From cfc09b1ecf0c6981494fd73dffe234416f66af10 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Tue, 11 Sep 2012 02:23:47 -0400 Subject: [PATCH] improve mips syscall asm constraints to use immediates, if possible by using the "ir" constraint (immediate or register) and the carefully constructed instruction addu $2,$0,%2 which can take either an immediate or a register for %2, the new inline asm admits maximal optimization with no register spillage to the stack when the compiler successfully performs constant propagration, but still works by allocating a register when the syscall number cannot be recognized as a constant. in the case of syscalls with 0-3 arguments it barely matters, but for 4-argument syscalls, using an immediate for the syscall number avoids creating a stack frame for the syscall wrapper function. --- arch/mips/syscall_arch.h | 33 +++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 12 deletions(-) diff --git a/arch/mips/syscall_arch.h b/arch/mips/syscall_arch.h index 58904765..b1e68ffb 100644 --- a/arch/mips/syscall_arch.h +++ b/arch/mips/syscall_arch.h @@ -10,8 +10,8 @@ #define __asm_syscall(...) do { \ register long r2 __asm__("$2"); \ __asm__ __volatile__ ( \ - "move $2,$7 ; syscall" \ - : "=&r"(r2), "=r"(r7) : __VA_ARGS__ \ + "addu $2,$0,%2 ; syscall" \ + : "=&r"(r2), "=r"(r7) : "ir"(n), __VA_ARGS__, "r"(r2) \ : "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13", \ "$14", "$15", "$24", "$25", "hi", "lo", "memory"); \ return r7 ? -r2 : r2; \ @@ -19,32 +19,41 @@ static inline long __syscall0(long n) { - register long r7 __asm__("$7") = n; - __asm_syscall("r"(r7)); + register long r7 __asm__("$7"); + __asm_syscall("i"(0)); } static inline long __syscall1(long n, long a) { - register long r7 __asm__("$7") = n; register long r4 __asm__("$4") = a; - __asm_syscall("r"(r7), "r"(r4)); + register long r7 __asm__("$7"); + __asm_syscall("r"(r4)); } static inline long __syscall2(long n, long a, long b) { - register long r7 __asm__("$7") = n; register long r4 __asm__("$4") = a; register long r5 __asm__("$5") = b; - __asm_syscall("r"(r7), "r"(r4), "r"(r5)); + register long r7 __asm__("$7"); + __asm_syscall("r"(r4), "r"(r5)); } static inline long __syscall3(long n, long a, long b, long c) { - register long r7 __asm__("$7") = n; register long r4 __asm__("$4") = a; register long r5 __asm__("$5") = b; register long r6 __asm__("$6") = c; - __asm_syscall("r"(r7), "r"(r4), "r"(r5), "r"(r6)); + register long r7 __asm__("$7"); + __asm_syscall("r"(r4), "r"(r5), "r"(r6)); +} + +static inline long __syscall4(long n, long a, long b, long c, long d) +{ + register long r4 __asm__("$4") = a; + register long r5 __asm__("$5") = b; + register long r6 __asm__("$6") = c; + register long r7 __asm__("$7") = d; + __asm_syscall("r"(r4), "r"(r5), "r"(r6), "r"(r7)); } #else @@ -69,13 +78,13 @@ static inline long __syscall3(long n, long a, long b, long c) return (__syscall)(n, a, b, c); } -#endif - static inline long __syscall4(long n, long a, long b, long c, long d) { return (__syscall)(n, a, b, c, d); } +#endif + static inline long __syscall5(long n, long a, long b, long c, long d, long e) { return (__syscall)(n, a, b, c, d, e); -- 2.25.1