On Thu, Oct 17, 2024 at 11:06 AM Kyrylo Tkachov <[email protected]> wrote:
>
> Hi Eikansh
>
> > On 16 Oct 2024, at 18:23, Eikansh Gupta <[email protected]> wrote:
> >
> > The pattern `a rrotate (32-b)` should be optimized to `a lrotate b`.
> > The same is also true for `a lrotate (32-b)`. It can be optimized to
> > `a rrotate b`.
> >
> > This patch adds following patterns:
> > a rrotate (32-b) -> a lrotate b
> > a lrotate (32-b) -> a rrotate b
> >
> > Bootstrapped and tested on x86_64-linux-gnu with no regressions.
> >
> > PR tree-optimization/109906
> >
> > gcc/ChangeLog:
> >
> > * match.pd (a rrotate (32-b) -> a lrotate b): New pattern
> > (a lrotate (32-b) -> a rrotate b): New pattern
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.dg/tree-ssa/pr109906.c: New test.
> >
> > Signed-off-by: Eikansh Gupta <[email protected]>
> > ---
> > gcc/match.pd | 9 ++++++
> > gcc/testsuite/gcc.dg/tree-ssa/pr109906.c | 41 ++++++++++++++++++++++++
> > 2 files changed, 50 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr109906.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index 5ec31ef6269..078ef050351 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -4861,6 +4861,15 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > build_int_cst (TREE_TYPE (@1),
> > element_precision (type)), @1); }))
> >
> > +/* a rrotate (32-b) -> a lrotate b */
> > +/* a lrotate (32-b) -> a rrotate b */
> > +(for rotate (lrotate rrotate)
> > + orotate (rrotate lrotate)
> > + (simplify
> > + (rotate @0 (minus INTEGER_CST@1 @2))
> > + (if (TYPE_PRECISION (TREE_TYPE (@0)) == wi::to_wide (@1))
Use element_precision (@0) - rotates can be used on vector types as
well and using
TYPE_PRECISION would ICE on them.
> > + (orotate @0 @2))))
>
> There is already a transformation for lrotate (x, C) into rotate (x, SIZE -
> C) around line 4937 in match.pd
> Isn’t there a risk that we enter an infinite recursion situation with this?
I don't think so.
The patch is OK with the adjustment.
Thanks,
Richard.
> Thanks,
> Kyrill
>
>
> > +
> > /* Turn (a OP c1) OP c2 into a OP (c1+c2). */
> > (for op (lrotate rrotate rshift lshift)
> > (simplify
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr109906.c
> > b/gcc/testsuite/gcc.dg/tree-ssa/pr109906.c
> > new file mode 100644
> > index 00000000000..9aa015d8c65
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr109906.c
> > @@ -0,0 +1,41 @@
> > +/* PR tree-optimization/109906 */
> > +/* { dg-do compile } */
> > +/* { dg-options "-O1 -fdump-tree-optimized-raw" } */
> > +/* { dg-require-effective-target int32 } */
> > +
> > +/* Implementation of rotate right operation */
> > +static inline
> > +unsigned rrotate(unsigned x, int t)
> > +{
> > + if (t >= 32) __builtin_unreachable();
> > + unsigned tl = x >> (t);
> > + unsigned th = x << (32 - t);
> > + return tl | th;
> > +}
> > +
> > +/* Here rotate left is achieved by doing rotate right by (32 - x) */
> > +unsigned rotateleft(unsigned t, int x)
> > +{
> > + return rrotate (t, 32 - x);
> > +}
> > +
> > +/* Implementation of rotate left operation */
> > +static inline
> > +unsigned lrotate(unsigned x, int t)
> > +{
> > + if (t >= 32) __builtin_unreachable();
> > + unsigned tl = x << (t);
> > + unsigned th = x >> (32 - t);
> > + return tl | th;
> > +}
> > +
> > +/* Here rotate right is achieved by doing rotate left by (32 - x) */
> > +unsigned rotateright(unsigned t, int x)
> > +{
> > + return lrotate (t, 32 - x);
> > +}
> > +
> > +/* Shouldn't have instruction for (32 - x). */
> > +/* { dg-final { scan-tree-dump-not "minus_expr" "optimized" } } */
> > +/* { dg-final { scan-tree-dump "rrotate_expr" "optimized" } } */
> > +/* { dg-final { scan-tree-dump "lrotate_expr" "optimized" } } */
> > --
> > 2.17.1
> >
>
