[PATCH v3 04/13] arm64: Import latest version of Cortex Strings' memmove

[Oliver Swede]

From: Sam Tebbs <sam.tebbs@xxxxxxx>

Import the latest version of Cortex Strings' memmove function.

The upstream source is src/aarch64/memmove.S as of commit 99b01ddb8e41
in https://git.linaro.org/toolchain/cortex-strings.git.

Signed-off-by: Sam Tebbs <sam.tebbs@xxxxxxx>
[ rm: update attribution, expand commit message ]
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Oliver Swede <oli.swede@xxxxxxx>
---
 arch/arm64/lib/memmove.S | 232 +++++++++++++--------------------------
 1 file changed, 78 insertions(+), 154 deletions(-)

diff --git a/arch/arm64/lib/memmove.S b/arch/arm64/lib/memmove.S
index 02cda2e33bde..d0977d0ad745 100644
--- a/arch/arm64/lib/memmove.S
+++ b/arch/arm64/lib/memmove.S
@@ -1,13 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
- * Copyright (C) 2013 ARM Ltd.
- * Copyright (C) 2013 Linaro.
+ * Copyright (c) 2013 Linaro Limited. All rights reserved.
+ * Copyright (c) 2015 ARM Ltd. All rights reserved.
  *
- * This code is based on glibc cortex strings work originally authored by Linaro
- * be found @
+ * This code is based on glibc Cortex Strings work originally authored by
+ * Linaro, found at:
  *
- * http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
- * files/head:/src/aarch64/
+ * https://git.linaro.org/toolchain/cortex-strings.git
  */
 
 #include <linux/linkage.h>
@@ -25,165 +24,90 @@
  * Returns:
  *	x0 - dest
  */
-dstin	.req	x0
-src	.req	x1
-count	.req	x2
-tmp1	.req	x3
-tmp1w	.req	w3
-tmp2	.req	x4
-tmp2w	.req	w4
-tmp3	.req	x5
-tmp3w	.req	w5
-dst	.req	x6
+/* Parameters and result.  */
+#define dstin	x0
+#define src	x1
+#define count	x2
+#define srcend	x3
+#define dstend	x4
+#define tmp1	x5
+#define A_l	x6
+#define A_h	x7
+#define B_l	x8
+#define B_h	x9
+#define C_l	x10
+#define C_h	x11
+#define D_l	x12
+#define D_h	x13
+#define E_l	count
+#define E_h	tmp1
 
-A_l	.req	x7
-A_h	.req	x8
-B_l	.req	x9
-B_h	.req	x10
-C_l	.req	x11
-C_h	.req	x12
-D_l	.req	x13
-D_h	.req	x14
+/* All memmoves up to 96 bytes are done by memcpy as it supports overlaps.
+   Larger backwards copies are also handled by memcpy. The only remaining
+   case is forward large copies.  The destination is aligned, and an
+   unrolled loop processes 64 bytes per iteration.
+*/
 
-	.weak memmove
+    .weak memmove
 SYM_FUNC_START_ALIAS(__memmove)
 SYM_FUNC_START_PI(memmove)
-	cmp	dstin, src
-	b.lo	__memcpy
-	add	tmp1, src, count
-	cmp	dstin, tmp1
-	b.hs	__memcpy		/* No overlap.  */
+	sub	tmp1, dstin, src
+	cmp	count, 96
+	ccmp	tmp1, count, 2, hi
+	b.hs	__memcpy
 
-	add	dst, dstin, count
-	add	src, src, count
-	cmp	count, #16
-	b.lo	.Ltail15  /*probably non-alignment accesses.*/
+	cbz	tmp1, 3f
+	add	dstend, dstin, count
+	add	srcend, src, count
 
-	ands	tmp2, src, #15     /* Bytes to reach alignment.  */
-	b.eq	.LSrcAligned
-	sub	count, count, tmp2
-	/*
-	* process the aligned offset length to make the src aligned firstly.
-	* those extra instructions' cost is acceptable. It also make the
-	* coming accesses are based on aligned address.
-	*/
-	tbz	tmp2, #0, 1f
-	ldrb	tmp1w, [src, #-1]!
-	strb	tmp1w, [dst, #-1]!
-1:
-	tbz	tmp2, #1, 2f
-	ldrh	tmp1w, [src, #-2]!
-	strh	tmp1w, [dst, #-2]!
-2:
-	tbz	tmp2, #2, 3f
-	ldr	tmp1w, [src, #-4]!
-	str	tmp1w, [dst, #-4]!
-3:
-	tbz	tmp2, #3, .LSrcAligned
-	ldr	tmp1, [src, #-8]!
-	str	tmp1, [dst, #-8]!
-
-.LSrcAligned:
-	cmp	count, #64
-	b.ge	.Lcpy_over64
+	/* 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.  */
 
-	/*
-	* Deal with small copies quickly by dropping straight into the
-	* exit block.
-	*/
-.Ltail63:
-	/*
-	* Copy up to 48 bytes of data. At this point we only need the
-	* bottom 6 bits of count to be accurate.
-	*/
-	ands	tmp1, count, #0x30
-	b.eq	.Ltail15
-	cmp	tmp1w, #0x20
-	b.eq	1f
-	b.lt	2f
-	ldp	A_l, A_h, [src, #-16]!
-	stp	A_l, A_h, [dst, #-16]!
+	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:
-	ldp	A_l, A_h, [src, #-16]!
-	stp	A_l, A_h, [dst, #-16]!
-2:
-	ldp	A_l, A_h, [src, #-16]!
-	stp	A_l, A_h, [dst, #-16]!
+	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
 
-.Ltail15:
-	tbz	count, #3, 1f
-	ldr	tmp1, [src, #-8]!
-	str	tmp1, [dst, #-8]!
-1:
-	tbz	count, #2, 2f
-	ldr	tmp1w, [src, #-4]!
-	str	tmp1w, [dst, #-4]!
+	/* 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:
-	tbz	count, #1, 3f
-	ldrh	tmp1w, [src, #-2]!
-	strh	tmp1w, [dst, #-2]!
-3:
-	tbz	count, #0, .Lexitfunc
-	ldrb	tmp1w, [src, #-1]
-	strb	tmp1w, [dst, #-1]
-
-.Lexitfunc:
-	ret
-
-.Lcpy_over64:
-	subs	count, count, #128
-	b.ge	.Lcpy_body_large
-	/*
-	* Less than 128 bytes to copy, so handle 64 bytes here and then jump
-	* to the tail.
-	*/
-	ldp	A_l, A_h, [src, #-16]
-	stp	A_l, A_h, [dst, #-16]
-	ldp	B_l, B_h, [src, #-32]
-	ldp	C_l, C_h, [src, #-48]
-	stp	B_l, B_h, [dst, #-32]
-	stp	C_l, C_h, [dst, #-48]
-	ldp	D_l, D_h, [src, #-64]!
-	stp	D_l, D_h, [dst, #-64]!
-
-	tst	count, #0x3f
-	b.ne	.Ltail63
-	ret
-
-	/*
-	* Critical loop. Start at a new cache line boundary. Assuming
-	* 64 bytes per line this ensures the entire loop is in one line.
-	*/
-	.p2align	L1_CACHE_SHIFT
-.Lcpy_body_large:
-	/* pre-load 64 bytes data. */
-	ldp	A_l, A_h, [src, #-16]
-	ldp	B_l, B_h, [src, #-32]
-	ldp	C_l, C_h, [src, #-48]
-	ldp	D_l, D_h, [src, #-64]!
-1:
-	/*
-	* interlace the load of next 64 bytes data block with store of the last
-	* loaded 64 bytes data.
-	*/
-	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.ge	1b
-	stp	A_l, A_h, [dst, #-16]
-	stp	B_l, B_h, [dst, #-32]
-	stp	C_l, C_h, [dst, #-48]
-	stp	D_l, D_h, [dst, #-64]!
+	ldp	E_l, E_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	E_l, E_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
 
-	tst	count, #0x3f
-	b.ne	.Ltail63
-	ret
 SYM_FUNC_END_PI(memmove)
 EXPORT_SYMBOL(memmove)
 SYM_FUNC_END_ALIAS(__memmove)
-- 
2.17.1