Patchwork [Ada] Fix bogus noreturn warning

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Submitter Eric Botcazou
Date June 27, 2010, 8:43 a.m.
Message ID <201006271043.21089.ebotcazou@adacore.com>
Download mbox | patch
Permalink /patch/57085/
State New
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Comments

Eric Botcazou - June 27, 2010, 8:43 a.m.
More precisely:

/home/eric/svn/gcc/gcc/testsuite/gnat.dg/noreturn3.adb: In 
function 'Noreturn3.Raise_Error':
/home/eric/svn/gcc/gcc/testsuite/gnat.dg/noreturn3.adb:25:6: 
warning: 'noreturn' function does return [enabled by default]

Fix shamelessly borrowed from the C front-end, tested on i586-suse-linux and 
applied on the mainline.


2010-06-27  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/trans.c: Include tree-flow.h.
	(gnu_switch_label_stack): Delete.
	(Case_Statement_to_gnu): Do not emit the goto at the end of a case if
	its associated block cannot fall through.  Do not emit the final label
	if no cases branche to it.
	* gcc-interface/Make-lang.in (ada/trans.o): Add $(TREE_FLOW_H).


2010-06-27  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/noreturn3.ad[sb]: New test.
Steven Bosscher - June 27, 2010, 12:41 p.m.
On Sun, Jun 27, 2010 at 10:43 AM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>
>        * gcc-interface/trans.c: Include tree-flow.h.

What is this necessary for? No front end should have to know
*anything* about tree-flow.h.

Ciao!
Steven
Eric Botcazou - June 27, 2010, 12:45 p.m.
> What is this necessary for? No front end should have to know
> *anything* about tree-flow.h.

block_may_fallthru is declared there.  See c-typeck.c, cp/decl.c and cp/tree.c 
for pre-existing counter-examples.

Patch

Index: gcc-interface/Make-lang.in
===================================================================
--- gcc-interface/Make-lang.in	(revision 161455)
+++ gcc-interface/Make-lang.in	(working copy)
@@ -1260,7 +1260,7 @@  ada/targtyps.o : ada/gcc-interface/targt
 	$(COMPILER) -c $(ALL_COMPILERFLAGS) -I.. $(ALL_CPPFLAGS) $< -o $@
 
 ada/trans.o : ada/gcc-interface/trans.c $(CONFIG_H) $(SYSTEM_H) coretypes.h \
-   $(TM_H) $(TREE_H) $(FLAGS_H) output.h tree-iterator.h \
+   $(TM_H) $(TREE_H) $(FLAGS_H) output.h tree-iterator.h $(TREE_FLOW_H) \
    $(GIMPLE_H) ada/gcc-interface/ada.h ada/adadecode.h ada/types.h \
    ada/atree.h ada/elists.h ada/namet.h ada/nlists.h ada/snames.h \
    ada/stringt.h ada/uintp.h ada/urealp.h ada/fe.h ada/sinfo.h ada/einfo.h \
Index: gcc-interface/trans.c
===================================================================
--- gcc-interface/trans.c	(revision 161455)
+++ gcc-interface/trans.c	(working copy)
@@ -33,6 +33,7 @@ 
 #include "output.h"
 #include "libfuncs.h"	/* For set_stack_check_libfunc.  */
 #include "tree-iterator.h"
+#include "tree-flow.h"
 #include "gimple.h"
 
 #include "ada.h"
@@ -168,9 +169,6 @@  static GTY(()) VEC(tree,gc) *gnu_return_
 /* Stack of LOOP_STMT nodes.  */
 static GTY(()) VEC(tree,gc) *gnu_loop_label_stack;
 
-/* Stack of labels for switch statements.  */
-static GTY(()) VEC(tree,gc) *gnu_switch_label_stack;
-
 /* The stacks for N_{Push,Pop}_*_Label.  */
 static GTY(()) VEC(tree,gc) *gnu_constraint_error_label_stack;
 static GTY(()) VEC(tree,gc) *gnu_storage_error_label_stack;
@@ -1908,9 +1906,9 @@  Attribute_to_gnu (Node_Id gnat_node, tre
 static tree
 Case_Statement_to_gnu (Node_Id gnat_node)
 {
-  tree gnu_result;
-  tree gnu_expr;
+  tree gnu_result, gnu_expr, gnu_label;
   Node_Id gnat_when;
+  bool may_fallthru = false;
 
   gnu_expr = gnat_to_gnu (Expression (gnat_node));
   gnu_expr = convert (get_base_type (TREE_TYPE (gnu_expr)), gnu_expr);
@@ -1933,8 +1931,7 @@  Case_Statement_to_gnu (Node_Id gnat_node
 
   /* We build a SWITCH_EXPR that contains the code with interspersed
      CASE_LABEL_EXPRs for each label.  */
-  VEC_safe_push (tree, gc, gnu_switch_label_stack,
-		 create_artificial_label (input_location));
+  gnu_label = create_artificial_label (input_location);
   start_stmt_group ();
 
   for (gnat_when = First_Non_Pragma (Alternatives (gnat_node));
@@ -2014,18 +2011,22 @@  Case_Statement_to_gnu (Node_Id gnat_node
 	 containing the Case statement.  */
       if (choices_added_p)
 	{
-	  add_stmt (build_stmt_group (Statements (gnat_when), true));
-	  add_stmt (build1 (GOTO_EXPR, void_type_node,
-			    VEC_last (tree, gnu_switch_label_stack)));
+	  tree group = build_stmt_group (Statements (gnat_when), true);
+	  bool group_may_fallthru = block_may_fallthru (group);
+	  add_stmt (group);
+	  if (group_may_fallthru)
+	    {
+	      add_stmt (build1 (GOTO_EXPR, void_type_node, gnu_label));
+	      may_fallthru = true;
+	    }
 	}
     }
 
-  /* Now emit a definition of the label all the cases branched to.  */
-  add_stmt (build1 (LABEL_EXPR, void_type_node,
-		    VEC_last (tree, gnu_switch_label_stack)));
+  /* Now emit a definition of the label the cases branche to, if any.  */
+  if (may_fallthru)
+    add_stmt (build1 (LABEL_EXPR, void_type_node, gnu_label));
   gnu_result = build3 (SWITCH_EXPR, TREE_TYPE (gnu_expr), gnu_expr,
 		       end_stmt_group (), NULL_TREE);
-  VEC_pop (tree, gnu_switch_label_stack);
 
   return gnu_result;
 }