https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89536
--- Comment #13 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> On the testcase, value is -2 and before your change it would derive
> correctly that if BIT_NOT_EXPR is -2, then rhs must be ~-2, i.e. 1, but
> after the patch it says rhs must be 0.
The oversight is actually on the integer_zerop predicate itself so:
Index: tree-ssa-dom.c
===================================================================
--- tree-ssa-dom.c (revision 269211)
+++ tree-ssa-dom.c (working copy)
@@ -348,7 +348,7 @@ edge_info::derive_equivalences (tree nam
&& TREE_CODE (rhs) == SSA_NAME
&& ssa_name_has_boolean_range (rhs))
{
- if (integer_zerop (value))
+ if ((TREE_INT_CST_LOW (value) & 1) == 0)
res = build_one_cst (TREE_TYPE (rhs));
else
res = build_zero_cst (TREE_TYPE (rhs));
is the immediate fix.
On the other hand, if your line of reasoning is correct, then we must restrict
both the BIT_AND_EXPR and the BIT_NOT_EXPR cases to bona-fide boolean types.
