RISC-V: Split riscv_process_target_attr with const char *args argument

This patch splits static bool riscv_process_target_attr
(tree args, location_t loc) into two functions:

- bool riscv_process_target_attr (const char *args, location_t loc)
- static bool riscv_process_target_attr (tree args, location_t loc)

Thus, we can call `riscv_process_target_attr` with a `const char *`
argument.  This is useful for implementation of `target_version`
attribute.

gcc/ChangeLog:

	* config/riscv/riscv-target-attr.cc (riscv_process_target_attr):
	Split into two functions with const char *args argument

gcc/config/riscv/riscv-protos.h

@@ -803,6 +803,8 @@ extern bool riscv_use_divmod_expander (void);
 void riscv_init_cumulative_args (CUMULATIVE_ARGS *, tree, rtx, tree, int);
 extern bool
 riscv_option_valid_attribute_p (tree, tree, tree, int);
+extern bool
+riscv_process_target_attr (const char *, location_t);
 extern void
 riscv_override_options_internal (struct gcc_options *);
 extern void riscv_option_override (void);

gcc/config/riscv/riscv-target-attr.cc

@@ -304,35 +304,13 @@ num_occurrences_in_str (char c, char *str)
   return res;
 }
 
-/* Parse the tree in ARGS that contains the target attribute information
+/* Parse the string in ARGS that contains the target attribute information
    and update the global target options space.  */
 
-static bool
-riscv_process_target_attr (tree args, location_t loc)
+bool
+riscv_process_target_attr (const char *args, location_t loc)
 {
-  if (TREE_CODE (args) == TREE_LIST)
-    {
-      do
-	{
-	  tree head = TREE_VALUE (args);
-	  if (head)
-	    {
-	      if (!riscv_process_target_attr (head, loc))
-		return false;
-	    }
-	  args = TREE_CHAIN (args);
-      } while (args);
-
-      return true;
-    }
-
-  if (TREE_CODE (args) != STRING_CST)
-    {
-      error_at (loc, "attribute %<target%> argument not a string");
-      return false;
-    }
-
-  size_t len = strlen (TREE_STRING_POINTER (args));
+  size_t len = strlen (args);
 
   /* No need to emit warning or error on empty string here, generic code already
      handle this case.  */
@@ -343,7 +321,7 @@ riscv_process_target_attr (tree args, location_t loc)
 
   std::unique_ptr<char[]> buf (new char[len+1]);
   char *str_to_check = buf.get ();
-  strcpy (str_to_check, TREE_STRING_POINTER (args));
+  strcpy (str_to_check, args);
 
   /* Used to catch empty spaces between semi-colons i.e.
      attribute ((target ("attr1;;attr2"))).  */
@@ -366,7 +344,7 @@ riscv_process_target_attr (tree args, location_t loc)
   if (num_attrs != num_semicolons + 1)
     {
       error_at (loc, "malformed %<target(\"%s\")%> attribute",
-		TREE_STRING_POINTER (args));
+		args);
       return false;
     }
 
@@ -376,6 +354,37 @@ riscv_process_target_attr (tree args, location_t loc)
   return true;
 }
 
+/* Parse the tree in ARGS that contains the target attribute information
+   and update the global target options space.  */
+
+static bool
+riscv_process_target_attr (tree args, location_t loc)
+{
+  if (TREE_CODE (args) == TREE_LIST)
+    {
+      do
+	{
+	  tree head = TREE_VALUE (args);
+	  if (head)
+	    {
+	      if (!riscv_process_target_attr (head, loc))
+		return false;
+	    }
+	  args = TREE_CHAIN (args);
+      } while (args);
+
+      return true;
+    }
+
+  if (TREE_CODE (args) != STRING_CST)
+    {
+      error_at (loc, "attribute %<target%> argument not a string");
+      return false;
+    }
+
+  return riscv_process_target_attr (TREE_STRING_POINTER (args), loc);
+}
+
 /* Implement TARGET_OPTION_VALID_ATTRIBUTE_P.
    This is used to process attribute ((target ("..."))).
    Note, that riscv_set_current_function() has not been called before,