sysdeps/ia64/memcmp.S

   1 /* Optimized version of the standard memcmp() function.
   2    This file is part of the GNU C Library.
   3    Copyright (C) 2000, 2001, 2004, 2011 Free Software Foundation, Inc.
   4    Contributed by Dan Pop <Dan.Pop@cern.ch>.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 /* Return: the result of the comparison
  22
  23    Inputs:
  24         in0:    dest (aka s1)
  25         in1:    src  (aka s2)
  26         in2:    byte count
  27
  28    In this form, it assumes little endian mode.  For big endian mode,
  29    the two shifts in .l2 must be inverted:
  30
  31         shl     tmp1[0] = r[1 + MEMLAT], sh1   // tmp1 = w0 << sh1
  32         shr.u   tmp2[0] = r[0 + MEMLAT], sh2   // tmp2 = w1 >> sh2
  33
  34    and all the mux1 instructions should be replaced by plain mov's.  */
  35
  36 #include <sysdep.h>
  37 #undef ret
  38
  39 #define OP_T_THRES      16
  40 #define OPSIZ           8
  41 #define MEMLAT          2
  42
  43 #define start           r15
  44 #define saved_pr        r17
  45 #define saved_lc        r18
  46 #define dest            r19
  47 #define src             r20
  48 #define len             r21
  49 #define asrc            r22
  50 #define tmp             r23
  51 #define value1          r24
  52 #define value2          r25
  53 #define sh2             r28
  54 #define sh1             r29
  55 #define loopcnt         r30
  56
  57 ENTRY(memcmp)
  58         .prologue
  59         alloc   r2 = ar.pfs, 3, 37, 0, 40
  60
  61         .rotr   r[MEMLAT + 2], q[MEMLAT + 5], tmp1[4], tmp2[4], val[2]
  62         .rotp   p[MEMLAT + 4 + 1]
  63
  64         mov     ret0 = r0               // by default return value = 0
  65         .save pr, saved_pr
  66         mov     saved_pr = pr           // save the predicate registers
  67         .save ar.lc, saved_lc
  68         mov     saved_lc = ar.lc        // save the loop counter
  69         .body
  70         mov     dest = in0              // dest
  71         mov     src = in1               // src
  72         mov     len = in2               // len
  73         sub     tmp = r0, in0           // tmp = -dest
  74         ;;
  75         and     loopcnt = 7, tmp                // loopcnt = -dest % 8
  76         cmp.ge  p6, p0 = OP_T_THRES, len        // is len <= OP_T_THRES
  77 (p6)    br.cond.spnt    .cmpfew                 // compare byte by byte
  78         ;;
  79         cmp.eq  p6, p0 = loopcnt, r0
  80 (p6)    br.cond.sptk .dest_aligned
  81         sub     len = len, loopcnt      // len -= -dest % 8
  82         adds    loopcnt = -1, loopcnt   // --loopcnt
  83         ;;
  84         mov     ar.lc = loopcnt
  85 .l1:                                    // copy -dest % 8 bytes
  86         ld1     value1 = [src], 1       // value = *src++
  87         ld1     value2 = [dest], 1
  88         ;;
  89         cmp.ne  p6, p0 = value1, value2
  90 (p6)    br.cond.spnt .done
  91         br.cloop.dptk .l1
  92 .dest_aligned:
  93         and     sh1 = 7, src            // sh1 = src % 8
  94         and     tmp = -8, len           // tmp = len & -OPSIZ
  95         and     asrc = -8, src          // asrc = src & -OPSIZ  -- align src
  96         shr.u   loopcnt = len, 3        // loopcnt = len / 8
  97         and     len = 7, len ;;         // len = len % 8
  98         shl     sh1 = sh1, 3            // sh1 = 8 * (src % 8)
  99         adds    loopcnt = -1, loopcnt   // --loopcnt
 100         mov     pr.rot = 1 << 16 ;;     // set rotating predicates
 101         sub     sh2 = 64, sh1           // sh2 = 64 - sh1
 102         mov     ar.lc = loopcnt         // set LC
 103         cmp.eq  p6, p0 = sh1, r0        // is the src aligned?
 104 (p6)    br.cond.sptk .src_aligned
 105         add     src = src, tmp          // src += len & -OPSIZ
 106         mov     ar.ec = MEMLAT + 4 + 1  // four more passes needed
 107         ld8     r[1] = [asrc], 8 ;;     // r[1] = w0
 108         .align  32
 109
 110 // We enter this loop with p6 cleared by the above comparison
 111
 112 .l2:
 113 (p[0])          ld8     r[0] = [asrc], 8                // r[0] = w1
 114 (p[0])          ld8     q[0] = [dest], 8
 115 (p[MEMLAT])     shr.u   tmp1[0] = r[1 + MEMLAT], sh1    // tmp1 = w0 >> sh1
 116 (p[MEMLAT])     shl     tmp2[0] = r[0 + MEMLAT], sh2    // tmp2 = w1 << sh2
 117 (p[MEMLAT+4])   cmp.ne  p6, p0 = q[MEMLAT + 4], val[1]
 118 (p[MEMLAT+3])   or      val[0] = tmp1[3], tmp2[3]       // val = tmp1 | tmp2
 119 (p6)            br.cond.spnt .l2exit
 120                 br.ctop.sptk    .l2
 121                 br.cond.sptk .cmpfew
 122 .l3exit:
 123         mux1    value1 = r[MEMLAT], @rev
 124         mux1    value2 = q[MEMLAT], @rev
 125         cmp.ne  p6, p0 = r0, r0 ;;      // clear p6
 126 .l2exit:
 127 (p6)    mux1    value1 = val[1], @rev
 128 (p6)    mux1    value2 = q[MEMLAT + 4], @rev ;;
 129         cmp.ltu p6, p7 = value2, value1 ;;
 130 (p6)    mov     ret0 = -1
 131 (p7)    mov     ret0 = 1
 132         mov     pr = saved_pr, -1       // restore the predicate registers
 133         mov     ar.lc = saved_lc        // restore the loop counter
 134         br.ret.sptk.many b0
 135 .src_aligned:
 136         cmp.ne  p6, p0 = r0, r0         // clear p6
 137         mov     ar.ec = MEMLAT + 1 ;;   // set EC
 138 .l3:
 139 (p[0])          ld8     r[0] = [src], 8
 140 (p[0])          ld8     q[0] = [dest], 8
 141 (p[MEMLAT])     cmp.ne  p6, p0 = r[MEMLAT], q[MEMLAT]
 142 (p6)            br.cond.spnt .l3exit
 143                 br.ctop.dptk .l3 ;;
 144 .cmpfew:
 145         cmp.eq  p6, p0 = len, r0        // is len == 0 ?
 146         adds    len = -1, len           // --len;
 147 (p6)    br.cond.spnt    .restore_and_exit ;;
 148         mov     ar.lc = len
 149 .l4:
 150         ld1     value1 = [src], 1
 151         ld1     value2 = [dest], 1
 152         ;;
 153         cmp.ne  p6, p0 = value1, value2
 154 (p6)    br.cond.spnt    .done
 155         br.cloop.dptk   .l4 ;;
 156 .done:
 157 (p6)    sub     ret0 = value2, value1   // don't execute it if falling thru
 158 .restore_and_exit:
 159         mov     pr = saved_pr, -1       // restore the predicate registers
 160         mov     ar.lc = saved_lc        // restore the loop counter
 161         br.ret.sptk.many b0
 162 END(memcmp)
 163
 164 weak_alias (memcmp, bcmp)
 165 libc_hidden_builtin_def (memcmp)