gcc memory consumption: amd64 v i386

[Steve Kargl]

On Sat, May 26, 2007 at 04:19:38PM +0200, Michiel Boland wrote:
> >>Hi. I noticed that compilation of xorg-server on i386 with the new gcc
> >>proceeds normally, whereas compilation on amd64 would crash because the
> >>compiler would consume all memory. The i386 and amd64 boxen have the same
> >>amount of RAM and swap, obviously. And they run, give or take a few hours,
> >>more or less same version of -CURRENT.
> >
> >It does not crash if you have enough swap. I have 2 GB swap and it
> >proceeded fine after some swapping.
> 
> The point I was trying to make (although perhaps not clearly enough) is 
> that there is no reason that a trivial source file takes up such a huge 
> amount of memory to compile. Especially since gcc 3.4.6 does not blow up 
> like that.

Major portions of the middle and back end of gcc were rewritten
in going from 3.4.6 to 4.x.  The TREE-SSA representation supposely
offers the possibility of better optimization passes, but it comes
at the moment with some memory pressure.  The GCC developers are
accutely aware of this issue, and are working on the problem. 

-- 
Steve