RISC-V: Base for complex extension implications

Thanks to the commit 48558a5 ("RISC-V: Allow nested implications for
extensions"), we can write complex extension implications in theory.
However, to actually do that, we need to pass more information to
check_func.

For example, we want to imply 'Zcf' from 'F' if and only if the 'Zce'
extension is also enabled and XLEN is 32.  Passing rps is a way to
enable this.

This commit prepares for such complex extension implications.

bfd/ChangeLog:

	* elfxx-riscv.c (struct riscv_implicit_subset) Move around and
	change check_func function prototype.
	(check_implicit_always): New arguments.
	(check_implicit_for_i): Likewise.
	(riscv_implicit_subsets): Add comment for this variable.
	(riscv_parse_add_implicit_subsets): Call check_func with
	new arguments.

bfd/elfxx-riscv.c

@@ -1064,35 +1064,44 @@ riscv_elf_ignore_reloc (bfd *abfd ATTRIBUTE_UNUSED,
   return bfd_reloc_ok;
 }
 
+/* Record all implicit information for the subsets.  */
+
+typedef struct riscv_implicit_subset
+{
+  const char *subset_name;
+  const char *implicit_name;
+  /* A function to determine if we need to add the implicit subset.  */
+  bool (*check_func) (riscv_parse_subset_t *,
+		      const struct riscv_implicit_subset *,
+		      const riscv_subset_t *);
+} riscv_implicit_subset_t;
+
 /* Always add the IMPLICIT for the SUBSET.  */
 
 static bool
-check_implicit_always (const char *implicit ATTRIBUTE_UNUSED,
-		       riscv_subset_t *subset ATTRIBUTE_UNUSED)
+check_implicit_always (riscv_parse_subset_t *rps ATTRIBUTE_UNUSED,
+		       const riscv_implicit_subset_t *implicit
+			   ATTRIBUTE_UNUSED,
+		       const riscv_subset_t *subset ATTRIBUTE_UNUSED)
 {
   return true;
 }
 
 /* Add the IMPLICIT only when the version of SUBSET less than 2.1.  */
 
 static bool
-check_implicit_for_i (const char *implicit ATTRIBUTE_UNUSED,
-		      riscv_subset_t *subset)
+check_implicit_for_i (riscv_parse_subset_t *rps ATTRIBUTE_UNUSED,
+		      const riscv_implicit_subset_t *implicit ATTRIBUTE_UNUSED,
+		      const riscv_subset_t *subset)
 {
   return (subset->major_version < 2
 	  || (subset->major_version == 2
 	      && subset->minor_version < 1));
 }
 
-/* Record all implicit information for the subsets.  */
-struct riscv_implicit_subset
-{
-  const char *subset_name;
-  const char *implicit_name;
-  /* A function to determine if we need to add the implicit subset.  */
-  bool (*check_func) (const char *, riscv_subset_t *);
-};
-static struct riscv_implicit_subset riscv_implicit_subsets[] =
+/* All extension implications.  */
+
+static riscv_implicit_subset_t riscv_implicit_subsets[] =
 {
   {"e", "i",		check_implicit_always},
   {"i", "zicsr",	check_implicit_for_i},
@@ -1905,7 +1914,7 @@ riscv_parse_extensions (riscv_parse_subset_t *rps,
 static void
 riscv_parse_add_implicit_subsets (riscv_parse_subset_t *rps)
 {
-  struct riscv_implicit_subset *t = riscv_implicit_subsets;
+  riscv_implicit_subset_t *t = riscv_implicit_subsets;
   bool finished = false;
   while (!finished)
     {
@@ -1917,7 +1926,7 @@ riscv_parse_add_implicit_subsets (riscv_parse_subset_t *rps)
 	  if (riscv_lookup_subset (rps->subset_list, t->subset_name, &subset)
 	      && !riscv_lookup_subset (rps->subset_list, t->implicit_name,
 				       &implicit_subset)
-	      && t->check_func (t->implicit_name, subset))
+	      && t->check_func (rps, t, subset))
 	    {
 	      riscv_parse_add_subset (rps, t->implicit_name,
 				      RISCV_UNKNOWN_VERSION,