Merge "Update to latest cortexa15 memcpy code."
This commit is contained in:
Christopher Ferris
Gerrit Code Review
commit
68fd78efa0
1 changed files with 245 additions and 66 deletions
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@ -24,81 +24,110 @@
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 2013 ARM Ltd
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the company may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/* Assumes neon instructions and a cache line size of 64 bytes. */
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/* Prototype: void *memcpy (void *dst, const void *src, size_t count). */
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// This version is tuned for the Cortex-A15 processor.
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#include <machine/cpu-features.h>
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#include <machine/asm.h>
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/*
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* This code assumes it is running on a processor that supports all arm v7
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* instructions, that supports neon instructions, and that has a 64 byte
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* cache line.
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*/
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.text
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.syntax unified
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.fpu neon
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#define CACHE_LINE_SIZE 64
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ENTRY(memcpy)
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// Assumes that n >= 0, and dst, src are valid pointers.
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// For any sizes less than 832 use the neon code that doesn't
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// care about the src alignment. This avoids any checks
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// for src alignment, and offers the best improvement since
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// smaller sized copies are dominated by the overhead of
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// the pre and post main loop.
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// For larger copies, if src and dst cannot both be aligned to
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// word boundaries, use the neon code.
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// For all other copies, align dst to a double word boundary
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// and copy using LDRD/STRD instructions.
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// Save registers (r0 holds the return value):
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// optimized push {r0, lr}.
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.save {r0, lr}
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/* start preloading as early as possible */
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pld [r1, #(CACHE_LINE_SIZE*0)]
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stmfd sp!, {r0, lr}
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pld [r1, #(CACHE_LINE_SIZE*1)]
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pld [r1, #(CACHE_LINE_SIZE*16)]
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push {r0, lr}
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/* do we have at least 16-bytes to copy (needed for alignment below) */
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cmp r2, #16
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blo 5f
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blo copy_less_than_16_unknown_align
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/* align destination to cache-line for the write-buffer */
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cmp r2, #832
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bge check_alignment
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copy_unknown_alignment:
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// Unknown alignment of src and dst.
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// Assumes that the first few bytes have already been prefetched.
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// Align destination to 128 bits. The mainloop store instructions
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// require this alignment or they will throw an exception.
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rsb r3, r0, #0
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ands r3, r3, #0xF
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beq 0f
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beq 2f
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/* copy up to 15-bytes (count in r3) */
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// Copy up to 15 bytes (count in r3).
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sub r2, r2, r3
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movs ip, r3, lsl #31
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ldrmib lr, [r1], #1
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strmib lr, [r0], #1
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ldrcsb ip, [r1], #1
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ldrcsb lr, [r1], #1
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strcsb ip, [r0], #1
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strcsb lr, [r0], #1
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itt mi
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ldrbmi lr, [r1], #1
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strbmi lr, [r0], #1
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itttt cs
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ldrbcs ip, [r1], #1
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ldrbcs lr, [r1], #1
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strbcs ip, [r0], #1
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strbcs lr, [r0], #1
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movs ip, r3, lsl #29
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bge 1f
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// copies 4 bytes, destination 32-bits aligned
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// Copies 4 bytes, dst 32 bits aligned before, at least 64 bits after.
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vld4.8 {d0[0], d1[0], d2[0], d3[0]}, [r1]!
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vst4.8 {d0[0], d1[0], d2[0], d3[0]}, [r0, :32]!
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1: bcc 2f
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// copies 8 bytes, destination 64-bits aligned
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// Copies 8 bytes, dst 64 bits aligned before, at least 128 bits after.
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vld1.8 {d0}, [r1]!
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vst1.8 {d0}, [r0, :64]!
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2:
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0: /* preload immediately the next cache line, which we may need */
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pld [r1, #(CACHE_LINE_SIZE*0)]
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pld [r1, #(CACHE_LINE_SIZE*1)]
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/* make sure we have at least 64 bytes to copy */
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2: // Make sure we have at least 64 bytes to copy.
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subs r2, r2, #64
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blo 2f
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/* Preload all the cache lines we need.
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* NOTE: The number of pld below depends on CACHE_LINE_SIZE,
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* ideally we would increase the distance in the main loop to
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* avoid the goofy code below. In practice this doesn't seem to make
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* a big difference.
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* NOTE: The value CACHE_LINE_SIZE * 4 was chosen through
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* experimentation.
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*/
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pld [r1, #(CACHE_LINE_SIZE*2)]
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pld [r1, #(CACHE_LINE_SIZE*3)]
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pld [r1, #(CACHE_LINE_SIZE*4)]
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1: /* The main loop copies 64 bytes at a time */
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1: // The main loop copies 64 bytes at a time.
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vld1.8 {d0 - d3}, [r1]!
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vld1.8 {d4 - d7}, [r1]!
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pld [r1, #(CACHE_LINE_SIZE*4)]
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@ -107,25 +136,24 @@ ENTRY(memcpy)
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vst1.8 {d4 - d7}, [r0, :128]!
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bhs 1b
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2: /* fix-up the remaining count and make sure we have >= 32 bytes left */
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add r2, r2, #64
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subs r2, r2, #32
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blo 4f
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2: // Fix-up the remaining count and make sure we have >= 32 bytes left.
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adds r2, r2, #32
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blo 3f
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3: /* 32 bytes at a time. These cache lines were already preloaded */
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// 32 bytes. These cache lines were already preloaded.
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vld1.8 {d0 - d3}, [r1]!
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subs r2, r2, #32
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sub r2, r2, #32
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vst1.8 {d0 - d3}, [r0, :128]!
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bhs 3b
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4: /* less than 32 left */
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3: // Less than 32 left.
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add r2, r2, #32
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tst r2, #0x10
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beq 5f
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// copies 16 bytes, 128-bits aligned
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beq copy_less_than_16_unknown_align
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// Copies 16 bytes, destination 128 bits aligned.
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vld1.8 {d0, d1}, [r1]!
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vst1.8 {d0, d1}, [r0, :128]!
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5: /* copy up to 15-bytes (count in r2) */
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copy_less_than_16_unknown_align:
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// Copy up to 15 bytes (count in r2).
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movs ip, r2, lsl #29
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bcc 1f
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vld1.8 {d0}, [r1]!
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@ -133,14 +161,165 @@ ENTRY(memcpy)
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1: bge 2f
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vld4.8 {d0[0], d1[0], d2[0], d3[0]}, [r1]!
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vst4.8 {d0[0], d1[0], d2[0], d3[0]}, [r0]!
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2: movs ip, r2, lsl #31
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ldrmib r3, [r1], #1
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ldrcsb ip, [r1], #1
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ldrcsb lr, [r1], #1
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strmib r3, [r0], #1
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strcsb ip, [r0], #1
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strcsb lr, [r0], #1
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ldmfd sp!, {r0, lr}
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bx lr
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2: // Copy 0 to 4 bytes.
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lsls r2, r2, #31
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itt ne
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ldrbne lr, [r1], #1
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strbne lr, [r0], #1
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itttt cs
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ldrbcs ip, [r1], #1
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ldrbcs lr, [r1]
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strbcs ip, [r0], #1
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strbcs lr, [r0]
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pop {r0, pc}
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check_alignment:
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// If src and dst cannot both be aligned to a word boundary,
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// use the unaligned copy version.
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eor r3, r0, r1
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ands r3, r3, #0x3
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bne copy_unknown_alignment
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// To try and improve performance, stack layout changed,
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// i.e., not keeping the stack looking like users expect
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// (highest numbered register at highest address).
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// TODO: Add debug frame directives.
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// We don't need exception unwind directives, because the code below
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// does not throw any exceptions and does not call any other functions.
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// Generally, newlib functions like this lack debug information for
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// assembler source.
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.save {r4, r5}
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strd r4, r5, [sp, #-8]!
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.save {r6, r7}
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strd r6, r7, [sp, #-8]!
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.save {r8, r9}
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strd r8, r9, [sp, #-8]!
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// Optimized for already aligned dst code.
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ands ip, r0, #3
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bne dst_not_word_aligned
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word_aligned:
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// Align the destination buffer to 8 bytes, to make sure double
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// loads and stores don't cross a cache line boundary,
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// as they are then more expensive even if the data is in the cache
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// (require two load/store issue cycles instead of one).
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// If only one of the buffers is not 8 bytes aligned,
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// then it's more important to align dst than src,
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// because there is more penalty for stores
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// than loads that cross a cacheline boundary.
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// This check and realignment are only done if there is >= 832
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// bytes to copy.
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// Dst is word aligned, but check if it is already double word aligned.
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ands r3, r0, #4
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beq 1f
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ldr r3, [r1], #4
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str r3, [r0], #4
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sub r2, #4
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1: // Can only get here if > 64 bytes to copy, so don't do check r2.
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sub r2, #64
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2: // Every loop iteration copies 64 bytes.
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.irp offset, #0, #8, #16, #24, #32
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ldrd r4, r5, [r1, \offset]
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strd r4, r5, [r0, \offset]
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.endr
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ldrd r4, r5, [r1, #40]
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ldrd r6, r7, [r1, #48]
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ldrd r8, r9, [r1, #56]
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// Keep the pld as far from the next load as possible.
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// The amount to prefetch was determined experimentally using
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// large sizes, and verifying the prefetch size does not affect
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// the smaller copies too much.
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// WARNING: If the ldrd and strd instructions get too far away
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// from each other, performance suffers. Three loads
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// in a row is the best tradeoff.
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pld [r1, #(CACHE_LINE_SIZE*16)]
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strd r4, r5, [r0, #40]
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strd r6, r7, [r0, #48]
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strd r8, r9, [r0, #56]
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add r0, r0, #64
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add r1, r1, #64
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subs r2, r2, #64
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bge 2b
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// Fix-up the remaining count and make sure we have >= 32 bytes left.
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adds r2, r2, #32
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blo 4f
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// Copy 32 bytes. These cache lines were already preloaded.
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.irp offset, #0, #8, #16, #24
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ldrd r4, r5, [r1, \offset]
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strd r4, r5, [r0, \offset]
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.endr
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add r1, r1, #32
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add r0, r0, #32
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sub r2, r2, #32
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4: // Less than 32 left.
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add r2, r2, #32
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tst r2, #0x10
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beq 5f
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// Copy 16 bytes.
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.irp offset, #0, #8
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ldrd r4, r5, [r1, \offset]
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strd r4, r5, [r0, \offset]
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.endr
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add r1, r1, #16
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add r0, r0, #16
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5: // Copy up to 15 bytes (count in r2).
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movs ip, r2, lsl #29
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bcc 1f
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// Copy 8 bytes.
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ldrd r4, r5, [r1], #8
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strd r4, r5, [r0], #8
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1: bge 2f
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// Copy 4 bytes.
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ldr r4, [r1], #4
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str r4, [r0], #4
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2: // Copy 0 to 4 bytes.
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lsls r2, r2, #31
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itt ne
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ldrbne lr, [r1], #1
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strbne lr, [r0], #1
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itttt cs
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ldrbcs ip, [r1], #1
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ldrbcs lr, [r1]
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strbcs ip, [r0], #1
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strbcs lr, [r0]
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// Restore registers: optimized pop {r0, pc}
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ldrd r8, r9, [sp], #8
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ldrd r6, r7, [sp], #8
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ldrd r4, r5, [sp], #8
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pop {r0, pc}
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dst_not_word_aligned:
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// Align dst to word.
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rsb ip, ip, #4
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cmp ip, #2
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itt gt
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ldrbgt lr, [r1], #1
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strbgt lr, [r0], #1
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itt ge
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ldrbge lr, [r1], #1
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strbge lr, [r0], #1
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ldrb lr, [r1], #1
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strb lr, [r0], #1
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sub r2, r2, ip
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// If src is not word aligned, jump to the unaligned code.
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ands ip, r1, #0x3
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beq word_aligned
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END(memcpy)
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