[Bug tree-optimization/28364] poor optimization choices when iterating over a std::string (probably not c++-specific)

["zackw at panix dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #20 from zackw at panix dot com  2006-07-13 08:25 -------
Subject: Re:  poor optimization choices when iterating over a std::string
(probably not c++-specific)

> > However, ch isn't just copying the loop header; it is also
> > copying the *entire body of the loop*, which nothing can fix. I call
> > that a clear bug.
>
> how do you define a loop header?

I was under the impression it was just the one basic block called out
in the .ch dump, e.g.

;; Loop 1
;;  header 6, latch 5
;;  depth 1, level 1, outer 0

-- basic block 6 happens to contain just the code from the syntactic
loop condition.  Andrew informs me that this is wrong, and that in
this case the header is the entire loop, but I will come back at that
with 'ch should never be duplicating the entire loop; if the header is
the entire loop, it should do something more sensible, like duplicate
just the first basic block or something.'


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28364