ARM assembler memory copy example

mem_copy.S

    .thumb_func
    .align 2
    .globl mem_copy
    .type mem_copy, %function
mem_copy:
    cmp r1, r2
    itte ne
    ldrne r3, [r0], #4
    strne r3, [r1], #4
    beq 1f
    b mem_copy
1:
    bx lr

mem_original.S

// Rowley CrossWorks, runtime support.
//
//  Copyright (c) 2001-2020 Rowley Associates Limited.
//
// This file may be distributed under the terms of the License Agreement
// provided with this software.
//
// THIS FILE IS PROVIDED AS IS WITH NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  .thumb_func
memory_copy:
  cmp r0, r1
  beq 2f
  subs r2, r2, r1
  beq 2f
1:
  ldrb r3, [r0]
  adds r0, r0, #1
  strb r3, [r1]
  adds r1, r1, #1
  subs r2, r2, #1
  bne 1b
2:
  bx lr

  .thumb_func
memory_set:
  cmp r0, r1
  beq 1f
  strb r2, [r0]
  adds r0, r0, #1
  b memory_set
1:
  bx lr

mem_updated.S

  .thumb_func
memory_copy:
  cmp r1, r2
  itte ne
  ldrne r3, [r0], #4
  strne r3, [r1], #4
  beq 1f
  b memory_copy
1:
  bx lr
// TODO: Something strange happens with CrossWorks build and memory_set
// function as it works with POR event only when BSS is zeroed on per byte basis
  .thumb_func
memory_set:
  cmp r0, r1
  itt lt
  strlt r2, [r0], #4
  blt memory_set
1:
  bx lr