[Haskell-cafe] How far compilers are allowed to go with optimizations?

[Brandon Allbery]

On Wed, Feb 6, 2013 at 6:45 AM, Jan Stolarek <jan.stolarek at p.lodz.pl> wrote:

> nevertheless I objected to his opinion, claiming that if compiler
> performed such a high-level
> optimization - replace underlying data structure with a different one and
> turn one algorithm into
> a completely different one - programmer wouldn't be able to reason about
> space behaviour of a
> program. I concluded that such a solution should not be built into a
> compiler but instead turned
> into an EDSL.
>

For what it's worth, the main dividing line between -O1 and -O2 in gcc is
that -O2 may change space or time behavior in unexpected ways.  (This may
explain e.g.
https://plus.google.com/u/0/102208456519922110915/posts/DZsZ6mvA4T6)

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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