mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-13 14:50:17 +00:00
d8cbc13ab6
This routine suffered a similar problem as stxncpy in needing to bias a potentially very large unsigned number with wraparound. This exposed a secondary problem where we didn't properly handle end-of-count condition for the second string input resulting in stratcliff failures.
278 lines
7.4 KiB
ArmAsm
278 lines
7.4 KiB
ArmAsm
/* Copyright (C) 1996-2012 Free Software Foundation, Inc.
|
|
Contributed by Richard Henderson (rth@tamu.edu)
|
|
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
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
/* Bytewise compare two null-terminated strings of length no longer than N. */
|
|
|
|
#include <sysdep.h>
|
|
|
|
.set noat
|
|
.set noreorder
|
|
|
|
/* EV6 only predicts one branch per octaword. We'll use these to push
|
|
subsequent branches back to the next bundle. This will generally add
|
|
a fetch+decode cycle to older machines, so skip in that case. */
|
|
#ifdef __alpha_fix__
|
|
# define ev6_unop unop
|
|
#else
|
|
# define ev6_unop
|
|
#endif
|
|
|
|
.text
|
|
|
|
ENTRY(strncmp)
|
|
#ifdef PROF
|
|
ldgp gp, 0(pv)
|
|
lda AT, _mcount
|
|
jsr AT, (AT), _mcount
|
|
.prologue 1
|
|
#else
|
|
.prologue 0
|
|
#endif
|
|
|
|
xor a0, a1, t2 # are s1 and s2 co-aligned?
|
|
beq a2, $zerolength
|
|
ldq_u t0, 0(a0) # load asap to give cache time to catch up
|
|
ldq_u t1, 0(a1)
|
|
lda t3, -1
|
|
and t2, 7, t2
|
|
srl t3, 1, t6
|
|
and a0, 7, t4 # find s1 misalignment
|
|
and a1, 7, t5 # find s2 misalignment
|
|
cmovlt a2, t6, a2 # bound neg count to LONG_MAX
|
|
addq a1, a2, a3 # s2+count
|
|
addq a2, t4, a2 # bias count by s1 misalignment
|
|
and a2, 7, t10 # ofs of last byte in s1 last word
|
|
srl a2, 3, a2 # remaining full words in s1 count
|
|
bne t2, $unaligned
|
|
|
|
/* On entry to this basic block:
|
|
t0 == the first word of s1.
|
|
t1 == the first word of s2.
|
|
t3 == -1. */
|
|
$aligned:
|
|
mskqh t3, a1, t8 # mask off leading garbage
|
|
ornot t1, t8, t1
|
|
ornot t0, t8, t0
|
|
cmpbge zero, t1, t7 # bits set iff null found
|
|
beq a2, $eoc # check end of count
|
|
bne t7, $eos
|
|
beq t10, $ant_loop
|
|
|
|
/* Aligned compare main loop.
|
|
On entry to this basic block:
|
|
t0 == an s1 word.
|
|
t1 == an s2 word not containing a null. */
|
|
|
|
.align 4
|
|
$a_loop:
|
|
xor t0, t1, t2 # e0 :
|
|
bne t2, $wordcmp # .. e1 (zdb)
|
|
ldq_u t1, 8(a1) # e0 :
|
|
ldq_u t0, 8(a0) # .. e1 :
|
|
|
|
subq a2, 1, a2 # e0 :
|
|
addq a1, 8, a1 # .. e1 :
|
|
addq a0, 8, a0 # e0 :
|
|
beq a2, $eoc # .. e1 :
|
|
|
|
cmpbge zero, t1, t7 # e0 :
|
|
beq t7, $a_loop # .. e1 :
|
|
|
|
br $eos
|
|
|
|
/* Alternate aligned compare loop, for when there's no trailing
|
|
bytes on the count. We have to avoid reading too much data. */
|
|
.align 4
|
|
$ant_loop:
|
|
xor t0, t1, t2 # e0 :
|
|
ev6_unop
|
|
ev6_unop
|
|
bne t2, $wordcmp # .. e1 (zdb)
|
|
|
|
subq a2, 1, a2 # e0 :
|
|
beq a2, $zerolength # .. e1 :
|
|
ldq_u t1, 8(a1) # e0 :
|
|
ldq_u t0, 8(a0) # .. e1 :
|
|
|
|
addq a1, 8, a1 # e0 :
|
|
addq a0, 8, a0 # .. e1 :
|
|
cmpbge zero, t1, t7 # e0 :
|
|
beq t7, $ant_loop # .. e1 :
|
|
|
|
br $eos
|
|
|
|
/* The two strings are not co-aligned. Align s1 and cope. */
|
|
/* On entry to this basic block:
|
|
t0 == the first word of s1.
|
|
t1 == the first word of s2.
|
|
t3 == -1.
|
|
t4 == misalignment of s1.
|
|
t5 == misalignment of s2.
|
|
t10 == misalignment of s1 end. */
|
|
.align 4
|
|
$unaligned:
|
|
/* If s1 misalignment is larger than s2 misalignment, we need
|
|
extra startup checks to avoid SEGV. */
|
|
subq a1, t4, a1 # adjust s2 for s1 misalignment
|
|
cmpult t4, t5, t9
|
|
subq a3, 1, a3 # last byte of s2
|
|
bic a1, 7, t8
|
|
mskqh t3, t5, t7 # mask garbage in s2
|
|
subq a3, t8, a3
|
|
ornot t1, t7, t7
|
|
srl a3, 3, a3 # remaining full words in s2 count
|
|
beq t9, $u_head
|
|
|
|
/* Failing that, we need to look for both eos and eoc within the
|
|
first word of s2. If we find either, we can continue by
|
|
pretending that the next word of s2 is all zeros. */
|
|
lda t2, 0 # next = zero
|
|
cmpeq a3, 0, t8 # eoc in the first word of s2?
|
|
cmpbge zero, t7, t7 # eos in the first word of s2?
|
|
or t7, t8, t8
|
|
bne t8, $u_head_nl
|
|
|
|
/* We know just enough now to be able to assemble the first
|
|
full word of s2. We can still find a zero at the end of it.
|
|
|
|
On entry to this basic block:
|
|
t0 == first word of s1
|
|
t1 == first partial word of s2.
|
|
t3 == -1.
|
|
t10 == ofs of last byte in s1 last word.
|
|
t11 == ofs of last byte in s2 last word. */
|
|
$u_head:
|
|
ldq_u t2, 8(a1) # load second partial s2 word
|
|
subq a3, 1, a3
|
|
$u_head_nl:
|
|
extql t1, a1, t1 # create first s2 word
|
|
mskqh t3, a0, t8
|
|
extqh t2, a1, t4
|
|
ornot t0, t8, t0 # kill s1 garbage
|
|
or t1, t4, t1 # s2 word now complete
|
|
cmpbge zero, t0, t7 # find eos in first s1 word
|
|
ornot t1, t8, t1 # kill s2 garbage
|
|
beq a2, $eoc
|
|
subq a2, 1, a2
|
|
bne t7, $eos
|
|
mskql t3, a1, t8 # mask out s2[1] bits we have seen
|
|
xor t0, t1, t4 # compare aligned words
|
|
or t2, t8, t8
|
|
bne t4, $wordcmp
|
|
cmpbge zero, t8, t7 # eos in high bits of s2[1]?
|
|
cmpeq a3, 0, t8 # eoc in s2[1]?
|
|
or t7, t8, t7
|
|
bne t7, $u_final
|
|
|
|
/* Unaligned copy main loop. In order to avoid reading too much,
|
|
the loop is structured to detect zeros in aligned words from s2.
|
|
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:
|
|
t2 == the unshifted low-bits from the next s2 word.
|
|
t10 == ofs of last byte in s1 last word.
|
|
t11 == ofs of last byte in s2 last word. */
|
|
.align 4
|
|
$u_loop:
|
|
extql t2, a1, t3 # e0 :
|
|
ldq_u t2, 16(a1) # .. e1 : load next s2 high bits
|
|
ldq_u t0, 8(a0) # e0 : load next s1 word
|
|
addq a1, 8, a1 # .. e1 :
|
|
|
|
addq a0, 8, a0 # e0 :
|
|
subq a3, 1, a3 # .. e1 :
|
|
extqh t2, a1, t1 # e0 :
|
|
cmpbge zero, t0, t7 # .. e1 : eos in current s1 word
|
|
|
|
or t1, t3, t1 # e0 :
|
|
beq a2, $eoc # .. e1 : eoc in current s1 word
|
|
subq a2, 1, a2 # e0 :
|
|
cmpbge zero, t2, t4 # .. e1 : eos in s2[1]
|
|
|
|
xor t0, t1, t3 # e0 : compare the words
|
|
ev6_unop
|
|
ev6_unop
|
|
bne t7, $eos # .. e1 :
|
|
|
|
cmpeq a3, 0, t5 # e0 : eoc in s2[1]
|
|
ev6_unop
|
|
ev6_unop
|
|
bne t3, $wordcmp # .. e1 :
|
|
|
|
or t4, t5, t4 # e0 : eos or eoc in s2[1].
|
|
beq t4, $u_loop # .. e1 (zdb)
|
|
|
|
/* We've found a zero in the low bits of the last s2 word. Get
|
|
the next s1 word and align them. */
|
|
.align 3
|
|
$u_final:
|
|
ldq_u t0, 8(a0)
|
|
extql t2, a1, t1
|
|
cmpbge zero, t1, t7
|
|
bne a2, $eos
|
|
|
|
/* We've hit end of count. Zero everything after the count
|
|
and compare whats left. */
|
|
.align 3
|
|
$eoc:
|
|
mskql t0, t10, t0
|
|
mskql t1, t10, t1
|
|
cmpbge zero, t1, t7
|
|
|
|
/* We've found a zero somewhere in a word we just read.
|
|
On entry to this basic block:
|
|
t0 == s1 word
|
|
t1 == s2 word
|
|
t7 == cmpbge mask containing the zero. */
|
|
.align 3
|
|
$eos:
|
|
negq t7, t6 # create bytemask of valid data
|
|
and t6, t7, t8
|
|
subq t8, 1, t6
|
|
or t6, t8, t7
|
|
zapnot t0, t7, t0 # kill the garbage
|
|
zapnot t1, t7, t1
|
|
xor t0, t1, v0 # ... and compare
|
|
beq v0, $done
|
|
|
|
/* Here we have two differing co-aligned words in t0 & t1.
|
|
Bytewise compare them and return (t0 > t1 ? 1 : -1). */
|
|
.align 3
|
|
$wordcmp:
|
|
cmpbge t0, t1, t2 # comparison yields bit mask of ge
|
|
cmpbge t1, t0, t3
|
|
xor t2, t3, t0 # bits set iff t0/t1 bytes differ
|
|
negq t0, t1 # clear all but least bit
|
|
and t0, t1, t0
|
|
lda v0, -1
|
|
and t0, t2, t1 # was bit set in t0 > t1?
|
|
cmovne t1, 1, v0
|
|
$done:
|
|
ret
|
|
|
|
.align 3
|
|
$zerolength:
|
|
clr v0
|
|
ret
|
|
|
|
END(strncmp)
|
|
libc_hidden_builtin_def (strncmp)
|