[gcc r13-5696] irange: Compare nonzero bits in irange with widest_int [PR108639]

[gcc r13-5696] irange: Compare nonzero bits in irange with widest_int [PR108639]

[Aldy Hernandez]

https://gcc.gnu.org/g:e261fcefb71e1270673f0457fcc73711f13d3079

commit r13-5696-ge261fcefb71e1270673f0457fcc73711f13d3079
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Thu Feb 2 18:08:44 2023 +0100

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

Diff:
---
 gcc/testsuite/gcc.c-torture/compile/pr108638.c | 12 ++++++++++++
 gcc/testsuite/gcc.c-torture/compile/pr108639.c | 11 +++++++++++
 gcc/value-range.cc                             | 11 +++++++++--
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr108638.c b/gcc/testsuite/gcc.c-torture/compile/pr108638.c
new file mode 100644
index 00000000000..755c151a09a
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr108638.c
@@ -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;
+}
diff --git a/gcc/testsuite/gcc.c-torture/compile/pr108639.c b/gcc/testsuite/gcc.c-torture/compile/pr108639.c
new file mode 100644
index 00000000000..ed826cc2f5a
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr108639.c
@@ -0,0 +1,11 @@
+/* PR tree-optimization/108639 */
+
+long long a;
+
+int
+main ()
+{
+  a = a ? 0 || 0 % 0 : 0;
+  a = a << a;
+  return 0;
+}
diff --git a/gcc/value-range.cc b/gcc/value-range.cc
index 26f6f26b01a..a535337c47a 100644
--- a/gcc/value-range.cc
+++ b/gcc/value-range.cc
@@ -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.  */