* attribs.c (decl_attributes): Avoid emitting a warning if

	ATTR_FLAG_BUILT_IN.
	* doc/rtl.texi (CALL_INSN_FUNCTION_USAGE): Use lowercase for rtx
	codes.  Document meaning of sets inside CALL_INSN_FUNCTION_USAGE.
	* c-family/c-common.c (DEF_ATTR_STRING): Define and undefine as
	necessary.
	* builtin-attrs.def (DEF_ATTR_FOR_STRING): Define.  Use it to
	define a string "1".
	(ATTR_RET1_NOTHROW_NONNULL_LEAF): New attr definition.
	* builtins.def (BUILT_IN_MEMCPY, BUILT_IN_MEMMOVE, BUILT_IN_MEMSET,
	BUILT_IN_STRCPY): Use it for these functions.
	* postreload.c (reload_combine): Deal with SETs inside
	CALL_INSN_FUNCTION_USAGE.
	* caller-save.c (setup_save_areas, save_call_clobbered_regs):
	Look for REG_RETURNED notes and use a cheap restore if possible.
	* ira-int.h (struct ira_allocno): New member cheap_calls_crossed_num.
	(ALLOCNO_CHEAP_CALLS_CROSSED_NUM): New macro.
	* ira-build.c (ira_create_allocno, create_cap_allocno,
	propagate_allocno_info, propagate_some_info_from_allocno,
	copy_info_to_removed_store_destination, ira_flattening): Handle it.
	* ira-lives.c (pseudo_regno_single_word_and_live_p,
	find_call_crossed_cheap_reg): New static functions.
	(process_bb_node_lives): Look for SETs in CALL_INSN_FUNCTION_USAGE,
	and set ALLOCNO_CHEAP_CALLS_CROSSED_NUM if possible.  Also make
	a REG_RETURNED note in that case.
	* ira.c (setup_reg_renumber): Change assert to allow cases where
	allocnos only cross calls for which they are cheap to restore.
	* ira-costs.c (ira_tune_allocno_costs): Compare
	ALLOCNO_CALLS_CROSSED_NUM to ALLOCNO_CHEAP_CALLS_CROSSED_NUM rather
	than 0.
	* reg-notes.def (REG_RETURNED): New note.
	* cse.c (cse_insn): Likewise.
	* sched-deps.c (sched_analyze_insn): Likewise.
	* expr.c (init_block_move_fn): Set a "fn spec" attribute.
	* calls.c (decl_return_flags): New static function.
	(expand_call): Generate a SET in CALL_INSN_FUNCTION_USAGE for
	functions that return one of their arguments.
	* lto/lto-lang.c (handle_fnspec_attribute): New static function.
	(lto_attribute_table): Add "fn spec".
	(DEF_ATTR_STRING): Define and undefine along with the other macros.
	* regcprop.c (struct kill_set_value_data): New.
	(kill_set_value): Interpret data as a pointer to such a struct.
	Do nothing if the caller wants the register to be ignored.
	(copyprop_hardreg_forward_1): Handle SETs in CALL_INSN_FUNCTION_USAGE.

testsuite/
	* gcc.target/i386/retarg.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@187459 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 52 insertions, 1 deletions

diff --git a/gcc/calls.c b/gcc/calls.c
index a01c4233357..03c92168a24 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -574,6 +574,41 @@ special_function_p (const_tree fndecl, int flags)
   return flags;
 }
 
+/* Similar to special_function_p; return a set of ERF_ flags for the
+   function FNDECL.  */
+static int
+decl_return_flags (tree fndecl)
+{
+  tree attr;
+  tree type = TREE_TYPE (fndecl);
+  if (!type)
+    return 0;
+
+  attr = lookup_attribute ("fn spec", TYPE_ATTRIBUTES (type));
+  if (!attr)
+    return 0;
+
+  attr = TREE_VALUE (TREE_VALUE (attr));
+  if (!attr || TREE_STRING_LENGTH (attr) < 1)
+    return 0;
+
+  switch (TREE_STRING_POINTER (attr)[0])
+    {
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+      return ERF_RETURNS_ARG | (TREE_STRING_POINTER (attr)[0] - '1');
+
+    case 'm':
+      return ERF_NOALIAS;
+
+    case '.':
+    default:
+      return 0;
+    }
+}
+
 /* Return nonzero when FNDECL represents a call to setjmp.  */
 
 int
@@ -2247,8 +2282,9 @@ expand_call (tree exp, rtx target, int ignore)
      (on machines that lack push insns), or 0 if space not preallocated.  */
   rtx argblock = 0;
 
-  /* Mask of ECF_ flags.  */
+  /* Mask of ECF_ and ERF_ flags.  */
   int flags = 0;
+  int return_flags = 0;
 #ifdef REG_PARM_STACK_SPACE
   /* Define the boundary of the register parm stack space that needs to be
      saved, if any.  */
@@ -2293,6 +2329,7 @@ expand_call (tree exp, rtx target, int ignore)
     {
       fntype = TREE_TYPE (fndecl);
       flags |= flags_from_decl_or_type (fndecl);
+      return_flags |= decl_return_flags (fndecl);
     }
   else
     {
@@ -3105,6 +3142,20 @@ expand_call (tree exp, rtx target, int ignore)
 						   VOIDmode, void_type_node,
 						   true);
 
+      if (pass == 1 && (return_flags & ERF_RETURNS_ARG))
+	{
+	  int arg_nr = return_flags & ERF_RETURN_ARG_MASK;
+	  if (PUSH_ARGS_REVERSED)
+	    arg_nr = num_actuals - arg_nr - 1;
+	  if (args[arg_nr].reg
+	      && valreg
+	      && REG_P (valreg)
+	      && GET_MODE (args[arg_nr].reg) == GET_MODE (valreg))
+	  call_fusage
+	    = gen_rtx_EXPR_LIST (TYPE_MODE (TREE_TYPE (args[arg_nr].tree_value)),
+				 gen_rtx_SET (VOIDmode, valreg, args[arg_nr].reg),
+				 call_fusage);
+	}
       /* All arguments and registers used for the call must be set up by
 	 now!  */