On Feb 11, 2014, at 1:24 AM, alan.b.pearce@stfc.ac.uk wrote:

> I believe the free mode [of XC8] now does a minimal optimisation so that =
any code generated will at least work in the way the code writer intended.

I dunno.  I downloaded the latest, in hopes that this would be true.  But i=
t's still producing rather weird code:

>From one of their "blinky" examples:

void delay() {
    int counter =3D 0;
    for (counter =3D 0; counter<10000; counter++) {
        ;
    }
}

7FD8	0E00	delay	MOVLW 0x0		;; 16 bits of 0 to counter.
7FDA	6E02		MOVWF 0x2, ACCESS
7FDC	0E00		MOVLW 0x0
7FDE	6E01		MOVWF counter, ACCESS
7FE0	0E00		MOVLW 0x0		;; and again (the source
7FE2	6E02		MOVWF 0x2, ACCESS	;;  does it twice, too, so
7FE4	0E00		MOVLW 0x0               ;;  I guess that's OK.)
7FE6	6E01		MOVWF counter, ACCESS
7FE8	5002    lp:	MOVF 0x2, W, ACCESS
7FEA	0A80		XORLW 0x80		;; Strange compare to 10000
7FEC	0F59		ADDLW 0x59              ;;  I guess it's jumping through hoops t=
o wind up with a sequence
7FEE	0E10		MOVLW 0x10              ;;   that skips appropriately at the end=
, rather than resolving
7FF0	B4D8		BTFSC STATUS, 2, ACCESS  ;;   the branch in the middle.  But=85 =
Eww!
7FF2	5C01		SUBWF counter, W, ACCESS
7FF4	B0D8		BTFSC STATUS, 0, ACCESS
7FF6	D003		BRA 0x7FFE              ;; (exit) end of strange compare
7FF8	4A01		INFSNZ counter, F, ACCESS
7FFA	2A02		INCF 0x2, F, ACCESS     ;; Pretty nice 16bit increment
7FFC	D7F5		BRA 0x7FE8              ;; (lp)
7FFE	0012	exit:	RETURN 0





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