| /* 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 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) |