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Diffstat (limited to 'sysdeps/alpha/strcmp.S')
| -rw-r--r-- | sysdeps/alpha/strcmp.S | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/sysdeps/alpha/strcmp.S b/sysdeps/alpha/strcmp.S new file mode 100644 index 0000000000..a9fa89327f --- /dev/null +++ b/sysdeps/alpha/strcmp.S @@ -0,0 +1,194 @@ +/* Copyright (C) 1996-2014 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. */ + +#include <sysdep.h> + + .set noat + .set noreorder + + .text + +ENTRY(strcmp) +#ifdef PROF + ldgp gp, 0(pv) + lda AT, _mcount + jmp AT, (AT), _mcount + .prologue 1 +#else + .prologue 0 +#endif + + ldq_u t0, 0(a0) # e0 : give cache time to catch up + xor a0, a1, t2 # .. e1 : are s1 and s2 co-aligned? + ldq_u t1, 0(a1) # e0 : + and t2, 7, t2 # .. e1 : + lda t3, -1 # e0 : + bne t2, $unaligned # .. e1 : + + /* On entry to this basic block: + t0 == the first destination word for masking back in + t1 == the first source word. + t3 == -1. */ + +$aligned: + mskqh t3, a0, t3 # e0 : + nop # .. e1 : + ornot t1, t3, t1 # e0 : + ornot t0, t3, t0 # .. e1 : + cmpbge zero, t1, t7 # e0 : bits set iff null found + bne t7, $eos # e1 (zdb) + + /* Aligned compare main loop. + On entry to this basic block: + t0 == an s1 word. + t1 == an s2 word not containing a null. */ + +$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 t7, $a_loop # .. e1 (zdb) + br $eos # e1 : + + /* The two strings are not co-aligned. Align s1 and cope. */ + +$unaligned: + and a0, 7, t4 # e0 : find s1 misalignment + and a1, 7, t5 # .. e1 : find s2 misalignment + subq a1, t4, a1 # e0 : + + /* If s2 misalignment is larger than s2 misalignment, we need + extra startup checks to avoid SEGV. */ + + cmplt t4, t5, t8 # .. e1 : + beq t8, $u_head # 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 : + + /* 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. */ + + extql t1, t5, t1 # e0 : + extql t0, a0, t0 # e0 : + cmpbge zero, t1, t7 # .. e1 : find that zero again + br $eos # e1 : and finish up + + .align 3 +$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 + cmpbge zero, t0, t7 # .. e1 : find zero in first s1 word + ornot t1, t3, t1 # e0 : kill s2 garbage + lda t3, -1 # .. e1 : + mskql t3, a1, t3 # e0 : mask for s2[1] bits we have seen + bne t7, $eos # .. e1 : + xor t0, t1, t4 # e0 : compare aligned words + bne t4, $wordcmp # .. e1 (zdb) + or t2, t3, t3 # e0 : + cmpbge zero, t3, t7 # e1 : + bne t7, $u_final # e1 : + + /* Unaligned copy main loop. In order to avoid reading too much, + the loop is structured to detect zeros in aligned words from s2. + This has, unfortunately, effectively pulled half of a loop + iteration out into the head and half into the tail, but it does + prevent nastiness from accumulating in the very thing we want + to run as fast as possible. + + On entry to this basic block: + t2 == the unshifted low-bits from the next s2 word. */ + + .align 3 +$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 : + extqh t2, a1, t1 # e0 : + cmpbge zero, t0, t7 # .. e1 : find zero in current s1 word + or t1, t3, t1 # e0 : + 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 + beq t4, $u_loop # .. e1 (zdb) + + /* We've found a zero in the low bits of the last s2 word. Get + the next s1 word and align them. */ +$u_final: + ldq_u t0, 8(a0) # e1 : + extql t2, a1, t1 # .. e0 : + cmpbge zero, t1, t7 # e0 : + + /* 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, $done # .. e1 : + + /* Here we have two differing co-aligned words in t0 & t1. + Bytewise compare them and return (t0 > t1 ? 1 : -1). */ +$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) + +$done: + ret # e1 : + + END(strcmp) +libc_hidden_builtin_def (strcmp) |