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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.
This commit is contained in:
Rich Felker 2012-09-11 02:23:47 -04:00
parent b94067eeae
commit cfc09b1ecf
1 changed files with 21 additions and 12 deletions
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33
arch/mips/syscall_arch.h
View File

@ -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);