283 lines
6.4 KiB
Diff
283 lines
6.4 KiB
Diff
commit dd1e63ab580d801926265007796f290b84747ec8
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Author: Wilco Dijkstra <wilco.dijkstra@arm.com>
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Date: Mon Sep 9 15:26:47 2024 +0100
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AArch64: Optimize memset
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Improve small memsets by avoiding branches and use overlapping stores.
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Use DC ZVA for copies over 128 bytes. Remove unnecessary code for ZVA sizes
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other than 64 and 128. Performance of random memset benchmark improves by 24%
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on Neoverse N1.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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(cherry picked from commit cec3aef32412779e207f825db0d057ebb4628ae8)
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diff --git a/sysdeps/aarch64/memset.S b/sysdeps/aarch64/memset.S
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index 7ef77ee8c926de21..caafb019e2b6217b 100644
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--- a/sysdeps/aarch64/memset.S
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+++ b/sysdeps/aarch64/memset.S
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@@ -1,4 +1,5 @@
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-/* Copyright (C) 2012-2024 Free Software Foundation, Inc.
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+/* Generic optimized memset using SIMD.
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+ Copyright (C) 2012-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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@@ -17,7 +18,6 @@
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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-#include "memset-reg.h"
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#ifndef MEMSET
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# define MEMSET memset
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@@ -25,130 +25,132 @@
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/* Assumptions:
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*
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- * ARMv8-a, AArch64, unaligned accesses
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+ * ARMv8-a, AArch64, Advanced SIMD, unaligned accesses.
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*
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*/
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-ENTRY (MEMSET)
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+#define dstin x0
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+#define val x1
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+#define valw w1
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+#define count x2
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+#define dst x3
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+#define dstend x4
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+#define zva_val x5
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+#define off x3
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+#define dstend2 x5
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+ENTRY (MEMSET)
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PTR_ARG (0)
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SIZE_ARG (2)
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dup v0.16B, valw
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+ cmp count, 16
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+ b.lo L(set_small)
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+
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add dstend, dstin, count
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+ cmp count, 64
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+ b.hs L(set_128)
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- cmp count, 96
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- b.hi L(set_long)
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- cmp count, 16
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- b.hs L(set_medium)
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- mov val, v0.D[0]
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+ /* Set 16..63 bytes. */
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+ mov off, 16
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+ and off, off, count, lsr 1
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+ sub dstend2, dstend, off
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+ str q0, [dstin]
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+ str q0, [dstin, off]
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+ str q0, [dstend2, -16]
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+ str q0, [dstend, -16]
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+ ret
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+ .p2align 4
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/* Set 0..15 bytes. */
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- tbz count, 3, 1f
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- str val, [dstin]
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- str val, [dstend, -8]
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- ret
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- nop
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-1: tbz count, 2, 2f
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- str valw, [dstin]
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- str valw, [dstend, -4]
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+L(set_small):
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+ add dstend, dstin, count
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+ cmp count, 4
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+ b.lo 2f
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+ lsr off, count, 3
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+ sub dstend2, dstend, off, lsl 2
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+ str s0, [dstin]
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+ str s0, [dstin, off, lsl 2]
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+ str s0, [dstend2, -4]
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+ str s0, [dstend, -4]
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ret
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+
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+ /* Set 0..3 bytes. */
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2: cbz count, 3f
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+ lsr off, count, 1
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strb valw, [dstin]
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- tbz count, 1, 3f
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- strh valw, [dstend, -2]
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+ strb valw, [dstin, off]
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+ strb valw, [dstend, -1]
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3: ret
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- /* Set 17..96 bytes. */
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-L(set_medium):
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- str q0, [dstin]
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- tbnz count, 6, L(set96)
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- str q0, [dstend, -16]
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- tbz count, 5, 1f
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- str q0, [dstin, 16]
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- str q0, [dstend, -32]
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-1: ret
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-
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.p2align 4
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- /* Set 64..96 bytes. Write 64 bytes from the start and
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- 32 bytes from the end. */
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-L(set96):
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- str q0, [dstin, 16]
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+L(set_128):
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+ bic dst, dstin, 15
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+ cmp count, 128
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+ b.hi L(set_long)
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+ stp q0, q0, [dstin]
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stp q0, q0, [dstin, 32]
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+ stp q0, q0, [dstend, -64]
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stp q0, q0, [dstend, -32]
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ret
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- .p2align 3
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- nop
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+ .p2align 4
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L(set_long):
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- and valw, valw, 255
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- bic dst, dstin, 15
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str q0, [dstin]
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- cmp count, 256
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- ccmp valw, 0, 0, cs
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- b.eq L(try_zva)
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-L(no_zva):
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- sub count, dstend, dst /* Count is 16 too large. */
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- sub dst, dst, 16 /* Dst is biased by -32. */
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- sub count, count, 64 + 16 /* Adjust count and bias for loop. */
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-1: stp q0, q0, [dst, 32]
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- stp q0, q0, [dst, 64]!
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-L(tail64):
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- subs count, count, 64
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- b.hi 1b
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-2: stp q0, q0, [dstend, -64]
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+ str q0, [dst, 16]
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+ tst valw, 255
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+ b.ne L(no_zva)
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+#ifndef ZVA64_ONLY
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+ mrs zva_val, dczid_el0
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+ and zva_val, zva_val, 31
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+ cmp zva_val, 4 /* ZVA size is 64 bytes. */
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+ b.ne L(zva_128)
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+#endif
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+ stp q0, q0, [dst, 32]
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+ bic dst, dstin, 63
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+ sub count, dstend, dst /* Count is now 64 too large. */
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+ sub count, count, 64 + 64 /* Adjust count and bias for loop. */
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+
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+ /* Write last bytes before ZVA loop. */
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+ stp q0, q0, [dstend, -64]
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stp q0, q0, [dstend, -32]
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+
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+ .p2align 4
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+L(zva64_loop):
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+ add dst, dst, 64
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+ dc zva, dst
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+ subs count, count, 64
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+ b.hi L(zva64_loop)
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ret
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-L(try_zva):
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-#ifndef ZVA64_ONLY
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.p2align 3
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- mrs tmp1, dczid_el0
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- tbnz tmp1w, 4, L(no_zva)
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- and tmp1w, tmp1w, 15
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- cmp tmp1w, 4 /* ZVA size is 64 bytes. */
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- b.ne L(zva_128)
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- nop
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-#endif
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- /* Write the first and last 64 byte aligned block using stp rather
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- than using DC ZVA. This is faster on some cores.
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- */
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- .p2align 4
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-L(zva_64):
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- str q0, [dst, 16]
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+L(no_zva):
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+ sub count, dstend, dst /* Count is 32 too large. */
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+ sub count, count, 64 + 32 /* Adjust count and bias for loop. */
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+L(no_zva_loop):
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stp q0, q0, [dst, 32]
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- bic dst, dst, 63
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stp q0, q0, [dst, 64]
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- stp q0, q0, [dst, 96]
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- sub count, dstend, dst /* Count is now 128 too large. */
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- sub count, count, 128+64+64 /* Adjust count and bias for loop. */
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- add dst, dst, 128
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-1: dc zva, dst
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add dst, dst, 64
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subs count, count, 64
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- b.hi 1b
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- stp q0, q0, [dst, 0]
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- stp q0, q0, [dst, 32]
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+ b.hi L(no_zva_loop)
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stp q0, q0, [dstend, -64]
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stp q0, q0, [dstend, -32]
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ret
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#ifndef ZVA64_ONLY
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- .p2align 3
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+ .p2align 4
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L(zva_128):
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- cmp tmp1w, 5 /* ZVA size is 128 bytes. */
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- b.ne L(zva_other)
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+ cmp zva_val, 5 /* ZVA size is 128 bytes. */
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+ b.ne L(no_zva)
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- str q0, [dst, 16]
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stp q0, q0, [dst, 32]
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stp q0, q0, [dst, 64]
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stp q0, q0, [dst, 96]
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bic dst, dst, 127
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sub count, dstend, dst /* Count is now 128 too large. */
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- sub count, count, 128+128 /* Adjust count and bias for loop. */
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- add dst, dst, 128
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-1: dc zva, dst
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- add dst, dst, 128
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+ sub count, count, 128 + 128 /* Adjust count and bias for loop. */
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+1: add dst, dst, 128
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+ dc zva, dst
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subs count, count, 128
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b.hi 1b
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stp q0, q0, [dstend, -128]
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@@ -156,35 +158,6 @@ L(zva_128):
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stp q0, q0, [dstend, -64]
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stp q0, q0, [dstend, -32]
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ret
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-
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-L(zva_other):
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- mov tmp2w, 4
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- lsl zva_lenw, tmp2w, tmp1w
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- add tmp1, zva_len, 64 /* Max alignment bytes written. */
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- cmp count, tmp1
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- blo L(no_zva)
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-
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- sub tmp2, zva_len, 1
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- add tmp1, dst, zva_len
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- add dst, dst, 16
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- subs count, tmp1, dst /* Actual alignment bytes to write. */
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- bic tmp1, tmp1, tmp2 /* Aligned dc zva start address. */
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- beq 2f
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-1: stp q0, q0, [dst], 64
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- stp q0, q0, [dst, -32]
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- subs count, count, 64
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- b.hi 1b
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-2: mov dst, tmp1
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- sub count, dstend, tmp1 /* Remaining bytes to write. */
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- subs count, count, zva_len
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- b.lo 4f
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-3: dc zva, dst
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- add dst, dst, zva_len
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- subs count, count, zva_len
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- b.hs 3b
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-4: add count, count, zva_len
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- sub dst, dst, 32 /* Bias dst for tail loop. */
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- b L(tail64)
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#endif
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END (MEMSET)
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