#587 8051 redundant calculations

[Konstantin Kim]

*redundant calculations for simple "char = (short>>4)&0x04"
; play_music.c:50: length = (note >> 4) & 0xf;
mov r1,_cvu_play_music_note_131072_8
mov a,(_cvu_play_music_note_131072_8 + 1)
swap a
xch a,r1
swap a
anl a,#0x0f
xrl a,r1
xch a,r1
anl a,#0x0f
xch a,r1
xrl a,r1
xch a,r1
anl ar1,#0x0f

[Konstantin Kim]

Ideally it should be managed on side of code generation.
Temporally we can patch particular cases by peephole rules

replace {
mov r%1,%2
mov a,(%2 + 1)
swap a
xch a,r%1
swap a
anl a,#0x0f
xrl a,r%1
xch a,r%1
anl a,#0x0f
xch a,r%1
xrl a,r%1
xch a,r%1
anl ar%1,#0x0f
mov a,r%1
} by {
; Peephole XXX5 (play_music.c) char = (short>>4)&0xf;
mov a,%2
swap a
anl a,#0x0f
}

replace {
mov r%1,%2
mov a,(%2 + 1)
clr c
rrc a
xch a,r%1
rrc a
xch a,r%1
clr c
rrc a
xch a,r%1
rrc a
xch a,r%1
mov a,#0x03
anl a,r%1
} by {
; Peephole XXX5 (play_music.c) char = (short>>2)&0x3;
mov a,%2
rr a
rr a
anl a,#0x03
}

[Frieder Ferlemann]

you can get to the intended code:

rfe_587.c:13: length = ((uint8_t)note >> 4) & 0xf;
      000016 E5*01            [12]  167     mov a,_note
      000018 C4               [12]  168     swap    a
      000019 54 0F            [12]  169     anl a,#0x0f
      00001B F5*00            [12]  170     mov _length,a

by giving the compiler an (uint8_t) hint. Appending a compilable snippet.

[Konstantin Kim]

Test code is rerefenced here https://github.com/roybaer/sdcc-wiki/wiki/Stm8-code-size
Hint is correct. At same time it is not so good idea to adjust existig test code to satisfy compiler.