[Mspgcc-users] autoincrement with byte move

[Ralf Guetlein]

Hi all,

as you see in the disassembly listing below, there is
a small lack of optimisation:

The compiler refuses to use autoincrement when moving
byte blocks. With integer values it works ok.

move bytes:
   6: ee 4f 00 00  mov.b @r15, 0(r14) ;
   a: 1f 53        inc r15  ;
   c: 1e 53        inc r14  ;

move integers:
  1c: be 4f 00 00  mov @r15+, 0(r14) ;
  20: 2e 53        incd r14  ;

I assume this can be fixed easily, but I'm not too much
involved in gcc programming now, so I ask for your support.

Regards,
Ralf

See the whole listing below:



test.o:     file format elf32-msp430

Disassembly of section .text:

00000000 <copybytes>:
void copybytes(char *src, char *dst, int len)
{
  while (len--)
   0: 3d 53        add #-1, r13 ;r3 As==11
   2: 3d 93        cmp #-1, r13 ;r3 As==11
   4: 07 24        jz $+16      ;abs 0x14
    *dst++ = *src++;
   6: ee 4f 00 00  mov.b @r15, 0(r14) ;
   a: 1f 53        inc r15  ;
   c: 1e 53        inc r14  ;
   e: 3d 53        add #-1, r13 ;r3 As==11
  10: 3d 93        cmp #-1, r13 ;r3 As==11
  12: f9 23        jnz $-12      ;abs 0x6
}
  14: 30 41        ret

00000016 <copywords>:


void copywords(int *src, int *dst, int len)
{
  while (len--)
  16: 3d 53        add #-1, r13 ;r3 As==11
  18: 3d 93        cmp #-1, r13 ;r3 As==11
  1a: 06 24        jz $+14      ;abs 0x28
    *dst++ = *src++;
  1c: be 4f 00 00  mov @r15+, 0(r14) ;
  20: 2e 53        incd r14  ;
  22: 3d 53        add #-1, r13 ;r3 As==11
  24: 3d 93        cmp #-1, r13 ;r3 As==11
  26: fa 23        jnz $-10      ;abs 0x1c
}
  28: 30 41        ret