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authorRich Felker <dalias@aerifal.cx>2012-09-11 02:23:47 -0400
committerRich Felker <dalias@aerifal.cx>2012-09-11 02:23:47 -0400
commitcfc09b1ecf0c6981494fd73dffe234416f66af10 (patch)
tree6771fdf3c0f6efad93919597e327da9ba0495877 /arch/mips/bits/fcntl.h
parentb94067eeae894b5a26170cebc378261f83ad00cb (diff)
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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.
Diffstat (limited to 'arch/mips/bits/fcntl.h')
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