HI-TECH Software Forums: Optimisations in PICC compiler

I like to research disasm lstings...
I'm testing PICC 9.60 PL3

1.
Disasm code 1:
Code:

 
21:      b = a > 1 ? 1 : 0;
   01E    3002     MOVLW 0x2
   01F    0220     SUBWF 0x20, W
   020    3000     MOVLW 0
   021    1803     BTFSC 0x3, 0
   022    3001     MOVLW 0x1
   023    00A1     MOVWF 0x21

I think it's good optimization.

Disasm code 2:
Code:

 
21:      b = a > 1 ? 4 : 0;
   01E    3002     MOVLW 0x2
   01F    0220     SUBWF 0x20, W
   020    1803     BTFSC 0x3, 0
   021    2824     GOTO 0x24
   022    3000     MOVLW 0
   023    2825     GOTO 0x25
   024    3004     MOVLW 0x4
   025    00A1     MOVWF 0x21

But it's no good. Why? If I compare 0 and 1 - it's good, but for another constants it not so.

2.
Code:

 
    20   013 2814    GOTO 0x14                              
    21   014 1283    BCF STATUS, 0x5
    22   015 1303    BCF STATUS, 0x6

goto on next address
It's goto from end of startup.as to main. Optimiser must remove it.

3.
Begin of interrupt handler:
Code:

 
6   005     0803     MOVF STATUS, W                         
7   006     0183     CLRF STATUS      <- Status cleared     
8   007     00A4     MOVWF 0x24                             
9   008     190B isr BTFSC INTCON, 0x2                      
10  009     110B     BCF INTCON, 0x2                        
11  00A     3010     MOVLW 0x10                             
12  00B     1283     BCF STATUS, 0x5  <-and two bits of Status cleared again (no need)        
13  00C     1303     BCF STATUS, 0x6

4. IRP tracking
Code:


		unsigned char *iter;
		unsigned char arr[10];
		iter = arr;
		*iter = 5;
		++iter;
		*iter = 7;

and disasm:
Code:


39   026     3025    MOVLW 0x25                             
40   027     00A4    MOVWF iter                             
41   028     0084    MOVWF FSR                              
42   029     1383    BCF STATUS, 0x7  <- clear IRP              
43   02A     3005    MOVLW 0x5                              
44   02B     0080    MOVWF INDF                             
45   02C     0AA4    INCF iter, F                           
46   02D     0824    MOVF iter, W                           
47   02E     0084    MOVWF FSR                              
48   02F     1383    BCF STATUS, 0x7  <- clear IRP again (no need)            
49   030     3007    MOVLW 0x7                              
50   031     0080    MOVWF INDF

If program use only banks 0 and 1 (OCG may ckeck it) IRP may be cleared only 1 time on startup.

opt.c: 7: ADCON0=0;
clrf 31 ;volatile
;opt.c: 8: ADCON1=0;
bsf 3,5 ;RP0=1, select bank1
clrf 31 ;volatile
;opt.c: 9: ADON=1;
bcf 3,5 ;RP0=0, select bank0
bsf 31,0



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