-*-linux-gnueabi csky-*-linux-gnuabiv2 hppa-*-linux-gnu i[4567]86-*-linux-gnu x86_64-*-linux-gnu Can build either x86_64 or x32 ia64-*-linux-gnu m68k-*-linux-gnu microblaze*-*-linux-gnu mips-*-linux-gnu mips64-*-linux-gnu powerpc-*-linux-gnu Hardware or software floating point, BE only. powerpc64*-*-linux-gnu Big-endian and little-endian. s390-*-linux-gnu s390x-*-linux-gnu riscv64-*-linux-gnu sh[34]-*-linux-gnu sparc*-*-linux-gnu sparc64*-*-linux-gnu If you are interested in doing a port, please contact the glibc maintainers; see http://www.gnu.org/software/libc/ for more information. See the file INSTALL to find out how to configure, build, and install the GNU C Library. You might also consider reading the WWW pages for the C library at http://www.gnu.org/software/libc/. The GNU C Library is (almost) completely documented by the Texinfo manual found in the `manual/' subdirectory. The manual is still being updated and contains some known errors and omissions; we regret that we do not have the resources to work on the manual as much as we would like. For corrections to the manual, please file a bug in the `manual' component, following the bug-reporting instructions below. Please be sure to check the manual in the current development sources to see if your problem has already been corrected. Please see http://www.gnu.org/software/libc/bugs.html for bug reporting information. We are now using the Bugzilla system to track all bug reports. This web page gives detailed information on how to report bugs properly. The GNU C Library is free software. See the file COPYING.LIB for copying conditions, and LICENSES for notices about a few contributions that require these additional notices to be distributed. License copyright years may be listed using range notation, e.g., 1996-2015, indicating that every year in the range, inclusive, is a copyrightable year that would otherwise be listed individually.