[Coco] Need some advice
ooogalapasooo at aol.com
Sat May 21 10:43:04 EDT 2016
Actually, the OS9 C compiler writes pretty fast code. I have done a few experiments with asm and C in OS9 and the results were pretty impressive.
The largest "overhead" in C is the fact that C passes all variables (no matter what size) on the stack in the form of integers. If you pass the letter "C", a long (4 bytes), and an int, to a function, C will "push" 8 bytes onto the stack, one of course is wasted as it's just "x0043" for "C" instead of "x43". Passing large amounts of "single byte" data can result in a lot of wasted memory as well as a possibility of a "Stack Oveflow".
Then on the other end, the receiving function must have code that "skips" the extra bytes to get the single bytes as it pulls the data from the stack, therefore wasting more space. Passing strictly integers or data with byte counts devisable by 2 help speed things up a bit, but in the end, the C code will be about 10-20% larger than the asm code and only "slightly" slower. Another point is that C puts ALL local variables on the stack and references them from there instead of doing direct memory reference. When going 3, 4, and 5 or more levels deep in functions, the stack can get pretty big, so care must be taken in variable use to keep the stack small.
C actually generates some routines that I would've never thought of in asm (as noted in the Mathieu's post). C's handling of large arrays and "linked list" arrays is very complex and hell to write in asm. C "just works".
Of course there are other points in OS9 C (K&R for the most part) that can be massaged at assembly level (yes, you can do that) that can speed C up quite a bit, but all in all, OS9 C does things (automatically) that would take hours of coding in asm to accomplish.
C's strong points lie in the precompiled libraries that allow the programmer to forget all the complex stuff and write straight forward code. Carl Kreider's libraries are well written and Mike Sweet's "CGFX7" graphics library make things flow nicely when working with graphics, menus, and windows.
The pointers system in C allow for faster code and writing code for large apps, handling large string sections, using multiple sources makes it easy to write code in nice neat "sections".
Any "time critical" code can be written in RMA assembler and integrated right into the C souces as RMA was written for using with C (it's the format C compiles to before assembly).
In the end, I can write large programs faster and more efficiently in C than I ever could in asm with only a slight increase in size and maybe 3-5% slower if even that.
MShell is written in 99% C code with only a couple of small RMA routines (like memory copies) for speed. I don't think I could have written such complex code in asm (I've tried). I haven't had any complaints on MShell's speed. In fact, it's faster than most OS9 graphics oriented programs.
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From: Mathieu Bouchard <matju at artengine.ca>
To: Randy Weaver <emceesquared at gmail.com>
Cc: 'CoCoList for Color Computer Enthusiasts' <coco at maltedmedia.com>
Sent: Fri, May 20, 2016 2:37 pm
Subject: Re: [Coco] Need some advice
Be warned that simple C compilers aren't able to produce machine code (or asm code) that runs as fast as what an average asm programmer can do in an average time, whereas sophisticated C compilers typically think of things that even asm experts wouldn't think of or bother with. A C compiler is likely to be "simple" if it's old, if it's made to fit in a small space, if it's written by one person, or if it's a sophisticated one that's been configured with optimisations turned off.Le 2016-05-19 à 22:30:00, Randy Weaver a écrit :> How would one rate language performance? And how does OS/9 come into > play? Is it ASSEMBLER/RS-DOS the fastest or are there OS/9 multi-tasking > goodness that would be better? What languages are there? I know about > the CMOC project . a C-like compiler for RS-DOS right? ______________________________________________________________________| Mathieu BOUCHARD --- tél: 514.623.3801, 514.383.3801 --- Montréal, QC-- Coco mailing listCoco at maltedmedia.comhttps://pairlist5.pair.net/mailman/listinfo/coco
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