Re: Is global optimization worth it?

Lance wrote:


> Actually, thats why I'm here. I have a compiler working, and the
>code it generates makes me cringe. But it works. So I did some
>research, and it turns out my compiler is a "naive" compiler. I need
>to recode the code generator so that it generates machine code the
>way I do: select instructions leading towards what I want, allocate
>registers (OK - I know, thats obvious - in hindsight) For now my goal
>is "simple" - the compiler should generate code that doesn't make me
>cringe. I am an experienced C/assembly (embedded systems) coder, so
>that will take some doing :( At this point, I've done enough research
>to know what I'm letting myself in for.


I see the other posters jumping directly to alias analysis, which
poses some theoretical restrictions on C optimisations. I donīt know
if this is actually a severe restriction in real life programs: many C
programs don't use floating point at all. So I think you can start
with some real gains as using as many registers as you can, avoiding
frame pointers, passing parameters in registers, strcpy inlining etc,
accessing globals by offset of a previous global etc.


I donīt think many assembly programmers do much alias analyses
either...


Rinie

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