Re: Canonicalize X u< X to UNORDERED_EXPR

[Marc Glisse <marc dot glisse at inria dot fr>]

On Mon, 2 May 2016, Richard Biener wrote:

> On Sat, Apr 30, 2016 at 8:44 PM, Marc Glisse <marc.glisse@inria.fr> wrote:
> > Hello,
> >
> > this case seemed to be missing in the various X cmp X transformations. It
> > does not change the generated code in the testcase.
> >
> > The missing :c is rather trivial. I can commit it separately if you prefer.
>
> I think it's not missing.  Commutating the first one is enough to eventually
> make the @1s match up.  I think you should get a diagnostic on a duplicate
> pattern when adding another :c (hmm, no, it's indeed "different" patterns but
> still redundant).

Let's see. The current pattern is
  (bitop (bit_and:c @0 @1) (bit_and @2 @1))

This matches:
(X & Y) ^ (Z & Y)
(Y & X) ^ (Z & Y)

If I have for instance (Y & X) ^ (Y & Z), I don't see how that is going to 
match, and indeed we don't simplify that. On the other hand, if I have 
bit_ior instead of bit_xor, then we have another very similar 
transformation a 100 lines up in match.pd

(for op (bit_and bit_ior)
     rop (bit_ior bit_and)
 (simplify
  (op (convert? (rop:c @0 @1)) (convert? (rop @0 @2)))

That one also commutes only one, but starting from a different match. We 
should probably reorganize them a bit.

> > Bootstrap+regtest on powerpc64le-unknown-linux-gnu.
>
> Ok for the new pattern.
>
> Thanks,
> Richard.
>
> > 2016-05-02  Marc Glisse  <marc.glisse@inria.fr>
> >
> > gcc/
> >         * match.pd ((A & B) OP (C & B)): Mark '&' as commutative.
> >         (X u< X, X u> X): New transformations
> >
> > gcc/testsuite/
> >         * gcc.dg/tree-ssa/unord.c: New testcase.
> >
> > --
> > Marc Glisse
> > Index: trunk/gcc/match.pd
> > ===================================================================
> > --- trunk/gcc/match.pd  (revision 235654)
> > +++ trunk/gcc/match.pd  (working copy)
> > @@ -783,21 +783,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >    @0)
> >   /* (~x | y) & x -> x & y */
> >   /* (~x & y) | x -> x | y */
> >   (simplify
> >    (bitop:c (rbitop:c (bit_not @0) @1) @0)
> >    (bitop @0 @1)))
> >
> >  /* Simplify (A & B) OP0 (C & B) to (A OP0 C) & B. */
> >  (for bitop (bit_and bit_ior bit_xor)
> >   (simplify
> > -  (bitop (bit_and:c @0 @1) (bit_and @2 @1))
> > +  (bitop (bit_and:c @0 @1) (bit_and:c @2 @1))
> >    (bit_and (bitop @0 @2) @1)))
> >
> >  /* (x | CST1) & CST2 -> (x & CST2) | (CST1 & CST2) */
> >  (simplify
> >    (bit_and (bit_ior @0 CONSTANT_CLASS_P@1) CONSTANT_CLASS_P@2)
> >    (bit_ior (bit_and @0 @2) (bit_and @1 @2)))
> >
> >  /* Combine successive equal operations with constants.  */
> >  (for bitop (bit_and bit_ior bit_xor)
> >   (simplify
> > @@ -1914,20 +1914,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> >   (simplify
> >    (cmp @0 @0)
> >    (if (cmp != NE_EXPR
> >         || ! FLOAT_TYPE_P (TREE_TYPE (@0))
> >         || ! HONOR_NANS (@0))
> >     { constant_boolean_node (false, type); })))
> >  (for cmp (unle unge uneq)
> >   (simplify
> >    (cmp @0 @0)
> >    { constant_boolean_node (true, type); }))
> > +(for cmp (unlt ungt)
> > + (simplify
> > +  (cmp @0 @0)
> > +  (unordered @0 @0)))
> >  (simplify
> >   (ltgt @0 @0)
> >   (if (!flag_trapping_math)
> >    { constant_boolean_node (false, type); }))
> >
> >  /* Fold ~X op ~Y as Y op X.  */
> >  (for cmp (simple_comparison)
> >   (simplify
> >    (cmp (bit_not@2 @0) (bit_not@3 @1))
> >    (if (single_use (@2) && single_use (@3))
> > Index: trunk/gcc/testsuite/gcc.dg/tree-ssa/unord.c
> > ===================================================================
> > --- trunk/gcc/testsuite/gcc.dg/tree-ssa/unord.c (revision 0)
> > +++ trunk/gcc/testsuite/gcc.dg/tree-ssa/unord.c (working copy)
> > @@ -0,0 +1,7 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O -fdump-tree-optimized" } */
> > +
> > +int f(double a){double b=a;return !__builtin_islessequal(a,b);}
> > +int g(double a){double b=a;return !__builtin_isgreaterequal(a,b);}
> > +
> > +/* { dg-final { scan-tree-dump-times " unord " 2 "optimized" } } */

--
Marc Glisse