On Fri, 30 Jan 2026, Andrew Pinski wrote:
> On Fri, Jan 30, 2026 at 9:20 AM Andrew Pinski
> <[email protected]> wrote:
> >
> > On Fri, Jan 30, 2026 at 7:18 AM Richard Biener <[email protected]> wrote:
> > >
> > > The following properly checks expr_no_side_effects_p on two patterns
> > > that turns a conditionally evaluated operand into unconditonal.
> > >
> > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
> > >
> > > PR middle-end/123887
> > > * match.pd ((zero_one ==/!= 0) ? .. z <op> y .. -> zero_one * z
> > > ..):
> > > Check evaluating z unconditionally has no side-effects, like
> > > trapping.
>
> I forgot to mention this patch looks ok otherwise.
Pushed.
> >
> > Looks like I had missed adding expr_no_side_effects_p to those
> > patterns when I did r15-3870-g6c5543d3d9c4bb.
> > The other patterns which have the same issue which is missed:
> > ```
> > /* (a ? x : y) != (b ? x : y) --> (a^b & (x != y)) ? TRUE : FALSE */
> > /* (a ? x : y) == (b ? x : y) --> (a^b & (x != y)) ? FALSE : TRUE */
> > /* (a ? x : y) != (b ? y : x) --> (a^b | (x == y)) ? FALSE : TRUE */
> > /* (a ? x : y) == (b ? y : x) --> (a^b | (x == y)) ? TRUE : FALSE */
> > /* These are only valid if x and y don't have NaNs. */
> > ```
> > With this testcase:
> > ```
> > [[gnu::noipa]]
> > int f(int a, int b, int *x)
> > {
> > return (a ? *x : 0) != (b ? *x : 0);
> > }
> > int main()
> > {
> > f(0, 0, 0);
> > return 0;
> > }
> > ``
Hmm, indeed. Will fix those.
Richard.
> >
> > I audited the other patterns (that you did not change) and only could
> > find the above one.
> >
> > Thanks,
> > Andrew
> >
> >
> >
> > >
> > > * gcc.dg/torture/pr123887.c: New testcase.
> > > ---
> > > gcc/match.pd | 6 ++++--
> > > gcc/testsuite/gcc.dg/torture/pr123887.c | 14 ++++++++++++++
> > > 2 files changed, 18 insertions(+), 2 deletions(-)
> > > create mode 100644 gcc/testsuite/gcc.dg/torture/pr123887.c
> > >
> > > diff --git a/gcc/match.pd b/gcc/match.pd
> > > index 05e8ea7a229..9b2da2be4c5 100644
> > > --- a/gcc/match.pd
> > > +++ b/gcc/match.pd
> > > @@ -5178,7 +5178,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > > (op:c @2 @1))
> > > (if (INTEGRAL_TYPE_P (type)
> > > && TYPE_PRECISION (type) > 1
> > > - && (INTEGRAL_TYPE_P (TREE_TYPE (@0))))
> > > + && INTEGRAL_TYPE_P (TREE_TYPE (@0))
> > > + && expr_no_side_effects_p (@2))
> > > (op (mult (convert:type @0) @2) @1))))
> > >
> > > /* (zero_one != 0) ? z <op> y : y -> ((typeof(y))zero_one * z) <op> y */
> > > @@ -5190,7 +5191,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > > @1)
> > > (if (INTEGRAL_TYPE_P (type)
> > > && TYPE_PRECISION (type) > 1
> > > - && (INTEGRAL_TYPE_P (TREE_TYPE (@0))))
> > > + && INTEGRAL_TYPE_P (TREE_TYPE (@0))
> > > + && expr_no_side_effects_p (@2))
> > > (op (mult (convert:type @0) @2) @1))))
> > >
> > > /* ?: Value replacement. */
> > > diff --git a/gcc/testsuite/gcc.dg/torture/pr123887.c
> > > b/gcc/testsuite/gcc.dg/torture/pr123887.c
> > > new file mode 100644
> > > index 00000000000..c2a9659c5b5
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.dg/torture/pr123887.c
> > > @@ -0,0 +1,14 @@
> > > +/* { dg-do run } */
> > > +
> > > +typedef struct {
> > > + unsigned s;
> > > +} struct_t;
> > > +
> > > +struct_t *p;
> > > +bool cond;
> > > +int v = 1;
> > > +int main()
> > > +{
> > > + int u = 1 + (cond ? p->s : 0);
> > > + return u - v;
> > > +}
> > > --
> > > 2.51.0
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
