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Date: Fri, 25 May 2007 21:48:29 +0200 (MEST)
From: Michiel Boland <Michiel.Boland@internl.net>
To: freebsd-current@freebsd.org
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Subject: gcc memory consumption: amd64 v i386
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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.

So it appears that memory consumption of gcc on amd64 is significantly 
greater than on i386. To test this further I created a very simple C 
source file:-

void n0() { }
void n1() { }
void n2() { }
void n3() { }
...
void n49998() { }
void n49999() { }

(i.e. a file with 50000 trivial function definitions.)

I compiled this file with several optimization levels, and then got the 
following

              no optimization    -O
   amd64        164M            445M
   i386         142M            247M

I was wondering if anyone can make any sense out of this.

Cheers
Michiel