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irange: Compare nonzero bits in irange with widest_int [PR108639]

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The problem here is we are trying to compare two ranges with different
precisions and the == operator in wide_int is complaining.

Interestingly, the problem is not the nonzero bits, but the fact that
the entire ranges have different precisions.  The reason we don't ICE
when comparing the sub-ranges, is because the code in
irange::operator== works on trees, and tree_int_cst_equal is
promoting the comparison to a widest int:

  if (TREE_CODE (t1) == INTEGER_CST
      && TREE_CODE (t2) == INTEGER_CST
      && wi::to_widest (t1) == wi::to_widest (t2))
    return 1;

This is why we don't see the ICE until the nonzero bits comparison is
done on wide ints.  I think we should maintain the current equality
behavior, and follow suit in the nonzero bit comparison.

I have also fixed the legacy equality code, even though technically
nonzero bits shouldn't appear in legacy.  But better safe than sorry.

	PR tree-optimization/108639

gcc/ChangeLog:

	* value-range.cc (irange::legacy_equal_p): Compare nonzero bits as
	widest_int.
	(irange::operator==): Same.
This commit is contained in:
Aldy Hernandez 2023-02-02 18:08:44 +01:00
parent 10bd26d6ef
commit e261fcefb7
3 changed files with 32 additions and 2 deletions
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12
gcc/testsuite/gcc.c-torture/compile/pr108638.c Normal file
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@ -0,0 +1,12 @@
/* PR tree-optimization/108638 */
long long a;
int b;
void
foo (void)
{
for (a = 0; a < __SIZEOF_LONG_LONG__ * __CHAR_BIT__; a++)
if (b)
b |= a << a;
}

11
gcc/testsuite/gcc.c-torture/compile/pr108639.c Normal file
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@ -0,0 +1,11 @@
/* PR tree-optimization/108639 */
long long a;
int
main ()
{
a = a ? 0 || 0 % 0 : 0;
a = a << a;
return 0;
}

11
gcc/value-range.cc
View file

@ -1259,7 +1259,10 @@ irange::legacy_equal_p (const irange &other) const
other.tree_lower_bound (0))
&& vrp_operand_equal_p (tree_upper_bound (0),
other.tree_upper_bound (0))
&& get_nonzero_bits () == other.get_nonzero_bits ());
&& (widest_int::from (get_nonzero_bits (),
TYPE_SIGN (type ()))
== widest_int::from (other.get_nonzero_bits (),
TYPE_SIGN (other.type ()))));
}
bool
@ -1294,7 +1297,11 @@ irange::operator== (const irange &other) const
|| !operand_equal_p (ub, ub_other, 0))
return false;
}
return get_nonzero_bits () == other.get_nonzero_bits ();
widest_int nz1 = widest_int::from (get_nonzero_bits (),
TYPE_SIGN (type ()));
widest_int nz2 = widest_int::from (other.get_nonzero_bits (),
TYPE_SIGN (other.type ()));
return nz1 == nz2;
}
/* Return TRUE if this is a symbolic range. */