PR tree-optimization/26854

	* c-decl.c (struct c_scope): Add field has_jump_unsafe_decl.
	(decl_jump_unsafe): Move higher in file, with no other change.
	(bind): Set has_jump_unsafe_decl if appropriate.
	(update_label_decls): Test has_jump_unsafe_decl to avoid loop.
	(check_earlier_gotos): Likewise.
	(c_check_switch_jump_warnings): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@169267 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 78fa228..31838c6 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2011-01-25  Ian Lance Taylor  <iant@google.com>
+
+       PR tree-optimization/26854
+       * c-decl.c (struct c_scope): Add field has_jump_unsafe_decl.
+       (decl_jump_unsafe): Move higher in file, with no other change.
+       (bind): Set has_jump_unsafe_decl if appropriate.
+       (update_label_decls): Test has_jump_unsafe_decl to avoid loop.
+       (check_earlier_gotos): Likewise.
+       (c_check_switch_jump_warnings): Likewise.
+
 2011-01-25  Jonathan Wakely  <jwakely.gcc@gmail.com>
 
        * doc/invoke.texi (Warning Options): Add missing hyphen.

diff --git a/gcc/c-decl.c b/gcc/c-decl.c
index 4d24c60..b438b06 100644 (file)
--- a/gcc/c-decl.c
+++ b/gcc/c-decl.c
@@ -404,6 +404,13 @@ struct GTY((chain_next ("%h.outer"))) c_scope {
      up searching for labels when popping scopes, particularly since
      labels are normally only found at function scope.  */
   BOOL_BITFIELD has_label_bindings : 1;
+
+  /* True if we should issue a warning if a goto statement crosses any
+     of the bindings.  We still need to check the list of bindings to
+     find the specific ones we need to warn about.  This is true if
+     decl_jump_unsafe would return true for any of the bindings.  This
+     is used to avoid looping over all the bindings unnecessarily.  */
+  BOOL_BITFIELD has_jump_unsafe_decl : 1;
 };
 
 /* The scope currently in effect.  */
@@ -554,6 +561,31 @@ add_stmt (tree t)
   return t;
 }
 \f
+/* Return true if we will want to say something if a goto statement
+   crosses DECL.  */
+
+static bool
+decl_jump_unsafe (tree decl)
+{
+  if (decl == error_mark_node || TREE_TYPE (decl) == error_mark_node)
+    return false;
+
+  /* Always warn about crossing variably modified types.  */
+  if ((TREE_CODE (decl) == VAR_DECL || TREE_CODE (decl) == TYPE_DECL)
+      && variably_modified_type_p (TREE_TYPE (decl), NULL_TREE))
+    return true;
+
+  /* Otherwise, only warn if -Wgoto-misses-init and this is an
+     initialized automatic decl.  */
+  if (warn_jump_misses_init
+      && TREE_CODE (decl) == VAR_DECL
+      && !TREE_STATIC (decl)
+      && DECL_INITIAL (decl) != NULL_TREE)
+    return true;
+
+  return false;
+}
+\f
 
 void
 c_print_identifier (FILE *file, tree node, int indent)
@@ -602,6 +634,9 @@ bind (tree name, tree decl, struct c_scope *scope, bool invisible,
   b->prev = scope->bindings;
   scope->bindings = b;
 
+  if (decl_jump_unsafe (decl))
+    scope->has_jump_unsafe_decl = 1;
+
   if (!name)
     return;
 
@@ -758,31 +793,6 @@ set_spot_bindings (struct c_spot_bindings *p, bool defining)
   p->left_stmt_expr = false;
 }
 
-/* Return true if we will want to say something if a goto statement
-   crosses DECL.  */
-
-static bool
-decl_jump_unsafe (tree decl)
-{
-  if (decl == error_mark_node || TREE_TYPE (decl) == error_mark_node)
-    return false;
-
-  /* Always warn about crossing variably modified types.  */
-  if ((TREE_CODE (decl) == VAR_DECL || TREE_CODE (decl) == TYPE_DECL)
-      && variably_modified_type_p (TREE_TYPE (decl), NULL_TREE))
-    return true;
-
-  /* Otherwise, only warn if -Wgoto-misses-init and this is an
-     initialized automatic decl.  */
-  if (warn_jump_misses_init
-      && TREE_CODE (decl) == VAR_DECL
-      && !TREE_STATIC (decl)
-      && DECL_INITIAL (decl) != NULL_TREE)
-    return true;
-
-  return false;
-}
-
 /* Update spot bindings P as we pop out of SCOPE.  Return true if we
    should push decls for a label.  */
 
@@ -969,6 +979,7 @@ update_label_decls (struct c_scope *scope)
            {
              struct c_label_vars *label_vars;
              struct c_binding *b1;
+             bool hjud;
              unsigned int ix;
              struct c_goto_bindings *g;
 
@@ -977,18 +988,26 @@ update_label_decls (struct c_scope *scope)
              label_vars = b->u.label;
 
              b1 = label_vars->label_bindings.bindings_in_scope;
+             if (label_vars->label_bindings.scope == NULL)
+               hjud = false;
+             else
+               hjud = label_vars->label_bindings.scope->has_jump_unsafe_decl;
              if (update_spot_bindings (scope, &label_vars->label_bindings))
                {
                  /* This label is defined in this scope.  */
-                 for (; b1 != NULL;  b1 = b1->prev)
+                 if (hjud)
                    {
-                     /* A goto from later in the function to this
-                        label will never see the initialization of
-                        B1, if any.  Save it to issue a warning if
-                        needed.  */
-                     if (decl_jump_unsafe (b1->decl))
-                       VEC_safe_push (tree, gc, label_vars->decls_in_scope,
-                                      b1->decl);
+                     for (; b1 != NULL; b1 = b1->prev)
+                       {
+                         /* A goto from later in the function to this
+                            label will never see the initialization
+                            of B1, if any.  Save it to issue a
+                            warning if needed.  */
+                         if (decl_jump_unsafe (b1->decl))
+                           VEC_safe_push (tree, gc,
+                                          label_vars->decls_in_scope,
+                                          b1->decl);
+                       }
                    }
                }
 
@@ -3165,12 +3184,15 @@ check_earlier_gotos (tree label, struct c_label_vars* label_vars)
       /* We have a goto to this label.  The goto is going forward.  In
         g->scope, the goto is going to skip any binding which was
         defined after g->bindings_in_scope.  */
-      for (b = g->goto_bindings.scope->bindings;
-          b != g->goto_bindings.bindings_in_scope;
-          b = b->prev)
+      if (g->goto_bindings.scope->has_jump_unsafe_decl)
        {
-         if (decl_jump_unsafe (b->decl))
-           warn_about_goto (g->loc, label, b->decl);
+         for (b = g->goto_bindings.scope->bindings;
+              b != g->goto_bindings.bindings_in_scope;
+              b = b->prev)
+           {
+             if (decl_jump_unsafe (b->decl))
+               warn_about_goto (g->loc, label, b->decl);
+           }
        }
 
       /* We also need to warn about decls defined in any scopes
@@ -3180,14 +3202,17 @@ check_earlier_gotos (tree label, struct c_label_vars* label_vars)
           scope = scope->outer)
        {
          gcc_assert (scope != NULL);
-         if (scope == label_vars->label_bindings.scope)
-           b = label_vars->label_bindings.bindings_in_scope;
-         else
-           b = scope->bindings;
-         for (; b != NULL; b = b->prev)
+         if (scope->has_jump_unsafe_decl)
            {
-             if (decl_jump_unsafe (b->decl))
-               warn_about_goto (g->loc, label, b->decl);
+             if (scope == label_vars->label_bindings.scope)
+               b = label_vars->label_bindings.bindings_in_scope;
+             else
+               b = scope->bindings;
+             for (; b != NULL; b = b->prev)
+               {
+                 if (decl_jump_unsafe (b->decl))
+                   warn_about_goto (g->loc, label, b->decl);
+               }
            }
        }
 
@@ -3303,6 +3328,10 @@ c_check_switch_jump_warnings (struct c_spot_bindings *switch_bindings,
       struct c_binding *b;
 
       gcc_assert (scope != NULL);
+
+      if (!scope->has_jump_unsafe_decl)
+       continue;
+
       for (b = scope->bindings; b != NULL; b = b->prev)
        {
          if (decl_jump_unsafe (b->decl))