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authorWaldemar Brodkorb <wbx@uclibc-ng.org>2016-10-04 06:51:35 +0200
committerWaldemar Brodkorb <wbx@openadk.org>2017-02-01 17:48:38 +0100
commitdba942c80dc2cfa5768a856fff98e22a755fdd27 (patch)
tree371e775cb6dfec085945f6834aeb9d3b6de36fbe /libc/string/aarch64/memcpy.S
parent9b457baf8d46329f7d7ee2aa084022bb0df88551 (diff)
add experimental aarch64 support
Ported over from GNU C Library and runtime tested in Qemu.
Diffstat (limited to 'libc/string/aarch64/memcpy.S')
-rw-r--r--libc/string/aarch64/memcpy.S230
1 files changed, 230 insertions, 0 deletions
diff --git a/libc/string/aarch64/memcpy.S b/libc/string/aarch64/memcpy.S
new file mode 100644
index 000000000..87b2552a2
--- /dev/null
+++ b/libc/string/aarch64/memcpy.S
@@ -0,0 +1,230 @@
+/* Copyright (C) 2012-2017 Free Software Foundation, Inc.
+
+ 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, unaligned accesses.
+ *
+ */
+
+#define dstin x0
+#define src x1
+#define count x2
+#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 G_l count
+#define G_h dst
+#define tmp1 x14
+
+ENTRY (memcpy)
+
+ prfm PLDL1KEEP, [src]
+ add srcend, src, count
+ add dstend, dstin, count
+ 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:
+ tbz count, 2, 1f
+ ldr A_lw, [src]
+ ldr A_hw, [srcend, -4]
+ str A_lw, [dstin]
+ str A_hw, [dstend, -4]
+ ret
+
+ /* Copy 0..3 bytes. Use a branchless sequence that copies the same
+ byte 3 times if count==1, or the 2nd byte twice if count==2. */
+1:
+ cbz count, 2f
+ lsr tmp1, count, 1
+ ldrb A_lw, [src]
+ ldrb A_hw, [srcend, -1]
+ ldrb B_lw, [src, tmp1]
+ strb A_lw, [dstin]
+ strb B_lw, [dstin, tmp1]
+ strb A_hw, [dstend, -1]
+2: 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 DST 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 64 bytes per iteration and prefetches one iteration ahead. */
+
+ .p2align 4
+L(copy_long):
+ and tmp1, dstin, 15
+ bic dst, dstin, 15
+ ldp D_l, D_h, [src]
+ sub src, src, tmp1
+ add count, count, tmp1 /* Count is now 16 too large. */
+ ldp A_l, A_h, [src, 16]
+ stp D_l, D_h, [dstin]
+ ldp B_l, B_h, [src, 32]
+ ldp C_l, C_h, [src, 48]
+ ldp D_l, D_h, [src, 64]!
+ subs count, count, 128 + 16 /* Test and readjust count. */
+ b.ls 2f
+1:
+ stp A_l, A_h, [dst, 16]
+ ldp A_l, A_h, [src, 16]
+ stp B_l, B_h, [dst, 32]
+ ldp B_l, B_h, [src, 32]
+ stp C_l, C_h, [dst, 48]
+ ldp C_l, C_h, [src, 48]
+ stp D_l, D_h, [dst, 64]!
+ ldp D_l, D_h, [src, 64]!
+ subs count, count, 64
+ b.hi 1b
+
+ /* 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. */
+2:
+ ldp E_l, E_h, [srcend, -64]
+ stp A_l, A_h, [dst, 16]
+ ldp A_l, A_h, [srcend, -48]
+ stp B_l, B_h, [dst, 32]
+ ldp B_l, B_h, [srcend, -32]
+ stp C_l, C_h, [dst, 48]
+ ldp C_l, C_h, [srcend, -16]
+ stp D_l, D_h, [dst, 64]
+ stp E_l, E_h, [dstend, -64]
+ stp A_l, A_h, [dstend, -48]
+ stp B_l, B_h, [dstend, -32]
+ stp C_l, C_h, [dstend, -16]
+ ret
+
+ .p2align 4
+L(move_long):
+ cbz tmp1, 3f
+
+ add srcend, src, count
+ add dstend, dstin, count
+
+ /* Align dstend 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 64 bytes per iteration and prefetches one iteration ahead. */
+
+ and tmp1, dstend, 15
+ ldp D_l, D_h, [srcend, -16]
+ sub srcend, srcend, tmp1
+ sub count, count, tmp1
+ ldp A_l, A_h, [srcend, -16]
+ stp D_l, D_h, [dstend, -16]
+ ldp B_l, B_h, [srcend, -32]
+ ldp C_l, C_h, [srcend, -48]
+ ldp D_l, D_h, [srcend, -64]!
+ sub dstend, dstend, tmp1
+ subs count, count, 128
+ b.ls 2f
+
+ nop
+1:
+ stp A_l, A_h, [dstend, -16]
+ ldp A_l, A_h, [srcend, -16]
+ stp B_l, B_h, [dstend, -32]
+ ldp B_l, B_h, [srcend, -32]
+ stp C_l, C_h, [dstend, -48]
+ ldp C_l, C_h, [srcend, -48]
+ stp D_l, D_h, [dstend, -64]!
+ ldp D_l, D_h, [srcend, -64]!
+ subs count, count, 64
+ b.hi 1b
+
+ /* 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 start even if
+ there is just 1 byte left. */
+2:
+ ldp G_l, G_h, [src, 48]
+ stp A_l, A_h, [dstend, -16]
+ ldp A_l, A_h, [src, 32]
+ stp B_l, B_h, [dstend, -32]
+ ldp B_l, B_h, [src, 16]
+ stp C_l, C_h, [dstend, -48]
+ ldp C_l, C_h, [src]
+ stp D_l, D_h, [dstend, -64]
+ stp G_l, G_h, [dstin, 48]
+ stp A_l, A_h, [dstin, 32]
+ stp B_l, B_h, [dstin, 16]
+ stp C_l, C_h, [dstin]
+3: ret
+
+END (memcpy)
+libc_hidden_def (memcpy)