250 lines
7.7 KiB
ArmAsm
250 lines
7.7 KiB
ArmAsm
/* Optimized version of the standard memmove() function.
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This file is part of the GNU C Library.
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Copyright (C) 2000-2022 Free Software Foundation, Inc.
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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, see
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<https://www.gnu.org/licenses/>. */
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/* Return: dest
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Inputs:
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in0: dest
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in1: src
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in2: byte count
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The core of the function is the memcpy implementation used in memcpy.S.
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When bytes have to be copied backwards, only the easy case, when
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all arguments are multiples of 8, is optimised.
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In this form, it assumes little endian mode. For big endian mode,
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sh1 must be computed using an extra instruction: sub sh1 = 64, sh1
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or the UM.be bit should be cleared at the beginning and set at the end. */
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#include <sysdep.h>
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#undef ret
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#define OP_T_THRES 16
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#define OPSIZ 8
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#define adest r15
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#define saved_pr r17
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#define saved_lc r18
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#define dest r19
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#define src r20
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#define len r21
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#define asrc r22
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#define tmp2 r23
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#define tmp3 r24
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#define tmp4 r25
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#define ptable r26
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#define ploop56 r27
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#define loopaddr r28
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#define sh1 r29
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#define loopcnt r30
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#define value r31
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#ifdef GAS_ALIGN_BREAKS_UNWIND_INFO
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# define ALIGN(n) { nop 0 }
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#else
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# define ALIGN(n) .align n
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#endif
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#define LOOP(shift) \
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ALIGN(32); \
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.loop##shift##: \
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(p[0]) ld8 r[0] = [asrc], 8 ; /* w1 */ \
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(p[MEMLAT+1]) st8 [dest] = value, 8 ; \
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(p[MEMLAT]) shrp value = r[MEMLAT], r[MEMLAT+1], shift ; \
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nop.b 0 ; \
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nop.b 0 ; \
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br.ctop.sptk .loop##shift ; \
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br.cond.sptk .cpyfew ; /* deal with the remaining bytes */
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#define MEMLAT 21
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#define Nrot (((2*MEMLAT+3) + 7) & ~7)
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ENTRY(memmove)
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.prologue
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alloc r2 = ar.pfs, 3, Nrot - 3, 0, Nrot
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.rotr r[MEMLAT + 2], q[MEMLAT + 1]
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.rotp p[MEMLAT + 2]
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mov ret0 = in0 // return value = dest
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.save pr, saved_pr
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mov saved_pr = pr // save the predicate registers
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.save ar.lc, saved_lc
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mov saved_lc = ar.lc // save the loop counter
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.body
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or tmp3 = in0, in1 ;; // tmp3 = dest | src
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or tmp3 = tmp3, in2 // tmp3 = dest | src | len
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mov dest = in0 // dest
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mov src = in1 // src
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mov len = in2 // len
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sub tmp2 = r0, in0 // tmp2 = -dest
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cmp.eq p6, p0 = in2, r0 // if (len == 0)
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(p6) br.cond.spnt .restore_and_exit;;// return dest;
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and tmp4 = 7, tmp3 // tmp4 = (dest | src | len) & 7
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cmp.le p6, p0 = dest, src // if dest <= src it's always safe
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(p6) br.cond.spnt .forward // to copy forward
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add tmp3 = src, len;;
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cmp.lt p6, p0 = dest, tmp3 // if dest > src && dest < src + len
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(p6) br.cond.spnt .backward // we have to copy backward
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.forward:
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shr.u loopcnt = len, 4 ;; // loopcnt = len / 16
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cmp.ne p6, p0 = tmp4, r0 // if ((dest | src | len) & 7 != 0)
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(p6) br.cond.sptk .next // goto next;
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// The optimal case, when dest, src and len are all multiples of 8
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and tmp3 = 0xf, len
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mov pr.rot = 1 << 16 // set rotating predicates
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mov ar.ec = MEMLAT + 1 ;; // set the epilog counter
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cmp.ne p6, p0 = tmp3, r0 // do we have to copy an extra word?
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adds loopcnt = -1, loopcnt;; // --loopcnt
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(p6) ld8 value = [src], 8;;
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(p6) st8 [dest] = value, 8 // copy the "odd" word
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mov ar.lc = loopcnt // set the loop counter
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cmp.eq p6, p0 = 8, len
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(p6) br.cond.spnt .restore_and_exit;;// the one-word special case
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adds adest = 8, dest // set adest one word ahead of dest
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adds asrc = 8, src ;; // set asrc one word ahead of src
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nop.b 0 // get the "golden" alignment for
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nop.b 0 // the next loop
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.l0:
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(p[0]) ld8 r[0] = [src], 16
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(p[0]) ld8 q[0] = [asrc], 16
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(p[MEMLAT]) st8 [dest] = r[MEMLAT], 16
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(p[MEMLAT]) st8 [adest] = q[MEMLAT], 16
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br.ctop.dptk .l0 ;;
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mov pr = saved_pr, -1 // restore the predicate registers
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mov ar.lc = saved_lc // restore the loop counter
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br.ret.sptk.many b0
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.next:
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cmp.ge p6, p0 = OP_T_THRES, len // is len <= OP_T_THRES
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and loopcnt = 7, tmp2 // loopcnt = -dest % 8
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(p6) br.cond.spnt .cpyfew // copy byte by byte
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;;
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cmp.eq p6, p0 = loopcnt, r0
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(p6) br.cond.sptk .dest_aligned
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sub len = len, loopcnt // len -= -dest % 8
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adds loopcnt = -1, loopcnt // --loopcnt
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;;
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mov ar.lc = loopcnt
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.l1: // copy -dest % 8 bytes
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ld1 value = [src], 1 // value = *src++
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;;
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st1 [dest] = value, 1 // *dest++ = value
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br.cloop.dptk .l1
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.dest_aligned:
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and sh1 = 7, src // sh1 = src % 8
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and tmp2 = -8, len // tmp2 = len & -OPSIZ
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and asrc = -8, src // asrc = src & -OPSIZ -- align src
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shr.u loopcnt = len, 3 // loopcnt = len / 8
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and len = 7, len;; // len = len % 8
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adds loopcnt = -1, loopcnt // --loopcnt
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addl tmp4 = @ltoff(.table), gp
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addl tmp3 = @ltoff(.loop56), gp
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mov ar.ec = MEMLAT + 1 // set EC
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mov pr.rot = 1 << 16;; // set rotating predicates
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mov ar.lc = loopcnt // set LC
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cmp.eq p6, p0 = sh1, r0 // is the src aligned?
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(p6) br.cond.sptk .src_aligned
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add src = src, tmp2 // src += len & -OPSIZ
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shl sh1 = sh1, 3 // sh1 = 8 * (src % 8)
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ld8 ploop56 = [tmp3] // ploop56 = &loop56
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ld8 ptable = [tmp4];; // ptable = &table
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add tmp3 = ptable, sh1;; // tmp3 = &table + sh1
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mov ar.ec = MEMLAT + 1 + 1 // one more pass needed
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ld8 tmp4 = [tmp3];; // tmp4 = loop offset
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sub loopaddr = ploop56,tmp4 // loopadd = &loop56 - loop offset
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ld8 r[1] = [asrc], 8;; // w0
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mov b6 = loopaddr;;
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br b6 // jump to the appropriate loop
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LOOP(8)
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LOOP(16)
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LOOP(24)
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LOOP(32)
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LOOP(40)
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LOOP(48)
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LOOP(56)
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.src_aligned:
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.l3:
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(p[0]) ld8 r[0] = [src], 8
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(p[MEMLAT]) st8 [dest] = r[MEMLAT], 8
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br.ctop.dptk .l3
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.cpyfew:
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cmp.eq p6, p0 = len, r0 // is len == 0 ?
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adds len = -1, len // --len;
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(p6) br.cond.spnt .restore_and_exit ;;
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mov ar.lc = len
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.l4:
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ld1 value = [src], 1
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;;
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st1 [dest] = value, 1
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br.cloop.dptk .l4 ;;
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.restore_and_exit:
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mov pr = saved_pr, -1 // restore the predicate registers
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mov ar.lc = saved_lc // restore the loop counter
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br.ret.sptk.many b0
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// In the case of a backward copy, optimise only the case when everything
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// is a multiple of 8, otherwise copy byte by byte. The backward copy is
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// used only when the blocks are overlapping and dest > src.
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.backward:
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shr.u loopcnt = len, 3 // loopcnt = len / 8
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add src = src, len // src points one byte past the end
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add dest = dest, len ;; // dest points one byte past the end
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mov ar.ec = MEMLAT + 1 // set the epilog counter
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mov pr.rot = 1 << 16 // set rotating predicates
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adds loopcnt = -1, loopcnt // --loopcnt
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cmp.ne p6, p0 = tmp4, r0 // if ((dest | src | len) & 7 != 0)
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(p6) br.cond.sptk .bytecopy ;; // copy byte by byte backward
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adds src = -8, src // src points to the last word
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adds dest = -8, dest // dest points to the last word
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mov ar.lc = loopcnt;; // set the loop counter
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.l5:
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(p[0]) ld8 r[0] = [src], -8
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(p[MEMLAT]) st8 [dest] = r[MEMLAT], -8
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br.ctop.dptk .l5
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br.cond.sptk .restore_and_exit
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.bytecopy:
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adds src = -1, src // src points to the last byte
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adds dest = -1, dest // dest points to the last byte
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adds loopcnt = -1, len;; // loopcnt = len - 1
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mov ar.lc = loopcnt;; // set the loop counter
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.l6:
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(p[0]) ld1 r[0] = [src], -1
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(p[MEMLAT]) st1 [dest] = r[MEMLAT], -1
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br.ctop.dptk .l6
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br.cond.sptk .restore_and_exit
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END(memmove)
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.rodata
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.align 8
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.table:
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data8 0 // dummy entry
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data8 .loop56 - .loop8
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data8 .loop56 - .loop16
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data8 .loop56 - .loop24
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data8 .loop56 - .loop32
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data8 .loop56 - .loop40
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data8 .loop56 - .loop48
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data8 .loop56 - .loop56
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libc_hidden_builtin_def (memmove)
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