http://gcc.gnu.org/ml/gcc-patches/2008-02/msg00110.html

[pf3gnuchains/gcc-fork.git] / gcc / tree-vrp.c

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 5f9a327..9b9cc03 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -5073,6 +5073,48 @@ vrp_evaluate_conditional (tree cond, tree stmt)
        }
     }
 
+  if (warn_type_limits
+      && ret
+      && TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison)
+    {
+      /* If the comparison is being folded and the operand on the LHS
+        is being compared against a constant value that is outside of
+        the natural range of OP0's type, then the predicate will
+        always fold regardless of the value of OP0.  If -Wtype-limits
+        was specified, emit a warning.  */
+      const char *warnmsg = NULL;
+      tree op0 = TREE_OPERAND (cond, 0);
+      tree op1 = TREE_OPERAND (cond, 1);
+      tree type = TREE_TYPE (op0);
+      value_range_t *vr0 = get_value_range (op0);
+
+      if (vr0->type != VR_VARYING
+         && INTEGRAL_TYPE_P (type)
+         && vrp_val_is_min (vr0->min)
+         && vrp_val_is_max (vr0->max)
+         && is_gimple_min_invariant (op1))
+       {
+         if (integer_zerop (ret))
+           warnmsg = G_("comparison always false due to limited range of "
+                        "data type");
+         else
+           warnmsg = G_("comparison always true due to limited range of "
+                        "data type");
+       }
+
+      if (warnmsg)
+       {
+         location_t locus;
+
+         if (!EXPR_HAS_LOCATION (stmt))
+           locus = input_location;
+         else
+           locus = EXPR_LOCATION (stmt);
+
+         warning (OPT_Wextra, "%H%s", &locus, warnmsg);
+       }
+    }
+
   return ret;
 }