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glibc/sysdeps/ia64/bzero.S

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/* Optimized version of the standard bzero() function.
This file is part of the GNU C Library.
Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
Contributed by Dan Pop for Itanium <Dan.Pop@cern.ch>.
Rewritten for McKinley by Sverre Jarp, HP Labs/CERN <Sverre.Jarp@cern.ch>
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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
/* Return: dest
Inputs:
in0: dest
in1: count
The algorithm is fairly straightforward: set byte by byte until we
we get to a 16B-aligned address, then loop on 128 B chunks using an
early store as prefetching, then loop on 32B chucks, then clear remaining
words, finally clear remaining bytes.
Since a stf.spill f0 can store 16B in one go, we use this instruction
to get peak speed. */
#include <sysdep.h>
#undef ret
#define dest in0
#define cnt in1
#define tmp r31
#define save_lc r30
#define ptr0 r29
#define ptr1 r28
#define ptr2 r27
#define ptr3 r26
#define ptr9 r24
#define loopcnt r23
#define linecnt r22
#define bytecnt r21
// This routine uses only scratch predicate registers (p6 - p15)
#define p_scr p6 // default register for same-cycle branches
#define p_unalgn p9
#define p_y p11
#define p_n p12
#define p_yy p13
#define p_nn p14
#define movi0 mov
#define MIN1 15
#define MIN1P1HALF 8
#define LINE_SIZE 128
#define LSIZE_SH 7 // shift amount
#define PREF_AHEAD 8
#define USE_FLP
#if defined(USE_INT)
#define store st8
#define myval r0
#elif defined(USE_FLP)
#define store stf8
#define myval f0
#endif
.align 64
ENTRY(bzero)
{ .mmi
.prologue
alloc tmp = ar.pfs, 2, 0, 0, 0
lfetch.nt1 [dest]
.save ar.lc, save_lc
movi0 save_lc = ar.lc
} { .mmi
.body
mov ret0 = dest // return value
nop.m 0
cmp.eq p_scr, p0 = cnt, r0
;; }
{ .mmi
and ptr2 = -(MIN1+1), dest // aligned address
and tmp = MIN1, dest // prepare to check for alignment
tbit.nz p_y, p_n = dest, 0 // Do we have an odd address? (M_B_U)
} { .mib
mov ptr1 = dest
nop.i 0
(p_scr) br.ret.dpnt.many rp // return immediately if count = 0
;; }
{ .mib
cmp.ne p_unalgn, p0 = tmp, r0
} { .mib // NB: # of bytes to move is 1
sub bytecnt = (MIN1+1), tmp // higher than loopcnt
cmp.gt p_scr, p0 = 16, cnt // is it a minimalistic task?
(p_scr) br.cond.dptk.many .move_bytes_unaligned // go move just a few (M_B_U)
;; }
{ .mmi
(p_unalgn) add ptr1 = (MIN1+1), ptr2 // after alignment
(p_unalgn) add ptr2 = MIN1P1HALF, ptr2 // after alignment
(p_unalgn) tbit.nz.unc p_y, p_n = bytecnt, 3 // should we do a st8 ?
;; }
{ .mib
(p_y) add cnt = -8, cnt
(p_unalgn) tbit.nz.unc p_yy, p_nn = bytecnt, 2 // should we do a st4 ?
} { .mib
(p_y) st8 [ptr2] = r0,-4
(p_n) add ptr2 = 4, ptr2
;; }
{ .mib
(p_yy) add cnt = -4, cnt
(p_unalgn) tbit.nz.unc p_y, p_n = bytecnt, 1 // should we do a st2 ?
} { .mib
(p_yy) st4 [ptr2] = r0,-2
(p_nn) add ptr2 = 2, ptr2
;; }
{ .mmi
mov tmp = LINE_SIZE+1 // for compare
(p_y) add cnt = -2, cnt
(p_unalgn) tbit.nz.unc p_yy, p_nn = bytecnt, 0 // should we do a st1 ?
} { .mmi
nop.m 0
(p_y) st2 [ptr2] = r0,-1
(p_n) add ptr2 = 1, ptr2
;; }
{ .mmi
(p_yy) st1 [ptr2] = r0
cmp.gt p_scr, p0 = tmp, cnt // is it a minimalistic task?
} { .mbb
(p_yy) add cnt = -1, cnt
(p_scr) br.cond.dpnt.many .fraction_of_line // go move just a few
;; }
{ .mib
nop.m 0
shr.u linecnt = cnt, LSIZE_SH
nop.b 0
;; }
.align 32
.l1b: // ------------------// L1B: store ahead into cache lines; fill later
{ .mmi
and tmp = -(LINE_SIZE), cnt // compute end of range
mov ptr9 = ptr1 // used for prefetching
and cnt = (LINE_SIZE-1), cnt // remainder
} { .mmi
mov loopcnt = PREF_AHEAD-1 // default prefetch loop
cmp.gt p_scr, p0 = PREF_AHEAD, linecnt // check against actual value
;; }
{ .mmi
(p_scr) add loopcnt = -1, linecnt
add ptr2 = 16, ptr1 // start of stores (beyond prefetch stores)
add ptr1 = tmp, ptr1 // first address beyond total range
;; }
{ .mmi
add tmp = -1, linecnt // next loop count
movi0 ar.lc = loopcnt
;; }
.pref_l1b:
{ .mib
stf.spill [ptr9] = f0, 128 // Do stores one cache line apart
nop.i 0
br.cloop.dptk.few .pref_l1b
;; }
{ .mmi
add ptr0 = 16, ptr2 // Two stores in parallel
movi0 ar.lc = tmp
;; }
.l1bx:
{ .mmi
stf.spill [ptr2] = f0, 32
stf.spill [ptr0] = f0, 32
;; }
{ .mmi
stf.spill [ptr2] = f0, 32
stf.spill [ptr0] = f0, 32
;; }
{ .mmi
stf.spill [ptr2] = f0, 32
stf.spill [ptr0] = f0, 64
cmp.lt p_scr, p0 = ptr9, ptr1 // do we need more prefetching?
;; }
{ .mmb
stf.spill [ptr2] = f0, 32
(p_scr) stf.spill [ptr9] = f0, 128
br.cloop.dptk.few .l1bx
;; }
{ .mib
cmp.gt p_scr, p0 = 8, cnt // just a few bytes left ?
(p_scr) br.cond.dpnt.many .move_bytes_from_alignment
;; }
.fraction_of_line:
{ .mib
add ptr2 = 16, ptr1
shr.u loopcnt = cnt, 5 // loopcnt = cnt / 32
;; }
{ .mib
cmp.eq p_scr, p0 = loopcnt, r0
add loopcnt = -1, loopcnt
(p_scr) br.cond.dpnt.many .store_words
;; }
{ .mib
and cnt = 0x1f, cnt // compute the remaining cnt
movi0 ar.lc = loopcnt
;; }
.align 32
.l2: // -----------------------------// L2A: store 32B in 2 cycles
{ .mmb
store [ptr1] = myval, 8
store [ptr2] = myval, 8
;; } { .mmb
store [ptr1] = myval, 24
store [ptr2] = myval, 24
br.cloop.dptk.many .l2
;; }
.store_words:
{ .mib
cmp.gt p_scr, p0 = 8, cnt // just a few bytes left ?
(p_scr) br.cond.dpnt.many .move_bytes_from_alignment // Branch
;; }
{ .mmi
store [ptr1] = myval, 8 // store
cmp.le p_y, p_n = 16, cnt //
add cnt = -8, cnt // subtract
;; }
{ .mmi
(p_y) store [ptr1] = myval, 8 // store
(p_y) cmp.le.unc p_yy, p_nn = 16, cnt
(p_y) add cnt = -8, cnt // subtract
;; }
{ .mmi // store
(p_yy) store [ptr1] = myval, 8
(p_yy) add cnt = -8, cnt // subtract
;; }
.move_bytes_from_alignment:
{ .mib
cmp.eq p_scr, p0 = cnt, r0
tbit.nz.unc p_y, p0 = cnt, 2 // should we terminate with a st4 ?
(p_scr) br.cond.dpnt.few .restore_and_exit
;; }
{ .mib
(p_y) st4 [ptr1] = r0,4
tbit.nz.unc p_yy, p0 = cnt, 1 // should we terminate with a st2 ?
;; }
{ .mib
(p_yy) st2 [ptr1] = r0,2
tbit.nz.unc p_y, p0 = cnt, 0 // should we terminate with a st1 ?
;; }
{ .mib
(p_y) st1 [ptr1] = r0
;; }
.restore_and_exit:
{ .mib
nop.m 0
movi0 ar.lc = save_lc
br.ret.sptk.many rp
;; }
.move_bytes_unaligned:
{ .mmi
.pred.rel "mutex",p_y, p_n
.pred.rel "mutex",p_yy, p_nn
(p_n) cmp.le p_yy, p_nn = 4, cnt
(p_y) cmp.le p_yy, p_nn = 5, cnt
(p_n) add ptr2 = 2, ptr1
} { .mmi
(p_y) add ptr2 = 3, ptr1
(p_y) st1 [ptr1] = r0, 1 // fill 1 (odd-aligned) byte
(p_y) add cnt = -1, cnt // [15, 14 (or less) left]
;; }
{ .mmi
(p_yy) cmp.le.unc p_y, p0 = 8, cnt
add ptr3 = ptr1, cnt // prepare last store
movi0 ar.lc = save_lc
} { .mmi
(p_yy) st2 [ptr1] = r0, 4 // fill 2 (aligned) bytes
(p_yy) st2 [ptr2] = r0, 4 // fill 2 (aligned) bytes
(p_yy) add cnt = -4, cnt // [11, 10 (o less) left]
;; }
{ .mmi
(p_y) cmp.le.unc p_yy, p0 = 8, cnt
add ptr3 = -1, ptr3 // last store
tbit.nz p_scr, p0 = cnt, 1 // will there be a st2 at the end ?
} { .mmi
(p_y) st2 [ptr1] = r0, 4 // fill 2 (aligned) bytes
(p_y) st2 [ptr2] = r0, 4 // fill 2 (aligned) bytes
(p_y) add cnt = -4, cnt // [7, 6 (or less) left]
;; }
{ .mmi
(p_yy) st2 [ptr1] = r0, 4 // fill 2 (aligned) bytes
(p_yy) st2 [ptr2] = r0, 4 // fill 2 (aligned) bytes
// [3, 2 (or less) left]
tbit.nz p_y, p0 = cnt, 0 // will there be a st1 at the end ?
} { .mmi
(p_yy) add cnt = -4, cnt
;; }
{ .mmb
(p_scr) st2 [ptr1] = r0 // fill 2 (aligned) bytes
(p_y) st1 [ptr3] = r0 // fill last byte (using ptr3)
br.ret.sptk.many rp
;; }
END(bzero)
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