Compiling gcc in 64 bits mode

[Jeremy Hall]

> I don't have any x86-64 (int64) systems. Is it better to use 64-bit on
> x86-64 even with the larger memory footprint (because the programming
> model is better (more registers, etc))?

I'd say yes.   As you suggest, there is more to x64 than the memory
footprint.  There are there are twice as many general purpose
registers amongst other things.   So for example more function
arguments are passed in registers than on the stack.

Here are some figures for a small program compiled identically on both
32 and 64 bits.

32 bit code
   Insns 15506,  Jumps 3218,  Mem refs 3819,  Stack refs 1671
64 bit code
   Insns 14631,  Jumps 3158,  Mem refs 3142,  Stack refs 1042

The 64 bit executable was only about 10% larger.

Jeremy