GCC IMA & general future proposal

[Scott Robert Ladd]

Kenneth Zadeck wrote:
> I should point out that the intel compiler is a bad example to base 
> anything on.  It is simply a marketing tool to sell more processors and 
> as such is designed to make benchmarks run particularly well on intel 
> hardware.  Anything else is not so good.  Remember that this is the 
> compiler that generates delibertly bad code to be used when you run on 
> an amd chip.

Is Intel's compiler relevant to GCC? Yes, particularly in the sense that 
without competition, software tends to stagnate. We all demand 
competition for Microsoft; it seems only fair that the GCC community set 
a calm and intelligent example of competition.

Certainly Intel's compilers are marketing tools -- but they also produce 
code that is faster than GCC for Real World(tm) applications, not just 
benchmarks. The BBC's Dirac video codec, for example, runs 10-15% faster 
when compiled with Intel's compiler.

I love GCC, which is why I'm working to make it better. Intel's compiler 
produces valid, working programs that is in many cases faster than GCC; 
it's a fact, whether we like it or not.

> It detects the cpu model and refuses to use any vector instructions even 
> though it knows the amd chips have them.  As such, they have guaranteed 
> that no one will use the compiler for anything except benchmarking.

Incorrect. I know many people who use Intel's compiler for production 
code, especially in the high-performance and Fortran communities.

Yes, I'm frustrated that Intel's EM64T compiler won't generate code that 
runs on my AMD Opterons. However, given the realities of the 
marketplace, I can't get angry at Intel for not supporting their 
competitor's hardware.

GCC's greatest strengths are its portability and openness. That does not 
mean we should not generate the finest possible code on individual 
platforms.

> The 
> ibm compiler is a better model.  This is the compiler that is used to 
> develop all ibm applications.

You may be correct. But most people do not have access to the IBM 
compiler, since it is not (to the best of my knowledge) available for 
non-commercial use. Anyone can download Intel's compilers and explore 
them, which is why it gets more consideration.

-- 
Scott Robert Ladd
site: http://www.coyotegulch.com
blog: http://chaoticcoyote.blogspot.com