mirror of
https://sourceware.org/git/glibc.git
synced 2025-01-11 11:50:06 +00:00
98ad631cd0
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. |
||
|---|---|---|
| .. | ||
| aarch64 | ||
| alpha | ||
| arm | ||
| generic | ||
| gnu | ||
| hppa | ||
| i386 | ||
| ia64 | ||
| ieee754 | ||
| init_array | ||
| m68k | ||
| mach | ||
| microblaze | ||
| mips | ||
| nacl | ||
| nios2 | ||
| nptl | ||
| posix | ||
| powerpc | ||
| pthread | ||
| s390 | ||
| sh | ||
| sparc | ||
| tile | ||
| unix | ||
| wordsize-32 | ||
| wordsize-64 | ||
| x86 | ||
| x86_64 | ||