visus
/
teensy-cores
Watch 1
Star 0
Fork 0
Code Issues 0 Pull Requests 0 Releases 0 Wiki Activity
Browse Source

Fast memcpy() on Teensy 3.0 & 3.1 

https://forum.pjrc.com/threads/27752-teensy-3-memcpy-has-gotten-slower
main
PaulStoffregen 9 years ago
parent
bd059d5af0
commit
b5284b3a1f
2 changed files with 342 additions and 0 deletions
Split View Show Diff Stats
  1. +13
    -0
      teensy3/WProgram.h
  2. +329
    -0
      teensy3/memcpy-armv7m.S

+ 13
- 0
teensy3/WProgram.h View File

@@ -58,4 +58,17 @@ long map(long, long, long, long, long);

#endif // __cplusplus


// Fast memcpy
#if defined(__MK20DX128__) || defined(__MK20DX256__)
#ifdef __cplusplus
extern "C" {
extern void *memcpy (void *dst, const void *src, size_t count);
}
#else
extern void *memcpy (void *dst, const void *src, size_t count);
#endif
#endif


#endif // WProgram_h

+ 329
- 0
teensy3/memcpy-armv7m.S View File

@@ -0,0 +1,329 @@
/*
* Copyright (c) 2013 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.
*/

#if defined(__MK20DX128__) || defined(__MK20DX256__)
#if defined (__ARM_ARCH_7M__) || defined (__ARM_ARCH_7EM__)
#define __ARM_FEATURE_UNALIGNED 1
/* This memcpy routine is optimised for Cortex-M3/M4 cores with/without
unaligned access.

If compiled with GCC, this file should be enclosed within following
pre-processing check:
if defined (__ARM_ARCH_7M__) || defined (__ARM_ARCH_7EM__)

Prototype: void *memcpy (void *dst, const void *src, size_t count);

The job will be done in 5 steps.
Step 1: Align src/dest pointers, copy mis-aligned if fail to align both
Step 2: Repeatedly copy big block size of __OPT_BIG_BLOCK_SIZE
Step 3: Repeatedly copy big block size of __OPT_MID_BLOCK_SIZE
Step 4: Copy word by word
Step 5: Copy byte-to-byte

Tunable options:
__OPT_BIG_BLOCK_SIZE: Size of big block in words. Default to 64.
__OPT_MID_BLOCK_SIZE: Size of big block in words. Default to 16.
*/
#ifndef __OPT_BIG_BLOCK_SIZE
#define __OPT_BIG_BLOCK_SIZE (4 * 16)
#endif

#ifndef __OPT_MID_BLOCK_SIZE
#define __OPT_MID_BLOCK_SIZE (4 * 4)
#endif

#if __OPT_BIG_BLOCK_SIZE == 16
#define BEGIN_UNROLL_BIG_BLOCK \
.irp offset, 0,4,8,12
#elif __OPT_BIG_BLOCK_SIZE == 32
#define BEGIN_UNROLL_BIG_BLOCK \
.irp offset, 0,4,8,12,16,20,24,28
#elif __OPT_BIG_BLOCK_SIZE == 64
#define BEGIN_UNROLL_BIG_BLOCK \
.irp offset, 0,4,8,12,16,20,24,28,32,36,40,44,48,52,56,60
#else
#error "Illegal __OPT_BIG_BLOCK_SIZE"
#endif

#if __OPT_MID_BLOCK_SIZE == 8
#define BEGIN_UNROLL_MID_BLOCK \
.irp offset, 0,4
#elif __OPT_MID_BLOCK_SIZE == 16
#define BEGIN_UNROLL_MID_BLOCK \
.irp offset, 0,4,8,12
#else
#error "Illegal __OPT_MID_BLOCK_SIZE"
#endif

#define END_UNROLL .endr

.syntax unified
.text
.align 2
.global memcpy
.thumb
.thumb_func
.type memcpy, %function
memcpy:
@ r0: dst
@ r1: src
@ r2: len
#ifdef __ARM_FEATURE_UNALIGNED
/* In case of UNALIGNED access supported, ip is not used in
function body. */
mov ip, r0
#else
push {r0}
#endif
orr r3, r1, r0
ands r3, r3, #3
bne .Lmisaligned_copy

.Lbig_block:
subs r2, __OPT_BIG_BLOCK_SIZE
blo .Lmid_block

/* Kernel loop for big block copy */
.align 2
.Lbig_block_loop:
BEGIN_UNROLL_BIG_BLOCK
#ifdef __ARM_ARCH_7EM__
ldr r3, [r1], #4
str r3, [r0], #4
END_UNROLL
#else /* __ARM_ARCH_7M__ */
ldr r3, [r1, \offset]
str r3, [r0, \offset]
END_UNROLL
adds r0, __OPT_BIG_BLOCK_SIZE
adds r1, __OPT_BIG_BLOCK_SIZE
#endif
subs r2, __OPT_BIG_BLOCK_SIZE
bhs .Lbig_block_loop

.Lmid_block:
adds r2, __OPT_BIG_BLOCK_SIZE - __OPT_MID_BLOCK_SIZE
blo .Lcopy_word_by_word

/* Kernel loop for mid-block copy */
.align 2
.Lmid_block_loop:
BEGIN_UNROLL_MID_BLOCK
#ifdef __ARM_ARCH_7EM__
ldr r3, [r1], #4
str r3, [r0], #4
END_UNROLL
#else /* __ARM_ARCH_7M__ */
ldr r3, [r1, \offset]
str r3, [r0, \offset]
END_UNROLL
adds r0, __OPT_MID_BLOCK_SIZE
adds r1, __OPT_MID_BLOCK_SIZE
#endif
subs r2, __OPT_MID_BLOCK_SIZE
bhs .Lmid_block_loop

.Lcopy_word_by_word:
adds r2, __OPT_MID_BLOCK_SIZE - 4
blo .Lcopy_less_than_4

/* Kernel loop for small block copy */
.align 2
.Lcopy_word_by_word_loop:
ldr r3, [r1], #4
str r3, [r0], #4
subs r2, #4
bhs .Lcopy_word_by_word_loop

.Lcopy_less_than_4:
adds r2, #4
beq .Ldone

lsls r2, r2, #31
itt ne
ldrbne r3, [r1], #1
strbne r3, [r0], #1

bcc .Ldone
#ifdef __ARM_FEATURE_UNALIGNED
ldrh r3, [r1]
strh r3, [r0]
#else
ldrb r3, [r1]
strb r3, [r0]
ldrb r3, [r1, #1]
strb r3, [r0, #1]
#endif /* __ARM_FEATURE_UNALIGNED */

.Ldone:
#ifdef __ARM_FEATURE_UNALIGNED
mov r0, ip
#else
pop {r0}
#endif
bx lr

.align 2
.Lmisaligned_copy:
#ifdef __ARM_FEATURE_UNALIGNED
/* Define label DST_ALIGNED to BIG_BLOCK. It will go to aligned copy
once destination is adjusted to aligned. */
#define Ldst_aligned Lbig_block

/* Copy word by word using LDR when alignment can be done in hardware,
i.e., SCTLR.A is set, supporting unaligned access in LDR and STR. */

cmp r2, #8
blo .Lbyte_copy

/* if src is aligned, just go to the big block loop. */
lsls r3, r1, #30
beq .Ldst_aligned
#else
/* if len < 12, misalignment adjustment has more overhead than
just byte-to-byte copy. Also, len must >=8 to guarantee code
afterward work correctly. */
cmp r2, #12
blo .Lbyte_copy
#endif /* __ARM_FEATURE_UNALIGNED */

/* Align dst only, not trying to align src. That is the because
handling of aligned src and misaligned dst need more overhead than
otherwise. By doing this the worst case is when initial src is aligned,
additional up to 4 byte additional copy will executed, which is
acceptable. */

ands r3, r0, #3
beq .Ldst_aligned

rsb r3, #4
subs r2, r3

lsls r3, r3, #31
itt ne
ldrbne r3, [r1], #1
strbne r3, [r0], #1

bcc .Ldst_aligned

#ifdef __ARM_FEATURE_UNALIGNED
ldrh r3, [r1], #2
strh r3, [r0], #2
b .Ldst_aligned
#else
ldrb r3, [r1], #1
strb r3, [r0], #1
ldrb r3, [r1], #1
strb r3, [r0], #1
/* Now that dst is aligned */
.Ldst_aligned:
/* if r1 is aligned now, it means r0/r1 has the same misalignment,
and they are both aligned now. Go aligned copy. */
ands r3, r1, #3
beq .Lbig_block

/* dst is aligned, but src isn't. Misaligned copy. */

push {r4, r5}
subs r2, #4

/* Backward r1 by misaligned bytes, to make r1 aligned.
Since we need to restore r1 to unaligned address after the loop,
we need keep the offset bytes to ip and sub it from r1 afterward. */
subs r1, r3
rsb ip, r3, #4

/* Pre-load on word */
ldr r4, [r1], #4

cmp r3, #2
beq .Lmisaligned_copy_2_2
cmp r3, #3
beq .Lmisaligned_copy_3_1

.macro mis_src_copy shift
1:
lsrs r4, r4, \shift
ldr r3, [r1], #4
lsls r5, r3, 32-\shift
orr r4, r4, r5
str r4, [r0], #4
mov r4, r3
subs r2, #4
bhs 1b
.endm

.Lmisaligned_copy_1_3:
mis_src_copy shift=8
b .Lsrc_misaligned_tail

.Lmisaligned_copy_3_1:
mis_src_copy shift=24
b .Lsrc_misaligned_tail

.Lmisaligned_copy_2_2:
/* For 2_2 misalignment, ldr is still faster than 2 x ldrh. */
mis_src_copy shift=16

.Lsrc_misaligned_tail:
adds r2, #4
subs r1, ip
pop {r4, r5}

#endif /* __ARM_FEATURE_UNALIGNED */

.Lbyte_copy:
subs r2, #4
blo .Lcopy_less_than_4

.Lbyte_copy_loop:
subs r2, #1
ldrb r3, [r1], #1
strb r3, [r0], #1
bhs .Lbyte_copy_loop

ldrb r3, [r1]
strb r3, [r0]
ldrb r3, [r1, #1]
strb r3, [r0, #1]
ldrb r3, [r1, #2]
strb r3, [r0, #2]

#ifdef __ARM_FEATURE_UNALIGNED
mov r0, ip
#else
pop {r0}
#endif
bx lr

.size memcpy, .-memcpy
#endif

#endif // __MK20DX128__ || __MK20DX256__


Write Preview
Loading…
Cancel
Save