Reducing compilation memory usage

Andrew Haley aph@redhat.com
Sun Jan 20 18:35:00 GMT 2008


Tony Wetmore wrote:
> Alejandro Pulver wrote:
>  >> RAM!  Of course we could make gcc more economical, and
>  >> we could somewhat reduce memory usage, but you're asking
>  >> for something really hard.
>  >
>  > I wasn't asking to change the program, I was just asking
>  > if there is an already existing option.
> 
> I think Andrew may have meant that you are asking GCC to do something 
> really hard, to optimize a single function that is so large.  And asking 
> the compiler to do something that hard has a price -- it requires lots 
> of memory, as you have discovered.

I was saying exactly that, thank you for clarifying.

The thing to realize is that it is really hard to do a great job of optimizing
huge functions.  So, it's quite likely that gcc will do a better job of
optimizing a bunch of small functions, with well-contained locality of variables,
than one huge function.

OK, so you will have the overhead of a function call.  But on most architectures
that isn't enormous.

Andrew.



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