Compiler Analysis: 3.3, 3.4, or tree-ssa?

[Scott Robert Ladd]

Matt Fago wrote:
>> The -O1, -O2, and -O3 options are general-purpose choices for 
>> producing good code in general circumstances.
> 
> Are they? How is this determined?

I'll amend my statement...

"The -O1, -O2, and -O3 options *SHOULD BE* general-purpose choices for 
producing good code in general circumstances."

> I think Acovea might allow the flags implied by these options to be 
> chosen in a more quantitative way. Obviously Acovia should give better 
> results when used with a specific code of interest.

I note that on some experiments, -O2 and -O3 produce *slower* code than 
does -O1; and in several cases, Acovea finds options sets that produce 
code which runs in 40% less time than it does when compiled with any of 
the predefined optimization sets.

We could define variations on the -O?? theme... -Ofp, for example, that 
optimizes for floating-point applications.

-- 
Scott Robert Ladd
Coyote Gulch Productions (http://www.coyotegulch.com)
Software Invention for High-Performance Computing