1/* Optimized version of the standard memcmp() function. 2 This file is part of the GNU C Library. 3 Copyright (C) 2000-2022 Free Software Foundation, Inc. 4 5 The GNU C Library is free software; you can redistribute it and/or 6 modify it under the terms of the GNU Lesser General Public 7 License as published by the Free Software Foundation; either 8 version 2.1 of the License, or (at your option) any later version. 9 10 The GNU C Library is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public 16 License along with the GNU C Library; if not, see 17 <https://www.gnu.org/licenses/>. */ 18 19/* Return: the result of the comparison 20 21 Inputs: 22 in0: dest (aka s1) 23 in1: src (aka s2) 24 in2: byte count 25 26 In this form, it assumes little endian mode. For big endian mode, 27 the two shifts in .l2 must be inverted: 28 29 shl tmp1[0] = r[1 + MEMLAT], sh1 // tmp1 = w0 << sh1 30 shr.u tmp2[0] = r[0 + MEMLAT], sh2 // tmp2 = w1 >> sh2 31 32 and all the mux1 instructions should be replaced by plain mov's. */ 33 34#include <sysdep.h> 35#undef ret 36 37#define OP_T_THRES 16 38#define OPSIZ 8 39#define MEMLAT 2 40 41#define start r15 42#define saved_pr r17 43#define saved_lc r18 44#define dest r19 45#define src r20 46#define len r21 47#define asrc r22 48#define tmp r23 49#define value1 r24 50#define value2 r25 51#define sh2 r28 52#define sh1 r29 53#define loopcnt r30 54 55ENTRY(memcmp) 56 .prologue 57 alloc r2 = ar.pfs, 3, 37, 0, 40 58 59 .rotr r[MEMLAT + 2], q[MEMLAT + 5], tmp1[4], tmp2[4], val[2] 60 .rotp p[MEMLAT + 4 + 1] 61 62 mov ret0 = r0 // by default return value = 0 63 .save pr, saved_pr 64 mov saved_pr = pr // save the predicate registers 65 .save ar.lc, saved_lc 66 mov saved_lc = ar.lc // save the loop counter 67 .body 68 mov dest = in0 // dest 69 mov src = in1 // src 70 mov len = in2 // len 71 sub tmp = r0, in0 // tmp = -dest 72 ;; 73 and loopcnt = 7, tmp // loopcnt = -dest % 8 74 cmp.ge p6, p0 = OP_T_THRES, len // is len <= OP_T_THRES 75(p6) br.cond.spnt .cmpfew // compare byte by byte 76 ;; 77 cmp.eq p6, p0 = loopcnt, r0 78(p6) br.cond.sptk .dest_aligned 79 sub len = len, loopcnt // len -= -dest % 8 80 adds loopcnt = -1, loopcnt // --loopcnt 81 ;; 82 mov ar.lc = loopcnt 83.l1: // copy -dest % 8 bytes 84 ld1 value1 = [src], 1 // value = *src++ 85 ld1 value2 = [dest], 1 86 ;; 87 cmp.ne p6, p0 = value1, value2 88(p6) br.cond.spnt .done 89 br.cloop.dptk .l1 90.dest_aligned: 91 and sh1 = 7, src // sh1 = src % 8 92 and tmp = -8, len // tmp = len & -OPSIZ 93 and asrc = -8, src // asrc = src & -OPSIZ -- align src 94 shr.u loopcnt = len, 3 // loopcnt = len / 8 95 and len = 7, len ;; // len = len % 8 96 shl sh1 = sh1, 3 // sh1 = 8 * (src % 8) 97 adds loopcnt = -1, loopcnt // --loopcnt 98 mov pr.rot = 1 << 16 ;; // set rotating predicates 99 sub sh2 = 64, sh1 // sh2 = 64 - sh1 100 mov ar.lc = loopcnt // set LC 101 cmp.eq p6, p0 = sh1, r0 // is the src aligned? 102(p6) br.cond.sptk .src_aligned 103 add src = src, tmp // src += len & -OPSIZ 104 mov ar.ec = MEMLAT + 4 + 1 // four more passes needed 105 ld8 r[1] = [asrc], 8 ;; // r[1] = w0 106 .align 32 107 108// We enter this loop with p6 cleared by the above comparison 109 110.l2: 111(p[0]) ld8 r[0] = [asrc], 8 // r[0] = w1 112(p[0]) ld8 q[0] = [dest], 8 113(p[MEMLAT]) shr.u tmp1[0] = r[1 + MEMLAT], sh1 // tmp1 = w0 >> sh1 114(p[MEMLAT]) shl tmp2[0] = r[0 + MEMLAT], sh2 // tmp2 = w1 << sh2 115(p[MEMLAT+4]) cmp.ne p6, p0 = q[MEMLAT + 4], val[1] 116(p[MEMLAT+3]) or val[0] = tmp1[3], tmp2[3] // val = tmp1 | tmp2 117(p6) br.cond.spnt .l2exit 118 br.ctop.sptk .l2 119 br.cond.sptk .cmpfew 120.l3exit: 121 mux1 value1 = r[MEMLAT], @rev 122 mux1 value2 = q[MEMLAT], @rev 123 cmp.ne p6, p0 = r0, r0 ;; // clear p6 124.l2exit: 125(p6) mux1 value1 = val[1], @rev 126(p6) mux1 value2 = q[MEMLAT + 4], @rev ;; 127 cmp.ltu p6, p7 = value2, value1 ;; 128(p6) mov ret0 = -1 129(p7) mov ret0 = 1 130 mov pr = saved_pr, -1 // restore the predicate registers 131 mov ar.lc = saved_lc // restore the loop counter 132 br.ret.sptk.many b0 133.src_aligned: 134 cmp.ne p6, p0 = r0, r0 // clear p6 135 mov ar.ec = MEMLAT + 1 ;; // set EC 136.l3: 137(p[0]) ld8 r[0] = [src], 8 138(p[0]) ld8 q[0] = [dest], 8 139(p[MEMLAT]) cmp.ne p6, p0 = r[MEMLAT], q[MEMLAT] 140(p6) br.cond.spnt .l3exit 141 br.ctop.dptk .l3 ;; 142.cmpfew: 143 cmp.eq p6, p0 = len, r0 // is len == 0 ? 144 adds len = -1, len // --len; 145(p6) br.cond.spnt .restore_and_exit ;; 146 mov ar.lc = len 147.l4: 148 ld1 value1 = [src], 1 149 ld1 value2 = [dest], 1 150 ;; 151 cmp.ne p6, p0 = value1, value2 152(p6) br.cond.spnt .done 153 br.cloop.dptk .l4 ;; 154.done: 155(p6) sub ret0 = value2, value1 // don't execute it if falling thru 156.restore_and_exit: 157 mov pr = saved_pr, -1 // restore the predicate registers 158 mov ar.lc = saved_lc // restore the loop counter 159 br.ret.sptk.many b0 160END(memcmp) 161 162weak_alias (memcmp, bcmp) 163strong_alias (memcmp, __memcmpeq) 164libc_hidden_builtin_def (memcmp) 165libc_hidden_def (__memcmpeq) 166