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glibc/sysdeps/alpha/stxncpy.S
Siddhesh Poyarekar 30891f35fa Remove "Contributed by" lines 
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date.  Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.

Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions.  These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.

The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively.  These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:

https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc
https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2021-09-03 22:06:44 +05:30

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/* Copyright (C) 1996-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<https://www.gnu.org/licenses/>. */
/* 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
t8 = bitmask (with one bit set) indicating the last byte written
t10 = bitmask (with one bit set) indicating the byte position of
the end of the range specified by COUNT
a0 = unaligned address of the last *word* written
a2 = the number of full words left in COUNT
Furthermore, v0, a3-a5, t11, and t12 are untouched.
*/
/* This is generally scheduled for the EV5, but should still be pretty
good for the EV4 too. */
#include <sysdep.h>
.set noat
.set noreorder
.text
.type __stxncpy, @function
.globl __stxncpy
.usepv __stxncpy, no
cfi_startproc
cfi_return_column (t9)
/* On entry to this basic block:
t0 == the first destination word for masking back in
t1 == the first source word. */
.align 3
stxncpy_aligned:
/* 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, t7 # .. e1 : bits set iff null found
or t0, t3, t0 # e0 :
beq a2, $a_eoc # .. e1 :
bne t7, $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, t7 # .. e1 (stall)
beq a2, $a_eoc # e1 :
beq t7, $a_loop # e1 :
/* Take care of the final (partial) word store. At this point
the end-of-count bit is set in t7 iff it applies.
On entry to this basic block we have:
t0 == the source word containing the null
t7 == the cmpbge mask that found it. */
$a_eos:
negq t7, t8 # e0 : find low bit set
and t7, t8, t8 # e1 (stall)
/* For the sake of the cache, don't read a destination word
if we're not going to need it. */
and t8, 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 t8, 1, t6 # .. e1 :
or t8, t6, t7 # e0 :
unop #
zapnot t0, t7, t0 # e0 : clear src bytes > null
zap t1, t7, 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, t7, t7
br $a_eos
.align 3
__stxncpy:
/* Are source and destination co-aligned? */
lda t2, -1
xor a0, a1, t1
srl t2, 1, t2
and a0, 7, t0 # find dest misalignment
cmovlt a2, t2, a2 # bound neg count to LONG_MAX
and t1, 7, t1
addq a2, t0, a2 # bias count by dest misalignment
subq a2, 1, a2
and a2, 7, t2
srl a2, 3, a2 # a2 = loop counter = (count - 1)/8
addq zero, 1, t10
sll t10, t2, t10 # t10 = bitmask of last count byte
bne t1, $unaligned
/* 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, t7 # e0 :
beq a2, $u_eocfin # .. e1 :
lda t6, -1 # e0 :
bne t7, $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, t7 # e0 : find nulls in second partial
addq a0, 8, a0 # .. e1 :
subq a2, 1, a2 # e0 :
bne t7, $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
cmpbge zero, t2, t7 # .. e1 : test new word for eos
nop # e0 :
bne t7, $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, t7 # .. e1 : test new word for eos
extqh t2, a1, t0 # e0 : extract low bits for current word
beq t7, $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
cmpbge zero, t0, t7 # e0 : is the null in this first bit?
bne t7, $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 # e0 :
$u_late_head_exit:
extql t2, a1, t0 # e0 :
cmpbge zero, t0, t7 # e0 :
or t7, t10, t6 # e1 :
cmoveq a2, t6, t7 # e0 :
/* Take care of a final (probably partial) result word.
On entry to this basic block:
t0 == assembled source word
t7 == cmpbge mask that found the null. */
$u_final:
negq t7, t6 # e0 : isolate low bit set
and t6, t7, t8 # e1 :
and t8, 0x80, t6 # e0 : avoid dest word load if we can
bne t6, 1f # .. e1 (zdb)
ldq_u t1, 0(a0) # e0 :
subq t8, 1, t6 # .. e1 :
or t6, t8, t7 # e0 :
zapnot t0, t7, t0 # .. e1 : kill source bytes > null
zap t1, t7, 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 : avoid src word load if we can
ldq_u t2, 8(a1) # e0 : load final src word
nop # .. e1 :
extqh t2, a1, t0 # e0 : extract high bits for last word
or t1, t0, t1 # e1 :
1: cmpbge zero, t1, t7
mov t1, t0
$u_eocfin: # end-of-count, final word
or t10, t7, t7
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 :
1:
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. */
cmplt t4, t5, t8 # e1 :
extql t1, a1, t1 # .. e0 : shift src into place
lda t2, -1 # e0 : for creating masks later
beq t8, $u_head # e1 :
mskqh t2, t5, t2 # e0 : begin src byte validity mask
cmpbge zero, t1, t7 # .. e1 : is there a zero?
extql t2, a1, t2 # e0 :
or t7, t10, t5 # .. e1 : test for end-of-count too
cmpbge zero, t2, t3 # e0 :
cmoveq a2, t5, t7 # .. e1 :
andnot t7, t3, t7 # e0 :
beq t7, $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 t7, t6 # .. e1 : build bitmask of bytes <= zero
mskqh t1, t4, t1 # e0 :
and t6, t7, t8 # .. e1 :
subq t8, 1, t6 # e0 :
or t6, t8, t7 # e1 :
zapnot t2, t7, t2 # e0 : prepare source word; mirror changes
zapnot t1, t7, 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 :
cfi_endproc
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