Patchwork Prevent 'control reaches end of non-void function' warning for DO_WHILE

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Submitter Tom de Vries
Date Jan. 22, 2012, 11:38 a.m.
Message ID <4F1BF53A.9070703@mentor.com>
Download mbox | patch
Permalink /patch/137234/
State New
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Comments

Tom de Vries - Jan. 22, 2012, 11:38 a.m.
On 09/12/11 10:45, Richard Guenther wrote:
> On Fri, Dec 9, 2011 at 9:38 AM, Tom de Vries <Tom_deVries@mentor.com> wrote:
>> Jakub,
>>
>> This patch fixes the problem reported in
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25973#c4 .
>>
>> The test-case listed there is:
>> ...
>> struct Block
>> {
>>  public:
>>    Block();
>>    ~Block();
>> };
>>
>> bool func( bool bar )
>> {
>>  Block block;
>>  bool foo = false;
>>
>>  if( !foo || bar )
>>    do { return true; } while( 0 );
>>  else
>>    do { return false; } while( 0 );
>> }
>> ...
>>
>> For O0, a spurious warning is generated:
>> ...
>> $ gcc -O0 -Wreturn-type block.C -S:
>> block.C: In function ‘bool func(bool)’:
>> block.C:17:1: warning: control reaches end of non-void function [-Wreturn-type]
>> ...
>>

> 
> Hm.  I would prefer if the gimplifier is fed GENERIC, not
> GENERIC plus FE specific codes ... (both C and C++ do
> "genericization" passes, but they actually do not transform
> all code to GENERIC).  Can you check if it's easy enough to
> lower DO_STMT during cp_genericize?

Richard,

I implement this approach in attached patch.

Bootstrapped and reg-tested on x86_64. OK for stage1? I would guess this patch
is too intrusive for stage4.

Furthermore, should I put PR c++/25973 in the log? The patch fixes the testcase
in comment 4, but doesn't seem related to the example listed in the description
field of the PR.

Thanks,
- Tom

2012-01-22  Tom de Vries  <tom@codesourcery.com>

	* cp-gimplify.c (begin_bc_block): Add location parameter and use as
	location argument to create_artificial_label.
	(finish_bc_block): Change return type to void.  Remove body_seq
	parameter, and add block parameter.  Append label to STMT_LIST and
	return in block.
	(gimplify_cp_loop, gimplify_for_stmt, gimplify_while_stmt)
	(gimplify_do_stmt, gimplify_switch_stmt): Remove function.
	(genericize_cp_loop, genericize_for_stmt, genericize_while_stmt)
	(genericize_do_stmt, genericize_switch_stmt, genericize_continue_stmt)
	(genericize_break_stmt, genericize_omp_for_stmt): New function.
	(cp_gimplify_omp_for): Remove bc_continue processing.
	(cp_gimplify_expr): Genericize VEC_INIT_EXPR.
	(cp_gimplify_expr): Mark FOR_STMT, WHILE_STMT, DO_STMT, SWITCH_STMT,
	CONTINUE_STMT, and BREAK_STMT as unreachable.
	(cp_genericize_r): Genericize FOR_STMT, WHILE_STMT, DO_STMT,
	SWITCH_STMT, CONTINUE_STMT, BREAK_STMT and OMP_FOR.
	(cp_genericize_tree): New function, factored out of ...
	(cp_genericize): ... this function.

	* g++.dg/pr51264-4.C: New test.
Jason Merrill - Feb. 18, 2012, 8:33 a.m.
On 01/22/2012 03:38 AM, Tom de Vries wrote:

Sorry I didn't notice this patch until now; please CC me on C++ patches, 
or at least mention C++ in the subject line.

> +      tree expr = NULL;
> +      append_to_statement_list (*block, &expr);
> +      *block = expr;

Rather than doing this dance here, I think it would be better to enhance 
append_to_statement_list to handle the case of the list argument being a 
non-list.

> +  cp_walk_tree (&incr, cp_genericize_r, data, NULL);
>
> +  if (incr && EXPR_P (incr))
> +    SET_EXPR_LOCATION (incr, start_locus);

It might be better to set the location on incr before genericizing, so 
that the location can trickle down.

> +         t = build1 (GOTO_EXPR, void_type_node, get_bc_label (bc_break));
> +         SET_EXPR_LOCATION (t, start_locus);

Here you can use build1_loc instead of two separate statements.

> -      /* If we use a LOOP_EXPR here, we have to feed the whole thing
> -        back through the main gimplifier to lower it.  Given that we
> -        have to gimplify the loop body NOW so that we can resolve
> -        break/continue stmts, seems easier to just expand to gotos.  */

Since we're now lowering the loop at genericize time rather than 
gimplify, what's the rationale for not using LOOP_EXPR/EXIT_EXPR?  We 
should still say something here.  I suppose the rationale is that the C 
front end currently goes straight to gotos.

>           if (cond != error_mark_node)
>             {
> -             gimplify_expr (&cond, &exit_seq, NULL, is_gimple_val, fb_rvalue);
> -             stmt = gimple_build_cond (NE_EXPR, cond,
> -                                       build_int_cst (TREE_TYPE (cond), 0),
> -                                       gimple_label_label (top),
> -                                       get_bc_label (bc_break));
> -             gimple_seq_add_stmt (&exit_seq, stmt);
> +             cond = build2 (NE_EXPR, boolean_type_node, cond,
> +                            build_int_cst (TREE_TYPE (cond), 0));

I don't think we still need this extra comparison to 0, that seems like 
a gimple-specific thing.

>    if (FOR_INIT_STMT (stmt))
> +    append_to_statement_list (FOR_INIT_STMT (stmt), &expr);
>
> +  genericize_cp_loop (&loop, EXPR_LOCATION (stmt), FOR_COND (stmt),
> +                     FOR_BODY (stmt), FOR_EXPR (stmt), 1, walk_subtrees, data);

The call to genericize_cp_loop will clear *walk_subtrees, which means we 
don't genericize the FOR_INIT_STMT.

> +  tree jump = build_and_jump (&label);

Again, let's use build1_loc.

> +  *stmt_p = build_and_jump (&label);
> +  SET_EXPR_LOCATION (*stmt_p, location);

And here.

> +  stmt = make_node (OMP_FOR);

Why make a new OMP_FOR rather than repurpose the one we already have? 
We've already modified its operands.

Jason

Patch

Index: gcc/cp/cp-gimplify.c
===================================================================
--- gcc/cp/cp-gimplify.c (revision 183325)
+++ gcc/cp/cp-gimplify.c (working copy)
@@ -34,6 +34,11 @@  along with GCC; see the file COPYING3.
 #include "flags.h"
 #include "splay-tree.h"
 
+/* Forward declarations.  */
+
+static tree cp_genericize_r (tree *, int *, void *);
+static void cp_genericize_tree (tree*);
+
 /* Local declarations.  */
 
 enum bc_t { bc_break = 0, bc_continue = 1 };
@@ -45,37 +50,42 @@  static tree bc_label[2];
 /* Begin a scope which can be exited by a break or continue statement.  BC
    indicates which.
 
-   Just creates a label and pushes it into the current context.  */
+   Just creates a label with location LOCATION and pushes it into the current
+   context.  */
 
 static tree
-begin_bc_block (enum bc_t bc)
+begin_bc_block (enum bc_t bc, location_t location)
 {
-  tree label = create_artificial_label (input_location);
+  tree label = create_artificial_label (location);
   DECL_CHAIN (label) = bc_label[bc];
   bc_label[bc] = label;
   return label;
 }
 
 /* Finish a scope which can be exited by a break or continue statement.
-   LABEL was returned from the most recent call to begin_bc_block.  BODY is
+   LABEL was returned from the most recent call to begin_bc_block.  BLOCK is
    an expression for the contents of the scope.
 
    If we saw a break (or continue) in the scope, append a LABEL_EXPR to
-   body.  Otherwise, just forget the label.  */
+   BLOCK.  Otherwise, just forget the label.  */
 
-static gimple_seq
-finish_bc_block (enum bc_t bc, tree label, gimple_seq body)
+static void
+finish_bc_block (tree *block, enum bc_t bc, tree label)
 {
   gcc_assert (label == bc_label[bc]);
 
   if (TREE_USED (label))
     {
-      gimple_seq_add_stmt (&body, gimple_build_label (label));
+      tree expr = NULL;
+      append_to_statement_list (*block, &expr);
+      *block = expr;
+
+      append_to_statement_list (build1 (LABEL_EXPR, void_type_node, label),
+				block);
     }
 
   bc_label[bc] = DECL_CHAIN (label);
   DECL_CHAIN (label) = NULL_TREE;
-  return body;
 }
 
 /* Get the LABEL_EXPR to represent a break or continue statement
@@ -183,173 +193,232 @@  genericize_if_stmt (tree *stmt_p)
    evaluated before the loop body as in while and for loops, or after the
    loop body as in do-while loops.  */
 
-static gimple_seq
-gimplify_cp_loop (tree cond, tree body, tree incr, bool cond_is_first)
-{
-  gimple top, entry, stmt;
-  gimple_seq stmt_list, body_seq, incr_seq, exit_seq;
-  tree cont_block, break_block;
-  location_t stmt_locus;
-
-  stmt_locus = input_location;
-  stmt_list = NULL;
-  body_seq = NULL;
-  incr_seq = NULL;
-  exit_seq = NULL;
-  entry = NULL;
+static void
+genericize_cp_loop (tree *stmt_p, location_t start_locus, tree cond, tree body,
+		    tree incr, bool cond_is_first, int *walk_subtrees,
+		    void *data)
+{
+  tree blab, clab;
+  tree entry = NULL, exit = NULL, t;
+  tree stmt_list = NULL;
+
+  blab = begin_bc_block (bc_break, start_locus);
+  clab = begin_bc_block (bc_continue, start_locus);
+
+  cp_walk_tree (&cond, cp_genericize_r, data, NULL);
+  cp_walk_tree (&body, cp_genericize_r, data, NULL);
+  cp_walk_tree (&incr, cp_genericize_r, data, NULL);
+  *walk_subtrees = 0;
 
-  break_block = begin_bc_block (bc_break);
-  cont_block = begin_bc_block (bc_continue);
+  if (incr && EXPR_P (incr))
+    SET_EXPR_LOCATION (incr, start_locus);
 
   /* If condition is zero don't generate a loop construct.  */
   if (cond && integer_zerop (cond))
     {
-      top = NULL;
       if (cond_is_first)
 	{
-	  stmt = gimple_build_goto (get_bc_label (bc_break));
-	  gimple_set_location (stmt, stmt_locus);
-	  gimple_seq_add_stmt (&stmt_list, stmt);
+	  t = build1 (GOTO_EXPR, void_type_node, get_bc_label (bc_break));
+	  SET_EXPR_LOCATION (t, start_locus);
+	  append_to_statement_list (t, &stmt_list);
 	}
     }
   else
     {
-      /* If we use a LOOP_EXPR here, we have to feed the whole thing
-	 back through the main gimplifier to lower it.  Given that we
-	 have to gimplify the loop body NOW so that we can resolve
-	 break/continue stmts, seems easier to just expand to gotos.  */
-      top = gimple_build_label (create_artificial_label (stmt_locus));
+      tree top = build1 (LABEL_EXPR, void_type_node,
+			 create_artificial_label (start_locus));
 
       /* If we have an exit condition, then we build an IF with gotos either
 	 out of the loop, or to the top of it.  If there's no exit condition,
 	 then we just build a jump back to the top.  */
+      exit = build1 (GOTO_EXPR, void_type_node, LABEL_EXPR_LABEL (top));
+
       if (cond && !integer_nonzerop (cond))
 	{
 	  if (cond != error_mark_node)
 	    { 
-	      gimplify_expr (&cond, &exit_seq, NULL, is_gimple_val, fb_rvalue);
-	      stmt = gimple_build_cond (NE_EXPR, cond,
-					build_int_cst (TREE_TYPE (cond), 0),
-					gimple_label_label (top),
-					get_bc_label (bc_break));
-	      gimple_seq_add_stmt (&exit_seq, stmt);
+	      cond = build2 (NE_EXPR, boolean_type_node, cond,
+			     build_int_cst (TREE_TYPE (cond), 0));
 	    }
 
+	  /* Canonicalize the loop condition to the end.  This means
+	     generating a branch to the loop condition.  Reuse the
+	     continue label, if possible.  */
 	  if (cond_is_first)
 	    {
 	      if (incr)
 		{
-		  entry = gimple_build_label 
-		    (create_artificial_label (stmt_locus));
-		  stmt = gimple_build_goto (gimple_label_label (entry));
+		  entry = build1 (LABEL_EXPR, void_type_node,
+				  create_artificial_label (start_locus));
+		  t = build1 (GOTO_EXPR, void_type_node,
+			      LABEL_EXPR_LABEL (entry));
 		}
 	      else
-		stmt = gimple_build_goto (get_bc_label (bc_continue));
-	      gimple_set_location (stmt, stmt_locus);
-	      gimple_seq_add_stmt (&stmt_list, stmt);
+		t = build1 (GOTO_EXPR, void_type_node,
+			    get_bc_label (bc_continue));
+	      SET_EXPR_LOCATION (t, start_locus);
+	      append_to_statement_list (t, &stmt_list);
 	    }
-	}
-      else
-	{
-	  stmt = gimple_build_goto (gimple_label_label (top));
-	  gimple_seq_add_stmt (&exit_seq, stmt);
-	}
-    }
 
-  gimplify_stmt (&body, &body_seq);
-  gimplify_stmt (&incr, &incr_seq);
+	  t = build1 (GOTO_EXPR, void_type_node, get_bc_label (bc_break));
+	  exit = fold_build3_loc (start_locus,
+				  COND_EXPR, void_type_node, cond, exit, t);
+	}
 
-  body_seq = finish_bc_block (bc_continue, cont_block, body_seq);
+      append_to_statement_list (top, &stmt_list);
+    }
 
-  gimple_seq_add_stmt (&stmt_list, top);
-  gimple_seq_add_seq (&stmt_list, body_seq);
-  gimple_seq_add_seq (&stmt_list, incr_seq);
-  gimple_seq_add_stmt (&stmt_list, entry);
-  gimple_seq_add_seq (&stmt_list, exit_seq);
+  append_to_statement_list (body, &stmt_list);
+  finish_bc_block (&stmt_list, bc_continue, clab);
+  append_to_statement_list (incr, &stmt_list);
+  append_to_statement_list (entry, &stmt_list);
+  append_to_statement_list (exit, &stmt_list);
+  finish_bc_block (&stmt_list, bc_break, blab);
 
-  annotate_all_with_location (stmt_list, stmt_locus);
+  if (stmt_list == NULL_TREE)
+    stmt_list = build1 (NOP_EXPR, void_type_node, integer_zero_node);
 
-  return finish_bc_block (bc_break, break_block, stmt_list);
+  *stmt_p = stmt_list;
 }
 
-/* Gimplify a FOR_STMT node.  Move the stuff in the for-init-stmt into the
-   prequeue and hand off to gimplify_cp_loop.  */
+/* Genericize a FOR_STMT node *STMT_P.  */
 
 static void
-gimplify_for_stmt (tree *stmt_p, gimple_seq *pre_p)
+genericize_for_stmt (tree *stmt_p, int *walk_subtrees, void *data)
 {
   tree stmt = *stmt_p;
-
+  tree expr = NULL;
+  tree loop;
   if (FOR_INIT_STMT (stmt))
-    gimplify_and_add (FOR_INIT_STMT (stmt), pre_p);
+    append_to_statement_list (FOR_INIT_STMT (stmt), &expr);
 
-  gimple_seq_add_seq (pre_p,
-		      gimplify_cp_loop (FOR_COND (stmt), FOR_BODY (stmt),
-					FOR_EXPR (stmt), 1));
-  *stmt_p = NULL_TREE;
+  genericize_cp_loop (&loop, EXPR_LOCATION (stmt), FOR_COND (stmt),
+		      FOR_BODY (stmt), FOR_EXPR (stmt), 1, walk_subtrees, data);
+  append_to_statement_list (loop, &expr);
+  *stmt_p = expr;
 }
 
-/* Gimplify a WHILE_STMT node.  */
+/* Genericize a WHILE_STMT node *STMT_P.  */
 
 static void
-gimplify_while_stmt (tree *stmt_p, gimple_seq *pre_p)
+genericize_while_stmt (tree *stmt_p, int *walk_subtrees, void *data)
 {
   tree stmt = *stmt_p;
-  gimple_seq_add_seq (pre_p,
-		      gimplify_cp_loop (WHILE_COND (stmt), WHILE_BODY (stmt),
-					NULL_TREE, 1));
-  *stmt_p = NULL_TREE;
+  genericize_cp_loop (stmt_p, EXPR_LOCATION (stmt), WHILE_COND (stmt),
+		      WHILE_BODY (stmt), NULL_TREE, 1, walk_subtrees, data);
 }
 
-/* Gimplify a DO_STMT node.  */
+/* Genericize a DO_STMT node *STMT_P.  */
 
 static void
-gimplify_do_stmt (tree *stmt_p, gimple_seq *pre_p)
+genericize_do_stmt (tree *stmt_p, int *walk_subtrees, void *data)
 {
   tree stmt = *stmt_p;
-  gimple_seq_add_seq (pre_p,
-		      gimplify_cp_loop (DO_COND (stmt), DO_BODY (stmt),
-					NULL_TREE, 0));
-  *stmt_p = NULL_TREE;
+  genericize_cp_loop (stmt_p, EXPR_LOCATION (stmt), DO_COND (stmt),
+		      DO_BODY (stmt), NULL_TREE, 0, walk_subtrees, data);
 }
 
-/* Genericize a SWITCH_STMT by turning it into a SWITCH_EXPR.  */
+/* Genericize a SWITCH_STMT node *STMT_P by turning it into a SWITCH_EXPR.  */
 
 static void
-gimplify_switch_stmt (tree *stmt_p, gimple_seq *pre_p)
+genericize_switch_stmt (tree *stmt_p, int *walk_subtrees, void *data)
 {
   tree stmt = *stmt_p;
-  tree break_block, body, t;
-  location_t stmt_locus = input_location;
-  gimple_seq seq = NULL;
+  tree break_block, body, cond, type;
+  location_t stmt_locus = EXPR_LOCATION (stmt);
 
-  break_block = begin_bc_block (bc_break);
+  break_block = begin_bc_block (bc_break, stmt_locus);
 
   body = SWITCH_STMT_BODY (stmt);
   if (!body)
     body = build_empty_stmt (stmt_locus);
+  cond = SWITCH_STMT_COND (stmt);
+  type = SWITCH_STMT_TYPE (stmt);
 
-  t = build3 (SWITCH_EXPR, SWITCH_STMT_TYPE (stmt),
-	      SWITCH_STMT_COND (stmt), body, NULL_TREE);
-  SET_EXPR_LOCATION (t, stmt_locus);
-  gimplify_and_add (t, &seq);
+  cp_walk_tree (&body, cp_genericize_r, data, NULL);
+  cp_walk_tree (&cond, cp_genericize_r, data, NULL);
+  cp_walk_tree (&type, cp_genericize_r, data, NULL);
+  *walk_subtrees = 0;
 
-  seq = finish_bc_block (bc_break, break_block, seq);
-  gimple_seq_add_seq (pre_p, seq);
-  *stmt_p = NULL_TREE;
+  *stmt_p = build3 (SWITCH_EXPR, type, cond, body, NULL_TREE);
+  SET_EXPR_LOCATION (*stmt_p, stmt_locus);
+  finish_bc_block (stmt_p, bc_break, break_block);
+}
+
+/* Genericize a CONTINUE_STMT node *STMT_P.  */
+
+static void
+genericize_continue_stmt (tree *stmt_p)
+{
+  tree stmt_list = NULL;
+  tree pred = build_predict_expr (PRED_CONTINUE, NOT_TAKEN);
+  tree label = get_bc_label (bc_continue);
+  tree jump = build_and_jump (&label);
+  location_t location = EXPR_LOCATION (*stmt_p);
+  append_to_statement_list (pred, &stmt_list);
+  SET_EXPR_LOCATION (jump, location);
+  append_to_statement_list (jump, &stmt_list);
+  *stmt_p = stmt_list;
+}
+
+/* Genericize a BREAK_STMT node *STMT_P.  */
+
+static void
+genericize_break_stmt (tree *stmt_p)
+{
+  tree label = get_bc_label (bc_break);
+  location_t location = EXPR_LOCATION (*stmt_p);
+  *stmt_p = build_and_jump (&label);
+  SET_EXPR_LOCATION (*stmt_p, location);
 }
 
-/* Hook into the middle of gimplifying an OMP_FOR node.  This is required
-   in order to properly gimplify CONTINUE statements.  Here we merely
-   manage the continue stack; the rest of the job is performed by the
-   regular gimplifier.  */
+/* Genericize a OMP_FOR node *STMT_P.  */
+
+static void
+genericize_omp_for_stmt (tree *stmt_p, int *walk_subtrees, void *data)
+{
+  tree stmt = *stmt_p;
+  tree clab, body, clauses, init, cond, incr, pre_body;
+  location_t locus = EXPR_LOCATION (stmt);
+
+  clab = begin_bc_block (bc_continue, locus);
+
+  body = OMP_FOR_BODY (stmt);
+  clauses = OMP_FOR_CLAUSES (stmt);
+  init = OMP_FOR_INIT (stmt);
+  cond = OMP_FOR_COND (stmt);
+  incr = OMP_FOR_INCR (stmt);
+  pre_body = OMP_FOR_PRE_BODY (stmt);
+
+  cp_walk_tree (&body, cp_genericize_r, data, NULL);
+  cp_walk_tree (&clauses, cp_genericize_r, data, NULL);
+  cp_walk_tree (&init, cp_genericize_r, data, NULL);
+  cp_walk_tree (&cond, cp_genericize_r, data, NULL);
+  cp_walk_tree (&incr, cp_genericize_r, data, NULL);
+  cp_walk_tree (&pre_body, cp_genericize_r, data, NULL);
+  *walk_subtrees = 0;
+
+  finish_bc_block (&body, bc_continue, clab);
+
+  stmt = make_node (OMP_FOR);
+
+  TREE_TYPE (stmt) = void_type_node;
+  OMP_FOR_INIT (stmt) = init;
+  OMP_FOR_COND (stmt) = cond;
+  OMP_FOR_INCR (stmt) = incr;
+  OMP_FOR_BODY (stmt) = body;
+  OMP_FOR_PRE_BODY (stmt) = pre_body;
+  OMP_FOR_CLAUSES (stmt) = clauses;
+  SET_EXPR_LOCATION (stmt, locus);
+  *stmt_p = stmt;
+}
+
+/* Hook into the middle of gimplifying an OMP_FOR node.  */
 
 static enum gimplify_status
 cp_gimplify_omp_for (tree *expr_p, gimple_seq *pre_p)
 {
   tree for_stmt = *expr_p;
-  tree cont_block;
-  gimple stmt;
   gimple_seq seq = NULL;
 
   /* Protect ourselves from recursion.  */
@@ -357,18 +426,7 @@  cp_gimplify_omp_for (tree *expr_p, gimpl
     return GS_UNHANDLED;
   OMP_FOR_GIMPLIFYING_P (for_stmt) = 1;
 
-  /* Note that while technically the continue label is enabled too soon
-     here, we should have already diagnosed invalid continues nested within
-     statement expressions within the INIT, COND, or INCR expressions.  */
-  cont_block = begin_bc_block (bc_continue);
-
   gimplify_and_add (for_stmt, &seq);
-  stmt = gimple_seq_last_stmt (seq);
-  if (gimple_code (stmt) == GIMPLE_OMP_FOR)
-    gimple_omp_set_body (stmt, finish_bc_block (bc_continue, cont_block,
-						gimple_omp_body (stmt)));
-  else
-    seq = finish_bc_block (bc_continue, cont_block, seq);
   gimple_seq_add_seq (pre_p, seq);
 
   OMP_FOR_GIMPLIFYING_P (for_stmt) = 0;
@@ -528,6 +586,7 @@  cp_gimplify_expr (tree *expr_p, gimple_s
 				  init, VEC_INIT_EXPR_VALUE_INIT (*expr_p),
 				  from_array,
 				  tf_warning_or_error);
+	cp_genericize_tree (expr_p);
 	ret = GS_OK;
 	input_location = loc;
       }
@@ -634,42 +693,17 @@  cp_gimplify_expr (tree *expr_p, gimple_s
       gcc_unreachable ();
 
     case FOR_STMT:
-      gimplify_for_stmt (expr_p, pre_p);
-      ret = GS_OK;
-      break;
-
     case WHILE_STMT:
-      gimplify_while_stmt (expr_p, pre_p);
-      ret = GS_OK;
-      break;
-
     case DO_STMT:
-      gimplify_do_stmt (expr_p, pre_p);
-      ret = GS_OK;
-      break;
-
     case SWITCH_STMT:
-      gimplify_switch_stmt (expr_p, pre_p);
-      ret = GS_OK;
-      break;
+    case CONTINUE_STMT:
+    case BREAK_STMT:
+      gcc_unreachable ();
 
     case OMP_FOR:
       ret = cp_gimplify_omp_for (expr_p, pre_p);
       break;
 
-    case CONTINUE_STMT:
-      gimple_seq_add_stmt (pre_p, gimple_build_predict (PRED_CONTINUE, NOT_TAKEN));
-      gimple_seq_add_stmt (pre_p, gimple_build_goto (get_bc_label (bc_continue)));
-      *expr_p = NULL_TREE;
-      ret = GS_ALL_DONE;
-      break;
-
-    case BREAK_STMT:
-      gimple_seq_add_stmt (pre_p, gimple_build_goto (get_bc_label (bc_break)));
-      *expr_p = NULL_TREE;
-      ret = GS_ALL_DONE;
-      break;
-
     case EXPR_STMT:
       gimplify_expr_stmt (expr_p);
       ret = GS_OK;
@@ -1102,17 +1136,45 @@  cp_genericize_r (tree *stmt_p, int *walk
     }
   else if (TREE_CODE (stmt) == CONVERT_EXPR)
     gcc_assert (!CONVERT_EXPR_VBASE_PATH (stmt));
+  else if (TREE_CODE (stmt) == FOR_STMT)
+    genericize_for_stmt (stmt_p, walk_subtrees, data);
+  else if (TREE_CODE (stmt) == WHILE_STMT)
+    genericize_while_stmt (stmt_p, walk_subtrees, data);
+  else if (TREE_CODE (stmt) == DO_STMT)
+    genericize_do_stmt (stmt_p, walk_subtrees, data);
+  else if (TREE_CODE (stmt) == SWITCH_STMT)
+    genericize_switch_stmt (stmt_p, walk_subtrees, data);
+  else if (TREE_CODE (stmt) == CONTINUE_STMT)
+    genericize_continue_stmt (stmt_p);
+  else if (TREE_CODE (stmt) == BREAK_STMT)
+    genericize_break_stmt (stmt_p);
+  else if (TREE_CODE (stmt) == OMP_FOR)
+    genericize_omp_for_stmt (stmt_p, walk_subtrees, data);
 
   pointer_set_insert (p_set, *stmt_p);
 
   return NULL;
 }
 
+/* Lower C++ front end trees to GENERIC in T_P.  */
+
+static void
+cp_genericize_tree (tree* t_p)
+{
+  struct cp_genericize_data wtd;
+
+  wtd.p_set = pointer_set_create ();
+  wtd.bind_expr_stack = NULL;
+  wtd.omp_ctx = NULL;
+  cp_walk_tree (t_p, cp_genericize_r, &wtd, NULL);
+  pointer_set_destroy (wtd.p_set);
+  VEC_free (tree, heap, wtd.bind_expr_stack);
+}
+
 void
 cp_genericize (tree fndecl)
 {
   tree t;
-  struct cp_genericize_data wtd;
 
   /* Fix up the types of parms passed by invisible reference.  */
   for (t = DECL_ARGUMENTS (fndecl); t; t = DECL_CHAIN (t))
@@ -1163,12 +1225,7 @@  cp_genericize (tree fndecl)
 
   /* We do want to see every occurrence of the parms, so we can't just use
      walk_tree's hash functionality.  */
-  wtd.p_set = pointer_set_create ();
-  wtd.bind_expr_stack = NULL;
-  wtd.omp_ctx = NULL;
-  cp_walk_tree (&DECL_SAVED_TREE (fndecl), cp_genericize_r, &wtd, NULL);
-  pointer_set_destroy (wtd.p_set);
-  VEC_free (tree, heap, wtd.bind_expr_stack);
+  cp_genericize_tree (&DECL_SAVED_TREE (fndecl));
 
   /* Do everything else.  */
   c_genericize (fndecl);
Index: gcc/testsuite/g++.dg/pr51264-4.C
===================================================================
--- /dev/null (new file)
+++ gcc/testsuite/g++.dg/pr51264-4.C (revision 0)
@@ -0,0 +1,30 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O0 -Werror -Wreturn-type" } */
+
+/* Test-case from http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25973#c4.  */
+
+struct Block
+{
+  public:
+  Block ();
+  ~Block ();
+};
+
+bool func (bool bar)
+{
+  Block block;
+  bool foo = false;
+
+  if (!foo || bar)
+    do
+      {
+	return true;
+      }
+    while (0);
+  else
+    do
+      {
+	return false;
+      }
+    while (0);
+}