[Bug tree-optimization/80541] Wrong constant folding

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80541

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
CCP with bit-tracking:

Visiting statement:
# RANGE [-1, 0]
_4 = (long int) b_10;
which is likely CONSTANT
Lattice value changed to VARYING.  Adding SSA edges to worklist.

Visiting statement:
# RANGE [0, 9223372036854775807] NONZERO 0
_5 = _4 * -9223372036854775808;
which is likely CONSTANT
Applying pattern match.pd:844, gimple-match.c:90
Lattice value changed to CONSTANT 0.  Adding SSA edges to worklist.
marking stmt to be not simulated again

this is bit_value_binop at work which IMHO is correct -- -1 * LONG_MIN
is invoking undefined behavior so _4 can only be zero and thus _5 is zero.

So the error happens earlier, somewhere in GENERIC folding where we transform
the initial expression to

  int x = (int) (1 % ((long int) b * -9223372036854775808(OVF) +
9223372036854775807));

which is from fold_plusminusmult where we fold

 b + (b * LONG_MAX) to b * (1 + LONG_MAX).

Thus this is effectively a duplicate of PR66313 (just a case that should
be obvious).