Re: EGCS performance ?

[David Edelsohn <dje at watson dot ibm dot com>]

>>>>> "Sergio Ruocco" writes:


RL> # GCC = egcs 1.1b                              781860.8
RL> # This is EGCS as of this morning.             829875.5

RL> # This is Intel's Optimizing Compiler 2.1.4.  1582278.5
RL> # Same compiler without the i/p analysis.     1088139.2

Sergio> ...I was surprised to see a large performance gulf (?) in such a
Sergio> simple test among EGCS and other "proprietary" compilers, and I'm
Sergio> wondering what is causing these gaps:

Sergio> If someone could test with a better benchmark EGCS vs. other
Sergio> compilers on different (RISC) architectures we could determine this
Sergio> performance gap still exists, and how much is due to x86 scheduling
Sergio> arcana (if they come on par) vs to machine-independent optimizations
Sergio> (if the 30-200% performance gulf stays).

	I would not be too concerned about Intel's compiler gap.  Intel's
compiler is optimized to make standard benchmarks look good, not to
produce efficient code for representative user applications.  There are
significant optimization opportunities for benchmarks which will harm
performance on general user code.  I believe that GCC explicitly has a
policy of not implementing those types of optimizations.  Anybody who
chooses a compiler based on industry benchmarks as opposed to benchmarking
their particular task deserves what they get.

David