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/* strlen.S: Sparc optimized strlen().
 *
 * This was hand optimized by davem@caip.rutgers.edu from
 * the C-code in GNU-libc.
 */

#include <asm/cprefix.h>

#define LO_MAGIC 0x01010101
#define HI_MAGIC 0x80808080

        .align 4
        .global C_LABEL(strlen)
C_LABEL(strlen):
        mov     %o0,%o1
        andcc   %o0,3,%g0               ! and with %o0 so no dependency problems
        be      scan_words
         sethi  %hi(HI_MAGIC),%g2       ! common case and most Sparcs predict taken

        ldsb    [%o0],%g2
still_not_word_aligned:
        cmp     %g2,0
        bne,a   1f
         add    %o0,1,%o0

        /* Ok, so there are tons of quick interlocks above for the
         * < 4 length string unaligned... not too common so I'm not
         * very concerned.
         */
        retl
         sub    %o0,%o1,%o0

1:
        andcc   %o0,3,%g0
        bne,a   still_not_word_aligned
         ldsb   [%o0],%g2

        /* HyperSparc executes each sethi/or pair in 1 cycle. */
        sethi   %hi(HI_MAGIC),%g2
scan_words:
        or      %g2,%lo(HI_MAGIC),%o3
        sethi   %hi(LO_MAGIC),%g3
        or      %g3,%lo(LO_MAGIC),%o2
next_word:
        ld      [%o0],%g2               ! no dependencies
next_word_preloaded:
        sub     %g2,%o2,%g2             ! lots of locks here
        andcc   %g2,%o3,%g0             ! and I dont like it...
        be      next_word
         add    %o0,4,%o0

        /* Check every byte. */
byte_zero:
        ldsb    [%o0-4],%g2
        cmp     %g2,0
        bne     byte_one
         add    %o0,-4,%g3

        retl
         sub    %g3,%o1,%o0

byte_one:
        ldsb    [%o0-3],%g2
        cmp     %g2,0
        bne,a   byte_two_and_three
         ldsb   [%o0-2],%g2

        sub     %g3,%o1,%o0
        retl
         add    %o0,1,%o0

byte_two_and_three:
        cmp     %g2,0
        be,a    found_it
         sub    %g3,%o1,%o0

        ldsb    [%o0-1],%g2
        cmp     %g2,0
        bne,a   next_word_preloaded
         ld     [%o0],%g2

        sub     %g3,%o1,%o0
        retl
         add    %o0,3,%o0

found_it:
        retl
         add    %o0,2,%o0