Tuesday, June 30, 2009

You don't get what you don't pay for

Sigh. Repeat after me: You can't have your cake and eat it too. You can't have your cake and ....

I've been test driving the Hi-Tech C Pro compiler for the PIC MCUs and much as I am thrilled that it works under MPLAB and is being offered completely free (Lite version) without firmware size or time period restrictions, I must say that the lack of optimization in the freeware version is rather depressing. The code it produces is quite inefficient.

For instance, for the PIC 10F20x series, for the given a static global variable the C statement "POTATO++" or "++POTATO" is translated into assembly by Hi-Tech Lite as follows:

MOVLW 0x1
MOVWF 0x13
MOVF 0x13, W
ADDWF 0x1e, F

Am scratching my head. Why the two middle instructions? Why not cut to the chase and have:

MOVLW 0x1
ADDWF 0x1e, F

Or better yet, why not just

INCF 0x1e, F

Wasting two to three bytes and instruction cycles in an MCU that has only 256 / 512 words of program space is just crazy.

I know I'm making a hasty conclusion but this one example of utter wastefulness shows me why this is freeware. I'm wondering how the versions with "Omniscient Code Generation" will compile the above. Hopefully you do get what you pay for.

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