Hi everyone!
Compiling the following C code, that reproduces the problem encountered,
with no optimizations (-O0) produces bad output file:
typedef unsigned long u32;
u32 var;
int main()
{
var = 12345678;
var >>= 16;
return var;
}
The listing file is as follows:
shift_noopt_orig.elf: file format elf32-msp430
Disassembly of section .text:
00003100 <__low_level_init>:
3100: b2 40 80 5a mov #23168, &0x0120 ;#0x5a80
3104: 20 01
00003106 <__do_copy_data>:
3106: 3f 40 00 00 mov #0, r15 ;#0x0000
310a: 0f 93 cmp #0, r15 ;r3 As==00
310c: 05 24 jz $+12 ;abs 0x3118
310e: 2f 83 decd r15 ;
3110: 9f 4f 5c 31 mov 12636(r15),4352(r15);
3114: 00 11
3116: fb 23 jnz $-8 ;abs 0x310e
00003118 <__do_clear_bss>:
3118: 3f 40 04 00 mov #4, r15 ;#0x0004
311c: 0f 93 cmp #0, r15 ;r3 As==00
311e: 04 24 jz $+10 ;abs 0x3128
3120: 1f 83 dec r15 ;
3122: cf 43 00 11 mov.b #0, 4352(r15);r3 As==00
3126: fc 23 jnz $-6 ;abs 0x3120
00003128 <__jump_to_main>:
3128: 30 40 32 31 br #0x3132 ;
0000312c <__ctors_end>:
312c: 30 40 30 31 br #0x3130 ;
00003130 <_unexpected_>:
3130: 00 13 reti
00003132 <main>:
3132: 31 40 00 31 mov #12544, r1 ;#0x3100
3136: 04 41 mov r1, r4 ;
3138: b2 40 4e 61 mov #24910, &0x1100 ;#0x614e
313c: 00 11
313e: b2 40 bc 00 mov #188, &0x1102 ;#0x00bc
3142: 02 11
3144: 82 43 02 11 mov #0, &0x1102 ;r3 As==00
3148: 92 42 02 11 mov &0x1102,&0x1100 ;0x1102
314c: 00 11
314e: 82 43 02 11 mov #0, &0x1102 ;r3 As==00
3152: 1f 42 00 11 mov &0x1100,r15 ;0x1100
3156: 30 40 5a 31 br #0x315a ;
0000315a <__stop_progExec__>:
315a: ff 3f jmp $+0 ;abs 0x315a
Disassembly of section .bss:
00001100 <__bss_start>:
1100: 00 00 beq
...
It seems that the instruction at address 3144h should not be present, only
the one at 314eh. The idea used is to move the HI word to the LO word and
then reset the HI word. The problem is that the HI part is reset before the
move take place and this way the result will always be 0.
It is important that this problem occurs only when compiling with no
optimizations.
Any suggestions on this matter are welcome.
Regards,
Alpar
