1 /* Optimized version of the standard bzero() function.
2 This file is part of the GNU C Library.
3 Copyright (C) 2000-2017 Free Software Foundation, Inc.
4 Contributed by Dan Pop for Itanium <Dan.Pop@cern.ch>.
5 Rewritten for McKinley by Sverre Jarp, HP Labs/CERN <Sverre.Jarp@cern.ch>
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, see
19 <http://www.gnu.org/licenses/>. */
27 The algorithm is fairly straightforward: set byte by byte until we
28 we get to a 16B-aligned address, then loop on 128 B chunks using an
29 early store as prefetching, then loop on 32B chucks, then clear remaining
30 words, finally clear remaining bytes.
31 Since a stf.spill f0 can store 16B in one go, we use this instruction
51 // This routine uses only scratch predicate registers (p6 - p15)
52 #define p_scr p6 // default register for same-cycle branches
64 #define LSIZE_SH 7 // shift amount
71 #elif defined(USE_FLP)
80 alloc tmp = ar.pfs, 2, 0, 0, 0
86 mov ret0 = dest // return value
88 cmp.eq p_scr, p0 = cnt, r0
91 and ptr2 = -(MIN1+1), dest // aligned address
92 and tmp = MIN1, dest // prepare to check for alignment
93 tbit.nz p_y, p_n = dest, 0 // Do we have an odd address? (M_B_U)
97 (p_scr) br.ret.dpnt.many rp // return immediately if count = 0
100 cmp.ne p_unalgn, p0 = tmp, r0
101 } { .mib // NB: # of bytes to move is 1
102 sub bytecnt = (MIN1+1), tmp // higher than loopcnt
103 cmp.gt p_scr, p0 = 16, cnt // is it a minimalistic task?
104 (p_scr) br.cond.dptk.many .move_bytes_unaligned // go move just a few (M_B_U)
107 (p_unalgn) add ptr1 = (MIN1+1), ptr2 // after alignment
108 (p_unalgn) add ptr2 = MIN1P1HALF, ptr2 // after alignment
109 (p_unalgn) tbit.nz.unc p_y, p_n = bytecnt, 3 // should we do a st8 ?
112 (p_y) add cnt = -8, cnt
113 (p_unalgn) tbit.nz.unc p_yy, p_nn = bytecnt, 2 // should we do a st4 ?
115 (p_y) st8 [ptr2] = r0,-4
116 (p_n) add ptr2 = 4, ptr2
119 (p_yy) add cnt = -4, cnt
120 (p_unalgn) tbit.nz.unc p_y, p_n = bytecnt, 1 // should we do a st2 ?
122 (p_yy) st4 [ptr2] = r0,-2
123 (p_nn) add ptr2 = 2, ptr2
126 mov tmp = LINE_SIZE+1 // for compare
127 (p_y) add cnt = -2, cnt
128 (p_unalgn) tbit.nz.unc p_yy, p_nn = bytecnt, 0 // should we do a st1 ?
131 (p_y) st2 [ptr2] = r0,-1
132 (p_n) add ptr2 = 1, ptr2
136 (p_yy) st1 [ptr2] = r0
137 cmp.gt p_scr, p0 = tmp, cnt // is it a minimalistic task?
139 (p_yy) add cnt = -1, cnt
140 (p_scr) br.cond.dpnt.many .fraction_of_line // go move just a few
144 shr.u linecnt = cnt, LSIZE_SH
149 .l1b: // ------------------// L1B: store ahead into cache lines; fill later
151 and tmp = -(LINE_SIZE), cnt // compute end of range
152 mov ptr9 = ptr1 // used for prefetching
153 and cnt = (LINE_SIZE-1), cnt // remainder
155 mov loopcnt = PREF_AHEAD-1 // default prefetch loop
156 cmp.gt p_scr, p0 = PREF_AHEAD, linecnt // check against actual value
159 (p_scr) add loopcnt = -1, linecnt
160 add ptr2 = 16, ptr1 // start of stores (beyond prefetch stores)
161 add ptr1 = tmp, ptr1 // first address beyond total range
164 add tmp = -1, linecnt // next loop count
165 movi0 ar.lc = loopcnt
169 stf.spill [ptr9] = f0, 128 // Do stores one cache line apart
171 br.cloop.dptk.few .pref_l1b
174 add ptr0 = 16, ptr2 // Two stores in parallel
179 stf.spill [ptr2] = f0, 32
180 stf.spill [ptr0] = f0, 32
183 stf.spill [ptr2] = f0, 32
184 stf.spill [ptr0] = f0, 32
187 stf.spill [ptr2] = f0, 32
188 stf.spill [ptr0] = f0, 64
189 cmp.lt p_scr, p0 = ptr9, ptr1 // do we need more prefetching?
192 stf.spill [ptr2] = f0, 32
193 (p_scr) stf.spill [ptr9] = f0, 128
194 br.cloop.dptk.few .l1bx
197 cmp.gt p_scr, p0 = 8, cnt // just a few bytes left ?
198 (p_scr) br.cond.dpnt.many .move_bytes_from_alignment
204 shr.u loopcnt = cnt, 5 // loopcnt = cnt / 32
207 cmp.eq p_scr, p0 = loopcnt, r0
208 add loopcnt = -1, loopcnt
209 (p_scr) br.cond.dpnt.many .store_words
212 and cnt = 0x1f, cnt // compute the remaining cnt
213 movi0 ar.lc = loopcnt
216 .l2: // -----------------------------// L2A: store 32B in 2 cycles
218 store [ptr1] = myval, 8
219 store [ptr2] = myval, 8
221 store [ptr1] = myval, 24
222 store [ptr2] = myval, 24
223 br.cloop.dptk.many .l2
227 cmp.gt p_scr, p0 = 8, cnt // just a few bytes left ?
228 (p_scr) br.cond.dpnt.many .move_bytes_from_alignment // Branch
232 store [ptr1] = myval, 8 // store
233 cmp.le p_y, p_n = 16, cnt //
234 add cnt = -8, cnt // subtract
237 (p_y) store [ptr1] = myval, 8 // store
238 (p_y) cmp.le.unc p_yy, p_nn = 16, cnt
239 (p_y) add cnt = -8, cnt // subtract
242 (p_yy) store [ptr1] = myval, 8
243 (p_yy) add cnt = -8, cnt // subtract
246 .move_bytes_from_alignment:
248 cmp.eq p_scr, p0 = cnt, r0
249 tbit.nz.unc p_y, p0 = cnt, 2 // should we terminate with a st4 ?
250 (p_scr) br.cond.dpnt.few .restore_and_exit
253 (p_y) st4 [ptr1] = r0,4
254 tbit.nz.unc p_yy, p0 = cnt, 1 // should we terminate with a st2 ?
257 (p_yy) st2 [ptr1] = r0,2
258 tbit.nz.unc p_y, p0 = cnt, 0 // should we terminate with a st1 ?
262 (p_y) st1 [ptr1] = r0
267 movi0 ar.lc = save_lc
271 .move_bytes_unaligned:
273 .pred.rel "mutex",p_y, p_n
274 .pred.rel "mutex",p_yy, p_nn
275 (p_n) cmp.le p_yy, p_nn = 4, cnt
276 (p_y) cmp.le p_yy, p_nn = 5, cnt
277 (p_n) add ptr2 = 2, ptr1
279 (p_y) add ptr2 = 3, ptr1
280 (p_y) st1 [ptr1] = r0, 1 // fill 1 (odd-aligned) byte
281 (p_y) add cnt = -1, cnt // [15, 14 (or less) left]
284 (p_yy) cmp.le.unc p_y, p0 = 8, cnt
285 add ptr3 = ptr1, cnt // prepare last store
286 movi0 ar.lc = save_lc
288 (p_yy) st2 [ptr1] = r0, 4 // fill 2 (aligned) bytes
289 (p_yy) st2 [ptr2] = r0, 4 // fill 2 (aligned) bytes
290 (p_yy) add cnt = -4, cnt // [11, 10 (o less) left]
293 (p_y) cmp.le.unc p_yy, p0 = 8, cnt
294 add ptr3 = -1, ptr3 // last store
295 tbit.nz p_scr, p0 = cnt, 1 // will there be a st2 at the end ?
297 (p_y) st2 [ptr1] = r0, 4 // fill 2 (aligned) bytes
298 (p_y) st2 [ptr2] = r0, 4 // fill 2 (aligned) bytes
299 (p_y) add cnt = -4, cnt // [7, 6 (or less) left]
302 (p_yy) st2 [ptr1] = r0, 4 // fill 2 (aligned) bytes
303 (p_yy) st2 [ptr2] = r0, 4 // fill 2 (aligned) bytes
304 // [3, 2 (or less) left]
305 tbit.nz p_y, p0 = cnt, 0 // will there be a st1 at the end ?
307 (p_yy) add cnt = -4, cnt
310 (p_scr) st2 [ptr1] = r0 // fill 2 (aligned) bytes
311 (p_y) st1 [ptr3] = r0 // fill last byte (using ptr3)