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

1 files changed, 16 insertions, 0 deletions

diff --git a/gcc/calls.c b/gcc/calls.c
index 1f691e84dfe..6f573f3b26e 100644
--- a/gcc/calls.c
+++ b/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.  */