RISC-V: Relax the order checking for the architecture string

* riscv-toolchain-conventions,
PR, https://github.com/riscv-non-isa/riscv-toolchain-conventions/pull/14
Issue, https://github.com/riscv-non-isa/riscv-toolchain-conventions/issues/11

* Refer to the commit afc41ffb,
RISC-V: Reorder the prefixed extensions which are out of order.

In the past we only allow to reorder the prefixed extensions.  But according
to the PR 14 in the riscv-toolchain-convention, we can also relax the order
checking to allow the whole extensions be written out of orders, including
the single standard extensions and the prefixed multi-letter extensions.
Just that we still need to follow the following rules as usual,

1. prefixed extensions need to be seperated with `_'.
2. prefixed extensions need complete <major>.<minor> version if set.

Please see the details in the march-ok-reorder gas testcase.

Passed the riscv-gnu-toolchain regressions.

bfd/
    * elfxx-riscv.c (enum riscv_prefix_ext_class): Changed RV_ISA_CLASS_UNKNOWN
    to RV_ISA_CLASS_SINGLE, since everything that does not belong to the
    multi-keyword will possible be a single extension for the current parser.
    (parse_config): Likewise.
    (riscv_get_prefix_class): Likewise.
    (riscv_compare_subsets): Likewise.
    (riscv_parse_std_ext): Removed, and merged with riscv_parse_prefixed_ext
    into riscv_parse_extensions.
    (riscv_parse_prefixed_ext): Likewise.
    (riscv_parse_subset): Only need to call riscv_parse_extensions to parse
    both single standard and prefixed extensions.
gas/
    * testsuite/gas/riscv/march-fail-order-std.d: Removed since the relaxed
    order checking.
    * testsuite/gas/riscv/march-fail-order-std.l: Likewise.
    * testsuite/gas/riscv/march-fail-order-x-std.d: Likewise.
    * testsuite/gas/riscv/march-fail-order-z-std.d: Likewise.
    * testsuite/gas/riscv/march-fail-order-zx-std.l: Likewise.
    * testsuite/gas/riscv/march-fail-unknown-std.l: Updated.
    * testsuite/gas/riscv/march-ok-reorder.d: New testcase.

bfd/elfxx-riscv.c

@@ -1275,7 +1275,7 @@ enum riscv_prefix_ext_class
   RV_ISA_CLASS_S,
   RV_ISA_CLASS_ZXM,
   RV_ISA_CLASS_X,
-  RV_ISA_CLASS_UNKNOWN
+  RV_ISA_CLASS_SINGLE
 };
 
 /* Record the strings of the prefixed extensions, and their corresponding
@@ -1296,7 +1296,7 @@ static const struct riscv_parse_prefix_config parse_config[] =
   {RV_ISA_CLASS_Z, "z"},
   {RV_ISA_CLASS_S, "s"},
   {RV_ISA_CLASS_X, "x"},
-  {RV_ISA_CLASS_UNKNOWN, NULL}
+  {RV_ISA_CLASS_SINGLE, NULL}
 };
 
 /* Get the prefixed name class for the extensions, the class also
@@ -1306,14 +1306,14 @@ static enum riscv_prefix_ext_class
 riscv_get_prefix_class (const char *arch)
 {
   int i = 0;
-  while (parse_config[i].class != RV_ISA_CLASS_UNKNOWN)
+  while (parse_config[i].class != RV_ISA_CLASS_SINGLE)
     {
       if (strncmp (arch, parse_config[i].prefix,
 		   strlen (parse_config[i].prefix)) == 0)
 	return parse_config[i].class;
       i++;
     }
-  return RV_ISA_CLASS_UNKNOWN;
+  return RV_ISA_CLASS_SINGLE;
 }
 
 /* Check KNOWN_EXTS to see if the EXT is supported.  */
@@ -1405,9 +1405,9 @@ riscv_compare_subsets (const char *subset1, const char *subset2)
   enum riscv_prefix_ext_class class1 = riscv_get_prefix_class (subset1);
   enum riscv_prefix_ext_class class2 = riscv_get_prefix_class (subset2);
 
-  if (class1 != RV_ISA_CLASS_UNKNOWN)
+  if (class1 != RV_ISA_CLASS_SINGLE)
     order1 = - (int) class1;
-  if (class2 != RV_ISA_CLASS_UNKNOWN)
+  if (class2 != RV_ISA_CLASS_SINGLE)
     order2 = - (int) class2;
 
   if (order1 == order2)
@@ -1659,7 +1659,7 @@ riscv_parsing_subset_version (const char *p,
   return p;
 }
 
-/* Parsing function for standard extensions.
+/* Parsing function for both standard and prefixed extensions.
 
    Return Value:
      Points to the end of extensions.
@@ -1670,9 +1670,9 @@ riscv_parsing_subset_version (const char *p,
      `p`: Curent parsing position.  */
 
 static const char *
-riscv_parse_std_ext (riscv_parse_subset_t *rps,
+riscv_parse_extensions (riscv_parse_subset_t *rps,
-		     const char *arch,
+			const char *arch,
-		     const char *p)
+			const char *p)
 {
   /* First letter must start with i, e or g.  */
   if (*p != 'e' && *p != 'i' && *p != 'g')
@@ -1683,79 +1683,7 @@ riscv_parse_std_ext (riscv_parse_subset_t *rps,
       return NULL;
     }
 
-  while (p != NULL && *p != '\0')
+  while (*p != '\0')
-    {
-      /* Stop when we parsed the known prefix class.  */
-      enum riscv_prefix_ext_class class = riscv_get_prefix_class (p);
-      if (class != RV_ISA_CLASS_UNKNOWN)
-	break;
-
-      if (*p == '_')
-	{
-	  p++;
-	  continue;
-	}
-
-      bool implicit = false;
-      int major = RISCV_UNKNOWN_VERSION;
-      int minor = RISCV_UNKNOWN_VERSION;
-      char subset[2] = {0, 0};
-
-      subset[0] = *p;
-
-      /* Check if the standard extension is supported.  */
-      if (riscv_ext_order[(subset[0] - 'a')] == 0)
-	{
-	  rps->error_handler
-	    (_("%s: unknown standard ISA extension `%c'"),
-	     arch, subset[0]);
-	  return NULL;
-	}
-
-      /* Checking canonical order.  */
-      if (rps->subset_list->tail != NULL
-	  && riscv_compare_subsets (rps->subset_list->tail->name, subset) > 0)
-	{
-	  rps->error_handler
-	    (_("%s: standard ISA extension `%c' is not "
-	       "in canonical order"), arch, subset[0]);
-	  return NULL;
-	}
-
-      p = riscv_parsing_subset_version (++p, &major, &minor);
-      /* Added g as an implicit extension.  */
-      if (subset[0] == 'g')
-	{
-	  implicit = true;
-	  major = RISCV_UNKNOWN_VERSION;
-	  minor = RISCV_UNKNOWN_VERSION;
-	}
-      riscv_parse_add_subset (rps, subset, major, minor, implicit);
-    }
-
-  return p;
-}
-
-/* Parsing function for prefixed extensions.
-
-   Return Value:
-     Points to the end of extension.
-
-   Arguments:
-     `rps`: Hooks and status for parsing extensions.
-     `arch`: Full ISA string.
-     `p`: Curent parsing position.  */
-
-static const char *
-riscv_parse_prefixed_ext (riscv_parse_subset_t *rps,
-			  const char *arch,
-			  const char *p)
-{
-  int major_version;
-  int minor_version;
-  enum riscv_prefix_ext_class class;
-
-  while (*p)
     {
       if (*p == '_')
 	{
@@ -1763,52 +1691,62 @@ riscv_parse_prefixed_ext (riscv_parse_subset_t *rps,
 	  continue;
 	}
 
-      class = riscv_get_prefix_class (p);
-      if (class == RV_ISA_CLASS_UNKNOWN)
-	{
-	  rps->error_handler
-	    (_("%s: unknown prefix class for the ISA extension `%s'"),
-	     arch, p);
-	  return NULL;
-	}
-
       char *subset = xstrdup (p);
-      char *q = subset;
+      char *q = subset;	/* Start of version.  */
       const char *end_of_version;
+      bool implicit = false;
 
-      /* Extract the whole prefixed extension by '_'.  */
+      enum riscv_prefix_ext_class class = riscv_get_prefix_class (p);
-      while (*++q != '\0' && *q != '_')
+      if (class == RV_ISA_CLASS_SINGLE)
-	;
-      /* Look forward to the first letter which is not <major>p<minor>.  */
-      bool find_any_version = false;
-      bool find_minor_version = false;
-      while (1)
 	{
-	  q--;
+	  if (riscv_ext_order[(*subset - 'a')] == 0)
-	  if (ISDIGIT (*q))
+	    {
-	    find_any_version = true;
+	      rps->error_handler
-	  else if (find_any_version
+		(_("%s: unknown standard ISA extension or prefix class `%c'"),
-		   && !find_minor_version
+		 arch, *subset);
-		   && *q == 'p'
+	      free (subset);
-		   && ISDIGIT (*(q - 1)))
+	      return NULL;
-	    find_minor_version = true;
+	    }
-	  else
+	  q++;
-	    break;
 	}
-      q++;
+      else
-
-      /* Check if the end of extension is 'p' or not.  If yes, then
-	 the second letter from the end cannot be number.  */
-      if (*(q - 1) == 'p' && ISDIGIT (*(q - 2)))
 	{
-	  *q = '\0';
+	  /* Extract the whole prefixed extension by '_'.  */
-	  rps->error_handler
+	  while (*++q != '\0' && *q != '_')
-	    (_("%s: invalid prefixed ISA extension `%s' ends with <number>p"),
+	    ;
-	     arch, subset);
+	  /* Look forward to the first letter which is not <major>p<minor>.  */
-	  free (subset);
+	  bool find_any_version = false;
-	  return NULL;
+	  bool find_minor_version = false;
+	  while (1)
+	    {
+	      q--;
+	      if (ISDIGIT (*q))
+		find_any_version = true;
+	      else if (find_any_version
+		       && !find_minor_version
+		       && *q == 'p'
+		       && ISDIGIT (*(q - 1)))
+	      find_minor_version = true;
+	      else
+		break;
+	    }
+	  q++;
+
+	  /* Check if the end of extension is 'p' or not.  If yes, then
+	     the second letter from the end cannot be number.  */
+	  if (*(q - 1) == 'p' && ISDIGIT (*(q - 2)))
+	    {
+	      *q = '\0';
+	      rps->error_handler
+		(_("%s: invalid prefixed ISA extension `%s' ends with <number>p"),
+		 arch, subset);
+	      free (subset);
+	      return NULL;
+	    }
 	}
 
+      int major_version = RISCV_UNKNOWN_VERSION;
+      int minor_version = RISCV_UNKNOWN_VERSION;
       end_of_version =
 	riscv_parsing_subset_version (q, &major_version, &minor_version);
       *q = '\0';
@@ -1818,8 +1756,9 @@ riscv_parse_prefixed_ext (riscv_parse_subset_t *rps,
 	  return NULL;
 	}
 
-      /* Check that the extension name is well-formed.  */
+      /* Check if the prefixed extension name is well-formed.  */
-      if (rps->check_unknown_prefixed_ext
+      if (class != RV_ISA_CLASS_SINGLE
+	  && rps->check_unknown_prefixed_ext
 	  && !riscv_recognized_prefixed_ext (subset))
 	{
 	  rps->error_handler
@@ -1829,13 +1768,22 @@ riscv_parse_prefixed_ext (riscv_parse_subset_t *rps,
 	  return NULL;
 	}
 
+      /* Added g as an implicit extension.  */
+      if (class == RV_ISA_CLASS_SINGLE
+	  && strcmp (subset, "g") == 0)
+	{
+	  implicit = true;
+	  major_version = RISCV_UNKNOWN_VERSION;
+	  minor_version = RISCV_UNKNOWN_VERSION;
+	}
       riscv_parse_add_subset (rps, subset,
 			      major_version,
-			      minor_version, false);
+			      minor_version, implicit);
       p += end_of_version - subset;
       free (subset);
 
-      if (*p != '\0' && *p != '_')
+      if (class != RV_ISA_CLASS_SINGLE
+	  && *p != '\0' && *p != '_')
 	{
 	  rps->error_handler
 	    (_("%s: prefixed ISA extension must separate with _"),
@@ -2008,16 +1956,8 @@ riscv_parse_subset (riscv_parse_subset_t *rps,
       return false;
     }
 
-  /* Parsing standard extension.  */
+  /* Parse single standard and prefixed extensions.  */
-  p = riscv_parse_std_ext (rps, arch, p);
+  if (riscv_parse_extensions (rps, arch, p) == NULL)
-
-  if (p == NULL)
-    return false;
-
-  /* Parse prefixed extensions.  */
-  p = riscv_parse_prefixed_ext (rps, arch, p);
-
-  if (p == NULL)
     return false;
 
   /* Finally add implicit extensions according to the current

gas/testsuite/gas/riscv/march-fail-order-std.d

@@ -1,3 +0,0 @@
-#as: -march=rv32iamfd
-#source: empty.s
-#error_output: march-fail-order-std.l

gas/testsuite/gas/riscv/march-fail-order-std.l

@@ -1,2 +0,0 @@
-.*Assembler messages:
-.*Error: .*standard ISA extension `m' is not in canonical order

gas/testsuite/gas/riscv/march-fail-order-x-std.d

@@ -1,3 +0,0 @@
-#as: -march=rv32i_xargle2p0_mafd
-#source: empty.s
-#error_output: march-fail-order-zx-std.l

gas/testsuite/gas/riscv/march-fail-order-z-std.d

@@ -1,3 +0,0 @@
-#as: -march=rv32i_zicsr2p0_mafd
-#source: empty.s
-#error_output: march-fail-order-zx-std.l

gas/testsuite/gas/riscv/march-fail-order-zx-std.l

@@ -1,2 +0,0 @@
-.*Assembler messages:
-.*Error: .*unknown prefix class for the ISA extension `mafd'

gas/testsuite/gas/riscv/march-fail-unknown-std.l

@@ -1,2 +1,2 @@
 .*Assembler messages:
-.*Error: .*unknown standard ISA extension `y'
+.*Error: .*unknown standard ISA extension or prefix class `y'

gas/testsuite/gas/riscv/march-ok-reorder.d

@@ -0,0 +1,7 @@
+#as: -misa-spec=20191213 -march=rv32i2azicsr_fc2p0dxfoo2p0_m1_xbar2p0_zba
+#source: empty.s
+#readelf: -A
+
+Attribute Section: riscv
+File Attributes
+  Tag_RISCV_arch: "rv32i2p0_m1p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0_zifencei2p0_zmmul1p0_zba1p0_xbar2p0_xfoo2p0"