[cc65] Re: Codesize parameter?

From: Ullrich von Bassewitz <uz1musoftware.de>
Date: 2009-09-13 00:12:37
On Sat, Sep 12, 2009 at 11:56:47PM +0200, Markus Stehr wrote:
> Am Samstag, den 12.09.2009, 22:16 +0200 schrieb Oliver Schmidt:
> > --codesize 400 ("productive" setting).
> Could someone please push me to the page explaining this parameter?
> I couldnt find it in the manual. :(

It is describe in several places in the cc65 manual but not in depth.

Every time, the code generator or the optimizer chooses between two different
sequences of code, it inspects the code size parameter. It tells the compiler
which code size increase for this single choice(!) is acceptable. The option
argument is a percentage, so --codesize 200 says, it is acceptable that when
choosing between two pieces of code, the faster one is acceptable, if the
increase of code size is not more than 200%.

This does not mean that the code grows by a factor of two when using
--codesize 200, because many replacements are smaller. In addition, inlining
code makes it visible to the optimizer, which will then be able to remove
parts or optimize it further. There are programs that get actually smaller
with a larger --codesize setting.

"-Oi" is actually a shortcut for "-O --codesize 200".



Ullrich von Bassewitz                                  uz@musoftware.de
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Received on Sun Sep 13 00:15:43 2009

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