libc: ARM64: optimize memmove

 This is an optimized memmove for AArch64.  All copies of up to 96
 bytes and all backward copies are done by the new memcpy.  The only
 remaining case is large forward copies which are done in the same way
 as the memcpy loop, but copying from the end rather than the start.

Change-Id: I635bd2798a755256f748b2af19b1a56fb85a40c6

1 files changed, 105 insertions, 281 deletions

diff --git a/libc/arch-arm64/generic/bionic/memmove.S b/libc/arch-arm64/generic/bionic/memmove.S
index 739ce49..c50112d 100644
--- a/libc/arch-arm64/generic/bionic/memmove.S
+++ b/libc/arch-arm64/generic/bionic/memmove.S
@@ -1,4 +1,4 @@
-/* Copyright (c) 2014, Linaro Limited
+/* Copyright (c) 2013, Linaro Limited
    All rights reserved.
 
    Redistribution and use in source and binary forms, with or without
@@ -22,14 +22,39 @@
    DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-*/
+   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
+
+/*
+ * Copyright (c) 2015 ARM Ltd
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the company may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
 
 /* Assumptions:
  *
- * ARMv8-a, AArch64
- * Unaligned accesses
- * wchar_t is 4 bytes
+ * ARMv8-a, AArch64, unaligned accesses, wchar_t is 4 bytes
  */
 
 #include <private/bionic_asm.h>
@@ -38,22 +63,25 @@
 #define dstin	x0
 #define src	x1
 #define count	x2
-#define tmp1	x3
-#define tmp1w	w3
-#define tmp2	x4
-#define tmp2w	w4
-#define tmp3	x5
-#define tmp3w	w5
-#define dst	x6
-
-#define A_l	x7
-#define A_h	x8
-#define B_l	x9
-#define B_h	x10
-#define C_l	x11
-#define C_h	x12
-#define D_l	x13
-#define D_h	x14
+#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
+
+/* 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.
+*/
 
 #if defined(WMEMMOVE)
 ENTRY(wmemmove)
@@ -61,267 +89,63 @@ ENTRY(wmemmove)
 #else
 ENTRY(memmove)
 #endif
-	cmp	dstin, src
-	b.lo	.Ldownwards
-	add	tmp1, src, count
-	cmp	dstin, tmp1
-	b.hs	memcpy		/* No overlap.  */
-
-	/* Upwards move with potential overlap.
-	 * Need to move from the tail backwards.  SRC and DST point one
-	 * byte beyond the remaining data to move.  */
-	add	dst, dstin, count
-	add	src, src, count
-	cmp	count, #64
-	b.ge	.Lmov_not_short_up
-
-	/* Deal with small moves quickly by dropping straight into the
-	 * exit block.  */
-.Ltail63up:
-	/* Move 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	.Ltail15up
-	sub	dst, dst, tmp1
-	sub	src, src, tmp1
-	cmp	tmp1w, #0x20
-	b.eq	1f
-	b.lt	2f
-	ldp	A_l, A_h, [src, #32]
-	stp	A_l, A_h, [dst, #32]
-1:
-	ldp	A_l, A_h, [src, #16]
-	stp	A_l, A_h, [dst, #16]
-2:
-	ldp	A_l, A_h, [src]
-	stp	A_l, A_h, [dst]
-.Ltail15up:
-	/* Move up to 15 bytes of data.  Does not assume additional data
-	 * being moved.  */
-	tbz	count, #3, 1f
-	ldr	tmp1, [src, #-8]!
-	str	tmp1, [dst, #-8]!
-1:
-	tbz	count, #2, 1f
-	ldr	tmp1w, [src, #-4]!
-	str	tmp1w, [dst, #-4]!
-1:
-	tbz	count, #1, 1f
-	ldrh	tmp1w, [src, #-2]!
-	strh	tmp1w, [dst, #-2]!
-1:
-	tbz	count, #0, 1f
-	ldrb	tmp1w, [src, #-1]
-	strb	tmp1w, [dst, #-1]
-1:
-	ret
-
-.Lmov_not_short_up:
-	/* We don't much care about the alignment of DST, but we want SRC
-	 * to be 128-bit (16 byte) aligned so that we don't cross cache line
-	 * boundaries on both loads and stores.  */
-	ands	tmp2, src, #15		/* Bytes to reach alignment.  */
-	b.eq	2f
-	sub	count, count, tmp2
-	/* Move enough data to reach alignment; unlike memcpy, we have to
-	 * be aware of the overlap, which means we can't move data twice.  */
-	tbz	tmp2, #3, 1f
-	ldr	tmp1, [src, #-8]!
-	str	tmp1, [dst, #-8]!
-1:
-	tbz	tmp2, #2, 1f
-	ldr	tmp1w, [src, #-4]!
-	str	tmp1w, [dst, #-4]!
-1:
-	tbz	tmp2, #1, 1f
-	ldrh	tmp1w, [src, #-2]!
-	strh	tmp1w, [dst, #-2]!
-1:
-	tbz	tmp2, #0, 1f
-	ldrb	tmp1w, [src, #-1]!
-	strb	tmp1w, [dst, #-1]!
-1:
-
-	/* There may be less than 63 bytes to go now.  */
-	cmp	count, #63
-	b.le	.Ltail63up
+	sub	tmp1, dstin, src
+	cmp	count, 96
+	ccmp	tmp1, count, 2, hi
+	b.hs	memcpy
+
+	cbz	tmp1, 3f
+	add	dstend, dstin, count
+	add	srcend, src, 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:
-	subs	count, count, #128
-	b.ge	.Lmov_body_large_up
-	/* Less than 128 bytes to move, so handle 64 here and then jump
-	 * to the tail.  */
-	ldp	A_l, A_h, [src, #-64]!
-	ldp	B_l, B_h, [src, #16]
-	ldp	C_l, C_h, [src, #32]
-	ldp	D_l, D_h, [src, #48]
-	stp	A_l, A_h, [dst, #-64]!
-	stp	B_l, B_h, [dst, #16]
-	stp	C_l, C_h, [dst, #32]
-	stp	D_l, D_h, [dst, #48]
-	tst	count, #0x3f
-	b.ne	.Ltail63up
-	ret
+	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
 
-	/* Critical loop.  Start at a new Icache line boundary.  Assuming
-	 * 64 bytes per line this ensures the entire loop is in one line.  */
-	.p2align 6
-.Lmov_body_large_up:
-	/* There are at least 128 bytes to move.  */
-	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:
-	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]!
-	tst	count, #0x3f
-	b.ne	.Ltail63up
-	ret
-
-
-.Ldownwards:
-	/* For a downwards move we can safely use memcpy provided that
-	 * DST is more than 16 bytes away from SRC.  */
-	sub	tmp1, src, #16
-	cmp	dstin, tmp1
-	b.ls	memcpy		/* May overlap, but not critically.  */
-
-	mov	dst, dstin	/* Preserve DSTIN for return value.  */
-	cmp	count, #64
-	b.ge	.Lmov_not_short_down
-
-	/* Deal with small moves quickly by dropping straight into the
-	 * exit block.  */
-.Ltail63down:
-	/* Move 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	.Ltail15down
-	add	dst, dst, tmp1
-	add	src, src, tmp1
-	cmp	tmp1w, #0x20
-	b.eq	1f
-	b.lt	2f
-	ldp	A_l, A_h, [src, #-48]
-	stp	A_l, A_h, [dst, #-48]
-1:
-	ldp	A_l, A_h, [src, #-32]
-	stp	A_l, A_h, [dst, #-32]
-2:
-	ldp	A_l, A_h, [src, #-16]
-	stp	A_l, A_h, [dst, #-16]
-.Ltail15down:
-	/* Move up to 15 bytes of data.  Does not assume additional data
-	   being moved.  */
-	tbz	count, #3, 1f
-	ldr	tmp1, [src], #8
-	str	tmp1, [dst], #8
-1:
-	tbz	count, #2, 1f
-	ldr	tmp1w, [src], #4
-	str	tmp1w, [dst], #4
-1:
-	tbz	count, #1, 1f
-	ldrh	tmp1w, [src], #2
-	strh	tmp1w, [dst], #2
-1:
-	tbz	count, #0, 1f
-	ldrb	tmp1w, [src]
-	strb	tmp1w, [dst]
-1:
-	ret
-
-.Lmov_not_short_down:
-	/* We don't much care about the alignment of DST, but we want SRC
-	 * to be 128-bit (16 byte) aligned so that we don't cross cache line
-	 * boundaries on both loads and stores.  */
-	neg	tmp2, src
-	ands	tmp2, tmp2, #15		/* Bytes to reach alignment.  */
-	b.eq	2f
-	sub	count, count, tmp2
-	/* Move enough data to reach alignment; unlike memcpy, we have to
-	 * be aware of the overlap, which means we can't move data twice.  */
-	tbz	tmp2, #3, 1f
-	ldr	tmp1, [src], #8
-	str	tmp1, [dst], #8
-1:
-	tbz	tmp2, #2, 1f
-	ldr	tmp1w, [src], #4
-	str	tmp1w, [dst], #4
-1:
-	tbz	tmp2, #1, 1f
-	ldrh	tmp1w, [src], #2
-	strh	tmp1w, [dst], #2
-1:
-	tbz	tmp2, #0, 1f
-	ldrb	tmp1w, [src], #1
-	strb	tmp1w, [dst], #1
-1:
-
-	/* There may be less than 63 bytes to go now.  */
-	cmp	count, #63
-	b.le	.Ltail63down
-2:
-	subs	count, count, #128
-	b.ge	.Lmov_body_large_down
-	/* Less than 128 bytes to move, so handle 64 here and then jump
-	 * to the tail.  */
-	ldp	A_l, A_h, [src]
-	ldp	B_l, B_h, [src, #16]
-	ldp	C_l, C_h, [src, #32]
-	ldp	D_l, D_h, [src, #48]
-	stp	A_l, A_h, [dst]
-	stp	B_l, B_h, [dst, #16]
-	stp	C_l, C_h, [dst, #32]
-	stp	D_l, D_h, [dst, #48]
-	tst	count, #0x3f
-	add	src, src, #64
-	add	dst, dst, #64
-	b.ne	.Ltail63down
-	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 6
-.Lmov_body_large_down:
-	/* There are at least 128 bytes to move.  */
-	ldp	A_l, A_h, [src, #0]
-	sub	dst, dst, #16		/* Pre-bias.  */
-	ldp	B_l, B_h, [src, #16]
-	ldp	C_l, C_h, [src, #32]
-	ldp	D_l, D_h, [src, #48]!	/* src += 64 - Pre-bias.  */
-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.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]
-	add	src, src, #16
-	add	dst, dst, #64 + 16
-	tst	count, #0x3f
-	b.ne	.Ltail63down
-	ret
 #if defined(WMEMMOVE)
 END(wmemmove)
 #else