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Diffstat (limited to 'sysdeps/aarch64/multiarch/memset_base64.S')
| -rw-r--r-- | sysdeps/aarch64/multiarch/memset_base64.S | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/sysdeps/aarch64/multiarch/memset_base64.S b/sysdeps/aarch64/multiarch/memset_base64.S new file mode 100644 index 0000000000..9a623259b9 --- /dev/null +++ b/sysdeps/aarch64/multiarch/memset_base64.S @@ -0,0 +1,178 @@ +/* Copyright (C) 2018 Free Software Foundation, Inc. + + This file is part of the GNU C Library. + + 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, see + <http://www.gnu.org/licenses/>. */ + +#include <sysdep.h> +#include "memset-reg.h" + +#ifndef MEMSET +# define MEMSET __memset_base64 +#endif + +#ifndef DC_ZVA_THRESHOLD +# define DC_ZVA_THRESHOLD 512 +#endif + +/* Assumptions: + * + * ARMv8-a, AArch64, unaligned accesses + * + */ + +ENTRY_ALIGN (MEMSET, 6) + + DELOUSE (0) + DELOUSE (2) + + bfi valw, valw, 8, 8 + bfi valw, valw, 16, 16 + bfi val, val, 32, 32 + + add dstend, dstin, count + + cmp count, 96 + b.hi L(set_long) + cmp count, 16 + b.hs L(set_medium) + + /* Set 0..15 bytes. */ + tbz count, 3, 1f + str val, [dstin] + str val, [dstend, -8] + ret + + .p2align 3 +1: tbz count, 2, 2f + str valw, [dstin] + str valw, [dstend, -4] + ret +2: cbz count, 3f + strb valw, [dstin] + tbz count, 1, 3f + strh valw, [dstend, -2] +3: ret + + .p2align 3 + /* Set 16..96 bytes. */ +L(set_medium): + stp val, val, [dstin] + tbnz count, 6, L(set96) + stp val, val, [dstend, -16] + tbz count, 5, 1f + stp val, val, [dstin, 16] + stp val, val, [dstend, -32] +1: ret + + .p2align 4 + /* Set 64..96 bytes. Write 64 bytes from the start and + 32 bytes from the end. */ +L(set96): + stp val, val, [dstin, 16] + stp val, val, [dstin, 32] + stp val, val, [dstin, 48] + stp val, val, [dstend, -32] + stp val, val, [dstend, -16] + ret + + .p2align 4 +L(set_long): + stp val, val, [dstin] + cmp count, DC_ZVA_THRESHOLD + ccmp val, 0, 0, cs + bic dst, dstin, 15 + b.eq L(zva_64) + + /* Small-size or non-zero memset does not use DC ZVA. */ + sub count, dstend, dst + + /* + * Adjust count and bias for loop. By substracting extra 1 from count, + * it is easy to use tbz instruction to check whether loop tailing + * count is less than 33 bytes, so as to bypass 2 unneccesary stps. + */ + sub count, count, 64+16+1 + nop + +1: stp val, val, [dst, 16] + stp val, val, [dst, 32] + stp val, val, [dst, 48] + stp val, val, [dst, 64]! + subs count, count, 64 + b.hs 1b + + tbz count, 5, 1f /* Remaining count is less than 33 bytes? */ + stp val, val, [dst, 16] + stp val, val, [dst, 32] +1: stp val, val, [dstend, -32] + stp val, val, [dstend, -16] + ret + + .p2align 3 +L(zva_64): + stp val, val, [dst, 16] + stp val, val, [dst, 32] + stp val, val, [dst, 48] + bic dst, dst, 63 + + /* + * Previous memory writes might cross cache line boundary, and cause + * cache line partially dirty. Zeroing this kind of cache line using + * DC ZVA will incur extra cost, for it requires loading untouched + * part of the line from memory before zeoring. + * + * So, write the first 64 byte aligned block using stp to force + * fully dirty cache line. + */ + stp val, val, [dst, 64] + stp val, val, [dst, 80] + stp val, val, [dst, 96] + stp val, val, [dst, 112] + + sub count, dstend, dst + /* + * Adjust count and bias for loop. By substracting extra 1 from count, + * it is easy to use tbz instruction to check whether loop tailing + * count is less than 33 bytes, so as to bypass 2 unneccesary stps. + */ + sub count, count, 128+64+64+1 + add dst, dst, 128 + nop + + /* DC ZVA sets 64 bytes each time. */ +1: dc zva, dst + add dst, dst, 64 + subs count, count, 64 + b.hs 1b + + /* + * Write the last 64 byte aligned block using stp to force fully + * dirty cache line. + */ + stp val, val, [dst, 0] + stp val, val, [dst, 16] + stp val, val, [dst, 32] + stp val, val, [dst, 48] + + tbz count, 5, 1f /* Remaining count is less than 33 bytes? */ + stp val, val, [dst, 64] + stp val, val, [dst, 80] +1: stp val, val, [dstend, -32] + stp val, val, [dstend, -16] + ret + +END (MEMSET) +libc_hidden_builtin_def (MEMSET) |