Loop optimization

[Walter Bright]

bearophile wrote:
> DMD compiler doesn't perform many optimizations,

This is simply false. DMD does an excellent job with integer and pointer 
operations. It does a so-so job with floating point.

There are probably over a thousand optimizations at all levels that dmd does 
with integer and pointer code.

Compare the generated code with and without -O. Even without -O, dmd does a long 
list of optimizations (such as common subexpression elimination).