On Thu, Oct 26, 2023 at 2:24 AM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> On Wed, Oct 25, 2023 at 5:37 AM Andrew Pinski <pins...@gmail.com> wrote:
> >
> > This adds a match pattern for `a != C1 ? abs(a) : C2` which gets simplified
> > to `abs(a)`. if C1 was originally *_MIN then change it over to use absu
> > instead
> > of abs.
> >
> > Bootstrapped and tested on x86_64-linux-gnu with no regressions.
> >
> > PR tree-optimization/111957
> >
> > gcc/ChangeLog:
> >
> > * match.pd (`a != C1 ? abs(a) : C2`): New pattern.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.dg/tree-ssa/phi-opt-40.c: New test.
> > ---
> > gcc/match.pd | 10 +++++++++
> > gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c | 25 ++++++++++++++++++++++
> > 2 files changed, 35 insertions(+)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
> >
> > diff --git a/gcc/match.pd b/gcc/match.pd
> > index 5df04ebba77..370ee35de52 100644
> > --- a/gcc/match.pd
> > +++ b/gcc/match.pd
> > @@ -5622,6 +5622,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > (if (wi::eq_p (wi::bit_not (wi::to_wide (@1)), wi::to_wide (@2)))
> > @3))
> >
> > +/* X != C1 ? abs(X) : C2 simplifies to abs(x) when abs(C1) == C2. */
> > +(for op (abs absu)
> > + (simplify
> > + (cond (ne @0 INTEGER_CST@1) (op@3 @0) INTEGER_CST@2)
> > + (if (wi::abs (wi::to_wide (@1)) == wi::to_wide (@2))
>
> Why not use
>
> (cond (ne @0 INTEGER_CST@1) (op@3 @0) @1)
Because that does not work for:
`a != -1 ? abs(a) : -1`
We want to match -1 and 1 here (in that order).
It just happens 0 and INT_MIN have the same value as their abs and
matches but we could expand it to match all others too.
Thanks,
Andrew
>
> ? OK with that change.
>
> Richard.
>
> > + (if (op != ABSU_EXPR && wi::only_sign_bit_p (wi::to_wide (@1)))
> > + (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); }
> > + (convert (absu:utype @0)))
> > + @3))))
> > +
> > /* (X + 1) > Y ? -X : 1 simplifies to X >= Y ? -X : 1 when
> > X is unsigned, as when X + 1 overflows, X is -1, so -X == 1. */
> > (simplify
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
> > b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
> > new file mode 100644
> > index 00000000000..a9011ce97fb
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-40.c
> > @@ -0,0 +1,25 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O1 -fdump-tree-phiopt" } */
> > +/* PR tree-optimization/111957 */
> > +
> > +int f(int a)
> > +{
> > + if (a)
> > + return a > 0 ? a : -a;
> > + return 0;
> > +}
> > +
> > +int f1(int x)
> > +{
> > + int intmin = (-1u >> 1);
> > + intmin = -intmin - 1;
> > + if (x != intmin)
> > + return x > 0 ? x : -x;
> > + return intmin;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump-times "if " 1 "phiopt1" } } */
> > +/* { dg-final { scan-tree-dump-not "if " "phiopt2" } } */
> > +/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 2 "phiopt1" } } */
> > +/* { dg-final { scan-tree-dump-times "ABS_EXPR <" 1 "phiopt2" } } */
> > +/* { dg-final { scan-tree-dump-times "ABSU_EXPR <" 1 "phiopt2" } } */
> > --
> > 2.34.1
> >
