re: Advantages of 64-bit vs 32-bit on old hardware

[matthew green <mrg%eterna.com.au@localhost>]

   Oh, and -Os is probably a bad idea if you want performance compared to
   say -O2.  Layout of instructions in the I$ is important for efficient
   instruction issue on USI and USII cpus.  Ideally you want 2 integer ops
   followed by 1 load/store and 1 branch or FP op to get optimal performance.
   Breaking this group across cache lines will require an extra cycle.  And
   being a superscalar, speculation is good for performance but bad for
   code size.  I don't think you're making the right tradeoff here.


it's actually quite common for -Os to beat -O2 in many benchmarks,
simply because it is -O2 + a bit more.  i believe some people /
projects use -Os by default.


but i completely agree that anyone who cares about performance
actually needs to test and compare speeds to really know what
works for their application.


.mrg.