jit: implement gcc_jit_rvalue_set_bool_require_tail_call

This implements the libgccjit support for must-tail-call via
a new:
  gcc_jit_rvalue_set_bool_require_tail_call
API entrypoint.

(I didn't implement a wrapper for this within the C++ bindings)

gcc/jit/ChangeLog:
	* docs/topics/compatibility.rst: Add LIBGCCJIT_ABI_6.
	* docs/topics/expressions.rst (Function calls): Add documentation
	of gcc_jit_rvalue_set_bool_require_tail_call.
	* docs/_build/texinfo/libgccjit.texi: Regenerate.
	* jit-common.h (gcc::jit::recording::base_call): Add forward decl.
	* jit-playback.c: Within namespace gcc::jit::playback...
	(context::build_call) Add "require_tail_call" param and use it
	to set CALL_EXPR_MUST_TAIL_CALL.
	(context::new_call): Add "require_tail_call" param.
	(context::new_call_through_ptr): Likewise.
	* jit-playback.h: Within namespace gcc::jit::playback...
	(context::new_call: Add "require_tail_call" param.
	(context::new_call_through_ptr): Likewise.
	(context::build_call): Likewise.
	* jit-recording.c: Within namespace gcc::jit::recording...
	(base_call::base_call): New constructor.
	(base_call::write_reproducer_tail_call): New method.
	(call::call): Update for inheritance from base_call.
	(call::replay_into): Provide m_require_tail_call to call
	to new_call.
	(call::write_reproducer): Call write_reproducer_tail_call.
	(call_through_ptr::call_through_ptr): Update for inheritance from
	base_call.
	(call_through_ptr::replay_into): Provide m_require_tail_call to call
	to new_call_through_ptr.
	(recording::call_through_ptr::write_reproducer): Call
	write_reproducer_tail_call.
	* jit-recording.h: Within namespace gcc::jit::recording...
	(rvalue::dyn_cast_base_call): New virtual function.
	(class base_call): New subclass of class rvalue.
	(class call): Inherit from base_call rather than directly from
	rvalue, moving get_precedence and m_args to base_call.
	(class call_through_ptr): Likewise.
	* libgccjit.c (gcc_jit_rvalue_set_bool_require_tail_call): New
	function.
	* libgccjit.h
	(LIBGCCJIT_HAVE_gcc_jit_rvalue_set_bool_require_tail_call): New
	macro.
	(gcc_jit_rvalue_set_bool_require_tail_call): New function.
	* libgccjit.map (LIBGCCJIT_ABI_6): New.
	(gcc_jit_rvalue_set_bool_require_tail_call): Add.

gcc/testsuite/ChangeLog:
	* jit.dg/all-non-failing-tests.h: Add
	test-factorial-must-tail-call.c.
	* jit.dg/test-error-impossible-must-tail-call.c: New test case.
	* jit.dg/test-factorial-must-tail-call.c: New test case.

From-SVN: r236531

11 files changed, 214 insertions, 38 deletions

diff --git a/gcc/jit/ChangeLog b/gcc/jit/ChangeLog
index f9320ec..1c3e1fc 100644
--- a/gcc/jit/ChangeLog
+++ b/gcc/jit/ChangeLog
@@ -1,3 +1,47 @@
+2016-05-20  David Malcolm  <dmalcolm@redhat.com>
+
+	* docs/topics/compatibility.rst: Add LIBGCCJIT_ABI_6.
+	* docs/topics/expressions.rst (Function calls): Add documentation
+	of gcc_jit_rvalue_set_bool_require_tail_call.
+	* docs/_build/texinfo/libgccjit.texi: Regenerate.
+	* jit-common.h (gcc::jit::recording::base_call): Add forward decl.
+	* jit-playback.c: Within namespace gcc::jit::playback...
+	(context::build_call) Add "require_tail_call" param and use it
+	to set CALL_EXPR_MUST_TAIL_CALL.
+	(context::new_call): Add "require_tail_call" param.
+	(context::new_call_through_ptr): Likewise.
+	* jit-playback.h: Within namespace gcc::jit::playback...
+	(context::new_call: Add "require_tail_call" param.
+	(context::new_call_through_ptr): Likewise.
+	(context::build_call): Likewise.
+	* jit-recording.c: Within namespace gcc::jit::recording...
+	(base_call::base_call): New constructor.
+	(base_call::write_reproducer_tail_call): New method.
+	(call::call): Update for inheritance from base_call.
+	(call::replay_into): Provide m_require_tail_call to call
+	to new_call.
+	(call::write_reproducer): Call write_reproducer_tail_call.
+	(call_through_ptr::call_through_ptr): Update for inheritance from
+	base_call.
+	(call_through_ptr::replay_into): Provide m_require_tail_call to call
+	to new_call_through_ptr.
+	(recording::call_through_ptr::write_reproducer): Call
+	write_reproducer_tail_call.
+	* jit-recording.h: Within namespace gcc::jit::recording...
+	(rvalue::dyn_cast_base_call): New virtual function.
+	(class base_call): New subclass of class rvalue.
+	(class call): Inherit from base_call rather than directly from
+	rvalue, moving get_precedence and m_args to base_call.
+	(class call_through_ptr): Likewise.
+	* libgccjit.c (gcc_jit_rvalue_set_bool_require_tail_call): New
+	function.
+	* libgccjit.h
+	(LIBGCCJIT_HAVE_gcc_jit_rvalue_set_bool_require_tail_call): New
+	macro.
+	(gcc_jit_rvalue_set_bool_require_tail_call): New function.
+	* libgccjit.map (LIBGCCJIT_ABI_6): New.
+	(gcc_jit_rvalue_set_bool_require_tail_call): Add.
+
 2016-05-17  David Malcolm  <dmalcolm@redhat.com>
 
 	* dummy-frontend.c: Include diagnostic.h.
diff --git a/gcc/jit/docs/topics/compatibility.rst b/gcc/jit/docs/topics/compatibility.rst
index d9eacf2..7abd050 100644
--- a/gcc/jit/docs/topics/compatibility.rst
+++ b/gcc/jit/docs/topics/compatibility.rst
@@ -135,3 +135,10 @@ entrypoints:
 -------------------
 ``LIBGCCJIT_ABI_5`` covers the addition of
 :func:`gcc_jit_context_set_bool_use_external_driver`
+
+.. _LIBGCCJIT_ABI_6:
+
+``LIBGCCJIT_ABI_6``
+-------------------
+``LIBGCCJIT_ABI_6`` covers the addition of
+:func:`gcc_jit_rvalue_set_bool_require_tail_call`
diff --git a/gcc/jit/docs/topics/expressions.rst b/gcc/jit/docs/topics/expressions.rst
index 0445332..261483c 100644
--- a/gcc/jit/docs/topics/expressions.rst
+++ b/gcc/jit/docs/topics/expressions.rst
@@ -424,6 +424,30 @@ Function calls
 
       The same caveat as for :c:func:`gcc_jit_context_new_call` applies.
 
+.. function:: void\
+              gcc_jit_rvalue_set_bool_require_tail_call (gcc_jit_rvalue *call,\
+                                                         int require_tail_call)
+
+   Given an :c:type:`gcc_jit_rvalue *` for a call created through
+   :c:func:`gcc_jit_context_new_call` or
+   :c:func:`gcc_jit_context_new_call_through_ptr`, mark/clear the
+   call as needing tail-call optimization.  The optimizer will
+   attempt to optimize the call into a jump instruction; if it is
+   unable to do do, an error will be emitted.
+
+   This may be useful when implementing functions that use the
+   continuation-passing style (e.g. for functional programming
+   languages), in which every function "returns" by calling a
+   "continuation" function pointer.  This call must be
+   guaranteed to be implemented as a jump, otherwise the program
+   could consume an arbitrary amount of stack space as it executed.
+
+   This entrypoint was added in :ref:`LIBGCCJIT_ABI_6`; you can test for
+   its presence using
+
+   .. code-block:: c
+
+      #ifdef LIBGCCJIT_HAVE_gcc_jit_rvalue_set_bool_require_tail_call
 
 Type-coercion
 *************
diff --git a/gcc/jit/jit-common.h b/gcc/jit/jit-common.h
index 8a6cd74..b48ea0d 100644
--- a/gcc/jit/jit-common.h
+++ b/gcc/jit/jit-common.h
@@ -126,6 +126,7 @@ namespace recording {
         class local;
 	class global;
         class param;
+      class base_call;
     class statement;
     class case_;
 
diff --git a/gcc/jit/jit-playback.c b/gcc/jit/jit-playback.c
index 156448d..c9f4084 100644
--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -854,7 +854,8 @@ playback::rvalue *
 playback::context::
 build_call (location *loc,
 	    tree fn_ptr,
-	    const auto_vec<rvalue *> *args)
+	    const auto_vec<rvalue *> *args,
+	    bool require_tail_call)
 {
   vec<tree, va_gc> *tree_args;
   vec_alloc (tree_args, args->length ());
@@ -868,9 +869,13 @@ build_call (location *loc,
   tree fn_type = TREE_TYPE (fn);
   tree return_type = TREE_TYPE (fn_type);
 
-  return new rvalue (this,
-		     build_call_vec (return_type,
-				     fn_ptr, tree_args));
+  tree call = build_call_vec (return_type,
+			      fn_ptr, tree_args);
+
+  if (require_tail_call)
+    CALL_EXPR_MUST_TAIL_CALL (call) = 1;
+
+  return new rvalue (this, call);
 
   /* see c-typeck.c: build_function_call
      which calls build_function_call_vec
@@ -890,7 +895,8 @@ playback::rvalue *
 playback::context::
 new_call (location *loc,
 	  function *func,
-	  const auto_vec<rvalue *> *args)
+	  const auto_vec<rvalue *> *args,
+	  bool require_tail_call)
 {
   tree fndecl;
 
@@ -902,7 +908,7 @@ new_call (location *loc,
 
   tree fn = build1 (ADDR_EXPR, build_pointer_type (fntype), fndecl);
 
-  return build_call (loc, fn, args);
+  return build_call (loc, fn, args, require_tail_call);
 }
 
 /* Construct a playback::rvalue instance (wrapping a tree) for a
@@ -912,12 +918,13 @@ playback::rvalue *
 playback::context::
 new_call_through_ptr (location *loc,
 		      rvalue *fn_ptr,
-		      const auto_vec<rvalue *> *args)
+		      const auto_vec<rvalue *> *args,
+		      bool require_tail_call)
 {
   gcc_assert (fn_ptr);
   tree t_fn_ptr = fn_ptr->as_tree ();
 
-  return build_call (loc, t_fn_ptr, args);
+  return build_call (loc, t_fn_ptr, args, require_tail_call);
 }
 
 /* Construct a tree for a cast.  */
diff --git a/gcc/jit/jit-playback.h b/gcc/jit/jit-playback.h
index 8f7a43d..c00c258 100644
--- a/gcc/jit/jit-playback.h
+++ b/gcc/jit/jit-playback.h
@@ -133,12 +133,14 @@ public:
   rvalue *
   new_call (location *loc,
 	    function *func,
-	    const auto_vec<rvalue *> *args);
+	    const auto_vec<rvalue *> *args,
+	    bool require_tail_call);
 
   rvalue *
   new_call_through_ptr (location *loc,
 			rvalue *fn_ptr,
-			const auto_vec<rvalue *> *args);
+			const auto_vec<rvalue *> *args,
+			bool require_tail_call);
 
   rvalue *
   new_cast (location *loc,
@@ -236,7 +238,8 @@ private:
   rvalue *
   build_call (location *loc,
 	      tree fn_ptr,
-	      const auto_vec<rvalue *> *args);
+	      const auto_vec<rvalue *> *args,
+	      bool require_tail_call);
 
   tree
   build_cast (location *loc,
diff --git a/gcc/jit/jit-recording.c b/gcc/jit/jit-recording.c
index 8f5f914..9376342 100644
--- a/gcc/jit/jit-recording.c
+++ b/gcc/jit/jit-recording.c
@@ -4681,6 +4681,39 @@ recording::cast::write_reproducer (reproducer &r)
 	   r.get_identifier_as_type (get_type ()));
 }
 
+/* The implementation of class gcc::jit::recording::base_call.  */
+
+/* The constructor for gcc::jit::recording::base_call.  */
+
+recording::base_call::base_call (context *ctxt,
+				 location *loc,
+				 type *type_,
+				 int numargs,
+				 rvalue **args)
+: rvalue (ctxt, loc, type_),
+  m_args (),
+  m_require_tail_call (0)
+{
+  for (int i = 0; i< numargs; i++)
+    m_args.safe_push (args[i]);
+}
+
+/* Subroutine for use by call and call_though_ptr's write_reproducer
+   methods.  */
+
+void
+recording::base_call::write_reproducer_tail_call (reproducer &r,
+						  const char *id)
+{
+  if (m_require_tail_call)
+    {
+      r.write ("  gcc_jit_rvalue_set_bool_require_tail_call (%s,  /* gcc_jit_rvalue *call*/\n"
+	       "                                             %i); /* int require_tail_call*/\n",
+	       id,
+	       1);
+    }
+}
+
 /* The implementation of class gcc::jit::recording::call.  */
 
 /* The constructor for gcc::jit::recording::call.  */
@@ -4690,12 +4723,9 @@ recording::call::call (recording::context *ctxt,
 		       recording::function *func,
 		       int numargs,
 		       rvalue **args)
-: rvalue (ctxt, loc, func->get_return_type ()),
-  m_func (func),
-  m_args ()
+: base_call (ctxt, loc, func->get_return_type (), numargs, args),
+  m_func (func)
 {
-  for (int i = 0; i< numargs; i++)
-    m_args.safe_push (args[i]);
 }
 
 /* Implementation of pure virtual hook recording::memento::replay_into
@@ -4711,7 +4741,8 @@ recording::call::replay_into (replayer *r)
 
   set_playback_obj (r->new_call (playback_location (r, m_loc),
 				 m_func->playback_function (),
-				 &playback_args));
+				 &playback_args,
+				 m_require_tail_call));
 }
 
 /* Implementation of pure virtual hook recording::rvalue::visit_children
@@ -4790,6 +4821,7 @@ recording::call::write_reproducer (reproducer &r)
 	   r.get_identifier (m_func),
 	   m_args.length (),
 	   args_id);
+  write_reproducer_tail_call (r, id);
 }
 
 /* The implementation of class gcc::jit::recording::call_through_ptr.  */
@@ -4801,14 +4833,12 @@ recording::call_through_ptr::call_through_ptr (recording::context *ctxt,
 					       recording::rvalue *fn_ptr,
 					       int numargs,
 					       rvalue **args)
-: rvalue (ctxt, loc,
-	  fn_ptr->get_type ()->dereference ()
-	    ->as_a_function_type ()->get_return_type ()),
-  m_fn_ptr (fn_ptr),
-  m_args ()
+: base_call (ctxt, loc,
+	     fn_ptr->get_type ()->dereference ()
+	       ->as_a_function_type ()->get_return_type (),
+	     numargs, args),
+  m_fn_ptr (fn_ptr)
 {
-  for (int i = 0; i< numargs; i++)
-    m_args.safe_push (args[i]);
 }
 
 /* Implementation of pure virtual hook recording::memento::replay_into
@@ -4824,7 +4854,8 @@ recording::call_through_ptr::replay_into (replayer *r)
 
   set_playback_obj (r->new_call_through_ptr (playback_location (r, m_loc),
 					     m_fn_ptr->playback_rvalue (),
-					     &playback_args));
+					     &playback_args,
+					     m_require_tail_call));
 }
 
 /* Implementation of pure virtual hook recording::rvalue::visit_children
@@ -4907,6 +4938,7 @@ recording::call_through_ptr::write_reproducer (reproducer &r)
 	   r.get_identifier_as_rvalue (m_fn_ptr),
 	   m_args.length (),
 	   args_id);
+  write_reproducer_tail_call (r, id);
 }
 
 /* The implementation of class gcc::jit::recording::array_access.  */
diff --git a/gcc/jit/jit-recording.h b/gcc/jit/jit-recording.h
index 1c3e763..0e3511c 100644
--- a/gcc/jit/jit-recording.h
+++ b/gcc/jit/jit-recording.h
@@ -960,8 +960,9 @@ public:
   void set_scope (function *scope);
   function *get_scope () const { return m_scope; }
 
-  /* Dynamic cast.  */
+  /* Dynamic casts.  */
   virtual param *dyn_cast_param () { return NULL; }
+  virtual base_call *dyn_cast_base_call () { return NULL; }
 
   virtual const char *access_as_rvalue (reproducer &r);
 
@@ -1418,7 +1419,36 @@ private:
   rvalue *m_rvalue;
 };
 
-class call : public rvalue
+class base_call : public rvalue
+{
+ public:
+  base_call (context *ctxt,
+	     location *loc,
+	     type *type_,
+	     int numargs,
+	     rvalue **args);
+
+  enum precedence get_precedence () const FINAL OVERRIDE
+  {
+    return PRECEDENCE_POSTFIX;
+  }
+
+  base_call *dyn_cast_base_call () FINAL OVERRIDE { return this; }
+
+  void set_require_tail_call (bool require_tail_call)
+  {
+    m_require_tail_call = require_tail_call;
+  }
+
+ protected:
+  void write_reproducer_tail_call (reproducer &r, const char *id);
+
+ protected:
+  auto_vec<rvalue *> m_args;
+  bool m_require_tail_call;
+};
+
+class call : public base_call
 {
 public:
   call (context *ctxt,
@@ -1434,17 +1464,12 @@ public:
 private:
   string * make_debug_string () FINAL OVERRIDE;
   void write_reproducer (reproducer &r) FINAL OVERRIDE;
-  enum precedence get_precedence () const FINAL OVERRIDE
-  {
-    return PRECEDENCE_POSTFIX;
-  }
 
 private:
   function *m_func;
-  auto_vec<rvalue *> m_args;
 };
 
-class call_through_ptr : public rvalue
+class call_through_ptr : public base_call
 {
 public:
   call_through_ptr (context *ctxt,
@@ -1460,14 +1485,9 @@ public:
 private:
   string * make_debug_string () FINAL OVERRIDE;
   void write_reproducer (reproducer &r) FINAL OVERRIDE;
-  enum precedence get_precedence () const FINAL OVERRIDE
-  {
-    return PRECEDENCE_POSTFIX;
-  }
 
 private:
   rvalue *m_fn_ptr;
-  auto_vec<rvalue *> m_args;
 };
 
 class array_access : public lvalue
diff --git a/gcc/jit/libgccjit.c b/gcc/jit/libgccjit.c
index 02ff50c..c2c6aeb 100644
--- a/gcc/jit/libgccjit.c
+++ b/gcc/jit/libgccjit.c
@@ -2950,3 +2950,23 @@ gcc_jit_timer_print (gcc_jit_timer *timer,
   timer->start (TV_TOTAL);
   timer->push (TV_JIT_CLIENT_CODE);
 }
+
+/* Public entrypoint.  See description in libgccjit.h.
+
+   After error-checking, the real work is effectively done by the
+   gcc::jit::base_call::set_require_tail_call setter in jit-recording.h.  */
+
+void
+gcc_jit_rvalue_set_bool_require_tail_call (gcc_jit_rvalue *rvalue,
+					   int require_tail_call)
+{
+  RETURN_IF_FAIL (rvalue, NULL, NULL, "NULL call");
+  JIT_LOG_FUNC (rvalue->get_context ()->get_logger ());
+
+  /* Verify that it's a call.  */
+  gcc::jit::recording::base_call *call = rvalue->dyn_cast_base_call ();
+  RETURN_IF_FAIL_PRINTF1 (call, NULL, NULL, "not a call: %s",
+			  rvalue->get_debug_string ());
+
+  call->set_require_tail_call (require_tail_call);
+}
diff --git a/gcc/jit/libgccjit.h b/gcc/jit/libgccjit.h
index a8b9f55..175cc16c 100644
--- a/gcc/jit/libgccjit.h
+++ b/gcc/jit/libgccjit.h
@@ -1374,6 +1374,19 @@ extern void
 gcc_jit_timer_print (gcc_jit_timer *timer,
 		     FILE *f_out);
 
+
+#define LIBGCCJIT_HAVE_gcc_jit_rvalue_set_bool_require_tail_call
+
+/* Mark/clear a call as needing tail-call optimization.
+
+   This API entrypoint was added in LIBGCCJIT_ABI_6; you can test for its
+   presence using
+     #ifdef LIBGCCJIT_HAVE_gcc_jit_rvalue_set_bool_require_tail_call
+*/
+extern void
+gcc_jit_rvalue_set_bool_require_tail_call (gcc_jit_rvalue *call,
+					   int require_tail_call);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/gcc/jit/libgccjit.map b/gcc/jit/libgccjit.map
index 65f3166..545b192 100644
--- a/gcc/jit/libgccjit.map
+++ b/gcc/jit/libgccjit.map
@@ -145,3 +145,8 @@ LIBGCCJIT_ABI_5 {
   global:
     gcc_jit_context_set_bool_use_external_driver;
 } LIBGCCJIT_ABI_4;
+
+LIBGCCJIT_ABI_6 {
+  global:
+    gcc_jit_rvalue_set_bool_require_tail_call;
+} LIBGCCJIT_ABI_5;