Re: Benefits of latest gas?

[Ian Lance Taylor <ian at wasabisystems dot com>]

Stan Shebs <shebs@apple.com> writes:

> As some of you may know, Mac OS X has long been using gas 1.38, pre-BFD
> and all, as its system assembler, heavily hacked to do Mach-O and
> support all of Apple's various extensions. Recently I had occasion
> to look at the some of the barbaric expression code in our version,
> and thinking "surely the latest code is much improved", went and looked
> at the latest version, and it didn't really seem changed by that much,
> which was disappointing. In fact, quite a bit of 1.38 seems the same as
> current gas sources.
> 
> Up to now I've been generally assuming that staying on the old gas was
> a poor strategy, and that the massive effort that would be needed to get
> Mach-O into latest gas would be an investment quickly repaid in better
> quality, better error-checking, etc. But now I'm not so sure. We really
> only have the one target (PPC), plus x86 for Darwin, so portability
> arguments aren't that compelling, and the assembler is pretty much in
> the noise compile-time-wise already.
> 
> So what are the features of latest gas vs 1.38 that would make my
> management whip out the checkbook for a merge/upgrade project?

I would say that the major new features are for people who program in
assembler: macros, better conditionals, better error handling, more
pseudo-ops.  For C/C++ code, I would say that as long as you stick
with Mach-O, you aren't going to see much improvement by upgrading to
the current assembler.  I don't even know whether the current
assembler is faster--the pre-2.0 versions were pretty fast.

Over time you might some savings as other people do work for
you--adding support for new processor variants, fixing bugs, speeding
up the assembler, etc.

But all in all I think you would be better off using that checkbook to
pay your kernel hackers to add ELF support.  That would get you the
current gas for free, and I think it would simplify your life quite a
bit over the long run.

Ian