On Tue, Oct 6, 2026 at 12:49 AM Richard Biener <[email protected]> wrote:
>
> On Tue, 29 Sep 2026, Richard Biener wrote:
>
> > In combine_comparisons, under flag_trapping_math, we check whether the
> > combined
> > comparison traps under the same conditions as the input comparisons:
> >
> > bool trap = (compcode & COMPCODE_UNORD) == 0
> > && (compcode != COMPCODE_EQ)
> > && (compcode != COMPCODE_ORD);
> >
> > When compcode is COMPCODE_FALSE or COMPCODE_TRUE trap is computed as true,
> > and combine_comparisons errorneously eliminates IEEE exceptions.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> >
> > OK?
>
> Jeff approved the followup to tree-ssa-ifcombine.cc and this one
> is almost obvious, so I pushed both together now.
Sorry I didn't get to this before but yes this is ok,
>
> Richard.
>
> > Thanks,
> > Richard.
> >
> > PR tree-optimization/53805
> > * fold-const.cc (combine_comparisons): Do not treat COMPCODE_FALSE
> > or COMPCODE_TRUE as trapping.
> >
> > * gcc.dg/tree-ssa/fp-trapping-and-1.c: New testcase.
> > ---
> > gcc/fold-const.cc | 4 +++-
> > gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c | 11 +++++++++++
> > 2 files changed, 14 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
> >
> > diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
> > index 8c5e558647c..cfeafd5c1d1 100644
> > --- a/gcc/fold-const.cc
> > +++ b/gcc/fold-const.cc
> > @@ -3085,7 +3085,9 @@ combine_comparisons (enum tree_code code, enum
> > tree_code lcode,
> > && (rcompcode != COMPCODE_ORD);
> > bool trap = (compcode & COMPCODE_UNORD) == 0
> > && (compcode != COMPCODE_EQ)
> > - && (compcode != COMPCODE_ORD);
> > + && (compcode != COMPCODE_ORD)
> > + && (compcode != COMPCODE_FALSE)
> > + && (compcode != COMPCODE_TRUE);
> >
> > /* In a short-circuited boolean expression the LHS might be
> > such that the RHS, if evaluated, will never trap. For
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
> > b/gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
> > new file mode 100644
> > index 00000000000..84946dc7cc1
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/fp-trapping-and-1.c
> > @@ -0,0 +1,11 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -ftrapping-math -fdump-tree-optimized" } */
> > +
> > +int
> > +f (double a, double b)
> > +{
> > + return (a > b) & (a < b);
> > +}
> > +
> > +/* { dg-final { scan-tree-dump-times " > " 1 "optimized" } } */
> > +/* { dg-final { scan-tree-dump-times " < " 1 "optimized" } } */
> >
>
> --
> Richard Biener <[email protected]>
> SUSE Software Solutions Germany GmbH,
> Frankenstrasse 146, 90461 Nuernberg, Germany;
> GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri; (HRB 36809, AG Nuernberg)
