Re: [RFA] Reimplement canonicalization of comparison arguments in match.pd

[Jeff Law <law@redhat.com>]

On 06/01/2015 05:15 AM, Richard Biener wrote:
>
> In addition to what Marc said we'd simplify 1 != 0 immediately anyway (to 1),
> so I don't think the special-cases should make a difference (and if they
> do I'd like to see a testcase!).
FWIW, I agree -- and across my testfiles I don't see any difference in 
the dumps with the special casing of 0 removed.


>
> Note that you should use a double-for here,
>
>   (for op (lt gt le ge)
>        iop (gt lt ge le)
>    (simplify ...
>      (if ...
>       (iop @1 @0)
>
> and drop the inner ifs.  You get op and iop iterated in lock-step.
> IMHO you should
> simply iterate over all comparison codes, thus
>
>   (for op (tcc_comparison)
>        iop (inverted_tcc_comparison)
>        nop (inverted_tcc_comparison_with_nans)
>    (...
>
> see the existing patterns using invert_tree_comparison.  Or not care
> about handling
> NANs correctly and guard with
>
>       && invert_tree_comparison (op, HONOR_NANS (..)) == iop
We actually want swapped_tcc_comparison.  We're swapping the operands, 
not inverting the comparison.  Swapping the operands also happens to be 
safe for FP, so no need to do anything special there.

Using Marc's suggestion for integrating canonicalization into the 
existing pattern seems the cleanest to me and that's what I'm testing now.

jeff