diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2d18fe3872345a891faef83c5e0ef3bfb37a5822..f19091cf26e3bf6e795d67fe2478681955230270 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2019-08-06  Kito Cheng  <kito.cheng@sifive.com>
+
+	* gcc/config/riscv/multilib-generator: (canonical_order): New.
+	(arch_canonicalize): Dito.
+	Apply arch_canonicalize for alts.
+
 2019-08-05  Martin Sebor  <msebor@redhat.com>
 
 	* doc/extend.texi (Common Variable Attributes): Document alias
diff --git a/gcc/config/riscv/multilib-generator b/gcc/config/riscv/multilib-generator
index a711153b3a374501cd5492a768789f77158c21a7..e58231c2756294b9ff6c216608aca327beb6747e 100755
--- a/gcc/config/riscv/multilib-generator
+++ b/gcc/config/riscv/multilib-generator
@@ -36,6 +36,41 @@ abis = collections.OrderedDict()
 required = []
 reuse = []
 
+canonical_order = "mafdqlcbjtpvn"
+
+def arch_canonicalize(arch):
+  # TODO: Support Z, S, H, or X extensions.
+  # TODO: Support implied extensions, e.g. D implied F in latest spec.
+  # TODO: Support extension version.
+  new_arch = ""
+  if arch[:5] in ['rv32e', 'rv32i', 'rv64i']:
+    new_arch = arch[:5]
+  else:
+    raise Exception("Unexpected arch: `%d`" % arch[:5])
+
+  # Find any Z, S, H or X
+  long_ext_prefixes = ['z', 's', 'h', 'x']
+  long_ext_prefixes_idx = map(lambda x: arch.find(x), long_ext_prefixes)
+
+  # Filter out any non-existent index.
+  long_ext_prefixes_idx = list(filter(lambda x: x != -1, long_ext_prefixes_idx))
+  if long_ext_prefixes_idx:
+    first_long_ext_idx = min(long_ext_prefixes_idx)
+    long_exts = arch[first_long_ext_idx:]
+    std_exts = arch[5:first_long_ext_idx]
+  else:
+    long_exts = ""
+    std_exts = arch[5:]
+
+  # Put extensions in canonical order.
+  for ext in canonical_order:
+    if ext in std_exts:
+      new_arch += ext
+
+  # Concat rest of the multi-char extensions.
+  new_arch += long_exts
+  return new_arch
+
 for cfg in sys.argv[1:]:
   (arch, abi, extra, ext) = cfg.split('-')
   arches[arch] = 1
@@ -43,7 +78,9 @@ for cfg in sys.argv[1:]:
   extra = list(filter(None, extra.split(',')))
   ext = list(filter(None, ext.split(',')))
   alts = sum([[x] + [x + y for y in ext] for x in [arch] + extra], [])
+  # TODO: We should expand g to imadzifencei once we support newer spec.
   alts = alts + [x.replace('imafd', 'g') for x in alts if 'imafd' in x]
+  alts = list(map(arch_canonicalize, alts))
   for alt in alts[1:]:
     arches[alt] = 1
     reuse.append('march.%s/mabi.%s=march.%s/mabi.%s' % (arch, abi, alt, abi))