On Tue, Aug 06, 2019 at 05:49:17PM +0100, Richard Earnshaw (lists) wrote: > On 06/08/2019 17:39, Segher Boessenkool wrote: > >>>What's wrong with describing the canonical form in your MD? You'll need > >>>some reversed condition code thingy, but that's it? > >> > >>It doesn't describe what the instruction does. The negation has a side > >>effect of setting the flags, but the flags are swapped because the > >>side-effect comparison is swapped from a normal compare. As I > >>mentioned, SELECT_CC_MODE doesn't help because it can't see the context > >>and the comparison just looks 'normal'. > > > >Sure, and we can work on making combine do what you want, but your existing > >pattern is *incorrect*. It needs fixing, and probably before we do other > >things. > > Why is it incorrect? It's not canonical, sure. But the cannonical form > does NOT describe what the instruction does.
More precisely: not having the canonical form of this in your MD is what is incorrect. Segher
