/* $NetBSD: memcpy_arm.S,v 1.5.40.1 2024/07/20 14:52:04 martin Exp $ */ /*- * Copyright (c) 1997 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Neil A. Carson and Mark Brinicombe * * 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. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``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 THE FOUNDATION OR CONTRIBUTORS * 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. */ #include /* * This is one fun bit of code ... * Some easy listening music is suggested while trying to understand this * code e.g. Iron Maiden * * For anyone attempting to understand it : * * The core code is implemented here with simple stubs for memcpy(). * * All local labels are prefixed with Lmemcpy_ * Following the prefix a label starting f is used in the forward copy code * while a label using b is used in the backwards copy code * The source and destination addresses determine whether a forward or * backward copy is performed. * Separate bits of code are used to deal with the following situations * for both the forward and backwards copy. * unaligned source address * unaligned destination address * Separate copy routines are used to produce an optimised result for each * of these cases. * The copy code will use LDM/STM instructions to copy up to 32 bytes at * a time where possible. * * Note: r12 (aka ip) can be trashed during the function along with * r0-r3 although r0-r2 have defined uses i.e. src, dest, len through out. * Additional registers are preserved prior to use i.e. r4, r5 & lr * * Apologies for the state of the comments ;-) */ /* LINTSTUB: Func: void *memcpy(void *dst, const void *src, size_t len) */ ENTRY(memcpy) /* save leaf functions having to store this away */ push {r0, lr} /* memcpy() returns dest addr */ subs r2, r2, #4 blo .Lmemcpy_l4 /* less than 4 bytes */ ands r12, r0, #3 bne .Lmemcpy_destul /* oh unaligned destination addr */ ands r12, r1, #3 bne .Lmemcpy_srcul /* oh unaligned source addr */ .Lmemcpy_t8: /* We have aligned source and destination */ subs r2, r2, #8 blo .Lmemcpy_l12 /* less than 12 bytes (4 from above) */ subs r2, r2, #0x14 blo .Lmemcpy_l32 /* less than 32 bytes (12 from above) */ push {r4} /* borrow r4 */ /* blat 32 bytes at a time */ /* XXX for really big copies perhaps we should use more registers */ .Lmemcpy_loop32: ldmia r1!, {r3, r4, r12, lr} stmia r0!, {r3, r4, r12, lr} ldmia r1!, {r3, r4, r12, lr} stmia r0!, {r3, r4, r12, lr} subs r2, r2, #0x20 bhs .Lmemcpy_loop32 cmn r2, #0x10 ldmiahs r1!, {r3, r4, r12, lr} /* blat a remaining 16 bytes */ stmiahs r0!, {r3, r4, r12, lr} subhs r2, r2, #0x10 pop {r4} /* return r4 */ .Lmemcpy_l32: adds r2, r2, #0x14 /* blat 12 bytes at a time */ .Lmemcpy_loop12: ldmiahs r1!, {r3, r12, lr} stmiahs r0!, {r3, r12, lr} subshs r2, r2, #0x0c bhs .Lmemcpy_loop12 .Lmemcpy_l12: adds r2, r2, #8 blo .Lmemcpy_l4 subs r2, r2, #4 ldrlo r3, [r1], #4 strlo r3, [r0], #4 ldmiahs r1!, {r3, r12} stmiahs r0!, {r3, r12} subhs r2, r2, #4 .Lmemcpy_l4: /* less than 4 bytes to go */ adds r2, r2, #4 #ifdef __APCS_26_ ldmiaeq sp!, {r0, pc}^ /* done */ #else popeq {r0, pc} /* done */ #endif /* copy the crud byte at a time */ cmp r2, #2 ldrb r3, [r1], #1 strb r3, [r0], #1 ldrbhs r3, [r1], #1 strbhs r3, [r0], #1 ldrbhi r3, [r1], #1 strbhi r3, [r0], #1 pop {r0, pc} /* erg - unaligned destination */ .Lmemcpy_destul: rsb r12, r12, #4 cmp r12, #2 /* align destination with byte copies */ ldrb r3, [r1], #1 strb r3, [r0], #1 ldrbhs r3, [r1], #1 strbhs r3, [r0], #1 ldrbhi r3, [r1], #1 strbhi r3, [r0], #1 subs r2, r2, r12 blo .Lmemcpy_l4 /* less the 4 bytes */ ands r12, r1, #3 beq .Lmemcpy_t8 /* we have an aligned source */ /* erg - unaligned source */ /* This is where it gets nasty ... */ .Lmemcpy_srcul: bic r1, r1, #3 ldr lr, [r1], #4 cmp r12, #2 bhi .Lmemcpy_srcul3 beq .Lmemcpy_srcul2 cmp r2, #0x0c blo .Lmemcpy_srcul1loop4 sub r2, r2, #0x0c push {r4, r5} .Lmemcpy_srcul1loop16: #ifdef __ARMEB__ mov r3, lr, lsl #8 #else mov r3, lr, lsr #8 #endif ldmia r1!, {r4, r5, r12, lr} #ifdef __ARMEB__ orr r3, r3, r4, lsr #24 mov r4, r4, lsl #8 orr r4, r4, r5, lsr #24 mov r5, r5, lsl #8 orr r5, r5, r12, lsr #24 mov r12, r12, lsl #8 orr r12, r12, lr, lsr #24 #else orr r3, r3, r4, lsl #24 mov r4, r4, lsr #8 orr r4, r4, r5, lsl #24 mov r5, r5, lsr #8 orr r5, r5, r12, lsl #24 mov r12, r12, lsr #8 orr r12, r12, lr, lsl #24 #endif stmia r0!, {r3-r5, r12} subs r2, r2, #0x10 bhs .Lmemcpy_srcul1loop16 pop {r4, r5} adds r2, r2, #0x0c blo .Lmemcpy_srcul1l4 .Lmemcpy_srcul1loop4: #ifdef __ARMEB__ mov r12, lr, lsl #8 #else mov r12, lr, lsr #8 #endif ldr lr, [r1], #4 #ifdef __ARMEB__ orr r12, r12, lr, lsr #24 #else orr r12, r12, lr, lsl #24 #endif str r12, [r0], #4 subs r2, r2, #4 bhs .Lmemcpy_srcul1loop4 .Lmemcpy_srcul1l4: sub r1, r1, #3 b .Lmemcpy_l4 .Lmemcpy_srcul2: cmp r2, #0x0c blo .Lmemcpy_srcul2loop4 sub r2, r2, #0x0c push {r4, r5} .Lmemcpy_srcul2loop16: #ifdef __ARMEB__ mov r3, lr, lsl #16 #else mov r3, lr, lsr #16 #endif ldmia r1!, {r4, r5, r12, lr} #ifdef __ARMEB__ orr r3, r3, r4, lsr #16 mov r4, r4, lsl #16 orr r4, r4, r5, lsr #16 mov r5, r5, lsl #16 orr r5, r5, r12, lsr #16 mov r12, r12, lsl #16 orr r12, r12, lr, lsr #16 #else orr r3, r3, r4, lsl #16 mov r4, r4, lsr #16 orr r4, r4, r5, lsl #16 mov r5, r5, lsr #16 orr r5, r5, r12, lsl #16 mov r12, r12, lsr #16 orr r12, r12, lr, lsl #16 #endif stmia r0!, {r3-r5, r12} subs r2, r2, #0x10 bhs .Lmemcpy_srcul2loop16 pop {r4, r5} adds r2, r2, #0x0c blo .Lmemcpy_srcul2l4 .Lmemcpy_srcul2loop4: #ifdef __ARMEB__ mov r12, lr, lsl #16 #else mov r12, lr, lsr #16 #endif ldr lr, [r1], #4 #ifdef __ARMEB__ orr r12, r12, lr, lsr #16 #else orr r12, r12, lr, lsl #16 #endif str r12, [r0], #4 subs r2, r2, #4 bhs .Lmemcpy_srcul2loop4 .Lmemcpy_srcul2l4: sub r1, r1, #2 b .Lmemcpy_l4 .Lmemcpy_srcul3: cmp r2, #0x0c blo .Lmemcpy_srcul3loop4 sub r2, r2, #0x0c push {r4, r5} .Lmemcpy_srcul3loop16: #ifdef __ARMEB__ mov r3, lr, lsl #24 #else mov r3, lr, lsr #24 #endif ldmia r1!, {r4, r5, r12, lr} #ifdef __ARMEB__ orr r3, r3, r4, lsr #8 mov r4, r4, lsl #24 orr r4, r4, r5, lsr #8 mov r5, r5, lsl #24 orr r5, r5, r12, lsr #8 mov r12, r12, lsl #24 orr r12, r12, lr, lsr #8 #else orr r3, r3, r4, lsl #8 mov r4, r4, lsr #24 orr r4, r4, r5, lsl #8 mov r5, r5, lsr #24 orr r5, r5, r12, lsl #8 mov r12, r12, lsr #24 orr r12, r12, lr, lsl #8 #endif stmia r0!, {r3-r5, r12} subs r2, r2, #0x10 bhs .Lmemcpy_srcul3loop16 pop {r4, r5} adds r2, r2, #0x0c blo .Lmemcpy_srcul3l4 .Lmemcpy_srcul3loop4: #ifdef __ARMEB__ mov r12, lr, lsl #24 #else mov r12, lr, lsr #24 #endif ldr lr, [r1], #4 #ifdef __ARMEB__ orr r12, r12, lr, lsr #8 #else orr r12, r12, lr, lsl #8 #endif str r12, [r0], #4 subs r2, r2, #4 bhs .Lmemcpy_srcul3loop4 .Lmemcpy_srcul3l4: sub r1, r1, #1 b .Lmemcpy_l4 END(memcpy)