Add a apply_pass_by_reference_rules helper

This patch adds a helper routine that applies pass-by-reference
semantics to an existing function_arg_info.

The c6x part means that c6x_function_arg and c6x_function_arg_advance
see the same "named" value as pass_by_reference did, rather than
pass_by_reference seeing "true" and the others seeing "false".
This doesn't matter because the c6x port doesn't care about namedness.

The rs6000.c patch removes an assignment to "type", but the only
later code to use it was the patched promote_mode line.

(The reason for patching these places despite the above is that
often target code gets used as a basis for new targets or changes
to existing ones.)

2019-08-20  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* calls.h (apply_pass_by_reference_rules): Declare.
	* calls.c (apply_pass_by_reference_rules): New function.
	* config/c6x/c6x.c (c6x_call_saved_register_used): Use it.
	* config/rs6000/rs6000-call.c (rs6000_parm_needs_stack): Likewise.
	* config/s390/s390.c (s390_call_saved_register_used): Likewise.
	* function.c (assign_parm_find_data_types): Likewise.
	* var-tracking.c (prepare_call_arguments): Likewise.

From-SVN: r274704

gcc/ChangeLog

 2019-08-20  Richard Sandiford  <richard.sandiford@arm.com>
 
+	* calls.h (apply_pass_by_reference_rules): Declare.
+	* calls.c (apply_pass_by_reference_rules): New function.
+	* config/c6x/c6x.c (c6x_call_saved_register_used): Use it.
+	* config/rs6000/rs6000-call.c (rs6000_parm_needs_stack): Likewise.
+	* config/s390/s390.c (s390_call_saved_register_used): Likewise.
+	* function.c (assign_parm_find_data_types): Likewise.
+	* var-tracking.c (prepare_call_arguments): Likewise.
+
+2019-08-20  Richard Sandiford  <richard.sandiford@arm.com>
+
 	* target.def (must_pass_in_stack): Take a function_arg_info instead
 	of a mode and a type.
 	* doc/tm.texi: Regenerate.

gcc/calls.c

@@ -935,6 +935,22 @@ pass_va_arg_by_reference (tree type)
   return pass_by_reference (NULL, function_arg_info (type, /*named=*/false));
 }
 
+/* Decide whether ARG, which occurs in the state described by CA,
+   should be passed by reference.  Return true if so and update
+   ARG accordingly.  */
+
+bool
+apply_pass_by_reference_rules (CUMULATIVE_ARGS *ca, function_arg_info &arg)
+{
+  if (pass_by_reference (ca, arg))
+    {
+      arg.type = build_pointer_type (arg.type);
+      arg.mode = TYPE_MODE (arg.type);
+      return true;
+    }
+  return false;
+}
+
 /* Return true if ARG, which is passed by reference, should be callee
    copied instead of caller copied.  */
 

gcc/calls.h

@@ -118,6 +118,8 @@ extern void fixup_tail_calls (void);
 
 extern bool pass_by_reference (CUMULATIVE_ARGS *, function_arg_info);
 extern bool pass_va_arg_by_reference (tree);
+extern bool apply_pass_by_reference_rules (CUMULATIVE_ARGS *,
+					   function_arg_info &);
 extern bool reference_callee_copied (CUMULATIVE_ARGS *,
 				     const function_arg_info &);
 extern void maybe_warn_alloc_args_overflow (tree, tree, tree[2], int[2]);

gcc/config/c6x/c6x.c

@@ -1088,8 +1088,6 @@ c6x_call_saved_register_used (tree call_expr)
   cumulative_args_t cum;
   HARD_REG_SET call_saved_regset;
   tree parameter;
-  machine_mode mode;
-  tree type;
   rtx parm_rtx;
   int i;
 
@@ -1107,19 +1105,9 @@ c6x_call_saved_register_used (tree call_expr)
       if (TREE_CODE (parameter) == ERROR_MARK)
 	return true;
 
-      type = TREE_TYPE (parameter);
-      gcc_assert (type);
-
-      mode = TYPE_MODE (type);
-      gcc_assert (mode);
-
-      if (pass_by_reference (&cum_v, function_arg_info (type, /*named=*/true)))
- 	{
- 	  mode = Pmode;
- 	  type = build_pointer_type (type);
- 	}
+      function_arg_info arg (TREE_TYPE (parameter), /*named=*/true);
+      apply_pass_by_reference_rules (&cum_v, arg);
 
-       function_arg_info arg (type, mode, /*named=*/false);
        parm_rtx = c6x_function_arg (cum, arg);
 
        c6x_function_arg_advance (cum, arg);

gcc/config/rs6000/rs6000-call.c

@@ -2170,7 +2170,6 @@ rs6000_pass_by_reference (cumulative_args_t, const function_arg_info &arg)
 static bool
 rs6000_parm_needs_stack (cumulative_args_t args_so_far, tree type)
 {
-  machine_mode mode;
   int unsignedp;
   rtx entry_parm;
 
@@ -2193,16 +2192,14 @@ rs6000_parm_needs_stack (cumulative_args_t args_so_far, tree type)
     type = TREE_TYPE (first_field (type));
 
   /* See if this arg was passed by invisible reference.  */
-  if (pass_by_reference (get_cumulative_args (args_so_far),
-			 function_arg_info (type, /*named=*/true)))
-    type = build_pointer_type (type);
+  function_arg_info arg (type, /*named=*/true);
+  apply_pass_by_reference_rules (get_cumulative_args (args_so_far), arg);
 
   /* Find mode as it is passed by the ABI.  */
   unsignedp = TYPE_UNSIGNED (type);
-  mode = promote_mode (type, TYPE_MODE (type), &unsignedp);
+  arg.mode = promote_mode (arg.type, arg.mode, &unsignedp);
 
   /* If we must pass in stack, we need a stack.  */
-  function_arg_info arg (type, mode, /*named=*/true);
   if (rs6000_must_pass_in_stack (arg))
     return true;
 

gcc/config/s390/s390.c

@@ -13309,8 +13309,6 @@ s390_call_saved_register_used (tree call_expr)
   CUMULATIVE_ARGS cum_v;
   cumulative_args_t cum;
   tree parameter;
-  machine_mode mode;
-  tree type;
   rtx parm_rtx;
   int reg, i;
 
@@ -13327,22 +13325,12 @@ s390_call_saved_register_used (tree call_expr)
       if (TREE_CODE (parameter) == ERROR_MARK)
 	return true;
 
-      type = TREE_TYPE (parameter);
-      gcc_assert (type);
-
-      mode = TYPE_MODE (type);
-      gcc_assert (mode);
-
       /* We assume that in the target function all parameters are
 	 named.  This only has an impact on vector argument register
 	 usage none of which is call-saved.  */
-      if (pass_by_reference (&cum_v, function_arg_info (type, /*named=*/true)))
-	{
-	  mode = Pmode;
-	  type = build_pointer_type (type);
-	}
+      function_arg_info arg (TREE_TYPE (parameter), /*named=*/true);
+      apply_pass_by_reference_rules (&cum_v, arg);
 
-       function_arg_info arg (type, mode, /*named=*/true);
        parm_rtx = s390_function_arg (cum, arg);
 
        s390_function_arg_advance (cum, arg);

gcc/function.c

@@ -2456,11 +2456,11 @@ assign_parm_find_data_types (struct assign_parm_data_all *all, tree parm,
   /* See if this arg was passed by invisible reference.  */
   {
     function_arg_info arg (passed_type, passed_mode, data->named_arg);
-    if (pass_by_reference (&all->args_so_far_v, arg))
+    if (apply_pass_by_reference_rules (&all->args_so_far_v, arg))
       {
-	passed_type = nominal_type = build_pointer_type (passed_type);
+	passed_type = nominal_type = arg.type;
 	data->passed_pointer = true;
-	passed_mode = nominal_mode = TYPE_MODE (nominal_type);
+	passed_mode = nominal_mode = arg.mode;
       }
   }
 

gcc/var-tracking.c

@@ -6426,28 +6426,24 @@ prepare_call_arguments (basic_block bb, rtx_insn *insn)
 	  }
 	if (t && t != void_list_node)
 	  {
-	    tree argtype = TREE_VALUE (t);
 	    rtx reg;
-	    function_arg_info orig_arg (argtype, /*named=*/true);
-	    if (pass_by_reference (&args_so_far_v, orig_arg))
-	      argtype = build_pointer_type (argtype);
-	    machine_mode mode = TYPE_MODE (argtype);
-	    function_arg_info arg (argtype, /*named=*/true);
+	    function_arg_info arg (TREE_VALUE (t), /*named=*/true);
+	    apply_pass_by_reference_rules (&args_so_far_v, arg);
 	    reg = targetm.calls.function_arg (args_so_far, arg);
-	    if (TREE_CODE (argtype) == REFERENCE_TYPE
-		&& INTEGRAL_TYPE_P (TREE_TYPE (argtype))
+	    if (TREE_CODE (arg.type) == REFERENCE_TYPE
+		&& INTEGRAL_TYPE_P (TREE_TYPE (arg.type))
 		&& reg
 		&& REG_P (reg)
-		&& GET_MODE (reg) == mode
-		&& (GET_MODE_CLASS (mode) == MODE_INT
-		    || GET_MODE_CLASS (mode) == MODE_PARTIAL_INT)
+		&& GET_MODE (reg) == arg.mode
+		&& (GET_MODE_CLASS (arg.mode) == MODE_INT
+		    || GET_MODE_CLASS (arg.mode) == MODE_PARTIAL_INT)
 		&& REG_P (x)
 		&& REGNO (x) == REGNO (reg)
-		&& GET_MODE (x) == mode
+		&& GET_MODE (x) == arg.mode
 		&& item)
 	      {
 		machine_mode indmode
-		  = TYPE_MODE (TREE_TYPE (argtype));
+		  = TYPE_MODE (TREE_TYPE (arg.type));
 		rtx mem = gen_rtx_MEM (indmode, x);
 		cselib_val *val = cselib_lookup (mem, indmode, 0, VOIDmode);
 		if (val && cselib_preserved_value_p (val))