346 lines
11 KiB
ArmAsm
346 lines
11 KiB
ArmAsm
/*
|
|
* arch/alpha/lib/stxncpy.S
|
|
* Contributed by Richard Henderson (rth@tamu.edu)
|
|
*
|
|
* Copy no more than COUNT bytes of the null-terminated string from
|
|
* SRC to DST.
|
|
*
|
|
* This is an internal routine used by strncpy, stpncpy, and strncat.
|
|
* As such, it uses special linkage conventions to make implementation
|
|
* of these public functions more efficient.
|
|
*
|
|
* On input:
|
|
* t9 = return address
|
|
* a0 = DST
|
|
* a1 = SRC
|
|
* a2 = COUNT
|
|
*
|
|
* Furthermore, COUNT may not be zero.
|
|
*
|
|
* On output:
|
|
* t0 = last word written
|
|
* t10 = bitmask (with one bit set) indicating the byte position of
|
|
* the end of the range specified by COUNT
|
|
* t12 = bitmask (with one bit set) indicating the last byte written
|
|
* a0 = unaligned address of the last *word* written
|
|
* a2 = the number of full words left in COUNT
|
|
*
|
|
* Furthermore, v0, a3-a5, t11, and $at are untouched.
|
|
*/
|
|
|
|
#include <asm/regdef.h>
|
|
|
|
.set noat
|
|
.set noreorder
|
|
|
|
.text
|
|
|
|
/* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that
|
|
doesn't like putting the entry point for a procedure somewhere in the
|
|
middle of the procedure descriptor. Work around this by putting the
|
|
aligned copy in its own procedure descriptor */
|
|
|
|
.ent stxncpy_aligned
|
|
.align 3
|
|
stxncpy_aligned:
|
|
.frame sp, 0, t9, 0
|
|
.prologue 0
|
|
|
|
/* On entry to this basic block:
|
|
t0 == the first destination word for masking back in
|
|
t1 == the first source word. */
|
|
|
|
/* Create the 1st output word and detect 0's in the 1st input word. */
|
|
lda t2, -1 # e1 : build a mask against false zero
|
|
mskqh t2, a1, t2 # e0 : detection in the src word
|
|
mskqh t1, a1, t3 # e0 :
|
|
ornot t1, t2, t2 # .. e1 :
|
|
mskql t0, a1, t0 # e0 : assemble the first output word
|
|
cmpbge zero, t2, t8 # .. e1 : bits set iff null found
|
|
or t0, t3, t0 # e0 :
|
|
beq a2, $a_eoc # .. e1 :
|
|
bne t8, $a_eos # .. e1 :
|
|
|
|
/* On entry to this basic block:
|
|
t0 == a source word not containing a null. */
|
|
|
|
$a_loop:
|
|
stq_u t0, 0(a0) # e0 :
|
|
addq a0, 8, a0 # .. e1 :
|
|
ldq_u t0, 0(a1) # e0 :
|
|
addq a1, 8, a1 # .. e1 :
|
|
subq a2, 1, a2 # e0 :
|
|
cmpbge zero, t0, t8 # .. e1 (stall)
|
|
beq a2, $a_eoc # e1 :
|
|
beq t8, $a_loop # e1 :
|
|
|
|
/* Take care of the final (partial) word store. At this point
|
|
the end-of-count bit is set in t8 iff it applies.
|
|
|
|
On entry to this basic block we have:
|
|
t0 == the source word containing the null
|
|
t8 == the cmpbge mask that found it. */
|
|
|
|
$a_eos:
|
|
negq t8, t12 # e0 : find low bit set
|
|
and t8, t12, t12 # e1 (stall)
|
|
|
|
/* For the sake of the cache, don't read a destination word
|
|
if we're not going to need it. */
|
|
and t12, 0x80, t6 # e0 :
|
|
bne t6, 1f # .. e1 (zdb)
|
|
|
|
/* We're doing a partial word store and so need to combine
|
|
our source and original destination words. */
|
|
ldq_u t1, 0(a0) # e0 :
|
|
subq t12, 1, t6 # .. e1 :
|
|
or t12, t6, t8 # e0 :
|
|
unop #
|
|
zapnot t0, t8, t0 # e0 : clear src bytes > null
|
|
zap t1, t8, t1 # .. e1 : clear dst bytes <= null
|
|
or t0, t1, t0 # e1 :
|
|
|
|
1: stq_u t0, 0(a0) # e0 :
|
|
ret (t9) # e1 :
|
|
|
|
/* Add the end-of-count bit to the eos detection bitmask. */
|
|
$a_eoc:
|
|
or t10, t8, t8
|
|
br $a_eos
|
|
|
|
.end stxncpy_aligned
|
|
|
|
.align 3
|
|
.ent __stxncpy
|
|
.globl __stxncpy
|
|
__stxncpy:
|
|
.frame sp, 0, t9, 0
|
|
.prologue 0
|
|
|
|
/* Are source and destination co-aligned? */
|
|
xor a0, a1, t1 # e0 :
|
|
and a0, 7, t0 # .. e1 : find dest misalignment
|
|
and t1, 7, t1 # e0 :
|
|
addq a2, t0, a2 # .. e1 : bias count by dest misalignment
|
|
subq a2, 1, a2 # e0 :
|
|
and a2, 7, t2 # e1 :
|
|
srl a2, 3, a2 # e0 : a2 = loop counter = (count - 1)/8
|
|
addq zero, 1, t10 # .. e1 :
|
|
sll t10, t2, t10 # e0 : t10 = bitmask of last count byte
|
|
bne t1, $unaligned # .. e1 :
|
|
|
|
/* We are co-aligned; take care of a partial first word. */
|
|
|
|
ldq_u t1, 0(a1) # e0 : load first src word
|
|
addq a1, 8, a1 # .. e1 :
|
|
|
|
beq t0, stxncpy_aligned # avoid loading dest word if not needed
|
|
ldq_u t0, 0(a0) # e0 :
|
|
br stxncpy_aligned # .. e1 :
|
|
|
|
|
|
/* The source and destination are not co-aligned. Align the destination
|
|
and cope. We have to be very careful about not reading too much and
|
|
causing a SEGV. */
|
|
|
|
.align 3
|
|
$u_head:
|
|
/* We know just enough now to be able to assemble the first
|
|
full source word. We can still find a zero at the end of it
|
|
that prevents us from outputting the whole thing.
|
|
|
|
On entry to this basic block:
|
|
t0 == the first dest word, unmasked
|
|
t1 == the shifted low bits of the first source word
|
|
t6 == bytemask that is -1 in dest word bytes */
|
|
|
|
ldq_u t2, 8(a1) # e0 : load second src word
|
|
addq a1, 8, a1 # .. e1 :
|
|
mskql t0, a0, t0 # e0 : mask trailing garbage in dst
|
|
extqh t2, a1, t4 # e0 :
|
|
or t1, t4, t1 # e1 : first aligned src word complete
|
|
mskqh t1, a0, t1 # e0 : mask leading garbage in src
|
|
or t0, t1, t0 # e0 : first output word complete
|
|
or t0, t6, t6 # e1 : mask original data for zero test
|
|
cmpbge zero, t6, t8 # e0 :
|
|
beq a2, $u_eocfin # .. e1 :
|
|
lda t6, -1 # e0 :
|
|
bne t8, $u_final # .. e1 :
|
|
|
|
mskql t6, a1, t6 # e0 : mask out bits already seen
|
|
nop # .. e1 :
|
|
stq_u t0, 0(a0) # e0 : store first output word
|
|
or t6, t2, t2 # .. e1 :
|
|
cmpbge zero, t2, t8 # e0 : find nulls in second partial
|
|
addq a0, 8, a0 # .. e1 :
|
|
subq a2, 1, a2 # e0 :
|
|
bne t8, $u_late_head_exit # .. e1 :
|
|
|
|
/* Finally, we've got all the stupid leading edge cases taken care
|
|
of and we can set up to enter the main loop. */
|
|
|
|
extql t2, a1, t1 # e0 : position hi-bits of lo word
|
|
beq a2, $u_eoc # .. e1 :
|
|
ldq_u t2, 8(a1) # e0 : read next high-order source word
|
|
addq a1, 8, a1 # .. e1 :
|
|
extqh t2, a1, t0 # e0 : position lo-bits of hi word (stall)
|
|
cmpbge zero, t2, t8 # .. e1 :
|
|
nop # e0 :
|
|
bne t8, $u_eos # .. e1 :
|
|
|
|
/* Unaligned copy main loop. In order to avoid reading too much,
|
|
the loop is structured to detect zeros in aligned source words.
|
|
This has, unfortunately, effectively pulled half of a loop
|
|
iteration out into the head and half into the tail, but it does
|
|
prevent nastiness from accumulating in the very thing we want
|
|
to run as fast as possible.
|
|
|
|
On entry to this basic block:
|
|
t0 == the shifted low-order bits from the current source word
|
|
t1 == the shifted high-order bits from the previous source word
|
|
t2 == the unshifted current source word
|
|
|
|
We further know that t2 does not contain a null terminator. */
|
|
|
|
.align 3
|
|
$u_loop:
|
|
or t0, t1, t0 # e0 : current dst word now complete
|
|
subq a2, 1, a2 # .. e1 : decrement word count
|
|
stq_u t0, 0(a0) # e0 : save the current word
|
|
addq a0, 8, a0 # .. e1 :
|
|
extql t2, a1, t1 # e0 : extract high bits for next time
|
|
beq a2, $u_eoc # .. e1 :
|
|
ldq_u t2, 8(a1) # e0 : load high word for next time
|
|
addq a1, 8, a1 # .. e1 :
|
|
nop # e0 :
|
|
cmpbge zero, t2, t8 # e1 : test new word for eos (stall)
|
|
extqh t2, a1, t0 # e0 : extract low bits for current word
|
|
beq t8, $u_loop # .. e1 :
|
|
|
|
/* We've found a zero somewhere in the source word we just read.
|
|
If it resides in the lower half, we have one (probably partial)
|
|
word to write out, and if it resides in the upper half, we
|
|
have one full and one partial word left to write out.
|
|
|
|
On entry to this basic block:
|
|
t0 == the shifted low-order bits from the current source word
|
|
t1 == the shifted high-order bits from the previous source word
|
|
t2 == the unshifted current source word. */
|
|
$u_eos:
|
|
or t0, t1, t0 # e0 : first (partial) source word complete
|
|
nop # .. e1 :
|
|
cmpbge zero, t0, t8 # e0 : is the null in this first bit?
|
|
bne t8, $u_final # .. e1 (zdb)
|
|
|
|
stq_u t0, 0(a0) # e0 : the null was in the high-order bits
|
|
addq a0, 8, a0 # .. e1 :
|
|
subq a2, 1, a2 # e1 :
|
|
|
|
$u_late_head_exit:
|
|
extql t2, a1, t0 # .. e0 :
|
|
cmpbge zero, t0, t8 # e0 :
|
|
or t8, t10, t6 # e1 :
|
|
cmoveq a2, t6, t8 # e0 :
|
|
nop # .. e1 :
|
|
|
|
/* Take care of a final (probably partial) result word.
|
|
On entry to this basic block:
|
|
t0 == assembled source word
|
|
t8 == cmpbge mask that found the null. */
|
|
$u_final:
|
|
negq t8, t6 # e0 : isolate low bit set
|
|
and t6, t8, t12 # e1 :
|
|
|
|
and t12, 0x80, t6 # e0 : avoid dest word load if we can
|
|
bne t6, 1f # .. e1 (zdb)
|
|
|
|
ldq_u t1, 0(a0) # e0 :
|
|
subq t12, 1, t6 # .. e1 :
|
|
or t6, t12, t8 # e0 :
|
|
zapnot t0, t8, t0 # .. e1 : kill source bytes > null
|
|
zap t1, t8, t1 # e0 : kill dest bytes <= null
|
|
or t0, t1, t0 # e1 :
|
|
|
|
1: stq_u t0, 0(a0) # e0 :
|
|
ret (t9) # .. e1 :
|
|
|
|
/* Got to end-of-count before end of string.
|
|
On entry to this basic block:
|
|
t1 == the shifted high-order bits from the previous source word */
|
|
$u_eoc:
|
|
and a1, 7, t6 # e1 :
|
|
sll t10, t6, t6 # e0 :
|
|
and t6, 0xff, t6 # e0 :
|
|
bne t6, 1f # .. e1 :
|
|
|
|
ldq_u t2, 8(a1) # e0 : load final src word
|
|
nop # .. e1 :
|
|
extqh t2, a1, t0 # e0 : extract low bits for last word
|
|
or t1, t0, t1 # e1 :
|
|
|
|
1: cmpbge zero, t1, t8
|
|
mov t1, t0
|
|
|
|
$u_eocfin: # end-of-count, final word
|
|
or t10, t8, t8
|
|
br $u_final
|
|
|
|
/* Unaligned copy entry point. */
|
|
.align 3
|
|
$unaligned:
|
|
|
|
ldq_u t1, 0(a1) # e0 : load first source word
|
|
|
|
and a0, 7, t4 # .. e1 : find dest misalignment
|
|
and a1, 7, t5 # e0 : find src misalignment
|
|
|
|
/* Conditionally load the first destination word and a bytemask
|
|
with 0xff indicating that the destination byte is sacrosanct. */
|
|
|
|
mov zero, t0 # .. e1 :
|
|
mov zero, t6 # e0 :
|
|
beq t4, 1f # .. e1 :
|
|
ldq_u t0, 0(a0) # e0 :
|
|
lda t6, -1 # .. e1 :
|
|
mskql t6, a0, t6 # e0 :
|
|
subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr
|
|
|
|
/* If source misalignment is larger than dest misalignment, we need
|
|
extra startup checks to avoid SEGV. */
|
|
|
|
1: cmplt t4, t5, t12 # e1 :
|
|
extql t1, a1, t1 # .. e0 : shift src into place
|
|
lda t2, -1 # e0 : for creating masks later
|
|
beq t12, $u_head # .. e1 :
|
|
|
|
extql t2, a1, t2 # e0 :
|
|
cmpbge zero, t1, t8 # .. e1 : is there a zero?
|
|
andnot t2, t6, t2 # e0 : dest mask for a single word copy
|
|
or t8, t10, t5 # .. e1 : test for end-of-count too
|
|
cmpbge zero, t2, t3 # e0 :
|
|
cmoveq a2, t5, t8 # .. e1 :
|
|
andnot t8, t3, t8 # e0 :
|
|
beq t8, $u_head # .. e1 (zdb)
|
|
|
|
/* At this point we've found a zero in the first partial word of
|
|
the source. We need to isolate the valid source data and mask
|
|
it into the original destination data. (Incidentally, we know
|
|
that we'll need at least one byte of that original dest word.) */
|
|
|
|
ldq_u t0, 0(a0) # e0 :
|
|
negq t8, t6 # .. e1 : build bitmask of bytes <= zero
|
|
mskqh t1, t4, t1 # e0 :
|
|
and t6, t8, t12 # .. e1 :
|
|
subq t12, 1, t6 # e0 :
|
|
or t6, t12, t8 # e1 :
|
|
|
|
zapnot t2, t8, t2 # e0 : prepare source word; mirror changes
|
|
zapnot t1, t8, t1 # .. e1 : to source validity mask
|
|
|
|
andnot t0, t2, t0 # e0 : zero place for source to reside
|
|
or t0, t1, t0 # e1 : and put it there
|
|
stq_u t0, 0(a0) # e0 :
|
|
ret (t9) # .. e1 :
|
|
|
|
.end __stxncpy
|