[Bug tree-optimization/68131] missed optimization and warning for broken overflow check

2023-10-24 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68131

--- Comment #5 from Andrew Pinski  ---
(In reply to Marc Glisse from comment #3)
> (In reply to Richard Biener from comment #2)
> > We indeed do not have this optimization, only A + CST CMP CST to A CMP CST'
> > and related.  Note that _9 might be negative so we also need range info
> > for this.  VRPs symbolic range stuff isn't good enough to simplify this.
> 
> If we want to simplify directly to false, I would expect a match.pd pattern
> using tree_expr_nonnegative_p to work in this case (conversion from a
> smaller unsigned). By the way, maybe tree_single_nonnegative_warnv_p could
> try looking at get_range_info before forwarding to
> gimple_stmt_nonnegative_warnv_p.

Oh I filed PR 111959 (and will be submitting a patch later today) for that.

[Bug tree-optimization/68131] missed optimization and warning for broken overflow check

2021-08-29 Thread pinskia at gcc dot gnu.org via Gcc-bugs 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68131

Andrew Pinski  changed:

   What|Removed |Added

   Target Milestone|--- |8.0
  Known to work||8.1.0
 Resolution|--- |FIXED
 Status|NEW |RESOLVED
  Known to fail||7.5.0

--- Comment #4 from Andrew Pinski  ---
Fixed by r8-3771.

There is no overflow here as unsigned short gets prompted to int and such.

[Bug tree-optimization/68131] missed optimization and warning for broken overflow check

2015-10-28 Thread glisse at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68131

Marc Glisse  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2015-10-28
  Component|rtl-optimization|tree-optimization
 Ever confirmed|0   |1

--- Comment #1 from Marc Glisse  ---
(in type int)
  _10 = _6 + _9;
  if (_6 > _10)

Indeed we fail to simplify that for some reason. If we did simplify, it might
print one of those "assuming signed overflow does not occur when assuming that
(X + c) < X is always false" warnings.

[Bug tree-optimization/68131] missed optimization and warning for broken overflow check

2015-10-28 Thread glisse at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68131

--- Comment #3 from Marc Glisse  ---
(In reply to Richard Biener from comment #2)
> We indeed do not have this optimization, only A + CST CMP CST to A CMP CST'
> and related.  Note that _9 might be negative so we also need range info
> for this.  VRPs symbolic range stuff isn't good enough to simplify this.

If we want to simplify directly to false, I would expect a match.pd pattern
using tree_expr_nonnegative_p to work in this case (conversion from a smaller
unsigned). By the way, maybe tree_single_nonnegative_warnv_p could try looking
at get_range_info before forwarding to gimple_stmt_nonnegative_warnv_p.

But the much simpler transformation: a+b b<0 does not require any VRP info
and would let the next VRP pass finish the work.

[Bug tree-optimization/68131] missed optimization and warning for broken overflow check

2015-10-28 Thread rguenth at gcc dot gnu.org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68131

Richard Biener  changed:

   What|Removed |Added

   Keywords||missed-optimization

--- Comment #2 from Richard Biener  ---
We indeed do not have this optimization, only A + CST CMP CST to A CMP CST'
and related.  Note that _9 might be negative so we also need range info
for this.  VRPs symbolic range stuff isn't good enough to simplify this.