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248 lines
7.2 KiB
ArmAsm
248 lines
7.2 KiB
ArmAsm
/* Copyright (C) 1996, 1997, 2003 Free Software Foundation, Inc.
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Contributed by Richard Henderson (rth@tamu.edu)
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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/* Bytewise compare two null-terminated strings of length no longer than N. */
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#include <sysdep.h>
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.set noat
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.set noreorder
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.text
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ENTRY(strncmp)
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#ifdef PROF
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ldgp gp, 0(pv)
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lda AT, _mcount
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jsr AT, (AT), _mcount
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.prologue 1
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#else
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.prologue 0
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#endif
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xor a0, a1, t2 # e0 : are s1 and s2 co-aligned?
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beq a2, $zerolength # .. e1 :
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ldq_u t0, 0(a0) # e0 : give cache time to catch up
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ldq_u t1, 0(a1) # .. e1 :
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and t2, 7, t2 # e0 :
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and a0, 7, t4 # .. e1 : find s1 misalignment
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lda t3, -1 # e0 :
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addq a2, t4, a2 # .. e1 : bias count by s1 misalignment
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and a2, 7, t10 # e1 : ofs of last byte in last word
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srl a2, 3, a2 # .. e0 : remaining full words in count
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and a1, 7, t5 # e0 : find s2 misalignment
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bne t2, $unaligned # .. e1 :
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/* On entry to this basic block:
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t0 == the first word of s1.
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t1 == the first word of s2.
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t3 == -1. */
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$aligned:
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mskqh t3, a1, t3 # e0 : mask off leading garbage
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nop # .. e1 :
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ornot t1, t3, t1 # e0 :
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ornot t0, t3, t0 # .. e1 :
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cmpbge zero, t1, t7 # e0 : bits set iff null found
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beq a2, $eoc # .. e1 : check end of count
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unop # e0 :
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bne t7, $eos # .. e1 :
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unop # e0 :
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beq t10, $ant_loop # .. e1 :
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/* Aligned compare main loop.
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On entry to this basic block:
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t0 == an s1 word.
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t1 == an s2 word not containing a null. */
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$a_loop:
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xor t0, t1, t2 # e0 :
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bne t2, $wordcmp # .. e1 (zdb)
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ldq_u t1, 8(a1) # e0 :
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ldq_u t0, 8(a0) # .. e1 :
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subq a2, 1, a2 # e0 :
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addq a1, 8, a1 # .. e1 :
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addq a0, 8, a0 # e0 :
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beq a2, $eoc # .. e1 :
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cmpbge zero, t1, t7 # e0 :
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beq t7, $a_loop # .. e1 :
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unop # e0 :
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br $eos # .. e1 :
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/* Alternate aligned compare loop, for when there's no trailing
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bytes on the count. We have to avoid reading too much data. */
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$ant_loop:
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xor t0, t1, t2 # e0 :
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bne t2, $wordcmp # .. e1 (zdb)
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subq a2, 1, a2 # e0 :
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beq a2, $zerolength # .. e1 :
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ldq_u t1, 8(a1) # e0 :
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ldq_u t0, 8(a0) # .. e1 :
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addq a1, 8, a1 # e0 :
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addq a0, 8, a0 # .. e1 :
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cmpbge zero, t1, t7 # e0 :
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beq t7, $ant_loop # .. e1 :
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unop # e0 :
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br $eos # .. e1 :
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/* The two strings are not co-aligned. Align s1 and cope. */
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$unaligned:
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subq a1, t4, a1 # e0 :
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unop # :
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/* If s2 misalignment is larger than s2 misalignment, we need
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extra startup checks to avoid SEGV. */
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cmplt t4, t5, t8 # .. e1 :
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beq t8, $u_head # e1 :
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mskqh t3, t5, t3 # e0 :
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ornot t1, t3, t3 # e0 :
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cmpbge zero, t3, t7 # e1 : is there a zero?
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beq t7, $u_head # e1 :
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/* We've found a zero in the first partial word of s2. Align
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our current s1 and s2 words and compare what we've got. */
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extql t1, t5, t1 # e0 :
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lda t3, -1 # .. e1 :
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insql t1, a0, t1 # e0 :
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mskqh t3, a0, t3 # e0 :
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ornot t1, t3, t1 # e0 :
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ornot t0, t3, t0 # .. e1 :
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cmpbge zero, t1, t7 # e0 : find that zero again
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beq a2, $eoc # .. e1 : and finish up
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br $eos # e1 :
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.align 3
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$u_head:
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/* We know just enough now to be able to assemble the first
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full word of s2. We can still find a zero at the end of it.
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On entry to this basic block:
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t0 == first word of s1
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t1 == first partial word of s2. */
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ldq_u t2, 8(a1) # e0 : load second partial s2 word
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lda t3, -1 # .. e1 : create leading garbage mask
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extql t1, a1, t1 # e0 : create first s2 word
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mskqh t3, a0, t3 # e0 :
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extqh t2, a1, t4 # e0 :
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ornot t0, t3, t0 # .. e1 : kill s1 garbage
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or t1, t4, t1 # e0 : s2 word now complete
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ornot t1, t3, t1 # e1 : kill s2 garbage
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cmpbge zero, t0, t7 # e0 : find zero in first s1 word
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beq a2, $eoc # .. e1 :
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lda t3, -1 # e0 :
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bne t7, $eos # .. e1 :
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subq a2, 1, a2 # e0 :
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xor t0, t1, t4 # .. e1 : compare aligned words
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mskql t3, a1, t3 # e0 : mask out s2[1] bits we have seen
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bne t4, $wordcmp # .. e1 :
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or t2, t3, t3 # e0 :
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cmpbge zero, t3, t7 # e1 : find zero in high bits of s2[1]
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bne t7, $u_final # e1 :
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/* Unaligned copy main loop. In order to avoid reading too much,
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the loop is structured to detect zeros in aligned words from s2.
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This has, unfortunately, effectively pulled half of a loop
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iteration out into the head and half into the tail, but it does
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prevent nastiness from accumulating in the very thing we want
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to run as fast as possible.
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On entry to this basic block:
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t2 == the unshifted low-bits from the next s2 word. */
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.align 3
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$u_loop:
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extql t2, a1, t3 # e0 :
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ldq_u t2, 16(a1) # .. e1 : load next s2 high bits
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ldq_u t0, 8(a0) # e0 : load next s1 word
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addq a1, 8, a1 # .. e1 :
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addq a0, 8, a0 # e0 :
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nop # .. e1 :
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extqh t2, a1, t1 # e0 :
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cmpbge zero, t0, t7 # .. e1 : find zero in current s1 word
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or t1, t3, t1 # e0 :
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beq a2, $eoc # .. e1 : check for end of count
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subq a2, 1, a2 # e0 :
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bne t7, $eos # .. e1 :
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xor t0, t1, t4 # e0 : compare the words
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bne t4, $wordcmp # .. e1 (zdb)
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cmpbge zero, t2, t4 # e0 : find zero in next low bits
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beq t4, $u_loop # .. e1 (zdb)
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/* We've found a zero in the low bits of the last s2 word. Get
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the next s1 word and align them. */
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$u_final:
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ldq_u t0, 8(a0) # e1 :
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extql t2, a1, t1 # .. e0 :
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cmpbge zero, t1, t7 # e0 :
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bne a2, $eos # .. e1 :
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/* We've hit end of count. Zero everything after the count
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and compare whats left. */
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.align 3
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$eoc:
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mskql t0, t10, t0
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mskql t1, t10, t1
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unop
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cmpbge zero, t1, t7
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/* We've found a zero somewhere in a word we just read.
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On entry to this basic block:
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t0 == s1 word
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t1 == s2 word
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t7 == cmpbge mask containing the zero. */
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$eos:
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negq t7, t6 # e0 : create bytemask of valid data
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and t6, t7, t8 # e1 :
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subq t8, 1, t6 # e0 :
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or t6, t8, t7 # e1 :
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zapnot t0, t7, t0 # e0 : kill the garbage
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zapnot t1, t7, t1 # .. e1 :
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xor t0, t1, v0 # e0 : and compare
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beq v0, $done # .. e1 :
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/* Here we have two differing co-aligned words in t0 & t1.
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Bytewise compare them and return (t0 > t1 ? 1 : -1). */
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.align 3
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$wordcmp:
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cmpbge t0, t1, t2 # e0 : comparison yields bit mask of ge
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cmpbge t1, t0, t3 # .. e1 :
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xor t2, t3, t0 # e0 : bits set iff t0/t1 bytes differ
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negq t0, t1 # e1 : clear all but least bit
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and t0, t1, t0 # e0 :
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lda v0, -1 # .. e1 :
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and t0, t2, t1 # e0 : was bit set in t0 > t1?
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cmovne t1, 1, v0 # .. e1 (zdb)
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$done:
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ret # e1 :
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.align 3
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$zerolength:
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clr v0
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ret
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END(strncmp)
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libc_hidden_builtin_def (strncmp)
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