memcpy.S

/*
 * memcpy - copy memory area
 *
 * Copyright (c) 2013-2022, Arm Limited.
 * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
 */

/*
   This memcpy routine is optimised for Cortex-A15 cores and takes advantage
   of VFP or NEON when built with the appropriate flags.

   Assumptions:

    ARMv6 (ARMv7-a if using Neon)
    ARM state
    Unaligned accesses

 */

#include "asmdefs.h"

	.syntax unified
	/* This implementation requires ARM state.  */
	.arm

#ifdef __ARM_NEON__

	.fpu	neon
	.arch	armv7-a
# define FRAME_SIZE	4
# define USE_VFP
# define USE_NEON

#elif !defined (__SOFTFP__)

	.arch	armv6
	.fpu	vfpv2
# define FRAME_SIZE	32
# define USE_VFP

#else
	.arch	armv6
# define FRAME_SIZE    32

#endif

/* Old versions of GAS incorrectly implement the NEON align semantics.  */
#ifdef BROKEN_ASM_NEON_ALIGN
#define ALIGN(addr, align) addr,:align
#else
#define ALIGN(addr, align) addr:align
#endif

#define PC_OFFSET	8	/* PC pipeline compensation.  */
#define INSN_SIZE	4

/* Call parameters.  */
#define dstin	r0
#define src	r1
#define count	r2

/* Locals.  */
#define tmp1	r3
#define dst	ip
#define tmp2	r10

#ifndef USE_NEON
/* For bulk copies using GP registers.  */
#define	A_l	r2		/* Call-clobbered.  */
#define	A_h	r3		/* Call-clobbered.  */
#define	B_l	r4
#define	B_h	r5
#define	C_l	r6
#define	C_h	r7
#define	D_l	r8
#define	D_h	r9
#endif

/* Number of lines ahead to pre-fetch data.  If you change this the code
   below will need adjustment to compensate.  */

#define prefetch_lines	5

#ifdef USE_VFP
	.macro	cpy_line_vfp vreg, base
	vstr	\vreg, [dst, #\base]
	vldr	\vreg, [src, #\base]
	vstr	d0, [dst, #\base + 8]
	vldr	d0, [src, #\base + 8]
	vstr	d1, [dst, #\base + 16]
	vldr	d1, [src, #\base + 16]
	vstr	d2, [dst, #\base + 24]
	vldr	d2, [src, #\base + 24]
	vstr	\vreg, [dst, #\base + 32]
	vldr	\vreg, [src, #\base + prefetch_lines * 64 - 32]
	vstr	d0, [dst, #\base + 40]
	vldr	d0, [src, #\base + 40]
	vstr	d1, [dst, #\base + 48]
	vldr	d1, [src, #\base + 48]
	vstr	d2, [dst, #\base + 56]
	vldr	d2, [src, #\base + 56]
	.endm

	.macro	cpy_tail_vfp vreg, base
	vstr	\vreg, [dst, #\base]
	vldr	\vreg, [src, #\base]
	vstr	d0, [dst, #\base + 8]
	vldr	d0, [src, #\base + 8]
	vstr	d1, [dst, #\base + 16]
	vldr	d1, [src, #\base + 16]
	vstr	d2, [dst, #\base + 24]
	vldr	d2, [src, #\base + 24]
	vstr	\vreg, [dst, #\base + 32]
	vstr	d0, [dst, #\base + 40]
	vldr	d0, [src, #\base + 40]
	vstr	d1, [dst, #\base + 48]
	vldr	d1, [src, #\base + 48]
	vstr	d2, [dst, #\base + 56]
	vldr	d2, [src, #\base + 56]
	.endm
#endif

ENTRY (__memcpy_arm)

	mov	dst, dstin	/* Preserve dstin, we need to return it.  */
	cmp	count, #64
	bhs	L(cpy_not_short)
	/* Deal with small copies quickly by dropping straight into the
	   exit block.  */

L(tail63unaligned):
#ifdef USE_NEON
	and	tmp1, count, #0x38
	rsb	tmp1, tmp1, #(56 - PC_OFFSET + INSN_SIZE)
	add	pc, pc, tmp1
	vld1.8	{d0}, [src]!	/* 14 words to go.  */
	vst1.8	{d0}, [dst]!
	vld1.8	{d0}, [src]!	/* 12 words to go.  */
	vst1.8	{d0}, [dst]!
	vld1.8	{d0}, [src]!	/* 10 words to go.  */
	vst1.8	{d0}, [dst]!
	vld1.8	{d0}, [src]!	/* 8 words to go.  */
	vst1.8	{d0}, [dst]!
	vld1.8	{d0}, [src]!	/* 6 words to go.  */
	vst1.8	{d0}, [dst]!
	vld1.8	{d0}, [src]!	/* 4 words to go.  */
	vst1.8	{d0}, [dst]!
	vld1.8	{d0}, [src]!	/* 2 words to go.  */
	vst1.8	{d0}, [dst]!

	tst	count, #4
	ldrne	tmp1, [src], #4
	strne	tmp1, [dst], #4
#else
	/* Copy up to 15 full words of data.  May not be aligned.  */
	/* Cannot use VFP for unaligned data.  */
	and	tmp1, count, #0x3c
	add	dst, dst, tmp1
	add	src, src, tmp1
	rsb	tmp1, tmp1, #(60 - PC_OFFSET/2 + INSN_SIZE/2)
	/* Jump directly into the sequence below at the correct offset.  */
	add	pc, pc, tmp1, lsl #1

	ldr	tmp1, [src, #-60]	/* 15 words to go.  */
	str	tmp1, [dst, #-60]

	ldr	tmp1, [src, #-56]	/* 14 words to go.  */
	str	tmp1, [dst, #-56]
	ldr	tmp1, [src, #-52]
	str	tmp1, [dst, #-52]

	ldr	tmp1, [src, #-48]	/* 12 words to go.  */
	str	tmp1, [dst, #-48]
	ldr	tmp1, [src, #-44]
	str	tmp1, [dst, #-44]

	ldr	tmp1, [src, #-40]	/* 10 words to go.  */
	str	tmp1, [dst, #-40]
	ldr	tmp1, [src, #-36]
	str	tmp1, [dst, #-36]

	ldr	tmp1, [src, #-32]	/* 8 words to go.  */
	str	tmp1, [dst, #-32]
	ldr	tmp1, [src, #-28]
	str	tmp1, [dst, #-28]

	ldr	tmp1, [src, #-24]	/* 6 words to go.  */
	str	tmp1, [dst, #-24]
	ldr	tmp1, [src, #-20]
	str	tmp1, [dst, #-20]

	ldr	tmp1, [src, #-16]	/* 4 words to go.  */
	str	tmp1, [dst, #-16]
	ldr	tmp1, [src, #-12]
	str	tmp1, [dst, #-12]

	ldr	tmp1, [src, #-8]	/* 2 words to go.  */
	str	tmp1, [dst, #-8]
	ldr	tmp1, [src, #-4]
	str	tmp1, [dst, #-4]
#endif

	lsls	count, count, #31
	ldrhcs	tmp1, [src], #2
	ldrbne	src, [src]		/* Src is dead, use as a scratch.  */
	strhcs	tmp1, [dst], #2
	strbne	src, [dst]
	bx	lr

L(cpy_not_short):
	/* At least 64 bytes to copy, but don't know the alignment yet.  */
	str	tmp2, [sp, #-FRAME_SIZE]!
	and	tmp2, src, #7
	and	tmp1, dst, #7
	cmp	tmp1, tmp2
	bne	L(cpy_notaligned)

#ifdef USE_VFP
	/* Magic dust alert!  Force VFP on Cortex-A9.  Experiments show
	   that the FP pipeline is much better at streaming loads and
	   stores.  This is outside the critical loop.  */
	vmov.f32	s0, s0
#endif

	/* SRC and DST have the same mutual 64-bit alignment, but we may
	   still need to pre-copy some bytes to get to natural alignment.
	   We bring SRC and DST into full 64-bit alignment.  */
	lsls	tmp2, dst, #29
	beq	1f
	rsbs	tmp2, tmp2, #0
	sub	count, count, tmp2, lsr #29
	ldrmi	tmp1, [src], #4
	strmi	tmp1, [dst], #4
	lsls	tmp2, tmp2, #2
	ldrhcs	tmp1, [src], #2
	ldrbne	tmp2, [src], #1
	strhcs	tmp1, [dst], #2
	strbne	tmp2, [dst], #1

1:
	subs	tmp2, count, #64	/* Use tmp2 for count.  */
	blo	L(tail63aligned)

	cmp	tmp2, #512
	bhs	L(cpy_body_long)

L(cpy_body_medium):			/* Count in tmp2.  */
#ifdef USE_VFP
1:
	vldr	d0, [src, #0]
	subs	tmp2, tmp2, #64
	vldr	d1, [src, #8]
	vstr	d0, [dst, #0]
	vldr	d0, [src, #16]
	vstr	d1, [dst, #8]
	vldr	d1, [src, #24]
	vstr	d0, [dst, #16]
	vldr	d0, [src, #32]
	vstr	d1, [dst, #24]
	vldr	d1, [src, #40]
	vstr	d0, [dst, #32]
	vldr	d0, [src, #48]
	vstr	d1, [dst, #40]
	vldr	d1, [src, #56]
	vstr	d0, [dst, #48]
	add	src, src, #64
	vstr	d1, [dst, #56]
	add	dst, dst, #64
	bhs	1b
	tst	tmp2, #0x3f
	beq	L(done)

L(tail63aligned):			/* Count in tmp2.  */
	and	tmp1, tmp2, #0x38
	add	dst, dst, tmp1
	add	src, src, tmp1
	rsb	tmp1, tmp1, #(56 - PC_OFFSET + INSN_SIZE)
	add	pc, pc, tmp1

	vldr	d0, [src, #-56]	/* 14 words to go.  */
	vstr	d0, [dst, #-56]
	vldr	d0, [src, #-48]	/* 12 words to go.  */
	vstr	d0, [dst, #-48]
	vldr	d0, [src, #-40]	/* 10 words to go.  */
	vstr	d0, [dst, #-40]
	vldr	d0, [src, #-32]	/* 8 words to go.  */
	vstr	d0, [dst, #-32]
	vldr	d0, [src, #-24]	/* 6 words to go.  */
	vstr	d0, [dst, #-24]
	vldr	d0, [src, #-16]	/* 4 words to go.  */
	vstr	d0, [dst, #-16]
	vldr	d0, [src, #-8]	/* 2 words to go.  */
	vstr	d0, [dst, #-8]
#else
	sub	src, src, #8
	sub	dst, dst, #8
1:
	ldrd	A_l, A_h, [src, #8]
	strd	A_l, A_h, [dst, #8]
	ldrd	A_l, A_h, [src, #16]
	strd	A_l, A_h, [dst, #16]
	ldrd	A_l, A_h, [src, #24]
	strd	A_l, A_h, [dst, #24]
	ldrd	A_l, A_h, [src, #32]
	strd	A_l, A_h, [dst, #32]
	ldrd	A_l, A_h, [src, #40]
	strd	A_l, A_h, [dst, #40]
	ldrd	A_l, A_h, [src, #48]
	strd	A_l, A_h, [dst, #48]
	ldrd	A_l, A_h, [src, #56]
	strd	A_l, A_h, [dst, #56]
	ldrd	A_l, A_h, [src, #64]!
	strd	A_l, A_h, [dst, #64]!
	subs	tmp2, tmp2, #64
	bhs	1b
	tst	tmp2, #0x3f
	bne	1f
	ldr	tmp2,[sp], #FRAME_SIZE
	bx	lr
1:
	add	src, src, #8
	add	dst, dst, #8

L(tail63aligned):			/* Count in tmp2.  */
	/* Copy up to 7 d-words of data.  Similar to Ltail63unaligned, but
	   we know that the src and dest are 64-bit aligned so we can use
	   LDRD/STRD to improve efficiency.  */
	/* TMP2 is now negative, but we don't care about that.  The bottom
	   six bits still tell us how many bytes are left to copy.  */

	and	tmp1, tmp2, #0x38
	add	dst, dst, tmp1
	add	src, src, tmp1
	rsb	tmp1, tmp1, #(56 - PC_OFFSET + INSN_SIZE)
	add	pc, pc, tmp1
	ldrd	A_l, A_h, [src, #-56]	/* 14 words to go.  */
	strd	A_l, A_h, [dst, #-56]
	ldrd	A_l, A_h, [src, #-48]	/* 12 words to go.  */
	strd	A_l, A_h, [dst, #-48]
	ldrd	A_l, A_h, [src, #-40]	/* 10 words to go.  */
	strd	A_l, A_h, [dst, #-40]
	ldrd	A_l, A_h, [src, #-32]	/* 8 words to go.  */
	strd	A_l, A_h, [dst, #-32]
	ldrd	A_l, A_h, [src, #-24]	/* 6 words to go.  */
	strd	A_l, A_h, [dst, #-24]
	ldrd	A_l, A_h, [src, #-16]	/* 4 words to go.  */
	strd	A_l, A_h, [dst, #-16]
	ldrd	A_l, A_h, [src, #-8]	/* 2 words to go.  */
	strd	A_l, A_h, [dst, #-8]

#endif
	tst	tmp2, #4
	ldrne	tmp1, [src], #4
	strne	tmp1, [dst], #4
	lsls	tmp2, tmp2, #31		/* Count (tmp2) now dead. */
	ldrhcs	tmp1, [src], #2
	ldrbne	tmp2, [src]
	strhcs	tmp1, [dst], #2
	strbne	tmp2, [dst]

L(done):
	ldr	tmp2, [sp], #FRAME_SIZE
	bx	lr

L(cpy_body_long):			/* Count in tmp2.  */

	/* Long copy.  We know that there's at least (prefetch_lines * 64)
	   bytes to go.  */
#ifdef USE_VFP
	/* Don't use PLD.  Instead, read some data in advance of the current
	   copy position into a register.  This should act like a PLD
	   operation but we won't have to repeat the transfer.  */

	vldr	d3, [src, #0]
	vldr	d4, [src, #64]
	vldr	d5, [src, #128]
	vldr	d6, [src, #192]
	vldr	d7, [src, #256]

	vldr	d0, [src, #8]
	vldr	d1, [src, #16]
	vldr	d2, [src, #24]
	add	src, src, #32

	subs	tmp2, tmp2, #prefetch_lines * 64 * 2
	blo	2f
1:
	cpy_line_vfp	d3, 0
	cpy_line_vfp	d4, 64
	cpy_line_vfp	d5, 128
	add	dst, dst, #3 * 64
	add	src, src, #3 * 64
	cpy_line_vfp	d6, 0
	cpy_line_vfp	d7, 64
	add	dst, dst, #2 * 64
	add	src, src, #2 * 64
	subs	tmp2, tmp2, #prefetch_lines * 64
	bhs	1b

2:
	cpy_tail_vfp	d3, 0
	cpy_tail_vfp	d4, 64
	cpy_tail_vfp	d5, 128
	add	src, src, #3 * 64
	add	dst, dst, #3 * 64
	cpy_tail_vfp	d6, 0
	vstr	d7, [dst, #64]
	vldr	d7, [src, #64]
	vstr	d0, [dst, #64 + 8]
	vldr	d0, [src, #64 + 8]
	vstr	d1, [dst, #64 + 16]
	vldr	d1, [src, #64 + 16]
	vstr	d2, [dst, #64 + 24]
	vldr	d2, [src, #64 + 24]
	vstr	d7, [dst, #64 + 32]
	add	src, src, #96
	vstr	d0, [dst, #64 + 40]
	vstr	d1, [dst, #64 + 48]
	vstr	d2, [dst, #64 + 56]
	add	dst, dst, #128
	add	tmp2, tmp2, #prefetch_lines * 64
	b	L(cpy_body_medium)
#else
	/* Long copy.  Use an SMS style loop to maximize the I/O
	   bandwidth of the core.  We don't have enough spare registers
	   to synthesise prefetching, so use PLD operations.  */
	/* Pre-bias src and dst.  */
	sub	src, src, #8
	sub	dst, dst, #8
	pld	[src, #8]
	pld	[src, #72]
	subs	tmp2, tmp2, #64
	pld	[src, #136]
	ldrd	A_l, A_h, [src, #8]
	strd	B_l, B_h, [sp, #8]
	ldrd	B_l, B_h, [src, #16]
	strd	C_l, C_h, [sp, #16]
	ldrd	C_l, C_h, [src, #24]
	strd	D_l, D_h, [sp, #24]
	pld	[src, #200]
	ldrd	D_l, D_h, [src, #32]!
	b	1f
	.p2align	6
2:
	pld	[src, #232]
	strd	A_l, A_h, [dst, #40]
	ldrd	A_l, A_h, [src, #40]
	strd	B_l, B_h, [dst, #48]
	ldrd	B_l, B_h, [src, #48]
	strd	C_l, C_h, [dst, #56]
	ldrd	C_l, C_h, [src, #56]
	strd	D_l, D_h, [dst, #64]!
	ldrd	D_l, D_h, [src, #64]!
	subs	tmp2, tmp2, #64
1:
	strd	A_l, A_h, [dst, #8]
	ldrd	A_l, A_h, [src, #8]
	strd	B_l, B_h, [dst, #16]
	ldrd	B_l, B_h, [src, #16]
	strd	C_l, C_h, [dst, #24]
	ldrd	C_l, C_h, [src, #24]
	strd	D_l, D_h, [dst, #32]
	ldrd	D_l, D_h, [src, #32]
	bcs	2b
	/* Save the remaining bytes and restore the callee-saved regs.  */
	strd	A_l, A_h, [dst, #40]
	add	src, src, #40
	strd	B_l, B_h, [dst, #48]
	ldrd	B_l, B_h, [sp, #8]
	strd	C_l, C_h, [dst, #56]
	ldrd	C_l, C_h, [sp, #16]
	strd	D_l, D_h, [dst, #64]
	ldrd	D_l, D_h, [sp, #24]
	add	dst, dst, #72
	tst	tmp2, #0x3f
	bne	L(tail63aligned)
	ldr	tmp2, [sp], #FRAME_SIZE
	bx	lr
#endif

L(cpy_notaligned):
	pld	[src]
	pld	[src, #64]
	/* There's at least 64 bytes to copy, but there is no mutual
	   alignment.  */
	/* Bring DST to 64-bit alignment.  */
	lsls	tmp2, dst, #29
	pld	[src, #(2 * 64)]
	beq	1f
	rsbs	tmp2, tmp2, #0
	sub	count, count, tmp2, lsr #29
	ldrmi	tmp1, [src], #4
	strmi	tmp1, [dst], #4
	lsls	tmp2, tmp2, #2
	ldrbne	tmp1, [src], #1
	ldrhcs	tmp2, [src], #2
	strbne	tmp1, [dst], #1
	strhcs	tmp2, [dst], #2
1:
	pld	[src, #(3 * 64)]
	subs	count, count, #64
	ldrlo	tmp2, [sp], #FRAME_SIZE
	blo	L(tail63unaligned)
	pld	[src, #(4 * 64)]

#ifdef USE_NEON
	vld1.8	{d0-d3}, [src]!
	vld1.8	{d4-d7}, [src]!
	subs	count, count, #64
	blo	2f
1:
	pld	[src, #(4 * 64)]
	vst1.8	{d0-d3}, [ALIGN (dst, 64)]!
	vld1.8	{d0-d3}, [src]!
	vst1.8	{d4-d7}, [ALIGN (dst, 64)]!
	vld1.8	{d4-d7}, [src]!
	subs	count, count, #64
	bhs	1b
2:
	vst1.8	{d0-d3}, [ALIGN (dst, 64)]!
	vst1.8	{d4-d7}, [ALIGN (dst, 64)]!
	ands	count, count, #0x3f
#else
	/* Use an SMS style loop to maximize the I/O bandwidth.  */
	sub	src, src, #4
	sub	dst, dst, #8
	subs	tmp2, count, #64	/* Use tmp2 for count.  */
	ldr	A_l, [src, #4]
	ldr	A_h, [src, #8]
	strd	B_l, B_h, [sp, #8]
	ldr	B_l, [src, #12]
	ldr	B_h, [src, #16]
	strd	C_l, C_h, [sp, #16]
	ldr	C_l, [src, #20]
	ldr	C_h, [src, #24]
	strd	D_l, D_h, [sp, #24]
	ldr	D_l, [src, #28]
	ldr	D_h, [src, #32]!
	b	1f
	.p2align	6
2:
	pld	[src, #(5 * 64) - (32 - 4)]
	strd	A_l, A_h, [dst, #40]
	ldr	A_l, [src, #36]
	ldr	A_h, [src, #40]
	strd	B_l, B_h, [dst, #48]
	ldr	B_l, [src, #44]
	ldr	B_h, [src, #48]
	strd	C_l, C_h, [dst, #56]
	ldr	C_l, [src, #52]
	ldr	C_h, [src, #56]
	strd	D_l, D_h, [dst, #64]!
	ldr	D_l, [src, #60]
	ldr	D_h, [src, #64]!
	subs	tmp2, tmp2, #64
1:
	strd	A_l, A_h, [dst, #8]
	ldr	A_l, [src, #4]
	ldr	A_h, [src, #8]
	strd	B_l, B_h, [dst, #16]
	ldr	B_l, [src, #12]
	ldr	B_h, [src, #16]
	strd	C_l, C_h, [dst, #24]
	ldr	C_l, [src, #20]
	ldr	C_h, [src, #24]
	strd	D_l, D_h, [dst, #32]
	ldr	D_l, [src, #28]
	ldr	D_h, [src, #32]
	bcs	2b

	/* Save the remaining bytes and restore the callee-saved regs.  */
	strd	A_l, A_h, [dst, #40]
	add	src, src, #36
	strd	B_l, B_h, [dst, #48]
	ldrd	B_l, B_h, [sp, #8]
	strd	C_l, C_h, [dst, #56]
	ldrd	C_l, C_h, [sp, #16]
	strd	D_l, D_h, [dst, #64]
	ldrd	D_l, D_h, [sp, #24]
	add	dst, dst, #72
	ands	count, tmp2, #0x3f
#endif
	ldr	tmp2, [sp], #FRAME_SIZE
	bne	L(tail63unaligned)
	bx	lr

END (__memcpy_arm)