starpu-max/gcc-plugin/src/starpu.c

/* GCC-StarPU
   Copyright (C) 2011, 2012 INRIA

   GCC-StarPU is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   GCC-StarPU is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GCC-StarPU.  If not, see <http://www.gnu.org/licenses/>.  */

/* Use extensions of the GNU C Library.  */
#define _GNU_SOURCE 1

#include <starpu-gcc/config.h>
/* We must include starpu.h here, otherwise gcc will complain about a poisoned
   malloc in xmmintrin.h. */
#include <starpu.h>  /* for `STARPU_CPU' & co.  */

/* #define ENABLE_TREE_CHECKING 1 */

#include <gcc-plugin.h>
#include <plugin-version.h>

#include <plugin.h>
#include <cpplib.h>
#include <tree.h>
#include <tree-iterator.h>
#include <flags.h>				  /* for `optimize' */

#ifdef HAVE_C_FAMILY_C_COMMON_H
# include <c-family/c-common.h>
#elif HAVE_C_COMMON_H
# include <c-common.h>
#endif

#ifdef HAVE_C_FAMILY_C_PRAGMA_H
# include <c-family/c-pragma.h>
#elif HAVE_C_PRAGMA_H
# include <c-pragma.h>
#endif

#include <tm.h>
#include <tree-pass.h>
#include <tree-flow.h>
#include <cgraph.h>
#include <gimple.h>
#include <toplev.h>

#include <stdio.h>

#include <starpu-gcc/utils.h>
#include <starpu-gcc/tasks.h>
#include <starpu-gcc/warn-unregistered.h>
#include <starpu-gcc/opencl.h>

/* Don't include the dreaded proprietary headers that we don't need anyway.
   In particular, this waives the obligation to reproduce their silly
   disclaimer.  */
#define STARPU_DONT_INCLUDE_CUDA_HEADERS


#ifndef STRINGIFY
# define STRINGIFY_(x) # x
# define STRINGIFY(x)  STRINGIFY_ (x)
#endif


#ifdef __cplusplus
extern "C" {
#endif

/* Declared with `C' linkage in <gcc-plugin.h>.  */
int plugin_is_GPL_compatible;

/* The name of this plug-in.  */
static const char plugin_name[] = "starpu";

/* Names of public attributes.  */
static const char heap_allocated_attribute_name[] = "heap_allocated";
static const char registered_attribute_name[] = "registered";

/* Names of attributes used internally.  */
static const char heap_allocated_orig_type_attribute_name[] =
  ".heap_allocated_original_type";

/* Cached function declarations.  */
static tree unpack_fn;

/* Targets supported by GCC-StarPU.  */
static int supported_targets = 0
#ifdef STARPU_USE_CPU
    | STARPU_CPU
#endif
#ifdef STARPU_USE_CUDA
    | STARPU_CUDA
#endif
#ifdef STARPU_USE_OPENCL
    | STARPU_OPENCL
#endif
    ;


/* Forward declarations.  */

static tree build_cpu_codelet_identifier (const_tree task);

static bool implicit_cpu_task_implementation_p (const_tree fn);


static bool heap_allocated_p (const_tree var_decl);
static bool registered_p (const_tree var_decl);

/* Compile-time assertions.  */

#if STARPU_GNUC_PREREQ (4, 6)
# define verify(cond, msg) _Static_assert ((cond), msg)
#else
# define verify(cond, msg) assert (cond);
#endif


/* Helpers.  */


/* Return POINTER plus OFFSET, where OFFSET is in bytes.  */

static tree
pointer_plus (tree pointer, size_t offset)
{
  gcc_assert (POINTER_TYPE_P (TREE_TYPE (pointer)));

  if (offset == 0)
    return pointer;
  else
    return build_binary_op (UNKNOWN_LOCATION, PLUS_EXPR,
			    pointer,
			    build_int_cstu (integer_type_node, offset),
			    false);
}

/* Build a reference to the INDEXth element of ARRAY.  `build_array_ref' is
   not exported, so we roll our own.
   FIXME: This version may not work for array types and doesn't do as much
   type-checking as `build_array_ref'.  */

static tree
array_ref (tree array, size_t index)
{
  gcc_assert (POINTER_TYPE_P (TREE_TYPE (array)));

  return build_indirect_ref (UNKNOWN_LOCATION,
			     pointer_plus (array, index),
			     RO_ARRAY_INDEXING);
}

/* Return the number of elements of ARRAY_TYPE, or NULL_TREE if ARRAY_TYPE is
   an incomplete type.  */

static tree
array_type_element_count (location_t loc, const_tree array_type)
{
  gcc_assert (TREE_CODE (array_type) == ARRAY_TYPE);

  tree count, domain = TYPE_DOMAIN (array_type);

  if (domain != NULL_TREE)
    {
      count = build_binary_op (loc, MINUS_EXPR,
			       TYPE_MAX_VALUE (domain),
			       TYPE_MIN_VALUE (domain),
			       false);
      count = build_binary_op (loc, PLUS_EXPR,
			       count,
			       build_int_cstu (integer_type_node, 1),
			       false);
      count = fold_convert (size_type_node, count);
    }
  else
    count = NULL_TREE;

  return count;
}


/* Debugging helpers.  */

static tree build_printf (const char *, ...)
  __attribute__ ((format (printf, 1, 2)));

static tree
build_printf (const char *fmt, ...)
{
  tree call;
  char *str;
  va_list args;

  va_start (args, fmt);
  vasprintf (&str, fmt, args);
  call = build_call_expr (builtin_decl_explicit (BUILT_IN_PUTS), 1,
	 		  build_string_literal (strlen (str) + 1, str));
  free (str);
  va_end (args);

  return call;
}

static tree
build_hello_world (void)
{
  return build_printf ("Hello, StarPU!");
}


/* Pragmas.  */

#define STARPU_PRAGMA_NAME_SPACE "starpu"

static void
handle_pragma_hello (struct cpp_reader *reader)
{
  add_stmt (build_hello_world ());
}

/* Process `#pragma starpu initialize'.
   TODO: Parse and initialize some of the fields of `starpu_conf'.  */

static void
handle_pragma_initialize (struct cpp_reader *reader)
{
  static tree init_fn;
  LOOKUP_STARPU_FUNCTION (init_fn, "starpu_init");

  location_t loc = cpp_peek_token (reader, 0)->src_loc;

  /* Call `starpu_init (NULL)'.  */
  tree init = build_call_expr (init_fn, 1, build_zero_cst (ptr_type_node));

  /* Introduce a local variable to hold the error code.  */

  tree error_var = build_decl (loc, VAR_DECL,
  			       create_tmp_var_name (".initialize_error"),
  			       integer_type_node);
  DECL_CONTEXT (error_var) = current_function_decl;
  DECL_ARTIFICIAL (error_var) = true;

  tree assignment = build2 (INIT_EXPR, TREE_TYPE (error_var),
			    error_var, init);

  tree cond = build3 (COND_EXPR, void_type_node,
		      build2 (NE_EXPR, boolean_type_node,
			      error_var, integer_zero_node),
		      build_error_statements (loc, error_var,
					      build_starpu_error_string,
					      "failed to initialize StarPU"),
		      NULL_TREE);

  tree stmts = NULL_TREE;
  append_to_statement_list (assignment, &stmts);
  append_to_statement_list (cond, &stmts);

  tree bind = build3 (BIND_EXPR, void_type_node, error_var, stmts,
  		      NULL_TREE);

  add_stmt (bind);
}

/* Process `#pragma starpu shutdown'.  */

static void
handle_pragma_shutdown (struct cpp_reader *reader)
{
  static tree shutdown_fn;
  LOOKUP_STARPU_FUNCTION (shutdown_fn, "starpu_shutdown");

  tree token;
  if (pragma_lex (&token) != CPP_EOF)
    error_at (cpp_peek_token (reader, 0)->src_loc,
	      "junk after %<starpu shutdown%> pragma");
  else
    /* Call `starpu_shutdown ()'.  */
    add_stmt (build_call_expr (shutdown_fn, 0));
}

static void
handle_pragma_wait (struct cpp_reader *reader)
{
  if (task_implementation_p (current_function_decl))
    {
      location_t loc;

      loc = cpp_peek_token (reader, 0)->src_loc;

      /* TODO: In the future we could generate a task for the continuation
	 and have it depend on what's before here.  */
      error_at (loc, "task implementation is not allowed to wait");
    }
  else
    {
      tree fndecl;

      fndecl = lookup_name (get_identifier ("starpu_task_wait_for_all"));
      gcc_assert (TREE_CODE (fndecl) == FUNCTION_DECL);

      add_stmt (build_call_expr (fndecl, 0));
    }
}

/* Build a `starpu_vector_data_register' call for the COUNT elements pointed
   to by POINTER.  */

static tree
build_data_register_call (location_t loc, tree pointer, tree count)
{
  tree pointer_type = TREE_TYPE (pointer);

  gcc_assert ((TREE_CODE (pointer_type)  == ARRAY_TYPE
	       && TYPE_DOMAIN (pointer_type) != NULL_TREE)
	      || POINTER_TYPE_P (pointer_type));
  gcc_assert (INTEGRAL_TYPE_P (TREE_TYPE (count)));

  static tree register_fn;
  LOOKUP_STARPU_FUNCTION (register_fn, "starpu_vector_data_register");

  /* Introduce a local variable to hold the handle.  */

  tree handle_var = build_decl (loc, VAR_DECL, create_tmp_var_name (".handle"),
				ptr_type_node);
  DECL_CONTEXT (handle_var) = current_function_decl;
  DECL_ARTIFICIAL (handle_var) = true;
  DECL_INITIAL (handle_var) = NULL_TREE;

  /* If PTR is an array, take its address.  */
  tree actual_pointer =
    POINTER_TYPE_P (pointer_type)
    ? pointer
    : build_addr (pointer, current_function_decl);

  /* Build `starpu_vector_data_register (&HANDLE_VAR, 0, POINTER,
                                         COUNT, sizeof *POINTER)'  */
  tree call =
    build_call_expr (register_fn, 5,
		     build_addr (handle_var, current_function_decl),
		     build_zero_cst (uintptr_type_node), /* home node */
		     actual_pointer, count,
		     size_in_bytes (TREE_TYPE (pointer_type)));

  return build3 (BIND_EXPR, void_type_node, handle_var, call,
		 NULL_TREE);
}

/* Return a `starpu_data_unregister' call for VAR.  */

static tree
build_data_unregister_call (location_t loc, tree var)
{
  static tree unregister_fn;
  LOOKUP_STARPU_FUNCTION (unregister_fn, "starpu_data_unregister");

  /* If VAR is an array, take its address.  */
  tree pointer =
    POINTER_TYPE_P (TREE_TYPE (var))
    ? var
    : build_addr (var, current_function_decl);

  /* Call `starpu_data_unregister (starpu_data_lookup (ptr))'.  */
  return build_call_expr (unregister_fn, 1,
			  build_pointer_lookup (pointer));
}


/* Process `#pragma starpu register VAR [COUNT]' and emit the corresponding
   `starpu_vector_data_register' call.  */

static void
handle_pragma_register (struct cpp_reader *reader)
{
  tree args, ptr, count_arg;
  location_t loc;

  loc = cpp_peek_token (reader, 0)->src_loc;

  args = read_pragma_expressions ("register", loc);
  if (args == NULL_TREE)
    /* Parse error, presumably already handled by the parser.  */
    return;

  /* First argument should be a pointer expression.  */
  ptr = TREE_VALUE (args);
  args = TREE_CHAIN (args);

  if (ptr == error_mark_node)
    return;

  tree ptr_type;

  if (DECL_P (ptr))
    {
      tree heap_attr =
	lookup_attribute (heap_allocated_orig_type_attribute_name,
			  DECL_ATTRIBUTES (ptr));

      if (heap_attr != NULL_TREE)
	/* PTR is `heap_allocated' so use its original array type to
	   determine its size.  */
	ptr_type = TREE_VALUE (heap_attr);
      else
	ptr_type = TREE_TYPE (ptr);
    }
  else
    ptr_type = TREE_TYPE (ptr);

  if (ptr_type == NULL_TREE)
    {
      /* PTR is a type-less thing, such as a STRING_CST.  */
      error_at (loc, "invalid %<register%> argument");
      return;
    }

  if (!POINTER_TYPE_P (ptr_type)
      && TREE_CODE (ptr_type) != ARRAY_TYPE)
    {
      error_at (loc, "%qE is neither a pointer nor an array", ptr);
      return;
    }

  /* Since we implicitly use sizeof (*PTR), `void *' is not allowed. */
  if (VOID_TYPE_P (TREE_TYPE (ptr_type)))
    {
      error_at (loc, "pointers to %<void%> not allowed "
		"in %<register%> pragma");
      return;
    }

  TREE_USED (ptr) = true;
#ifdef DECL_READ_P
  if (DECL_P (ptr))
    DECL_READ_P (ptr) = true;
#endif

  if (TREE_CODE (ptr_type) == ARRAY_TYPE
      && !DECL_EXTERNAL (ptr)
      && !TREE_STATIC (ptr)
      && !(TREE_CODE (ptr) == VAR_DECL && heap_allocated_p (ptr))
      && !MAIN_NAME_P (DECL_NAME (current_function_decl)))
    warning_at (loc, 0, "using an on-stack array as a task input "
		"considered unsafe");

  /* Determine the number of elements in the vector.  */
  tree count = NULL_TREE;

  if (TREE_CODE (ptr_type) == ARRAY_TYPE)
    count = array_type_element_count (loc, ptr_type);

  /* Second argument is optional but should be an integer.  */
  count_arg = (args == NULL_TREE) ? NULL_TREE : TREE_VALUE (args);
  if (args != NULL_TREE)
    args = TREE_CHAIN (args);

  if (count_arg == NULL_TREE)
    {
      /* End of line reached: check whether the array size was
	 determined.  */
      if (count == NULL_TREE)
	{
	  error_at (loc, "cannot determine size of array %qE", ptr);
	  return;
	}
    }
  else if (count_arg == error_mark_node)
    /* COUNT_ARG could not be parsed and an error was already reported.  */
    return;
  else if (!INTEGRAL_TYPE_P (TREE_TYPE (count_arg)))
    {
      error_at (loc, "%qE is not an integer", count_arg);
      return;
    }
  else
    {
      TREE_USED (count_arg) = true;
#ifdef DECL_READ_P
      if (DECL_P (count_arg))
	DECL_READ_P (count_arg) = true;
#endif

      if (count != NULL_TREE)
	{
	  /* The number of elements of this array was already determined.  */
	  inform (loc,
		  "element count can be omitted for bounded array %qE",
		  ptr);

	  if (count_arg != NULL_TREE)
	    {
	      if (TREE_CODE (count_arg) == INTEGER_CST)
		{
		  if (!tree_int_cst_equal (count, count_arg))
		    error_at (loc, "specified element count differs "
			      "from actual size of array %qE",
			      ptr);
		}
	      else
		/* Using a variable to determine the array size whereas the
		   array size is actually known statically.  This looks like
		   unreasonable code, so error out.  */
		error_at (loc, "determining array size at run-time "
			  "although array size is known at compile-time");
	    }
	}
      else
	count = count_arg;
    }

  /* Any remaining args?  */
  if (args != NULL_TREE)
    error_at (loc, "junk after %<starpu register%> pragma");

  /* Add a data register call.  */
  add_stmt (build_data_register_call (loc, ptr, count));
}

/* Process `#pragma starpu acquire VAR' and emit the corresponding
   `starpu_data_acquire' call.  */

static void
handle_pragma_acquire (struct cpp_reader *reader)
{
  static tree acquire_fn;
  LOOKUP_STARPU_FUNCTION (acquire_fn, "starpu_data_acquire");

  tree args, var;
  location_t loc;

  loc = cpp_peek_token (reader, 0)->src_loc;

  args = read_pragma_expressions ("acquire", loc);
  if (args == NULL_TREE)
    return;

  var = TREE_VALUE (args);

  if (var == error_mark_node)
    return;
  else if (TREE_CODE (TREE_TYPE (var)) != POINTER_TYPE
	   && TREE_CODE (TREE_TYPE (var)) != ARRAY_TYPE)
    {
      error_at (loc, "%qE is neither a pointer nor an array", var);
      return;
    }
  else if (TREE_CHAIN (args) != NULL_TREE)
    error_at (loc, "junk after %<starpu acquire%> pragma");

  /* If VAR is an array, take its address.  */
  tree pointer =
    POINTER_TYPE_P (TREE_TYPE (var))
    ? var
    : build_addr (var, current_function_decl);

  /* Call `starpu_data_acquire (starpu_data_lookup (ptr), STARPU_RW)'.
     TODO: Support modes other than RW.  */
  add_stmt (build_call_expr (acquire_fn, 2,
			     build_pointer_lookup (pointer),
			     build_int_cst (integer_type_node, STARPU_RW)));
}

/* Process `#pragma starpu release VAR' and emit the corresponding
   `starpu_data_release' call.  */

static void
handle_pragma_release (struct cpp_reader *reader)
{
  static tree release_fn;
  LOOKUP_STARPU_FUNCTION (release_fn, "starpu_data_release");

  tree args, var;
  location_t loc;

  loc = cpp_peek_token (reader, 0)->src_loc;

  args = read_pragma_expressions ("release", loc);
  if (args == NULL_TREE)
    return;

  var = TREE_VALUE (args);

  if (var == error_mark_node)
    return;
  else if (TREE_CODE (TREE_TYPE (var)) != POINTER_TYPE
	   && TREE_CODE (TREE_TYPE (var)) != ARRAY_TYPE)
    {
      error_at (loc, "%qE is neither a pointer nor an array", var);
      return;
    }
  else if (TREE_CHAIN (args) != NULL_TREE)
    error_at (loc, "junk after %<starpu release%> pragma");

  /* If VAR is an array, take its address.  */
  tree pointer =
    POINTER_TYPE_P (TREE_TYPE (var))
    ? var
    : build_addr (var, current_function_decl);

  /* Call `starpu_data_release (starpu_data_lookup (ptr))'.  */
  add_stmt (build_call_expr (release_fn, 1,
			     build_pointer_lookup (pointer)));
}

/* Process `#pragma starpu unregister VAR' and emit the corresponding
   `starpu_data_unregister' call.  */

static void
handle_pragma_unregister (struct cpp_reader *reader)
{
  tree args, var;
  location_t loc;

  loc = cpp_peek_token (reader, 0)->src_loc;

  args = read_pragma_expressions ("unregister", loc);
  if (args == NULL_TREE)
    return;

  var = TREE_VALUE (args);

  if (var == error_mark_node)
    return;
  else if (TREE_CODE (TREE_TYPE (var)) != POINTER_TYPE
	   && TREE_CODE (TREE_TYPE (var)) != ARRAY_TYPE)
    {
      error_at (loc, "%qE is neither a pointer nor an array", var);
      return;
    }
  else if (TREE_CHAIN (args) != NULL_TREE)
    error_at (loc, "junk after %<starpu unregister%> pragma");

  add_stmt (build_data_unregister_call (loc, var));
}

/* Handle the `debug_tree' pragma (for debugging purposes.)  */

static void
handle_pragma_debug_tree (struct cpp_reader *reader)
{
  tree args, obj;
  location_t loc;

  loc = cpp_peek_token (reader, 0)->src_loc;

  args = read_pragma_expressions ("debug_tree", loc);
  if (args == NULL_TREE)
    /* Parse error, presumably already handled by the parser.  */
    return;

  obj = TREE_VALUE (args);
  args = TREE_CHAIN (args);

  if (obj == error_mark_node)
    return;

  if (args != NULL_TREE)
    warning_at (loc, 0, "extraneous arguments ignored");

  inform (loc, "debug_tree:");
  debug_tree (obj);
  printf ("\n");
}

/* Handle the `#pragma starpu add_target TARGET', which tells GCC-StarPU to
   consider TARGET ("cpu", "opencl", etc.) as supported.  This pragma is
   undocumented and only meant to be used for testing purposes.  */

static void
handle_pragma_add_target (struct cpp_reader *reader)
{
  tree args, obj;
  location_t loc;

  loc = cpp_peek_token (reader, 0)->src_loc;

  args = read_pragma_expressions ("add_target", loc);
  if (args == NULL_TREE)
    /* Parse error, presumably already handled by the parser.  */
    return;

  obj = TREE_VALUE (args);
  args = TREE_CHAIN (args);

  if (obj == error_mark_node)
    return;

  if (args != NULL_TREE)
    warning_at (loc, 0, "extraneous arguments ignored");

  if (TREE_CODE (obj) == STRING_CST)
    {
      int new_target = task_implementation_target_to_int (obj);
      if (obj == 0)
	error_at (loc, "unsupported target %qE", obj);
      else
	supported_targets |= new_target;
    }
  else
    error_at (loc, "expecting string literal");
}

static void
register_pragmas (void *gcc_data, void *user_data)
{
  c_register_pragma (STARPU_PRAGMA_NAME_SPACE, "hello",
		     handle_pragma_hello);
  c_register_pragma (STARPU_PRAGMA_NAME_SPACE, "debug_tree",
		     handle_pragma_debug_tree);
  c_register_pragma (STARPU_PRAGMA_NAME_SPACE, "add_target",
		     handle_pragma_add_target);

  c_register_pragma_with_expansion (STARPU_PRAGMA_NAME_SPACE, "initialize",
				    handle_pragma_initialize);
  c_register_pragma (STARPU_PRAGMA_NAME_SPACE, "wait",
		     handle_pragma_wait);
  c_register_pragma_with_expansion (STARPU_PRAGMA_NAME_SPACE, "register",
				    handle_pragma_register);
  c_register_pragma_with_expansion (STARPU_PRAGMA_NAME_SPACE, "acquire",
				    handle_pragma_acquire);
  c_register_pragma_with_expansion (STARPU_PRAGMA_NAME_SPACE, "release",
				    handle_pragma_release);
  c_register_pragma_with_expansion (STARPU_PRAGMA_NAME_SPACE, "unregister",
				    handle_pragma_unregister);
  c_register_pragma_with_expansion (STARPU_PRAGMA_NAME_SPACE, "opencl",
				    handle_pragma_opencl);
  c_register_pragma (STARPU_PRAGMA_NAME_SPACE, "shutdown",
		     handle_pragma_shutdown);
}


/* Attributes.  */

/* Handle the `task' function attribute.  */

static tree
handle_task_attribute (tree *node, tree name, tree args,
		       int flags, bool *no_add_attrs)
{
  tree fn;

  fn = *node;

  /* Get rid of the `task' attribute by default so that FN isn't further
     processed when it's erroneous.  */
  *no_add_attrs = true;

  if (TREE_CODE (fn) != FUNCTION_DECL)
    error_at (DECL_SOURCE_LOCATION (fn),
	      "%<task%> attribute only applies to functions");
  else
    {
      if (!VOID_TYPE_P (TREE_TYPE (TREE_TYPE (fn))))
	/* Raise an error but keep going to avoid spitting out too many
	   errors at the user's face.  */
	error_at (DECL_SOURCE_LOCATION (fn),
		  "task return type must be %<void%>");

      if (count (pointer_type_p, TYPE_ARG_TYPES (TREE_TYPE (fn)))
	  > STARPU_NMAXBUFS)
	error_at (DECL_SOURCE_LOCATION (fn),
		  "maximum number of pointer parameters exceeded");

      /* Turn FN into an actual task.  */
      taskify_function (fn);
    }

  /* Lookup & cache function declarations for later reuse.  */
  LOOKUP_STARPU_FUNCTION (unpack_fn, "starpu_codelet_unpack_args");

  return NULL_TREE;
}

/* Handle the `task_implementation (WHERE, TASK)' attribute.  WHERE is a
   string constant ("cpu", "cuda", etc.), and TASK is the identifier of a
   function declared with the `task' attribute.  */

static tree
handle_task_implementation_attribute (tree *node, tree name, tree args,
				      int flags, bool *no_add_attrs)
{
  location_t loc;
  tree fn, where, task_decl;

  /* FIXME:TODO: To change the order to (TASK, WHERE):
	  tree cleanup_id = TREE_VALUE (TREE_VALUE (attr));
	  tree cleanup_decl = lookup_name (cleanup_id);
  */

  fn = *node;
  where = TREE_VALUE (args);
  task_decl = TREE_VALUE (TREE_CHAIN (args));

  if (implicit_cpu_task_implementation_p (task_decl))
    /* TASK_DECL is actually a CPU implementation.  Implicit CPU task
       implementations can lead to this situation, because the task is
       renamed and modified to become a CPU implementation.  */
    task_decl = task_implementation_task (task_decl);

  loc = DECL_SOURCE_LOCATION (fn);

  /* Get rid of the `task_implementation' attribute by default so that FN
     isn't further processed when it's erroneous.  */
  *no_add_attrs = true;

  /* Mark FN as used to placate `-Wunused-function' when FN is erroneous
     anyway.  */
  TREE_USED (fn) = true;

  if (TREE_CODE (fn) != FUNCTION_DECL)
    error_at (loc,
	      "%<task_implementation%> attribute only applies to functions");
  else if (TREE_CODE (where) != STRING_CST)
    error_at (loc, "string constant expected "
	      "as the first %<task_implementation%> argument");
  else if (TREE_CODE (task_decl) != FUNCTION_DECL)
    error_at (loc, "%qE is not a function", task_decl);
  else if (lookup_attribute (task_attribute_name,
			DECL_ATTRIBUTES (task_decl)) == NULL_TREE)
    error_at (loc, "function %qE lacks the %<task%> attribute",
	      DECL_NAME (task_decl));
  else if (TYPE_CANONICAL (TREE_TYPE (fn))
	   != TYPE_CANONICAL (TREE_TYPE (task_decl)))
    error_at (loc, "type differs from that of task %qE",
	      DECL_NAME (task_decl));
  else
    {
      /* Add FN to the list of implementations of TASK_DECL.  */
      add_task_implementation (task_decl, fn, where);

      /* Keep the attribute.  */
      *no_add_attrs = false;
    }

  return NULL_TREE;
}

/* Return true when VAR is an automatic variable with complete array type;
   otherwise, return false, and emit error messages mentioning ATTRIBUTE.  */

static bool
automatic_array_variable_p (const char *attribute, tree var)
{
  gcc_assert (TREE_CODE (var) == VAR_DECL);

  location_t loc;

  loc = DECL_SOURCE_LOCATION (var);

  if (DECL_EXTERNAL (var))
    error_at (loc, "attribute %qs cannot be used on external declarations",
	      attribute);
  else if (TREE_PUBLIC (var) || TREE_STATIC (var))
    {
      error_at (loc, "attribute %qs cannot be used on global variables",
		attribute);
      TREE_TYPE (var) = error_mark_node;
    }
  else if (TREE_CODE (TREE_TYPE (var)) != ARRAY_TYPE)
    {
      error_at (loc, "variable %qE must have an array type",
		DECL_NAME (var));
      TREE_TYPE (var) = error_mark_node;
    }
  else if (TYPE_SIZE (TREE_TYPE (var)) == NULL_TREE)
    {
      error_at (loc, "variable %qE has an incomplete array type",
		DECL_NAME (var));
      TREE_TYPE (var) = error_mark_node;
    }
  else
    return true;

  return false;
}

/* Handle the `heap_allocated' attribute on variable *NODE.  */

static tree
handle_heap_allocated_attribute (tree *node, tree name, tree args,
				 int flags, bool *no_add_attrs)
{
  tree var = *node;

  if (automatic_array_variable_p (heap_allocated_attribute_name, var))
    {
      /* Turn VAR into a pointer that feels like an array.  This is what's
	 done for PARM_DECLs that have an array type.  */

      location_t loc = DECL_SOURCE_LOCATION (var);
      tree array_type = TREE_TYPE (var);
      tree element_type = TREE_TYPE (array_type);
      tree pointer_type = build_pointer_type (element_type);

      /* Keep a copy of VAR's original type.  */
      DECL_ATTRIBUTES (var) =
	tree_cons (get_identifier (heap_allocated_orig_type_attribute_name),
		   array_type, DECL_ATTRIBUTES (var));

      TREE_TYPE (var) = pointer_type;
      DECL_SIZE (var) = TYPE_SIZE (pointer_type);
      DECL_SIZE_UNIT (var) = TYPE_SIZE_UNIT (pointer_type);
      DECL_ALIGN (var) = TYPE_ALIGN (pointer_type);
      DECL_USER_ALIGN (var) = false;
      DECL_MODE (var) = TYPE_MODE (pointer_type);

      tree malloc_fn = lookup_name (get_identifier ("starpu_malloc"));
      gcc_assert (malloc_fn != NULL_TREE);

      tree alloc = build_call_expr (malloc_fn, 2,
				    build_addr (var, current_function_decl),
				    TYPE_SIZE_UNIT (array_type));
      TREE_SIDE_EFFECTS (alloc) = true;

      /* Add a destructor for VAR.  Instead of consing the `cleanup'
	 attribute for VAR, directly use `push_cleanup'.  This guarantees
	 that CLEANUP_ID is looked up in the right context, and allows us to
	 pass VAR directly to `starpu_free', instead of `&VAR'.

	 TODO: Provide a way to disable this.  */

      static tree cleanup_decl;
      LOOKUP_STARPU_FUNCTION (cleanup_decl, "starpu_free");

      if (registered_p (var))
	{
	  /* A `registered' attribute has already been processed, and thus a
	     cleanup for it has been pushed.  However, we want that cleanup
	     to appear before ours, and our allocation to appear before the
	     registration, so swap them.  */
	  tree_stmt_iterator it;
	  tree parent, try_finally, registration;

#ifdef stmt_list_stack
# ifdef VEC_index /* 4.7 */
	  gcc_assert (VEC_length (tree, stmt_list_stack) > 1);
	  parent = VEC_index (tree, stmt_list_stack,
			      VEC_length (tree, stmt_list_stack) - 2);
# else
#  error not ported to 4.8!
# endif
#else  /* 4.6 and before */
	  parent = TREE_CHAIN (cur_stmt_list);
#endif

	  gcc_assert (parent != NULL_TREE
		      && TREE_CODE (parent) == STATEMENT_LIST);

	  it = tsi_last (parent);
	  try_finally = tsi_stmt (it);
	  gcc_assert (TREE_CODE (try_finally) == TRY_FINALLY_EXPR);

	  tsi_prev (&it);
	  registration =
	    build_data_register_call (loc, var,
				      array_type_element_count
				       (loc, array_type));

	  add_stmt (registration);
	  *tsi_stmt_ptr (it) = alloc;

	  push_cleanup (var, build_data_unregister_call (loc, var), false);
	  TREE_OPERAND (try_finally, 1) = build_call_expr (cleanup_decl, 1, var);
	}
      else
	{
	  /* Push the allocation and cleanup in order.  */
	  add_stmt (alloc);
	  push_cleanup (var, build_call_expr (cleanup_decl, 1, var), false);
	}

      /* Keep the attribute.  */
      *no_add_attrs = false;
    }

  return NULL_TREE;
}

/* Handle the `registered' attribute on variable *NODE.  */

static tree
handle_registered_attribute (tree *node, tree name, tree args,
			     int flags, bool *no_add_attrs)
{
  location_t loc;
  tree var = *node;

  loc = DECL_SOURCE_LOCATION (var);

  bool heap_p = heap_allocated_p (var);

  /* When VAR has the `heap_allocated' attribute, we know it has a complete
     array type.  */

  if (heap_p
      || automatic_array_variable_p (registered_attribute_name, var))
    {
      /* FIXME: This warning cannot be emitted here, because the
	 `heap_allocated' attribute may be processed later.  */
      /* if (!heap_p */
      /* 	  && !MAIN_NAME_P (DECL_NAME (current_function_decl))) */
      /* 	warning_at (loc, 0, "using an on-stack array as a task input " */
      /* 		    "considered unsafe"); */

      tree ptr_type, heap_attr =
	lookup_attribute (heap_allocated_orig_type_attribute_name,
			  DECL_ATTRIBUTES (var));

      if (heap_attr != NULL_TREE)
	/* PTR is `heap_allocated' so use its original array type to
	   determine its size.  */
	ptr_type = TREE_VALUE (heap_attr);
      else
	ptr_type = TREE_TYPE (var);

      tree count = array_type_element_count (loc, ptr_type);

      add_stmt (build_data_register_call (loc, var, count));

      push_cleanup (var,
		    build_data_unregister_call (DECL_SOURCE_LOCATION (var),
						var),
		    false);
    }

  return NULL_TREE;
}

/* Handle the `output' attribute on type *NODE, which should be the type of a
   PARM_DECL of a task or task implementation.  */

static tree
handle_output_attribute (tree *node, tree name, tree args,
			 int flags, bool *no_add_attrs)
{
  tree type = *node;

  gcc_assert (TYPE_P (type));

  if (!POINTER_TYPE_P (type) && TREE_CODE (type) != ARRAY_TYPE)
    error ("%<output%> attribute not allowed for non-pointer types");
  else
    /* Keep the attribute.  */
    *no_add_attrs = false;

  return NULL_TREE;
}

/* Return true when FN is an implicit CPU task implementation.  */

static bool
implicit_cpu_task_implementation_p (const_tree fn)
{
  if (task_implementation_p (fn)
      && task_implementation_where (fn) == STARPU_CPU)
    {
      /* XXX: Hackish heuristic.  */
      const_tree cpu_id;
      cpu_id = build_cpu_codelet_identifier (task_implementation_task (fn));
      return cpu_id == DECL_NAME (fn);
    }

  return false;
}

/* Return true when VAR_DECL has the `heap_allocated' attribute.  */

static bool
heap_allocated_p (const_tree var_decl)
{
  gcc_assert (TREE_CODE (var_decl) == VAR_DECL);

  return lookup_attribute (heap_allocated_attribute_name,
			   DECL_ATTRIBUTES (var_decl)) != NULL_TREE;
}

/* Return true when VAR_DECL has the `registered' attribute.  */

static bool
registered_p (const_tree var_decl)
{
  gcc_assert (TREE_CODE (var_decl) == VAR_DECL);

  return lookup_attribute (registered_attribute_name,
			   DECL_ATTRIBUTES (var_decl)) != NULL_TREE;
}

static void
register_task_attributes (void *gcc_data, void *user_data)
{
  static const struct attribute_spec task_attr =
    {
      task_attribute_name, 0, 0, true, false, false,
      handle_task_attribute
#ifdef HAVE_ATTRIBUTE_SPEC_AFFECTS_TYPE_IDENTITY
      , false
#endif
    };

  static const struct attribute_spec task_implementation_attr =
    {
      task_implementation_attribute_name, 2, 2, true, false, false,
      handle_task_implementation_attribute
#ifdef HAVE_ATTRIBUTE_SPEC_AFFECTS_TYPE_IDENTITY
      , false
#endif
    };

  static const struct attribute_spec heap_allocated_attr =
    {
      heap_allocated_attribute_name, 0, 0, true, false, false,
      handle_heap_allocated_attribute
#ifdef HAVE_ATTRIBUTE_SPEC_AFFECTS_TYPE_IDENTITY
      , false
#endif
    };

  static const struct attribute_spec registered_attr =
    {
      registered_attribute_name, 0, 0, true, false, false,
      handle_registered_attribute
#ifdef HAVE_ATTRIBUTE_SPEC_AFFECTS_TYPE_IDENTITY
      , false
#endif
    };

  static const struct attribute_spec output_attr =
    {
      output_attribute_name, 0, 0, true, true, false,
      handle_output_attribute
#ifdef HAVE_ATTRIBUTE_SPEC_AFFECTS_TYPE_IDENTITY
      , true /* affects type identity */
#endif
    };

  register_attribute (&task_attr);
  register_attribute (&task_implementation_attr);
  register_attribute (&heap_allocated_attr);
  register_attribute (&registered_attr);
  register_attribute (&output_attr);
}



/* Return the type of a codelet function, i.e.,
   `void (*) (void **, void *)'.  */

static tree
build_codelet_wrapper_type (void)
{
  tree void_ptr_ptr;

  void_ptr_ptr = build_pointer_type (ptr_type_node);

  return build_function_type_list (void_type_node,
				   void_ptr_ptr, ptr_type_node,
				   NULL_TREE);
}

/* Return an identifier for the wrapper of TASK_IMPL, a task
   implementation.  */

static tree
build_codelet_wrapper_identifier (tree task_impl)
{
  static const char suffix[] = ".task_implementation_wrapper";

  tree id;
  char *cl_name;
  const char *task_name;

  id = DECL_NAME (task_impl);
  task_name = IDENTIFIER_POINTER (id);

  cl_name = (char *) alloca (IDENTIFIER_LENGTH (id) + strlen (suffix) + 1);
  memcpy (cl_name, task_name, IDENTIFIER_LENGTH (id));
  strcpy (&cl_name[IDENTIFIER_LENGTH (id)], suffix);

  return get_identifier (cl_name);
}

/* Return a function of type `void (*) (void **, void *)' that calls function
   TASK_IMPL, the FUNCTION_DECL of a task implementation whose prototype may
   be arbitrary.  */

static tree
build_codelet_wrapper_definition (tree task_impl)
{
  location_t loc;
  tree task_decl, wrapper_name, decl;

  loc = DECL_SOURCE_LOCATION (task_impl);
  task_decl = task_implementation_task (task_impl);

  wrapper_name = build_codelet_wrapper_identifier (task_impl);
  decl = build_decl (loc, FUNCTION_DECL, wrapper_name,
		     build_codelet_wrapper_type ());

  local_define (tree, build_local_var, (const_tree type))
  {
    tree var, t;
    const char *seed;

    t = TREE_VALUE (type);
    seed = POINTER_TYPE_P (t) ? "pointer_arg" : "scalar_arg";

    var = build_decl (loc, VAR_DECL, create_tmp_var_name (seed), t);
    DECL_CONTEXT (var) = decl;
    DECL_ARTIFICIAL (var) = true;

    return var;
  };

  /* Return the body of the wrapper, which unpacks `cl_args' and calls the
     user-defined task implementation.  */

  local_define (tree, build_body, (tree wrapper_decl, tree vars))
  {
    bool opencl_p;
    tree stmts = NULL, call, v;
    VEC(tree, gc) *args;

    opencl_p = (task_implementation_where (task_impl) == STARPU_OPENCL);

    /* Build `var0 = STARPU_VECTOR_GET_PTR (buffers[0]); ...' or
       `var0 = STARPU_VECTOR_GET_DEV_HANDLE (buffers[0])' for OpenCL.  */

    size_t index = 0;
    for (v = vars; v != NULL_TREE; v = TREE_CHAIN (v))
      {
	if (POINTER_TYPE_P (TREE_TYPE (v)))
	  {
	    /* Compute `void *VDESC = buffers[0];'.  */
	    tree vdesc = array_ref (DECL_ARGUMENTS (wrapper_decl), index);

	    /* Use the right field, depending on OPENCL_P.  */
	    size_t offset =
	      opencl_p
	      ? offsetof (struct starpu_vector_interface, dev_handle)
	      : offsetof (struct starpu_vector_interface, ptr);

	    gcc_assert (POINTER_TYPE_P (TREE_TYPE (vdesc)));

	    /* Compute `type *PTR = *(type **) VDESC;'.  */
	    tree ptr =
	      build_indirect_ref (UNKNOWN_LOCATION,
				  fold_convert (build_pointer_type (TREE_TYPE (v)),
						pointer_plus (vdesc, offset)),
				  RO_ARRAY_INDEXING);

	    append_to_statement_list (build2 (MODIFY_EXPR, TREE_TYPE (v),
					      v, ptr),
				      &stmts);

	    index++;
	  }
      }

    /* Build `starpu_codelet_unpack_args (cl_args, &var1, &var2, ...)'.  */

    args = NULL;
    VEC_safe_push (tree, gc, args, TREE_CHAIN (DECL_ARGUMENTS (wrapper_decl)));
    for (v = vars; v != NULL_TREE; v = TREE_CHAIN (v))
      {
	if (!POINTER_TYPE_P (TREE_TYPE (v)))
	  VEC_safe_push (tree, gc, args, build_addr (v, wrapper_decl));
      }

    if (VEC_length (tree, args) > 1)
      {
	call = build_call_expr_loc_vec (UNKNOWN_LOCATION, unpack_fn, args);
	TREE_SIDE_EFFECTS (call) = 1;
	append_to_statement_list (call, &stmts);
      }

    /* Build `my_task_impl (var1, var2, ...)'.  */

    args = NULL;
    for (v = vars; v != NULL_TREE; v = TREE_CHAIN (v))
      VEC_safe_push (tree, gc, args, v);

    call = build_call_expr_loc_vec (UNKNOWN_LOCATION, task_impl, args);
    TREE_SIDE_EFFECTS (call) = 1;
    append_to_statement_list (call, &stmts);

    tree bind;
    bind = build3 (BIND_EXPR, void_type_node, vars, stmts,
		   DECL_INITIAL (wrapper_decl));
    TREE_TYPE (bind) = TREE_TYPE (TREE_TYPE (wrapper_decl));

    return bind;
  };

  /* Return the parameter list of the wrapper:
     `(void **BUFFERS, void *CL_ARGS)'.  */

  local_define (tree, build_parameters, (tree wrapper_decl))
  {
    tree param1, param2;

    param1 = build_decl (loc, PARM_DECL,
			 create_tmp_var_name ("buffers"),
			 build_pointer_type (ptr_type_node));
    DECL_ARG_TYPE (param1) = ptr_type_node;
    DECL_CONTEXT (param1) = wrapper_decl;
    TREE_USED (param1) = true;

    param2 = build_decl (loc, PARM_DECL,
			 create_tmp_var_name ("cl_args"),
			 ptr_type_node);
    DECL_ARG_TYPE (param2) = ptr_type_node;
    DECL_CONTEXT (param2) = wrapper_decl;
    TREE_USED (param2) = true;

    return chainon (param1, param2);
  };

  tree vars, result;

  vars = map (build_local_var,
	      list_remove (void_type_p,
			   TYPE_ARG_TYPES (TREE_TYPE (task_decl))));

  DECL_CONTEXT (decl) = NULL_TREE;
  DECL_ARGUMENTS (decl) = build_parameters (decl);

  result = build_decl (loc, RESULT_DECL, NULL_TREE, void_type_node);
  DECL_CONTEXT (result) = decl;
  DECL_ARTIFICIAL (result) = true;
  DECL_IGNORED_P (result) = true;
  DECL_RESULT (decl) = result;

  DECL_INITIAL (decl) = build_block (vars, NULL_TREE, decl, NULL_TREE);

  DECL_SAVED_TREE (decl) = build_body (decl, vars);

  TREE_PUBLIC (decl) = TREE_PUBLIC (task_impl);
  TREE_STATIC (decl) = true;
  TREE_USED (decl) = true;
  DECL_ARTIFICIAL (decl) = true;
  DECL_EXTERNAL (decl) = false;
  DECL_UNINLINABLE (decl) = true;

  rest_of_decl_compilation (decl, true, 0);

  struct function *prev_cfun = cfun;
  set_cfun (NULL);
  allocate_struct_function (decl, false);
  cfun->function_end_locus = DECL_SOURCE_LOCATION (task_impl);

  cgraph_finalize_function (decl, false);

  /* Mark DECL as needed so that it doesn't get removed by
     `cgraph_remove_unreachable_nodes' when it's not public.  */
  cgraph_mark_needed_node (cgraph_get_node (decl));

  set_cfun (prev_cfun);

  return decl;
}

/* Define one wrapper function for each implementation of TASK.  TASK should
   be the FUNCTION_DECL of a task.  */

static void
define_codelet_wrappers (tree task)
{
  local_define (void, define, (tree task_impl))
  {
    tree wrapper_def;

    wrapper_def = build_codelet_wrapper_definition (task_impl);

    DECL_ATTRIBUTES (task_impl) =
      tree_cons (get_identifier (task_implementation_wrapper_attribute_name),
		 wrapper_def,
		 DECL_ATTRIBUTES (task_impl));
  };

  for_each (define, task_implementation_list (task));
}

/* Return the identifier for an automatically-generated CPU codelet of
   TASK.  */

static tree
build_cpu_codelet_identifier (const_tree task)
{
  static const char suffix[] = ".cpu_implementation";

  tree id;
  char *cl_name;
  const char *task_name;

  id = DECL_NAME (task);
  task_name = IDENTIFIER_POINTER (id);

  cl_name = (char *) alloca (IDENTIFIER_LENGTH (id) + strlen (suffix) + 1);
  memcpy (cl_name, task_name, IDENTIFIER_LENGTH (id));
  strcpy (&cl_name[IDENTIFIER_LENGTH (id)], suffix);

  return get_identifier (cl_name);
}

static void
handle_pre_genericize (void *gcc_data, void *user_data)
{
  tree fn = (tree) gcc_data;

  gcc_assert (TREE_CODE (fn) == FUNCTION_DECL);

  if (task_p (fn) && TREE_STATIC (fn))
    {
      /* The user defined a body for task FN, which we interpret as being the
	 body of an implicit CPU task implementation for FN.  Thus, rename FN
	 and turn it into the "cpu" implementation of a task that we create
	 under FN's original name (this is easier than moving the body to a
	 different function, which would require traversing the body to
	 rewrite all references to FN to point to the new function.)  Later,
	 `lower_starpu' rewrites calls to FN as calls to the newly created
	 task.  */

      tree task_name = DECL_NAME (fn);

      tree cpu_impl = fn;
      DECL_NAME (cpu_impl) = build_cpu_codelet_identifier (fn);
      if (verbose_output_p)
	inform (DECL_SOURCE_LOCATION (fn),
		"implicit CPU implementation renamed from %qE to %qE",
		task_name, DECL_NAME (cpu_impl));

      tree task = build_decl (DECL_SOURCE_LOCATION (fn), FUNCTION_DECL,
			      task_name, TREE_TYPE (fn));

      TREE_PUBLIC (task) = TREE_PUBLIC (fn);
      TREE_PUBLIC (cpu_impl) = false;

      taskify_function (task);

      /* Inherit the task implementation list from FN.  */
      tree impls = lookup_attribute (task_implementation_list_attribute_name,
				     DECL_ATTRIBUTES (fn));
      gcc_assert (impls != NULL_TREE);
      impls = TREE_VALUE (impls);

      DECL_ATTRIBUTES (task) =
	tree_cons (get_identifier (task_implementation_list_attribute_name),
		   impls, DECL_ATTRIBUTES (task));

      /* Make CPU_IMPL an implementation of FN.  */
      DECL_ATTRIBUTES (cpu_impl) =
	tree_cons (get_identifier (task_implementation_attribute_name),
		   tree_cons (NULL_TREE, build_string (3, "cpu"),
			      tree_cons (NULL_TREE, task, NULL_TREE)),
		   NULL_TREE);

      add_task_implementation (task, cpu_impl, build_string (3, "cpu"));

      /* And now, process CPU_IMPL.  */
    }

  if (task_implementation_p (fn))
    {
      tree task = task_implementation_task (fn);

      if (!TREE_STATIC (task))
	{
	  /* TASK lacks a body.  Declare its codelet, intantiate its codelet
	     wrappers, and its body in this compilation unit.  */


	  /* Declare TASK's codelet.  It cannot be defined yet because the
	     complete list of tasks isn't available at this point.  */
	  declare_codelet (task);

	  /* Build its body.  */
	  current_function_decl = task;
	  define_task (task);
	  current_function_decl = fn;

	  /* Compile TASK's body.  */
	  rest_of_decl_compilation (task, true, 0);
	  allocate_struct_function (task, false);
	  cgraph_finalize_function (task, false);
	  cgraph_mark_needed_node (cgraph_get_node (task));
	}
    }
}

/* Raise warnings if TASK doesn't meet the basic criteria.  */

static void
validate_task (tree task)
{
  gcc_assert (task_p (task));

  int where = task_where (task);

  /* If TASK has no implementations, things will barf elsewhere anyway.  */

  if (task_implementation_list (task) != NULL_TREE)
    if ((where & supported_targets) == 0)
      error_at (DECL_SOURCE_LOCATION (task),
		"none of the implementations of task %qE can be used",
		DECL_NAME (task));
}

/* Raise an error when IMPL doesn't satisfy the constraints of a task
   implementations, such as not invoking another task.  */

static void
validate_task_implementation (tree impl)
{
  gcc_assert (task_implementation_p (impl));

  const struct cgraph_node *cgraph;
  const struct cgraph_edge *callee;

  cgraph = cgraph_get_node (impl);

  /* When a definition of IMPL is available, check its callees.  */
  if (cgraph != NULL)
    for (callee = cgraph->callees;
	 callee != NULL;
	 callee = callee->next_callee)
      {
	if (task_p (callee->callee->decl))
	  {
	    location_t loc;

	    loc = gimple_location (callee->call_stmt);
	    error_at (loc, "task %qE cannot be invoked from task implementation %qE",
		      DECL_NAME (callee->callee->decl),
		      DECL_NAME (impl));
	  }
      }
}

static unsigned int
lower_starpu (void)
{
  tree fndecl;
  const struct cgraph_node *cgraph;
  const struct cgraph_edge *callee;

  fndecl = current_function_decl;
  gcc_assert (TREE_CODE (fndecl) == FUNCTION_DECL);

  if (task_p (fndecl))
    {
      /* Make sure the task and its implementations are valid.  */

      validate_task (fndecl);

      for_each (validate_task_implementation,
		task_implementation_list (fndecl));

      /* Generate a `struct starpu_codelet' structure and a wrapper function for
	 each implementation of TASK_DECL.  This cannot be done earlier
	 because we need to have a complete list of task implementations.  */

      define_codelet_wrappers (fndecl);

      tree cl_def = task_codelet_declaration (fndecl);
      DECL_INITIAL (cl_def) = build_codelet_initializer (fndecl);
      TREE_STATIC (cl_def) = true;
      DECL_EXTERNAL (cl_def) = false;

      varpool_finalize_decl (cl_def);
    }

  /* This pass should occur after `build_cgraph_edges'.  */
  cgraph = cgraph_get_node (fndecl);
  gcc_assert (cgraph != NULL);

  if (MAIN_NAME_P (DECL_NAME (fndecl)))
    {
      /* Check whether FNDECL initializes StarPU and emit a warning if it
	 doesn't.  */
      bool initialized;

      for (initialized = false, callee = cgraph->callees;
	   !initialized && callee != NULL;
	   callee = callee->next_callee)
	{
	  initialized =
	    DECL_NAME (callee->callee->decl) == get_identifier ("starpu_init");
	}

      if (!initialized)
	warning_at (DECL_SOURCE_LOCATION (fndecl), 0,
		    "%qE does not initialize StarPU", DECL_NAME (fndecl));
    }

  for (callee = cgraph->callees;
       callee != NULL;
       callee = callee->next_callee)
    {
      gcc_assert (callee->callee != NULL);

      tree callee_decl, caller_decl;

      callee_decl = callee->callee->decl;
      caller_decl = callee->caller->decl;

      if (implicit_cpu_task_implementation_p (callee_decl)
	  && !DECL_ARTIFICIAL (caller_decl))
	{
	  /* Rewrite the call to point to the actual task beneath
	     CALLEE_DECL.  */
	  callee_decl = task_implementation_task (callee_decl);
	  if (verbose_output_p)
	    inform (gimple_location (callee->call_stmt),
		    "call to %qE rewritten as a call to task %qE",
		    DECL_NAME (callee->callee->decl),
		    DECL_NAME (callee_decl));

	  gimple_call_set_fn (callee->call_stmt,
			      build_addr (callee_decl, callee->caller->decl));
	}

      if (task_p (callee_decl))
	{
	  if (verbose_output_p)
	    inform (gimple_location (callee->call_stmt),
		    "%qE calls task %qE",
		    DECL_NAME (fndecl), DECL_NAME (callee_decl));
	}
    }

  return 0;
}

static struct opt_pass pass_lower_starpu =
  {
    designated_field_init (type, GIMPLE_PASS),
    designated_field_init (name, "lower_starpu"),
    designated_field_init (gate, NULL),
    designated_field_init (execute, lower_starpu),

    /* The rest is zeroed.  */
  };


/* Initialization.  */

/* Directory where to look up <starpu.h> instead of `STARPU_INCLUDE_DIR'.  */
static const char *include_dir;

static void
define_cpp_macros (void *gcc_data, void *user_data)
{
  cpp_define (parse_in, "STARPU_GCC_PLUGIN=0");

  if (include_dir)
    {
      /* Get the header from the user-specified directory.  This is useful
	 when running the test suite, before StarPU is installed.  */
      char header[strlen (include_dir) + sizeof ("/starpu.h")];
      strcpy (header, include_dir);
      strcat (header, "/starpu.h");
      cpp_push_include (parse_in, header);
    }
  else
    cpp_push_include (parse_in, STARPU_INCLUDE_DIR "/starpu.h");
}

int
plugin_init (struct plugin_name_args *plugin_info,
	     struct plugin_gcc_version *version)
{
  /* `plugin_default_version_check' happens to be stricter than necessary
     (for instance, it fails when the `buildstamp' field of the plug-in
     doesn't match that of GCC), so write our own check and make more relax
     and more verbose.  */

#define VERSION_CHECK(field)						\
  do									\
    {									\
      if (strcmp (gcc_version. field, version-> field) != 0)		\
	{								\
	  error_at (UNKNOWN_LOCATION, "plug-in version check for `"	\
		    STRINGIFY (field) "' failed: expected `%s', "	\
		    "got `%s'",						\
		    gcc_version. field, version-> field);		\
	  return 1;							\
	}								\
    }									\
  while (0)

  VERSION_CHECK (basever);			  /* e.g., "4.6.2" */
  VERSION_CHECK (devphase);
  VERSION_CHECK (revision);
  VERSION_CHECK (configuration_arguments);

#undef VERSION_CHECK

  register_callback (plugin_name, PLUGIN_START_UNIT,
		     define_cpp_macros, NULL);
  register_callback (plugin_name, PLUGIN_PRAGMAS,
		     register_pragmas, NULL);
  register_callback (plugin_name, PLUGIN_ATTRIBUTES,
		     register_task_attributes, NULL);
  register_callback (plugin_name, PLUGIN_PRE_GENERICIZE,
  		     handle_pre_genericize, NULL);

  /* Register our pass so that it happens after `build_cgraph_edges' has been
     done.  */

  struct register_pass_info pass_info =
    {
      designated_field_init (pass, &pass_lower_starpu),
      designated_field_init (reference_pass_name, "*build_cgraph_edges"),
      designated_field_init (ref_pass_instance_number, 1),
      designated_field_init (pos_op, PASS_POS_INSERT_AFTER)
    };

  register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP,
		     NULL, &pass_info);

#if HAVE_DECL_PTR_DEREFS_MAY_ALIAS_P
  /* This warning pass is only available when `ptr_derefs_may_alias_p' is
     available, with GCC >= 4.6.  */

  struct register_pass_info pass_info2 =
    {
      designated_field_init (pass, &pass_warn_starpu_unregistered),
      designated_field_init (reference_pass_name, "ssa"),
      designated_field_init (ref_pass_instance_number, 1),
      designated_field_init (pos_op, PASS_POS_INSERT_AFTER)
    };

  if (optimize)
    /* Using `TODO_rebuild_alias' allows us to have more accurate aliasing
       info.  However, `TODO_rebuild_alias' cannot be used when optimizations
       are turned off.  See <http://gcc.gnu.org/ml/gcc/2012-10/msg00104.html>
       for details.  */
    pass_warn_starpu_unregistered.todo_flags_start = TODO_rebuild_alias;

  register_callback (plugin_name, PLUGIN_PASS_MANAGER_SETUP,
		     NULL, &pass_info2);
#endif

  include_dir = getenv ("STARPU_GCC_INCLUDE_DIR");
  opencl_include_dirs = tree_cons (NULL_TREE, build_string (1, "."),
				   NULL_TREE);

  int arg;
  for (arg = 0; arg < plugin_info->argc; arg++)
    {
      if (strcmp (plugin_info->argv[arg].key, "include-dir") == 0)
	{
	  if (plugin_info->argv[arg].value == NULL)
	    error_at (UNKNOWN_LOCATION, "missing directory name for option "
		      "%<-fplugin-arg-starpu-include-dir%>");
	  else
	    /* XXX: We assume that `value' has an infinite lifetime.  */
	    include_dir = plugin_info->argv[arg].value;
	}
      else if (strcmp (plugin_info->argv[arg].key, "opencl-include-dir") == 0)
	{
	  if (plugin_info->argv[arg].value == NULL)
	    error_at (UNKNOWN_LOCATION, "missing directory name for option "
		      "%<-fplugin-arg-starpu-opencl-include-dir%>");
	  else
	    {
	      tree dir = build_string (strlen (plugin_info->argv[arg].value),
				       plugin_info->argv[arg].value);
	      opencl_include_dirs = tree_cons (NULL_TREE, dir,
					       opencl_include_dirs);
	    }
	}
      else if (strcmp (plugin_info->argv[arg].key, "verbose") == 0)
	verbose_output_p = true;
      else
	error_at (UNKNOWN_LOCATION, "invalid StarPU plug-in argument %qs",
		  plugin_info->argv[arg].key);
    }

  /* Keep the directories in the order in which they appear.  */
  opencl_include_dirs = nreverse (opencl_include_dirs);

  return 0;
}

#ifdef __cplusplus
}
#endif