-/* Copyright (C) 1996 Free Software Foundation, Inc.
+/* Copyright (C) 1996-2019 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 Library General Public License as
- published by the Free Software Foundation; either version 2 of the
- License, or (at your option) any later version.
+ 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
- Library General Public License for more details.
+ Lesser General Public License for more details.
- You should have received a copy of the GNU Library General Public
- License along with the GNU C Library; see the file COPYING.LIB. If
- not, write to the Free Software Foundation, Inc., 675 Mass Ave,
- Cambridge, MA 02139, USA. */
+ 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/>. */
/* Bytewise compare two null-terminated strings of length no longer than N. */
.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)
.prologue 0
#endif
- xor a0, a1, t2 # e0 : are s1 and s2 co-aligned?
- beq a2, $zerolength # .. e1 :
- ldq_u t0, 0(a0) # e0 : give cache time to catch up
- ldq_u t1, 0(a1) # .. e1 :
- and t2, 7, t2 # e0 :
- and a0, 7, t4 # .. e1 : find s1 misalignment
- lda t3, -1 # e0 :
- addq a2, t4, a2 # .. e1 : bias count by s1 misalignment
- and a2, 7, t10 # e1 : ofs of last byte in last word
- srl a2, 3, a2 # .. e0 : remaining full words in count
- and a1, 7, t5 # e0 : find s2 misalignment
- bne t2, $unaligned # .. e1 :
+ 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, t3 # e0 : mask off leading garbage
- nop # .. e1 :
- ornot t1, t3, t1 # e0 :
- ornot t0, t3, t0 # .. e1 :
- cmpbge zero, t1, t7 # e0 : bits set iff null found
- beq a2, $eoc # .. e1 : check end of count
- subq a2, 1, a2 # e0 :
- bne t7, $eos # .. e1 :
+ 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 :
- addq a1, 8, a1 # e0 :
- addq a0, 8, a0 # .. e1 :
- cmpbge zero, t1, t7 # e0 :
- beq a2, $eoc # .. 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 $eos # e1 :
- /* The two strings are not co-aligned. Align s1 and cope. */
-$unaligned:
- subq a1, t4, a1 # e0 :
- unop # :
+ br $eos
- /* If s2 misalignment is larger than s2 misalignment, we need
- extra startup checks to avoid SEGV. */
+ /* Alternate aligned compare loop, for when there's no trailing
+ bytes on the count. We have to avoid reading too much data. */
+ .align 4
+$ant_loop:
+ xor t0, t1, t2 # e0 :
+ ev6_unop
+ ev6_unop
+ bne t2, $wordcmp # .. e1 (zdb)
- cmplt t4, t5, t8 # .. e1 :
- beq t8, $u_head # e1 :
+ subq a2, 1, a2 # e0 :
+ beq a2, $zerolength # .. e1 :
+ ldq_u t1, 8(a1) # e0 :
+ ldq_u t0, 8(a0) # .. e1 :
- mskqh t3, t5, t3 # e0 :
- ornot t1, t3, t3 # e0 :
- cmpbge zero, t3, t7 # e1 : is there a zero?
- beq t7, $u_head # e1 :
+ addq a1, 8, a1 # e0 :
+ addq a0, 8, a0 # .. e1 :
+ cmpbge zero, t1, t7 # e0 :
+ beq t7, $ant_loop # .. e1 :
- /* We've found a zero in the first partial word of s2. Align
- our current s1 and s2 words and compare what we've got. */
+ br $eos
- extql t1, t5, t1 # e0 :
- lda t3, -1 # .. e1 :
- insql t1, a0, t1 # e0 :
- mskqh t3, a0, t3 # e0 :
- ornot t1, t3, t1 # e0 :
- ornot t0, t3, t0 # .. e1 :
- cmpbge zero, t1, t7 # e0 : find that zero again
- beq a2, $eoc # .. e1 : and finish up
- br $eos # e1 :
+ /* The two strings are not co-aligned. Align s1 and cope. */
+ /* On entry to this basic block:
+ t0 == the first word of s1.
+ t1 == the first word of s2.
+ t3 == -1.
+ t4 == misalignment of s1.
+ t5 == misalignment of s2.
+ t10 == misalignment of s1 end. */
+ .align 4
+$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, $u_head_nl
- .align 3
-$u_head:
/* 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. */
-
- ldq_u t2, 8(a1) # e0 : load second partial s2 word
- lda t3, -1 # .. e1 : create leading garbage mask
- extql t1, a1, t1 # e0 : create first s2 word
- mskqh t3, a0, t3 # e0 :
- extqh t2, a1, t4 # e0 :
- ornot t0, t3, t0 # .. e1 : kill s1 garbage
- or t1, t4, t1 # e0 : s2 word now complete
- ornot t1, t3, t1 # e1 : kill s2 garbage
- cmpbge zero, t0, t7 # e0 : find zero in first s1 word
- beq a2, $eoc # .. e1 :
- lda t3, -1 # e0 :
- bne t7, $eos # .. e1 :
- subq a2, 1, a2 # e0 :
- xor t0, t1, t4 # .. e1 : compare aligned words
- mskql t3, a1, t3 # e0 : mask out s2[1] bits we have seen
- bne t4, $wordcmp # .. e1 :
- or t2, t3, t3 # e0 :
- cmpbge zero, t3, t7 # e1 : find zero in high bits of s2[1]
- bne t7, $u_final # e1 :
+ t1 == first partial word of s2.
+ t3 == -1.
+ t10 == ofs of last byte in s1 last word.
+ t11 == ofs of last byte in s2 last word. */
+$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.
to run as fast as possible.
On entry to this basic block:
- t2 == the unshifted low-bits from the next s2 word. */
-
- .align 3
+ 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 :
- nop # .. e1 :
+ subq a3, 1, a3 # .. e1 :
extqh t2, a1, t1 # e0 :
- cmpbge zero, t0, t7 # .. e1 : find zero in current s1 word
+ cmpbge zero, t0, t7 # .. e1 : eos in current s1 word
+
or t1, t3, t1 # e0 :
- beq a2, $eoc # .. e1 : check for end of count
+ 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 :
- xor t0, t1, t4 # e0 : compare the words
- bne t4, $wordcmp # .. e1 (zdb)
- cmpbge zero, t2, t4 # e0 : find zero in next low bits
+
+ 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) # e1 :
- extql t2, a1, t1 # .. e0 :
- cmpbge zero, t1, t7 # e0 :
- bne a2, $eos # .. e1 :
+ 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 # e0 : create bytemask of valid data
- and t6, t7, t8 # e1 :
- subq t8, 1, t6 # e0 :
- or t6, t8, t7 # e1 :
- zapnot t0, t7, t0 # e0 : kill the garbage
- zapnot t1, t7, t1 # .. e1 :
- xor t0, t1, v0 # e0 : and compare
- beq v0, $done # .. e1 :
+ 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). */
+ Bytewise compare them and return (t0 > t1 ? 1 : -1). */
+ .align 3
$wordcmp:
- cmpbge t0, t1, t2 # e0 : comparison yields bit mask of ge
- cmpbge t1, t0, t3 # .. e1 :
- xor t2, t3, t0 # e0 : bits set iff t0/t1 bytes differ
- negq t0, t1 # e1 : clear all but least bit
- and t0, t1, t0 # e0 :
- lda v0, -1 # .. e1 :
- and t0, t2, t1 # e0 : was bit set in t0 > t1?
- cmovne t1, 1, v0 # .. e1 (zdb)
-
+ 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 # e1 :
+ ret
+ .align 3
$zerolength:
clr v0
ret
END(strncmp)
+libc_hidden_builtin_def (strncmp)
projects / thirdparty / glibc.git / blobdiff