RISC-V: Relax the -march string for accept any order

-march was require canonical order before, however it's not easy for
most user when we have so many extension, so this patch is relax the
constraint, -march accept the ISA string in any order, it only has few
requirement:

1. Must start with rv[32|64][e|i|g].
2. Multi-letter and single letter extension must be separated by
   at least one underscore(`_`).

gcc/ChangeLog:

	* common/config/riscv/riscv-common.cc
	(riscv_subset_list::parse_single_std_ext): New parameter.
	(riscv_subset_list::parse_single_multiletter_ext): Ditto.
	(riscv_subset_list::parse_single_ext): Ditto.
	(riscv_subset_list::parse): Relax the order for the input of ISA
	string.
	* config/riscv/riscv-subset.h
	(riscv_subset_list::parse_single_std_ext): New parameter.
	(riscv_subset_list::parse_single_multiletter_ext): Ditto.
	(riscv_subset_list::parse_single_ext): Ditto.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/arch-33.c: New.
	* gcc.target/riscv/arch-34.c: New.

1 files changed, 3 insertions, 3 deletions

diff --git a/gcc/config/riscv/riscv-subset.h b/gcc/config/riscv/riscv-subset.h
index c8117d8..a80f913 100644
--- a/gcc/config/riscv/riscv-subset.h
+++ b/gcc/config/riscv/riscv-subset.h
@@ -71,12 +71,12 @@ private:
 
   const char *parse_std_ext (const char *);
 
-  const char *parse_single_std_ext (const char *);
+  const char *parse_single_std_ext (const char *, bool);
 
   const char *parse_multiletter_ext (const char *, const char *,
 				     const char *);
   const char *parse_single_multiletter_ext (const char *, const char *,
-					    const char *);
+					    const char *, bool);
 
   void handle_implied_ext (const char *);
   bool check_implied_ext ();
@@ -101,7 +101,7 @@ public:
   riscv_subset_list *clone () const;
 
   static riscv_subset_list *parse (const char *, location_t);
-  const char *parse_single_ext (const char *);
+  const char *parse_single_ext (const char *, bool exact_single_p = true);
 
   const riscv_subset_t *begin () const {return m_head;};
   const riscv_subset_t *end () const {return NULL;};