On Tue, Apr 13, 2010 at 17:00, Kevin P. Fleming <kpfleming@xxxxxxxxxx> wrote: > Tom Browder wrote: >> I see the new -fipa-sra option for gcc 4.5 and its explanation and >> wonder how replacing an argument passed by reference with an argument >> passed by value is an optimization (I assume something magic is going >> on behind the scenes). > > Well... a pointer to an int on an x86-64 platform is 8 bytes on the > stack instead of 4, and slower access to the contents of the int. If the > int is never modified in the called function, passing a copy of the int > on the stack instead is clearly a win. Thanks, Kevin, I was asleep--I immediately thought of structures and containers--duh! (But perhaps the text could be more explicitly worded for us dense heads.) Regards, -Tom
