[RISC-V] add implied extension repeatly until stable

Call handle_implied_ext repeatly until there's no
new subset added into the subset list.

gcc/ChangeLog:

	* common/config/riscv/riscv-common.cc (riscv_subset_list::riscv_subset_list):
	init m_subset_num to 0.
	(riscv_subset_list::add): increase m_subset_num once a subset added.
	(riscv_subset_list::finalize): call handle_implied_ext repeatly
	until no change in m_subset_num.
	* config/riscv/riscv-subset.h: add m_subset_num member.

Signed-off-by: Fei Gao <gaofei@eswincomputing.com>
(cherry picked from commit 682731d)

gcc/common/config/riscv/riscv-common.cc

@@ -458,7 +458,8 @@ riscv_subset_t::riscv_subset_t ()
 }
 
 riscv_subset_list::riscv_subset_list (const char *arch, location_t loc)
-  : m_arch (arch), m_loc (loc), m_head (NULL), m_tail (NULL), m_xlen (0)
+  : m_arch (arch), m_loc (loc), m_head (NULL), m_tail (NULL), m_xlen (0),
+    m_subset_num (0)
 {
 }
 
@@ -709,6 +710,7 @@ riscv_subset_list::add (const char *subset, int major_version,
       return;
     }
 
+  m_subset_num++;
   riscv_subset_t *s = new riscv_subset_t ();
   riscv_subset_t *itr;
 
@@ -1472,9 +1474,15 @@ void
 riscv_subset_list::finalize ()
 {
   riscv_subset_t *subset;
+  unsigned pre_subset_num;
 
-  for (subset = m_head; subset != NULL; subset = subset->next)
-    handle_implied_ext (subset->name.c_str ());
+  do
+    {
+      pre_subset_num = m_subset_num;
+      for (subset = m_head; subset != NULL; subset = subset->next)
+	handle_implied_ext (subset->name.c_str ());
+    }
+  while (pre_subset_num != m_subset_num);
 
   gcc_assert (check_implied_ext ());
 

gcc/config/riscv/riscv-subset.h

@@ -65,6 +65,9 @@ class riscv_subset_list
   /* Allow adding the same extension more than once.  */
   bool m_allow_adding_dup;
 
+  /* Number of subsets. */
+  unsigned m_subset_num;
+
   riscv_subset_list (const char *, location_t);
 
   const char *parsing_subset_version (const char *, const char *, unsigned *,