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/*
* arch/alpha/lib/strlen_user.S
*
* Return the length of the string including the NUL terminator
* (strlen+1) or zero if an error occurred.
*/
#include <alpha/regdef.h>
/* Allow an exception for an insn; exit if we get one. */
#define EX(x,y...) \
99: x,##y; \
.section __ex_table,"a"; \
.gprel32 99b; \
lda v0, $exception-99b(zero); \
.previous
.set noreorder
.set noat
.text
.globl __strlen_user
.ent __strlen_user
.frame sp, 0, ra
.align 3
__strlen_user:
.prologue 0
EX( ldq_u t0, 0(a0) ) # load first quadword (a0 may be misaligned)
lda t1, -1(zero)
insqh t1, a0, t1
andnot a0, 7, v0
or t1, t0, t0
subq a0, 1, a0 # get our +1 for the return
cmpbge zero, t0, t1 # t1 <- bitmask: bit i == 1 <==> i-th byte == 0
bne t1, $found
$loop: EX( ldq t0, 8(v0) )
addq v0, 8, v0 # addr += 8
cmpbge zero, t0, t1
beq t1, $loop
$found: negq t1, t2 # clear all but least set bit
and t1, t2, t1
and t1, 0xf0, t2 # binary search for that set bit
and t1, 0xcc, t3
and t1, 0xaa, t4
cmovne t2, 4, t2
cmovne t3, 2, t3
cmovne t4, 1, t4
addq t2, t3, t2
addq v0, t4, v0
addq v0, t2, v0
nop # dual issue next two on ev4 and ev5
subq v0, a0, v0
$exception:
ret
.end __strlen_user
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