path: root/arch/x86_64
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authorRich Felker <>2012-09-11 02:23:47 -0400
committerRich Felker <>2012-09-11 02:23:47 -0400
commitcfc09b1ecf0c6981494fd73dffe234416f66af10 (patch)
tree6771fdf3c0f6efad93919597e327da9ba0495877 /arch/x86_64
parentb94067eeae894b5a26170cebc378261f83ad00cb (diff)
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/x86_64')
0 files changed, 0 insertions, 0 deletions