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Re: [patch] Lno branch merge part 8 -- canonical induction variablecreation
On Sat, 21 Aug 2004, Zdenek Dvorak wrote:
> Hello,
>
> > The simplest fix is to add a test for "TYPE_UNSIGNED () || flag_wrapv"
> > to the problematic transformation in your code.
>
> unfortunately this is not possible since it would totally cripple whole
> optimization (many of interesting induction variables are signed).
In that case the flags will need adding to expressions.
Note that loop optimizations with wrapping signed induction variables have
to allow for the possibility that the loop might wrap around (induction
variable, being incremented, goes from positive to negative) unless you
can prove the loop bounds are such that this doesn't happen.
--
Joseph S. Myers http://www.srcf.ucam.org/~jsm28/gcc/
jsm@polyomino.org.uk (personal mail)
jsm28@gcc.gnu.org (Bugzilla assignments and CCs)