diff options
Diffstat (limited to 'sysdeps/aarch64/multiarch/memcpy_falkor.S')
| -rw-r--r-- | sysdeps/aarch64/multiarch/memcpy_falkor.S | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/sysdeps/aarch64/multiarch/memcpy_falkor.S b/sysdeps/aarch64/multiarch/memcpy_falkor.S new file mode 100644 index 0000000000..cdc2de4750 --- /dev/null +++ b/sysdeps/aarch64/multiarch/memcpy_falkor.S @@ -0,0 +1,191 @@ +/* Optimized memcpy for Qualcomm Falkor processor. + Copyright (C) 2017-2018 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> + +/* Assumptions: + + ARMv8-a, AArch64, falkor, unaligned accesses. */ + +#define dstin x0 +#define src x1 +#define count x2 +#define dst x3 +#define srcend x4 +#define dstend x5 +#define tmp1 x14 +#define A_x x6 +#define B_x x7 +#define A_w w6 +#define B_w w7 + +#define A_q q0 +#define B_q q1 +#define C_q q2 +#define D_q q3 +#define E_q q4 +#define F_q q5 +#define G_q q6 + +/* Copies are split into 3 main cases: + + 1. Small copies of up to 32 bytes + 2. Medium copies of 33..128 bytes which are fully unrolled + 3. Large copies of more than 128 bytes. + + Large copies align the sourceto a quad word and use an unrolled loop + processing 64 bytes per iteration. + + FALKOR-SPECIFIC DESIGN: + + The smallest copies (32 bytes or less) focus on optimal pipeline usage, + which is why the redundant copies of 0-3 bytes have been replaced with + conditionals, since the former would unnecessarily break across multiple + issue groups. The medium copy group has been enlarged to 128 bytes since + bumping up the small copies up to 32 bytes allows us to do that without + cost and also allows us to reduce the size of the prep code before loop64. + + The copy loop uses only one register q0. This is to ensure that all loads + hit a single hardware prefetcher which can get correctly trained to prefetch + a single stream. + + The non-temporal stores help optimize cache utilization. */ + +#if IS_IN (libc) +ENTRY_ALIGN (__memcpy_falkor, 6) + + cmp count, 32 + add srcend, src, count + add dstend, dstin, count + b.ls L(copy32) + ldr A_q, [src] + cmp count, 128 + str A_q, [dstin] + b.hi L(copy_long) + + /* Medium copies: 33..128 bytes. */ + sub tmp1, count, 1 + ldr A_q, [src, 16] + ldr B_q, [srcend, -32] + ldr C_q, [srcend, -16] + tbz tmp1, 6, 1f + ldr D_q, [src, 32] + ldr E_q, [src, 48] + str D_q, [dstin, 32] + str E_q, [dstin, 48] + ldr F_q, [srcend, -64] + ldr G_q, [srcend, -48] + str F_q, [dstend, -64] + str G_q, [dstend, -48] +1: + str A_q, [dstin, 16] + str B_q, [dstend, -32] + str C_q, [dstend, -16] + ret + + .p2align 4 + /* Small copies: 0..32 bytes. */ +L(copy32): + /* 16-32 */ + cmp count, 16 + b.lo 1f + ldr A_q, [src] + ldr B_q, [srcend, -16] + str A_q, [dstin] + str B_q, [dstend, -16] + ret + .p2align 4 +1: + /* 8-15 */ + tbz count, 3, 1f + ldr A_x, [src] + ldr B_x, [srcend, -8] + str A_x, [dstin] + str B_x, [dstend, -8] + ret + .p2align 4 +1: + /* 4-7 */ + tbz count, 2, 1f + ldr A_w, [src] + ldr B_w, [srcend, -4] + str A_w, [dstin] + str B_w, [dstend, -4] + ret + .p2align 4 +1: + /* 2-3 */ + tbz count, 1, 1f + ldrh A_w, [src] + ldrh B_w, [srcend, -2] + strh A_w, [dstin] + strh B_w, [dstend, -2] + ret + .p2align 4 +1: + /* 0-1 */ + tbz count, 0, 1f + ldrb A_w, [src] + strb A_w, [dstin] +1: + ret + + /* Align SRC to 16 bytes and copy; that way at least one of the + accesses is aligned throughout the copy sequence. + + The count is off by 0 to 15 bytes, but this is OK because we trim + off the last 64 bytes to copy off from the end. Due to this the + loop never runs out of bounds. */ + .p2align 6 +L(copy_long): + sub count, count, 64 + 16 + and tmp1, src, 15 + bic src, src, 15 + sub dst, dstin, tmp1 + add count, count, tmp1 + +L(loop64): + ldr A_q, [src, 16]! + str A_q, [dst, 16] + ldr A_q, [src, 16]! + subs count, count, 64 + str A_q, [dst, 32] + ldr A_q, [src, 16]! + str A_q, [dst, 48] + ldr A_q, [src, 16]! + str A_q, [dst, 64]! + b.hi L(loop64) + + /* Write the last full set of 64 bytes. The remainder is at most 64 + bytes, so it is safe to always copy 64 bytes from the end even if + there is just 1 byte left. */ +L(last64): + ldr E_q, [srcend, -64] + str E_q, [dstend, -64] + ldr D_q, [srcend, -48] + str D_q, [dstend, -48] + ldr C_q, [srcend, -32] + str C_q, [dstend, -32] + ldr B_q, [srcend, -16] + str B_q, [dstend, -16] + ret + +END (__memcpy_falkor) +libc_hidden_builtin_def (__memcpy_falkor) +#endif |