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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.
This commit is contained in:
H.J. Lu
parent
83c01ab32b
commit
98ad631cd0
24
ChangeLog
24
ChangeLog
@ -1,3 +1,27 @@
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2015-10-15 H.J. Lu <hongjiu.lu@intel.com>
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* sysdeps/unix/sysv/linux/i386/libc-do-syscall.S
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(__libc_do_syscall): Defined only if !__GNUC_PREREQ (5,0).
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* sysdeps/unix/sysv/linux/i386/sysdep.h: Define assembler macros
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only if !__GNUC_PREREQ (5,0).
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(INTERNAL_SYSCALL_MAIN_6): Optimize for GCC 5.
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(INTERNAL_SYSCALL_MAIN_INLINE): Likewise.
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(INTERNAL_SYSCALL_NCS): Likewise.
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(LOADREGS_0): New macro for GCC 5.
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(ASMARGS_0): Likewise.
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(LOADREGS_1): Likewise.
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(ASMARGS_1): Likewise.
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(LOADREGS_2): Likewise.
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(ASMARGS_2): Likewise.
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(LOADREGS_3): Likewise.
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(ASMARGS_3): Likewise.
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(LOADREGS_4): Likewise.
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(ASMARGS_4): Likewise.
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(LOADREGS_5): Likewise.
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(ASMARGS_5): Likewise.
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(LOADREGS_6): Likewise.
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(ASMARGS_6): Likewise.
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2015-10-15 H.J. Lu <hongjiu.lu@intel.com>
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* sysdeps/unix/sysv/linux/i386/Makefile (CFLAGS-mmap.c): Add
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@ -18,6 +18,8 @@
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#include <sysdep.h>
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#if !__GNUC_PREREQ (5,0)
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/* %eax, %ecx, %edx and %esi contain the values expected by the kernel.
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%edi points to a structure with the values of %ebx, %edi and %ebp. */
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@ -48,3 +50,4 @@ ENTRY (__libc_do_syscall)
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cfi_restore (ebx)
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ret
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END (__libc_do_syscall)
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#endif
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@ -227,6 +227,7 @@
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extern int __syscall_error (int)
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attribute_hidden __attribute__ ((__regparm__ (1)));
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#if !__GNUC_PREREQ (5,0)
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/* We need some help from the assembler to generate optimal code. We
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define some macros here which later will be used. */
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asm (".L__X'%ebx = 1\n\t"
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@ -266,6 +267,7 @@ struct libc_do_syscall_args
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{
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int ebx, edi, ebp;
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};
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#endif
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/* Define a macro which expands inline into the wrapper code for a system
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call. */
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@ -322,7 +324,11 @@ struct libc_do_syscall_args
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INTERNAL_SYSCALL_MAIN_INLINE(name, err, 5, args)
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/* Each object using 6-argument inline syscalls must include a
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definition of __libc_do_syscall. */
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#define INTERNAL_SYSCALL_MAIN_6(name, err, arg1, arg2, arg3, \
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#if __GNUC_PREREQ (5,0)
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# define INTERNAL_SYSCALL_MAIN_6(name, err, args...) \
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INTERNAL_SYSCALL_MAIN_INLINE(name, err, 6, args)
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#else /* GCC 5 */
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# define INTERNAL_SYSCALL_MAIN_6(name, err, arg1, arg2, arg3, \
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arg4, arg5, arg6) \
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struct libc_do_syscall_args _xv = \
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{ \
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@ -336,12 +342,50 @@ struct libc_do_syscall_args
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: "=a" (resultvar) \
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: "i" (__NR_##name), "c" (arg2), "d" (arg3), "S" (arg4), "D" (&_xv) \
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: "memory", "cc")
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#endif /* GCC 5 */
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#define INTERNAL_SYSCALL(name, err, nr, args...) \
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({ \
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register unsigned int resultvar; \
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INTERNAL_SYSCALL_MAIN_##nr (name, err, args); \
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(int) resultvar; })
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#ifdef I386_USE_SYSENTER
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# if __GNUC_PREREQ (5,0)
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# ifdef SHARED
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# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
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LOADREGS_##nr(args) \
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asm volatile ( \
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"call *%%gs:%P2" \
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: "=a" (resultvar) \
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: "a" (__NR_##name), "i" (offsetof (tcbhead_t, sysinfo)) \
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ASMARGS_##nr(args) : "memory", "cc")
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# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
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({ \
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register unsigned int resultvar; \
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LOADREGS_##nr(args) \
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asm volatile ( \
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"call *%%gs:%P2" \
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: "=a" (resultvar) \
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: "a" (name), "i" (offsetof (tcbhead_t, sysinfo)) \
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ASMARGS_##nr(args) : "memory", "cc"); \
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(int) resultvar; })
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# else
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# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
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LOADREGS_##nr(args) \
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asm volatile ( \
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"call *_dl_sysinfo" \
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: "=a" (resultvar) \
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: "a" (__NR_##name) ASMARGS_##nr(args) : "memory", "cc")
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# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
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({ \
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register unsigned int resultvar; \
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LOADREGS_##nr(args) \
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asm volatile ( \
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"call *_dl_sysinfo" \
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: "=a" (resultvar) \
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: "a" (name) ASMARGS_##nr(args) : "memory", "cc"); \
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(int) resultvar; })
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# endif
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# else /* GCC 5 */
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# ifdef SHARED
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# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
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EXTRAVAR_##nr \
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@ -387,7 +431,25 @@ struct libc_do_syscall_args
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: "0" (name) ASMFMT_##nr(args) : "memory", "cc"); \
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(int) resultvar; })
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# endif
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# endif /* GCC 5 */
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#else
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# if __GNUC_PREREQ (5,0)
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# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
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LOADREGS_##nr(args) \
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asm volatile ( \
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"int $0x80" \
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: "=a" (resultvar) \
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: "a" (__NR_##name) ASMARGS_##nr(args) : "memory", "cc")
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# define INTERNAL_SYSCALL_NCS(name, err, nr, args...) \
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({ \
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register unsigned int resultvar; \
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LOADREGS_##nr(args) \
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asm volatile ( \
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"int $0x80" \
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: "=a" (resultvar) \
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: "a" (name) ASMARGS_##nr(args) : "memory", "cc"); \
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(int) resultvar; })
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# else /* GCC 5 */
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# define INTERNAL_SYSCALL_MAIN_INLINE(name, err, nr, args...) \
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EXTRAVAR_##nr \
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asm volatile ( \
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@ -408,6 +470,7 @@ struct libc_do_syscall_args
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: "=a" (resultvar) \
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: "0" (name) ASMFMT_##nr(args) : "memory", "cc"); \
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(int) resultvar; })
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# endif /* GCC 5 */
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#endif
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#undef INTERNAL_SYSCALL_DECL
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@ -472,6 +535,36 @@ struct libc_do_syscall_args
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# define RESTOREARGS_5
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#endif
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#if __GNUC_PREREQ (5,0)
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# define LOADREGS_0()
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# define ASMARGS_0()
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# define LOADREGS_1(arg1) \
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LOADREGS_0 ()
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# define ASMARGS_1(arg1) \
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ASMARGS_0 (), "b" ((unsigned int) (arg1))
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# define LOADREGS_2(arg1, arg2) \
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LOADREGS_1 (arg1)
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# define ASMARGS_2(arg1, arg2) \
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ASMARGS_1 (arg1), "c" ((unsigned int) (arg2))
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# define LOADREGS_3(arg1, arg2, arg3) \
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LOADREGS_2 (arg1, arg2)
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# define ASMARGS_3(arg1, arg2, arg3) \
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ASMARGS_2 (arg1, arg2), "d" ((unsigned int) (arg3))
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# define LOADREGS_4(arg1, arg2, arg3, arg4) \
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LOADREGS_3 (arg1, arg2, arg3)
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# define ASMARGS_4(arg1, arg2, arg3, arg4) \
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ASMARGS_3 (arg1, arg2, arg3), "S" ((unsigned int) (arg4))
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# define LOADREGS_5(arg1, arg2, arg3, arg4, arg5) \
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LOADREGS_4 (arg1, arg2, arg3, arg4)
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# define ASMARGS_5(arg1, arg2, arg3, arg4, arg5) \
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ASMARGS_4 (arg1, arg2, arg3, arg4), "D" ((unsigned int) (arg5))
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# define LOADREGS_6(arg1, arg2, arg3, arg4, arg5, arg6) \
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register unsigned int _a6 asm ("ebp") = (unsigned int) (arg6); \
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LOADREGS_5 (arg1, arg2, arg3, arg4, arg5)
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# define ASMARGS_6(arg1, arg2, arg3, arg4, arg5, arg6) \
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ASMARGS_5 (arg1, arg2, arg3, arg4, arg5), "r" (_a6)
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#endif /* GCC 5 */
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#define ASMFMT_0()
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#ifdef __PIC__
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# define ASMFMT_1(arg1) \
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