RISC-V: The 'multilib-generator' enhancement.

Think about this case:
  ./multilib-generator rv32imc-ilp32-rv32imac,rv32imacxthead-f
Here are 2 problems:
  1. A unexpected 'xtheadf' extension was made.
  2. The arch 'rv32imac' was not be created.
This modification fix these two, and also sorts 'multi-letter'.

gcc/ChangeLog:
	* config/riscv/arch-canonicalize (longext_sort): New function for
	 sorting 'multi-letter'.
	* config/riscv/multilib-generator: Adjusting the loop of 'alt' in
	'alts'.	The 'arch' may not be the first of 'alts'.
	(_expand_combination): Add underline for the 'ext' without '*'.
	This is because, a single-letter extension can always be treated well
	with a '_' prefix, but it cannot be separated out if it is appended
	to a multi-letter.

2 files changed, 20 insertions, 6 deletions

diff --git a/gcc/config/riscv/arch-canonicalize b/gcc/config/riscv/arch-canonicalize
index 057a803..ea95a06 100755
--- a/gcc/config/riscv/arch-canonicalize
+++ b/gcc/config/riscv/arch-canonicalize
@@ -74,8 +74,20 @@ def arch_canonicalize(arch):
   # becasue we just append extensions list to the arch string.
   std_exts += list(filter(lambda x:len(x) == 1, long_exts))
 
+  def longext_sort (exts):
+    if not exts.startswith("zxm") and exts.startswith("z"):
+      # If "Z" extensions are named, they should be ordered first by CANONICAL.
+      if exts[1] not in CANONICAL_ORDER:
+        raise Exception("Unsupported extension `%s`" % exts)
+      canonical_sort = CANONICAL_ORDER.index(exts[1])
+    else:
+      canonical_sort = -1
+    return (exts.startswith("x"), exts.startswith("zxm"),
+            LONG_EXT_PREFIXES.index(exts[0]), canonical_sort, exts[1:])
+
   # Multi-letter extension must be in lexicographic order.
-  long_exts = list(sorted(filter(lambda x:len(x) != 1, long_exts)))
+  long_exts = list(sorted(filter(lambda x:len(x) != 1, long_exts),
+                          key=longext_sort))
 
   # Put extensions in canonical order.
   for ext in CANONICAL_ORDER:
diff --git a/gcc/config/riscv/multilib-generator b/gcc/config/riscv/multilib-generator
index 7fc6cc2..a204543 100755
--- a/gcc/config/riscv/multilib-generator
+++ b/gcc/config/riscv/multilib-generator
@@ -68,15 +68,15 @@ def arch_canonicalize(arch):
 def _expand_combination(ext):
   exts = list(ext.split("*"))
 
-  # No need to expand if there is no `*`.
-  if len(exts) == 1:
-    return [(exts[0],)]
-
   # Add underline to every extension.
   # e.g.
   #  _b * zvamo => _b * _zvamo
   exts = list(map(lambda x: '_' + x, exts))
 
+  # No need to expand if there is no `*`.
+  if len(exts) == 1:
+    return [(exts[0],)]
+
   # Generate combination!
   ext_combs = []
   for comb_len in range(1, len(exts)+1):
@@ -147,7 +147,9 @@ for cfg in sys.argv[1:]:
   # Drop duplicated entry.
   alts = unique(alts)
 
-  for alt in alts[1:]:
+  for alt in alts:
+    if alt == arch:
+      continue
     arches[alt] = 1
     reuse.append('march.%s/mabi.%s=march.%s/mabi.%s' % (arch, abi, alt, abi))
   required.append('march=%s/mabi=%s' % (arch, abi))