Re: Java vs C/Objective-C performance question
Re: Java vs C/Objective-C performance question
- Subject: Re: Java vs C/Objective-C performance question
- From: Dietrich Epp <email@hidden>
- Date: Mon, 17 Mar 2003 14:13:45 -0800
On Monday, March 17, 2003, at 07:20 AM, Chris Ridd wrote:
[snip]
Actually I've no idea if gcc on PPC produces excellent code or not, so
your
sarcasm is lost on me :-) Do you have any good references to
up-to-date PPC
compiler comparisons?
I was basing it off of code that I've disassembled from GCC output, and
that most of GCC's optimization tricks are processor-independent. It
would be awesome if there were a site that had a quick description of
each of the ppc compilers and the options you can give them, with their
effects on performance. Until I find that site, I'll just blindly
trust GCC. I did find this site, however:
http://www.redhat.com/software/gnupro/technical/gnupro_gcc.html
[snip]
I was expecting (without reading the documentation :-) that -O3 would
unroll
loops, but obviously it doesn't.
Is the loop-unrolling behaviour you're seeing processor-independent?
The loop-unrolling mechanism is processor independent, but it's not
included in -O3 because it's only helpful in rare circumstances, like
bogus benchmarks. Most other places where you'd want to unroll loops
are clear enough that you'd unroll the loop in the C code itself, or
write it in assembly.
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