On Thu, May 2, 2024 at 4:00 PM Richard Biener <rguent...@suse.de> wrote:
>
> On Tue, 23 Apr 2024, Manolis Tsamis wrote:
>
> > The original motivation for this pattern was that the following function
> > does
> > not fold to 'return 1':
> >
> > int foo(int *a, int j)
> > {
> > int k = j - 1;
> > return a[j - 1] == a[k];
> > }
> >
> > The expression ((unsigned long) (X +- C1) * C2) appears frequently as part
> > of
> > address calculations (e.g. arrays). These patterns help fold and simplify
> > more
> > expressions.
> >
> > PR tree-optimization/109393
> >
> > gcc/ChangeLog:
> >
> > * match.pd: Add new patterns for ((T)(A +- CST1)) * CST2 and
> > ((T)(A +- CST1)) * CST2 + CST3.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.dg/pr109393.c: New test.
> >
> > Signed-off-by: Manolis Tsamis <manolis.tsa...@vrull.eu>
> > ---
> >
> > gcc/match.pd | 30 ++++++++++++++++++++++++++++++
> > gcc/testsuite/gcc.dg/pr109393.c | 16 ++++++++++++++++
> > 2 files changed, 46 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.dg/pr109393.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index d401e7503e6..13c828ba70d 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -3650,6 +3650,36 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > (plus (convert @0) (op @2 (convert @1))))))
> > #endif
> >
> > +/* ((T)(A + CST1)) * CST2 + CST3
> > + -> ((T)(A) * CST2) + ((T)CST1 * CST2 + CST3)
> > + Where (A + CST1) doesn't need to have a single use. */
> > +#if GIMPLE
> > + (for op (plus minus)
> > + (simplify
> > + (plus (mult (convert:s (op @0 INTEGER_CST@1)) INTEGER_CST@2)
> > INTEGER_CST@3)
> > + (if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
> > + && TREE_CODE (type) == INTEGER_TYPE
> > + && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
> > + && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
> > + && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
> > + && TYPE_OVERFLOW_WRAPS (type))
> > + (op (mult @2 (convert @0)) (plus (mult @2 (convert @1)) @3)))))
> > +#endif
> > +
> > +/* ((T)(A + CST1)) * CST2 -> ((T)(A) * CST2) + ((T)CST1 * CST2) */
> > +#if GIMPLE
> > + (for op (plus minus)
> > + (simplify
> > + (mult (convert:s (op:s @0 INTEGER_CST@1)) INTEGER_CST@2)
> > + (if (TREE_CODE (TREE_TYPE (@0)) == INTEGER_TYPE
>
> Please use INTEGRAL_TYPE_P
>
> > + && TREE_CODE (type) == INTEGER_TYPE
> > + && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0))
> > + && TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (@0))
> > + && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@0))
> > + && TYPE_OVERFLOW_WRAPS (type))
> > + (op (mult @2 (convert @0)) (mult @2 (convert @1))))))
>
> (mult @2 (convert @0)) is non-canonical for no good reason if @0
> isn't constant - constant should be 2nd, please swap operands here.
>
> > +#endif
>
> The first pattern is an extension of the second, why's the first
> necessary at all? The add of CST3 is unchanged (OK, you seem to
> associate here, but that's again a different thing).
>
> I'd say the 2nd pattern is OK with the above changes but the first
> looks redundant.
>
Hi Richard,
Thanks for the comments, I'll fix these.
The difference is that the second uses op:s while the first uses just op.
In the second case if A + CST1 has other uses expanding the pattern
may not be a good idea but in the first case it always is because we
know + CST1 * CST2 will merge with + CST3.
Thanks,
Manolis
> Thanks,
> Richard.
>
> > +
> > /* (T)(A) +- (T)(B) -> (T)(A +- B) only when (A +- B) could be simplified
> > to a simple value. */
> > (for op (plus minus)
> > diff --git a/gcc/testsuite/gcc.dg/pr109393.c
> > b/gcc/testsuite/gcc.dg/pr109393.c
> > new file mode 100644
> > index 00000000000..e9051273672
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/pr109393.c
> > @@ -0,0 +1,16 @@
> > +/* PR tree-optimization/109393 */
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fdump-tree-optimized" } */
> > +/* { dg-final { scan-tree-dump-times "return 1;" 2 "optimized" } } */
> > +
> > +int foo(int *a, int j)
> > +{
> > + int k = j - 1;
> > + return a[j - 1] == a[k];
> > +}
> > +
> > +int bar(int *a, int j)
> > +{
> > + int k = j - 1;
> > + return (&a[j + 1] - 2) == &a[k];
> > +}
> >
>
> --
> Richard Biener <rguent...@suse.de>
> SUSE Software Solutions Germany GmbH,
> Frankenstrasse 146, 90461 Nuernberg, Germany;
> GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
