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| author | H.J. Lu <hjl.tools@gmail.com> | 2015-10-15 05:23:42 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2015-10-15 05:23:58 -0700 |
| commit | 98ad631cd0a77205734abf4f2bb368a8560a08cf (patch) | |
| tree | 0c1c77ca47f7db8df6bf81395ad0d3d5ad91f82f /ChangeLog | |
| parent | 83c01ab32b9aa7b27e4e88ed2969d14549e33c5c (diff) | |
| download | glibc-98ad631cd0a77205734abf4f2bb368a8560a08cf.tar glibc-98ad631cd0a77205734abf4f2bb368a8560a08cf.tar.gz glibc-98ad631cd0a77205734abf4f2bb368a8560a08cf.tar.bz2 glibc-98ad631cd0a77205734abf4f2bb368a8560a08cf.zip | |
Optimize i386 syscall inlining for GCC 5
Since GCC 5 and above can properly spill %ebx when needed, we can inline
syscalls with 6 arguments if GCC 5 or above is used to compile glibc.
This patch rewrites INTERNAL_SYSCALL macros and skips __libc_do_syscall
for GCC 5.
For sysdeps/unix/sysv/linux/i386/brk.c, with -O2 -march=i686
-mtune=generic, GCC 5.2 now generates:
<__brk>:
0: push %ebx
1: mov $0x2d,%eax
6: mov 0x8(%esp),%ebx
a: call b <__brk+0xb> b: R_386_PC32 __x86.get_pc_thunk.dx
f: add $0x2,%edx 11: R_386_GOTPC _GLOBAL_OFFSET_TABLE_
15: call *%gs:0x10
1c: mov 0x0(%edx),%edx 1e: R_386_GOT32 __curbrk
22: cmp %eax,%ebx
24: mov %eax,(%edx)
26: ja 30 <__brk+0x30>
28: xor %eax,%eax
2a: pop %ebx
2b: ret
instead of
<__brk>:
0: push %ebx
1: mov 0x8(%esp),%ecx
5: call 6 <__brk+0x6> 6: R_386_PC32 __x86.get_pc_thunk.bx
a: add $0x2,%ebx c: R_386_GOTPC _GLOBAL_OFFSET_TABLE_
10: xchg %ecx,%ebx
12: mov $0x2d,%eax
17: call *%gs:0x10
1e: xchg %ecx,%ebx
20: mov %eax,%edx
22: mov 0x0(%ebx),%eax 24: R_386_GOT32 __curbrk
28: mov %edx,(%eax)
2a: xor %eax,%eax
2c: cmp %edx,%ecx
2e: ja 38 <__brk+0x38>
30: pop %ebx
31: ret
The new one is shorter by 2 instructions.
* sysdeps/unix/sysv/linux/i386/libc-do-syscall.S
(__libc_do_syscall): Defined only if !__GNUC_PREREQ (5,0).
* sysdeps/unix/sysv/linux/i386/sysdep.h: Define assembler macros
only if !__GNUC_PREREQ (5,0).
(INTERNAL_SYSCALL_MAIN_6): Optimize for GCC 5.
(INTERNAL_SYSCALL_MAIN_INLINE): Likewise.
(INTERNAL_SYSCALL_NCS): Likewise.
(LOADREGS_0): New macro for GCC 5.
(ASMARGS_0): Likewise.
(LOADREGS_1): Likewise.
(ASMARGS_1): Likewise.
(LOADREGS_2): Likewise.
(ASMARGS_2): Likewise.
(LOADREGS_3): Likewise.
(ASMARGS_3): Likewise.
(LOADREGS_4): Likewise.
(ASMARGS_4): Likewise.
(LOADREGS_5): Likewise.
(ASMARGS_5): Likewise.
(LOADREGS_6): Likewise.
(ASMARGS_6): Likewise.
Diffstat (limited to 'ChangeLog')
| -rw-r--r-- | ChangeLog | 24 |
1 files changed, 24 insertions, 0 deletions
@@ -1,5 +1,29 @@ 2015-10-15 H.J. Lu <hongjiu.lu@intel.com> + * sysdeps/unix/sysv/linux/i386/libc-do-syscall.S + (__libc_do_syscall): Defined only if !__GNUC_PREREQ (5,0). + * sysdeps/unix/sysv/linux/i386/sysdep.h: Define assembler macros + only if !__GNUC_PREREQ (5,0). + (INTERNAL_SYSCALL_MAIN_6): Optimize for GCC 5. + (INTERNAL_SYSCALL_MAIN_INLINE): Likewise. + (INTERNAL_SYSCALL_NCS): Likewise. + (LOADREGS_0): New macro for GCC 5. + (ASMARGS_0): Likewise. + (LOADREGS_1): Likewise. + (ASMARGS_1): Likewise. + (LOADREGS_2): Likewise. + (ASMARGS_2): Likewise. + (LOADREGS_3): Likewise. + (ASMARGS_3): Likewise. + (LOADREGS_4): Likewise. + (ASMARGS_4): Likewise. + (LOADREGS_5): Likewise. + (ASMARGS_5): Likewise. + (LOADREGS_6): Likewise. + (ASMARGS_6): Likewise. + +2015-10-15 H.J. Lu <hongjiu.lu@intel.com> + * sysdeps/unix/sysv/linux/i386/Makefile (CFLAGS-mmap.c): Add -fomit-frame-pointer. (CFLAGS-mmap64.c): Likewise. |