Optimizations documentation

[Tim Prince]

Ira Rosen wrote:
> Here is the link to the vectorizer's documentation:
> http://gcc.gnu.org/projects/tree-ssa/vectorization.html
>
>
>   
Thanks, but I take what it says there with some grains of salt.  Yes, 
-O3 implies -ftree-vectorize on x86_64, but I seem to have to specify 
the option on other targets.  Also, I have not understood the 
limitations of -freassociative-math.
Several gcc vectorization test cases currently throw FAIL on certain 
targets, but not on others.  I don't know if that is a significant issue.
g++-4.3 seems well ahead of other compilers in ability to vectorize STL 
iterators:
http://softwarecommunity.intel.com/Wiki/HighPerformanceComputing/688.htm