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Diffstat (limited to 'sysdeps/aarch64/multiarch/memmove_falkor.S')
| -rw-r--r-- | sysdeps/aarch64/multiarch/memmove_falkor.S | 232 |
1 files changed, 232 insertions, 0 deletions
diff --git a/sysdeps/aarch64/multiarch/memmove_falkor.S b/sysdeps/aarch64/multiarch/memmove_falkor.S new file mode 100644 index 0000000000..3a4e6a2a8e --- /dev/null +++ b/sysdeps/aarch64/multiarch/memmove_falkor.S @@ -0,0 +1,232 @@ +/* Copyright (C) 2017 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 dstlen x3 +#define dst x3 +#define srcend x4 +#define dstend x5 +#define A_l x6 +#define A_lw w6 +#define A_h x7 +#define A_hw w7 +#define B_l x8 +#define B_lw w8 +#define B_h x9 +#define C_l x10 +#define C_h x11 +#define D_l x12 +#define D_h x13 +#define E_l src +#define E_h count +#define F_l srcend +#define F_h dst +#define tmp1 x14 + +/* Alias with A_l and A_h to train the prefetcher. */ +#define Q_l x22 +#define Q_h x23 + +/* RATIONALE: + + The copy has 4 distinct parts: + * Small copies of 16 bytes and under + * Medium sized copies of 17-96 bytes + * Large copies where the source address is higher than the destination + (forward copies) + * Large copies where the destination address is higher than the source + (copy backward, or move). + + We use only two registerpairs x6,x7 and x22,x23 for the copies and copy 32 + bytes at a time to correctly train the hardware prefetcher for better + throughput. */ +ENTRY_ALIGN (__memmove_falkor, 6) + + sub tmp1, dstin, src + add srcend, src, count + add dstend, dstin, count + cmp count, 96 + ccmp tmp1, count, 2, hi + b.lo L(move_long) + + cmp count, 16 + b.ls L(copy16) + cmp count, 96 + b.hi L(copy_long) + + /* Medium copies: 17..96 bytes. */ + sub tmp1, count, 1 + ldp A_l, A_h, [src] + tbnz tmp1, 6, L(copy96) + ldp D_l, D_h, [srcend, -16] + tbz tmp1, 5, 1f + ldp B_l, B_h, [src, 16] + ldp C_l, C_h, [srcend, -32] + stp B_l, B_h, [dstin, 16] + stp C_l, C_h, [dstend, -32] +1: + stp A_l, A_h, [dstin] + stp D_l, D_h, [dstend, -16] + ret + + .p2align 4 + /* Small copies: 0..16 bytes. */ +L(copy16): + cmp count, 8 + b.lo 1f + ldr A_l, [src] + ldr A_h, [srcend, -8] + str A_l, [dstin] + str A_h, [dstend, -8] + ret + .p2align 4 +1: + /* 4-7 */ + tbz count, 2, 1f + ldr A_lw, [src] + ldr A_hw, [srcend, -4] + str A_lw, [dstin] + str A_hw, [dstend, -4] + ret + .p2align 4 +1: + /* 2-3 */ + tbz count, 1, 1f + ldrh A_lw, [src] + ldrh A_hw, [srcend, -2] + strh A_lw, [dstin] + strh A_hw, [dstend, -2] + ret + .p2align 4 +1: + /* 0-1 */ + tbz count, 0, 1f + ldrb A_lw, [src] + strb A_lw, [dstin] +1: ret + + .p2align 4 + /* Copy 64..96 bytes. Copy 64 bytes from the start and + 32 bytes from the end. */ +L(copy96): + ldp B_l, B_h, [src, 16] + ldp C_l, C_h, [src, 32] + ldp D_l, D_h, [src, 48] + ldp E_l, E_h, [srcend, -32] + ldp F_l, F_h, [srcend, -16] + stp A_l, A_h, [dstin] + stp B_l, B_h, [dstin, 16] + stp C_l, C_h, [dstin, 32] + stp D_l, D_h, [dstin, 48] + stp E_l, E_h, [dstend, -32] + stp F_l, F_h, [dstend, -16] + ret + + /* Align SRC to 16 byte alignment so that we don't cross cache line + boundaries on both loads and stores. There are at least 96 bytes + to copy, so copy 16 bytes unaligned and then align. The loop + copies 32 bytes per iteration and prefetches one iteration ahead. */ + + .p2align 4 +L(copy_long): + sub count, count, 64 + 16 /* Test and readjust count. */ + mov B_l, Q_l + mov B_h, Q_h + ldp A_l, A_h, [src] + and tmp1, src, 15 + bic src, src, 15 + sub dst, dstin, tmp1 + add count, count, tmp1 /* Count is now 16 too large. */ + ldp Q_l, Q_h, [src, 16]! + stp A_l, A_h, [dstin] + ldp A_l, A_h, [src, 16]! + +L(loop64): + subs count, count, 32 + stp Q_l, Q_h, [dst, 16] + ldp Q_l, Q_h, [src, 16]! + stp A_l, A_h, [dst, 32]! + ldp A_l, A_h, [src, 16]! + b.hi L(loop64) + + /* Write the last full set of 32 bytes. The remainder is at most 32 + bytes, so it is safe to always copy 32 bytes from the end even if + there is just 1 byte left. */ +L(last64): + ldp C_l, C_h, [srcend, -32] + stp Q_l, Q_h, [dst, 16] + ldp Q_l, Q_h, [srcend, -16] + stp A_l, A_h, [dst, 32] + stp C_l, C_h, [dstend, -32] + stp Q_l, Q_h, [dstend, -16] + mov Q_l, B_l + mov Q_h, B_h + ret + + .p2align 4 +L(move_long): + cbz tmp1, 3f + + mov B_l, Q_l + mov B_h, Q_h + + /* Align SRCEND to 16 byte alignment so that we don't cross cache line + boundaries on both loads and stores. There are at least 96 bytes + to copy, so copy 16 bytes unaligned and then align. The loop + copies 32 bytes per iteration and prefetches one iteration ahead. */ + + ldp A_l, A_h, [srcend, -16] + and tmp1, srcend, 15 + sub srcend, srcend, tmp1 + ldp Q_l, Q_h, [srcend, -16]! + stp A_l, A_h, [dstend, -16] + sub count, count, tmp1 + ldp A_l, A_h, [srcend, -16]! + sub dstend, dstend, tmp1 + sub count, count, 64 + +1: + subs count, count, 32 + stp Q_l, Q_h, [dstend, -16] + ldp Q_l, Q_h, [srcend, -16]! + stp A_l, A_h, [dstend, -32]! + ldp A_l, A_h, [srcend, -16]! + b.hi 1b + + /* Write the last full set of 32 bytes. The remainder is at most 32 + bytes, so it is safe to always copy 32 bytes from the start even if + there is just 1 byte left. */ +2: + ldp C_l, C_h, [src, 16] + stp Q_l, Q_h, [dstend, -16] + ldp Q_l, Q_h, [src] + stp A_l, A_h, [dstend, -32] + stp C_l, C_h, [dstin, 16] + stp Q_l, Q_h, [dstin] + mov Q_l, B_l + mov Q_h, B_h +3: ret + +END (__memmove_falkor) +libc_hidden_builtin_def (__memmove_falkor) |