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

	PR 33738
	* tree-vrp.c (vrp_evaluate_conditional): With
	-Wtype-limits, emit a warning when comparing against a
	constant outside the natural range of OP0's type.

testsuite/ChangeLog

	PR 33738
	* testsuite/g++.dg/warn/pr33738.C: New.

From-SVN: r132111

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4f81c24..13b13df 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2008-02-04  Diego Novillo  <dnovillo@google.com>
+
+       http://gcc.gnu.org/ml/gcc-patches/2008-02/msg00110.html
+
+       PR 33738
+       * tree-vrp.c (vrp_evaluate_conditional): With
+       -Wtype-limits, emit a warning when comparing against a
+       constant outside the natural range of OP0's type.
+
 2008-02-04  Richard Guenther  <rguenther@suse.de>
 
        PR middle-end/33631

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7ea61af..cc6a362 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,10 @@
+2008-02-04  Diego Novillo  <dnovillo@google.com>
+
+       http://gcc.gnu.org/ml/gcc-patches/2008-02/msg00110.html
+
+       PR 33738
+       * testsuite/g++.dg/warn/pr33738.C: New.
+
 2008-02-04  Daniel Franke  <franke.daniel@gmail.com>
 
        * gfortran.dg/where_operator_assign_4.f90: Fix typo in error message

diff --git a/gcc/testsuite/g++.dg/warn/pr33738.C b/gcc/testsuite/g++.dg/warn/pr33738.C
new file mode 100644 (file)
index 0000000..8847b6e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/pr33738.C
@@ -0,0 +1,26 @@
+// { dg-do run }
+// { dg-options "-O2 -Wtype-limits" }
+extern void link_error (void);
+
+enum Alpha {
+ ZERO = 0, ONE, TWO, THREE
+};
+
+Alpha a2;
+
+int m1 = -1;
+int GetM1() {
+ return m1;
+}
+
+int main() {
+ a2 = static_cast<Alpha>(GetM1());
+ if (a2 == -1) {       // { dg-warning "always false due" }
+    link_error ();
+ }
+ if (-1 == a2) {       // { dg-warning "always false due" }
+    link_error ();
+ }
+ return 0;
+}
+

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;
 }