diff --git a/benchmarks/compare.py b/benchmarks/compare.py
index 9bdf787138..8d62d94272 100755
--- a/benchmarks/compare.py
+++ b/benchmarks/compare.py
@@ -58,7 +58,7 @@ def Benchmark(outbase, bench_cpu=True, runs=12, fasttable=False):
 
 
 baseline = "master"
-bench_cpu = True
+bench_cpu = False
 fasttable = False
 
 if len(sys.argv) > 1:
diff --git a/tests/bindings/lua/test_upb.lua b/tests/bindings/lua/test_upb.lua
index 84178aa79c..0f4a3d2725 100644
--- a/tests/bindings/lua/test_upb.lua
+++ b/tests/bindings/lua/test_upb.lua
@@ -91,6 +91,69 @@ function test_msg_map()
   assert_equal(12, msg2.map_int32_int32[6])
 end
 
+function test_map_sorting()
+  function msg_with_int32_entries(start, expand)
+    local msg = test_messages_proto3.TestAllTypesProto3()
+    for i=start,start + 8 do
+      msg.map_int32_int32[i] = i * 2
+    end
+
+    if expand then
+      for i=start+20,200 do
+        msg.map_int32_int32[i] = i
+      end
+      for i=start+20,200 do
+        msg.map_int32_int32[i] = nil
+      end
+    end
+    return msg
+  end
+
+  function msg_with_msg_entries(expand)
+    local msg = test_messages_proto3.TestAllTypesProto3()
+    -- 8! = 40320 possible orderings makes it overwhelmingly likely that two
+    -- random orderings will be different.
+    for i=1,8 do
+      local submsg = test_messages_proto3.TestAllTypesProto3.NestedMessage()
+      submsg.corecursive = msg_with_int32_entries(i, expand)
+      msg.map_string_nested_message[tostring(i)] = submsg
+    end
+
+    expand = false
+    if expand then
+      for i=21,2000 do
+        local submsg = test_messages_proto3.TestAllTypesProto3.NestedMessage()
+        submsg.corecursive = msg_with_int32_entries(i, expand)
+        msg.map_string_nested_message[tostring(i)] = submsg
+      end
+      for i=21,2000 do
+        msg.map_string_nested_message[tostring(i)] = nil
+      end
+    end
+    return msg
+  end
+
+  -- Create two messages with the same contents but (hopefully) different
+  -- map table orderings.
+  local msg = msg_with_msg_entries(false)
+  local msg2 = msg_with_msg_entries(true)
+
+  local text1 = upb.text_encode(msg)
+  local text2 = upb.text_encode(msg2)
+  assert_equal(text1, text2)
+
+  local binary1 = upb.encode(msg, {upb.ENCODE_DETERMINISTIC})
+  local binary2 = upb.encode(msg2, {upb.ENCODE_DETERMINISTIC})
+  assert_equal(binary1, binary2)
+
+  -- Non-sorted map should compare different.
+  local text3 = upb.text_encode(msg, {upb.TXTENC_NOSORT})
+  assert_not_equal(text1, text3)
+
+  local binary3 = upb.encode(msg)
+  assert_not_equal(binary1, binary3)
+end
+
 function test_utf8()
   local proto2_msg = test_messages_proto2.TestAllTypesProto2()
   proto2_msg.optional_string = "\xff"
diff --git a/upb/bindings/lua/def.c b/upb/bindings/lua/def.c
index 3bf1d9654f..ca277c8354 100644
--- a/upb/bindings/lua/def.c
+++ b/upb/bindings/lua/def.c
@@ -53,12 +53,12 @@ static void lupb_wrapper_pushwrapper(lua_State *L, int narg, const void *def,
 /* lupb_msgdef_pushsubmsgdef()
  *
  * Pops the msgdef wrapper at the top of the stack and replaces it with a msgdef
- * wrapper for field |f| of this msgdef.
+ * wrapper for field |f| of this msgdef (submsg may not be direct, for example it
+ * may be the submessage of the map value).
  */
 void lupb_msgdef_pushsubmsgdef(lua_State *L, const upb_fielddef *f) {
   const upb_msgdef *m = upb_fielddef_msgsubdef(f);
   assert(m);
-  assert(upb_fielddef_containingtype(f) == lupb_msgdef_check(L, -1));
   lupb_wrapper_pushwrapper(L, -1, m, LUPB_MSGDEF);
   lua_replace(L, -2);  /* Replace msgdef with submsgdef. */
 }
@@ -337,6 +337,26 @@ static int lupb_msgdef_oneofcount(lua_State *L) {
   return 1;
 }
 
+static bool lupb_msgdef_pushnested(lua_State *L, int msgdef, int name) {
+  const upb_msgdef *m = lupb_msgdef_check(L, msgdef);
+  lupb_wrapper_pushsymtab(L, msgdef);
+  upb_symtab *symtab = lupb_symtab_check(L, -1);
+  lua_pop(L, 1);
+
+  /* Construct full package.Message.SubMessage name. */
+  lua_pushstring(L, upb_msgdef_fullname(m));
+  lua_pushstring(L, ".");
+  lua_pushvalue(L, name);
+  lua_concat(L, 3);
+  const char *nested_name = lua_tostring(L, -1);
+
+  /* Try lookup. */
+  const upb_msgdef *nested = upb_symtab_lookupmsg(symtab, nested_name);
+  if (!nested) return false;
+  lupb_wrapper_pushwrapper(L, msgdef, nested, LUPB_MSGDEF);
+  return true;
+}
+
 /* lupb_msgdef_field()
  *
  * Handles:
@@ -430,6 +450,13 @@ static int lupb_msgdef_fullname(lua_State *L) {
   return 1;
 }
 
+static int lupb_msgdef_index(lua_State *L) {
+  if (!lupb_msgdef_pushnested(L, 1, 2)) {
+    luaL_error(L, "No such nested message");
+  }
+  return 1;
+}
+
 static int lupb_msgoneofiter_next(lua_State *L) {
   const upb_msgdef *m = lupb_msgdef_check(L, lua_upvalueindex(1));
   int *index = lua_touserdata(L, lua_upvalueindex(2));
@@ -471,6 +498,7 @@ static int lupb_msgdef_tostring(lua_State *L) {
 
 static const struct luaL_Reg lupb_msgdef_mm[] = {
   {"__call", lupb_msg_pushnew},
+  {"__index", lupb_msgdef_index},
   {"__len", lupb_msgdef_fieldcount},
   {"__tostring", lupb_msgdef_tostring},
   {NULL, NULL}
diff --git a/upb/bindings/lua/msg.c b/upb/bindings/lua/msg.c
index 6a2ecb36c7..0c4c35f2c4 100644
--- a/upb/bindings/lua/msg.c
+++ b/upb/bindings/lua/msg.c
@@ -187,6 +187,13 @@ static void lupb_arena_fuse(lua_State *L, int to, int from) {
   upb_arena_fuse(to_arena, from_arena);
 }
 
+static void lupb_arena_fuseobjs(lua_State *L, int to, int from) {
+  lua_getiuservalue(L, to, LUPB_ARENA_INDEX);
+  lua_getiuservalue(L, from, LUPB_ARENA_INDEX);
+  lupb_arena_fuse(L, lua_absindex(L, -2), lua_absindex(L, -1));
+  lua_pop(L, 2);
+}
+
 static int lupb_arena_gc(lua_State *L) {
   upb_arena *a = lupb_arena_check(L, 1);
   upb_arena_free(a);
@@ -398,6 +405,10 @@ static int lupb_array_newindex(lua_State *L) {
     upb_array_set(larray->arr, n, msgval);
   }
 
+  if (larray->type == UPB_TYPE_MESSAGE) {
+    lupb_arena_fuseobjs(L, 1, 3);
+  }
+
   return 0;  /* 1 for chained assignments? */
 }
 
@@ -535,6 +546,9 @@ static int lupb_map_newindex(lua_State *L) {
   } else {
     upb_msgval val = lupb_tomsgval(L, lmap->value_type, 3, 1, LUPB_COPY);
     upb_map_set(map, key, val, lupb_arenaget(L, 1));
+    if (lmap->value_type == UPB_TYPE_MESSAGE) {
+      lupb_arena_fuseobjs(L, 1, 3);
+    }
   }
 
   return 0;
@@ -600,21 +614,26 @@ static upb_msg *lupb_msg_check(lua_State *L, int narg) {
   return msg->msg;
 }
 
-static const upb_fielddef *lupb_msg_checkfield(lua_State *L, int msg,
-                                               int field) {
+static const upb_msgdef *lupb_msg_getmsgdef(lua_State *L, int msg) {
+  lua_getiuservalue(L, msg, LUPB_MSGDEF_INDEX);
+  const upb_msgdef *m = lupb_msgdef_check(L, -1);
+  lua_pop(L, 1);
+  return m;
+}
+
+static const upb_fielddef *lupb_msg_tofield(lua_State *L, int msg, int field) {
   size_t len;
   const char *fieldname = luaL_checklstring(L, field, &len);
-  const upb_msgdef *m;
-  const upb_fielddef *f;
+  const upb_msgdef *m = lupb_msg_getmsgdef(L, msg);
+  return upb_msgdef_ntof(m, fieldname, len);
+}
 
-  lua_getiuservalue(L, msg, LUPB_MSGDEF_INDEX);
-  m = lupb_msgdef_check(L, -1);
-  f = upb_msgdef_ntof(m, fieldname, len);
+static const upb_fielddef *lupb_msg_checkfield(lua_State *L, int msg,
+                                               int field) {
+  const upb_fielddef *f = lupb_msg_tofield(L, msg, field);
   if (f == NULL) {
-    luaL_error(L, "no such field '%s'", fieldname);
+    luaL_error(L, "no such field '%s'", lua_tostring(L, field));
   }
-  lua_pop(L, 1);
-
   return f;
 }
 
@@ -813,10 +832,7 @@ static int lupb_msg_newindex(lua_State *L) {
   }
 
   if (merge_arenas) {
-    lua_getiuservalue(L, 1, LUPB_ARENA_INDEX);
-    lua_getiuservalue(L, 3, LUPB_ARENA_INDEX);
-    lupb_arena_fuse(L, lua_absindex(L, -2), lua_absindex(L, -1));
-    lua_pop(L, 2);
+    lupb_arena_fuseobjs(L, 1, 3);
   }
 
   upb_msg_set(msg, f, msgval, lupb_arenaget(L, 1));
@@ -907,6 +923,46 @@ static int lupb_decode(lua_State *L) {
   return 1;
 }
 
+/**
+ * lupb_msg_textencode()
+ *
+ * Handles:
+ *   text_string = upb.text_encode(msg, {upb.TXTENC_SINGLELINE})
+ */
+static int lupb_textencode(lua_State *L) {
+  int argcount = lua_gettop(L);
+  upb_msg *msg = lupb_msg_check(L, 1);
+  const upb_msgdef *m;
+  char buf[1024];
+  size_t size;
+  int options = 0;
+
+  lua_getiuservalue(L, 1, LUPB_MSGDEF_INDEX);
+  m = lupb_msgdef_check(L, -1);
+
+  if (argcount > 1) {
+    size_t len = lua_rawlen(L, 2);
+    for (size_t i = 1; i <= len; i++) {
+      lua_rawgeti(L, 2, i);
+      options |= lupb_checkuint32(L, -1);
+      lua_pop(L, 1);
+    }
+  }
+
+  size = upb_text_encode(msg, m, NULL, options, buf, sizeof(buf));
+
+  if (size < sizeof(buf)) {
+    lua_pushlstring(L, buf, size);
+  } else {
+    char *ptr = malloc(size + 1);
+    upb_text_encode(msg, m, NULL, options, ptr, size + 1);
+    lua_pushlstring(L, ptr, size);
+    free(ptr);
+  }
+
+  return 1;
+}
+
 /**
  * lupb_encode()
  *
@@ -914,17 +970,28 @@ static int lupb_decode(lua_State *L) {
  *   bin_string = upb.encode(msg)
  */
 static int lupb_encode(lua_State *L) {
+  int argcount = lua_gettop(L);
   const upb_msg *msg = lupb_msg_check(L, 1);
   const upb_msglayout *layout;
   upb_arena *arena = lupb_arena_pushnew(L);
   size_t size;
   char *result;
+  int options = 0;
+
+  if (argcount > 1) {
+    size_t len = lua_rawlen(L, 2);
+    for (size_t i = 1; i <= len; i++) {
+      lua_rawgeti(L, 2, i);
+      options |= lupb_checkuint32(L, -1);
+      lua_pop(L, 1);
+    }
+  }
 
   lua_getiuservalue(L, 1, LUPB_MSGDEF_INDEX);
   layout = upb_msgdef_layout(lupb_msgdef_check(L, -1));
   lua_pop(L, 1);
 
-  result = upb_encode(msg, (const void*)layout, arena, &size);
+  result = upb_encode_ex(msg, (const void*)layout, options, arena, &size);
 
   if (!result) {
     lua_pushstring(L, "Error encoding protobuf.");
@@ -936,11 +1003,17 @@ static int lupb_encode(lua_State *L) {
   return 1;
 }
 
+static void lupb_setfieldi(lua_State *L, const char *field, int i) {
+  lua_pushinteger(L, i);
+  lua_setfield(L, -2, field);
+}
+
 static const struct luaL_Reg lupb_msg_toplevel_m[] = {
   {"Array", lupb_array_new},
   {"Map", lupb_map_new},
   {"decode", lupb_decode},
   {"encode", lupb_encode},
+  {"text_encode", lupb_textencode},
   {NULL, NULL}
 };
 
@@ -952,5 +1025,11 @@ void lupb_msg_registertypes(lua_State *L) {
   lupb_register_type(L, LUPB_MAP,   NULL, lupb_map_mm);
   lupb_register_type(L, LUPB_MSG,   NULL, lupb_msg_mm);
 
+  lupb_setfieldi(L, "TXTENC_SINGLELINE", UPB_TXTENC_SINGLELINE);
+  lupb_setfieldi(L, "TXTENC_SKIPUNKNOWN", UPB_TXTENC_SKIPUNKNOWN);
+  lupb_setfieldi(L, "TXTENC_NOSORT", UPB_TXTENC_NOSORT);
+
+  lupb_setfieldi(L, "ENCODE_DETERMINISTIC", UPB_ENCODE_DETERMINISTIC);
+
   lupb_cacheinit(L);
 }
diff --git a/upb/bindings/lua/upb.c b/upb/bindings/lua/upb.c
index 3630ae2ef3..c247c03746 100644
--- a/upb/bindings/lua/upb.c
+++ b/upb/bindings/lua/upb.c
@@ -84,6 +84,24 @@ int lua_getiuservalue(lua_State *L, int index, int n) {
 }
 #endif
 
+/* We use this function as the __index metamethod when a type has both methods
+ * and an __index metamethod. */
+int lupb_indexmm(lua_State *L) {
+  /* Look up in __index table (which is a closure param). */
+  lua_pushvalue(L, 2);
+  lua_rawget(L, lua_upvalueindex(1));
+  if (!lua_isnil(L, -1)) {
+    return 1;
+  }
+
+  /* Not found, chain to user __index metamethod. */
+  lua_pushvalue(L, lua_upvalueindex(2));
+  lua_pushvalue(L, 1);
+  lua_pushvalue(L, 2);
+  lua_call(L, 2, 1);
+  return 1;
+}
+
 void lupb_register_type(lua_State *L, const char *name, const luaL_Reg *m,
                         const luaL_Reg *mm) {
   luaL_newmetatable(L, name);
@@ -93,14 +111,17 @@ void lupb_register_type(lua_State *L, const char *name, const luaL_Reg *m,
   }
 
   if (m) {
-    /* Methods go in the mt's __index method.  This implies that you can'
-     * implement __index and also have methods. */
-    lua_getfield(L, -1, "__index");
-    lupb_assert(L, lua_isnil(L, -1));
-    lua_pop(L, 1);
-
-    lua_createtable(L, 0, 0);
+    lua_createtable(L, 0, 0);  /* __index table */
     lupb_setfuncs(L, m);
+
+    /* Methods go in the mt's __index slot.  If the user also specified an
+     * __index metamethod, use our custom lupb_indexmm() that can check both. */
+    lua_getfield(L, -2, "__index");
+    if (lua_isnil(L, -1)) {
+      lua_pop(L, 1);
+    } else {
+      lua_pushcclosure(L, &lupb_indexmm, 2);
+    }
     lua_setfield(L, -2, "__index");
   }
 
diff --git a/upb/decode.h b/upb/decode.h
index 00419ab373..eff4b8bd3d 100644
--- a/upb/decode.h
+++ b/upb/decode.h
@@ -15,6 +15,8 @@ extern "C" {
 #endif
 
 enum {
+  /* If set, strings will alias the input buffer instead of copying into the
+   * arena. */
   UPB_DECODE_ALIAS = 1,
 };
 
diff --git a/upb/encode.c b/upb/encode.c
index 6d36619d62..c1fe02decb 100644
--- a/upb/encode.c
+++ b/upb/encode.c
@@ -32,6 +32,8 @@ typedef struct {
   jmp_buf err;
   upb_alloc *alloc;
   char *buf, *ptr, *limit;
+  int options;
+  _upb_mapsorter sorter;
 } upb_encstate;
 
 static size_t upb_roundup_pow2(size_t bytes) {
@@ -341,31 +343,48 @@ static void encode_array(upb_encstate *e, const char *field_mem,
   }
 }
 
+static void encode_mapentry(upb_encstate *e, uint32_t number,
+                            const upb_msglayout *layout,
+                            const upb_map_entry *ent) {
+  const upb_msglayout_field *key_field = &layout->fields[0];
+  const upb_msglayout_field *val_field = &layout->fields[1];
+  size_t pre_len = e->limit - e->ptr;
+  size_t size;
+  encode_scalar(e, &ent->v, layout, val_field, false);
+  encode_scalar(e, &ent->k, layout, key_field, false);
+  size = (e->limit - e->ptr) - pre_len;
+  encode_varint(e, size);
+  encode_tag(e, number, UPB_WIRE_TYPE_DELIMITED);
+}
+
 static void encode_map(upb_encstate *e, const char *field_mem,
                        const upb_msglayout *m, const upb_msglayout_field *f) {
   const upb_map *map = *(const upb_map**)field_mem;
-  const upb_msglayout *entry = m->submsgs[f->submsg_index];
-  const upb_msglayout_field *key_field = &entry->fields[0];
-  const upb_msglayout_field *val_field = &entry->fields[1];
-  upb_strtable_iter i;
-  if (map == NULL) {
-    return;
-  }
+  const upb_msglayout *layout = m->submsgs[f->submsg_index];
+  UPB_ASSERT(layout->field_count == 2);
 
-  upb_strtable_begin(&i, &map->table);
-  for(; !upb_strtable_done(&i); upb_strtable_next(&i)) {
-    size_t pre_len = e->limit - e->ptr;
-    size_t size;
-    upb_strview key = upb_strtable_iter_key(&i);
-    const upb_value val = upb_strtable_iter_value(&i);
+  if (map == NULL) return;
+
+  if (e->options & UPB_ENCODE_DETERMINISTIC) {
+    _upb_sortedmap sorted;
+    _upb_mapsorter_pushmap(&e->sorter, layout->fields[0].descriptortype, map,
+                           &sorted);
     upb_map_entry ent;
-    _upb_map_fromkey(key, &ent.k, map->key_size);
-    _upb_map_fromvalue(val, &ent.v, map->val_size);
-    encode_scalar(e, &ent.v, entry, val_field, false);
-    encode_scalar(e, &ent.k, entry, key_field, false);
-    size = (e->limit - e->ptr) - pre_len;
-    encode_varint(e, size);
-    encode_tag(e, f->number, UPB_WIRE_TYPE_DELIMITED);
+    while (_upb_sortedmap_next(&e->sorter, map, &sorted, &ent)) {
+      encode_mapentry(e, f->number, layout, &ent);
+    }
+    _upb_mapsorter_popmap(&e->sorter, &sorted);
+  } else {
+    upb_strtable_iter i;
+    upb_strtable_begin(&i, &map->table);
+    for(; !upb_strtable_done(&i); upb_strtable_next(&i)) {
+      upb_strview key = upb_strtable_iter_key(&i);
+      const upb_value val = upb_strtable_iter_value(&i);
+      upb_map_entry ent;
+      _upb_map_fromkey(key, &ent.k, map->key_size);
+      _upb_map_fromvalue(val, &ent.v, map->val_size);
+      encode_mapentry(e, f->number, layout, &ent);
+    }
   }
 }
 
@@ -414,28 +433,32 @@ static void encode_message(upb_encstate *e, const char *msg,
   *size = (e->limit - e->ptr) - pre_len;
 }
 
-char *upb_encode(const void *msg, const upb_msglayout *m, upb_arena *arena,
-                 size_t *size) {
+char *upb_encode_ex(const void *msg, const upb_msglayout *m, int options,
+                    upb_arena *arena, size_t *size) {
   upb_encstate e;
   e.alloc = upb_arena_alloc(arena);
   e.buf = NULL;
   e.limit = NULL;
   e.ptr = NULL;
+  e.options = options;
+  _upb_mapsorter_init(&e.sorter);
+  char *ret = NULL;
 
   if (UPB_SETJMP(e.err)) {
     *size = 0;
-    return NULL;
-  }
-
-  encode_message(&e, msg, m, size);
-
-  *size = e.limit - e.ptr;
-
-  if (*size == 0) {
-    static char ch;
-    return &ch;
+    ret = NULL;
   } else {
-    UPB_ASSERT(e.ptr);
-    return e.ptr;
+    encode_message(&e, msg, m, size);
+    *size = e.limit - e.ptr;
+    if (*size == 0) {
+      static char ch;
+      ret = &ch;
+    } else {
+      UPB_ASSERT(e.ptr);
+      ret = e.ptr;
+    }
   }
+
+  _upb_mapsorter_destroy(&e.sorter);
+  return ret;
 }
diff --git a/upb/encode.h b/upb/encode.h
index 6842777058..8ff51ab626 100644
--- a/upb/encode.h
+++ b/upb/encode.h
@@ -7,12 +7,32 @@
 
 #include "upb/msg.h"
 
+/* Must be last. */
+#include "upb/port_def.inc"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-char *upb_encode(const void *msg, const upb_msglayout *l, upb_arena *arena,
-                 size_t *size);
+enum {
+  /* If set, the results of serializing will be deterministic across all
+   * instances of this binary. There are no guarantees across different
+   * binary builds.
+   *
+   * If your proto contains maps, the encoder will need to malloc()/free()
+   * memory during encode. */
+  UPB_ENCODE_DETERMINISTIC = 1,
+};
+
+char *upb_encode_ex(const void *msg, const upb_msglayout *l, int options,
+                    upb_arena *arena, size_t *size);
+
+UPB_INLINE char *upb_encode(const void *msg, const upb_msglayout *l,
+                            upb_arena *arena, size_t *size) {
+  return upb_encode_ex(msg, l, 0, arena, size);
+}
+
+#include "upb/port_undef.inc"
 
 #ifdef __cplusplus
 }  /* extern "C" */
diff --git a/upb/msg.c b/upb/msg.c
index 1dbb8b0fab..876a06d6fa 100644
--- a/upb/msg.c
+++ b/upb/msg.c
@@ -139,3 +139,118 @@ upb_map *_upb_map_new(upb_arena *a, size_t key_size, size_t value_size) {
 
   return map;
 }
+
+static void _upb_mapsorter_getkeys(const void *_a, const void *_b, void *a_key,
+                                   void *b_key, size_t size) {
+  const upb_tabent *const*a = _a;
+  const upb_tabent *const*b = _b;
+  upb_strview a_tabkey = upb_tabstrview((*a)->key);
+  upb_strview b_tabkey = upb_tabstrview((*b)->key);
+  _upb_map_fromkey(a_tabkey, a_key, size);
+  _upb_map_fromkey(b_tabkey, b_key, size);
+}
+
+static int _upb_mapsorter_cmpi64(const void *_a, const void *_b) {
+  int64_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 8);
+  return a - b;
+}
+
+static int _upb_mapsorter_cmpu64(const void *_a, const void *_b) {
+  uint64_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 8);
+  return a - b;
+}
+
+static int _upb_mapsorter_cmpi32(const void *_a, const void *_b) {
+  int32_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 4);
+  return a - b;
+}
+
+static int _upb_mapsorter_cmpu32(const void *_a, const void *_b) {
+  uint32_t a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 4);
+  return a - b;
+}
+
+static int _upb_mapsorter_cmpbool(const void *_a, const void *_b) {
+  bool a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, 1);
+  return a - b;
+}
+
+static int _upb_mapsorter_cmpstr(const void *_a, const void *_b) {
+  upb_strview a, b;
+  _upb_mapsorter_getkeys(_a, _b, &a, &b, UPB_MAPTYPE_STRING);
+  size_t common_size = UPB_MIN(a.size, b.size);
+  int cmp = memcmp(a.data, b.data, common_size);
+  if (cmp) return cmp;
+  return a.size - b.size;
+}
+
+bool _upb_mapsorter_pushmap(_upb_mapsorter *s, upb_descriptortype_t key_type,
+                            const upb_map *map, _upb_sortedmap *sorted) {
+  int map_size = _upb_map_size(map);
+  sorted->start = s->size;
+  sorted->pos = sorted->start;
+  sorted->end = sorted->start + map_size;
+
+  /* Grow s->entries if necessary. */
+  if (sorted->end > s->cap) {
+    s->cap = _upb_lg2ceilsize(sorted->end);
+    s->entries = realloc(s->entries, s->cap * sizeof(*s->entries));
+    if (!s->entries) return false;
+  }
+
+  s->size = sorted->end;
+
+  /* Copy non-empty entries from the table to s->entries. */
+  upb_tabent const**dst = &s->entries[sorted->start];
+  const upb_tabent *src = map->table.t.entries;
+  const upb_tabent *end = src + upb_table_size(&map->table.t);
+  for (; src < end; src++) {
+    if (!upb_tabent_isempty(src)) {
+      *dst = src;
+      dst++;
+    }
+  }
+  UPB_ASSERT(dst == &s->entries[sorted->end]);
+
+  /* Sort entries according to the key type. */
+
+  int (*compar)(const void *, const void *);
+
+  switch (key_type) {
+    case UPB_DESCRIPTOR_TYPE_INT64:
+    case UPB_DESCRIPTOR_TYPE_SFIXED64:
+    case UPB_DESCRIPTOR_TYPE_SINT64:
+      compar = _upb_mapsorter_cmpi64;
+      break;
+    case UPB_DESCRIPTOR_TYPE_UINT64:
+    case UPB_DESCRIPTOR_TYPE_FIXED64:
+      compar = _upb_mapsorter_cmpu64;
+      break;
+    case UPB_DESCRIPTOR_TYPE_INT32:
+    case UPB_DESCRIPTOR_TYPE_SINT32:
+    case UPB_DESCRIPTOR_TYPE_SFIXED32:
+    case UPB_DESCRIPTOR_TYPE_ENUM:
+      compar = _upb_mapsorter_cmpi32;
+      break;
+    case UPB_DESCRIPTOR_TYPE_UINT32:
+    case UPB_DESCRIPTOR_TYPE_FIXED32:
+      compar = _upb_mapsorter_cmpu32;
+      break;
+    case UPB_DESCRIPTOR_TYPE_BOOL:
+      compar = _upb_mapsorter_cmpbool;
+      break;
+    case UPB_DESCRIPTOR_TYPE_STRING:
+      compar = _upb_mapsorter_cmpstr;
+      break;
+    default:
+      UPB_UNREACHABLE();
+  }
+
+  qsort(&s->entries[sorted->start], map_size, sizeof(*s->entries), compar);
+  return true;
+}
diff --git a/upb/msg.h b/upb/msg.h
index 36c57b32cd..9b4557ac18 100644
--- a/upb/msg.h
+++ b/upb/msg.h
@@ -9,11 +9,13 @@
 #define UPB_MSG_H_
 
 #include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "upb/table.int.h"
 #include "upb/upb.h"
 
+/* Must be last. */
 #include "upb/port_def.inc"
 
 #ifdef __cplusplus
@@ -553,6 +555,53 @@ UPB_INLINE void _upb_msg_map_set_value(void* msg, const void* val, size_t size)
   }
 }
 
+/** _upb_mapsorter *************************************************************/
+
+/* _upb_mapsorter sorts maps and provides ordered iteration over the entries.
+ * Since maps can be recursive (map values can be messages which contain other maps).
+ * _upb_mapsorter can contain a stack of maps. */
+
+typedef struct {
+  upb_tabent const**entries;
+  int size;
+  int cap;
+} _upb_mapsorter;
+
+typedef struct {
+  int start;
+  int pos;
+  int end;
+} _upb_sortedmap;
+
+UPB_INLINE void _upb_mapsorter_init(_upb_mapsorter *s) {
+  s->entries = NULL;
+  s->size = 0;
+  s->cap = 0;
+}
+
+UPB_INLINE void _upb_mapsorter_destroy(_upb_mapsorter *s) {
+  if (s->entries) free(s->entries);
+}
+
+bool _upb_mapsorter_pushmap(_upb_mapsorter *s, upb_descriptortype_t key_type,
+                            const upb_map *map, _upb_sortedmap *sorted);
+
+UPB_INLINE void _upb_mapsorter_popmap(_upb_mapsorter *s, _upb_sortedmap *sorted) {
+  s->size = sorted->start;
+}
+
+UPB_INLINE bool _upb_sortedmap_next(_upb_mapsorter *s, const upb_map *map,
+                                    _upb_sortedmap *sorted,
+                                    upb_map_entry *ent) {
+  if (sorted->pos == sorted->end) return false;
+  const upb_tabent *tabent = s->entries[sorted->pos++];
+  upb_strview key = upb_tabstrview(tabent->key);
+  _upb_map_fromkey(key, &ent->k, map->key_size);
+  upb_value val = {tabent->val.val};
+  _upb_map_fromvalue(val, &ent->v, map->val_size);
+  return true;
+}
+
 #undef PTR_AT
 
 #ifdef __cplusplus
diff --git a/upb/table.int.h b/upb/table.int.h
index ab67cc34d6..49caac463e 100644
--- a/upb/table.int.h
+++ b/upb/table.int.h
@@ -147,10 +147,17 @@ UPB_INLINE char *upb_tabstr(upb_tabkey key, uint32_t *len) {
   return mem + sizeof(*len);
 }
 
+UPB_INLINE upb_strview upb_tabstrview(upb_tabkey key) {
+  upb_strview ret;
+  uint32_t len;
+  ret.data = upb_tabstr(key, &len);
+  ret.size = len;
+  return ret;
+}
 
 /* upb_tabval *****************************************************************/
 
-typedef struct {
+typedef struct upb_tabval {
   uint64_t val;
 } upb_tabval;
 
diff --git a/upb/text_encode.c b/upb/text_encode.c
index 3e9630d8cd..028cc29e09 100644
--- a/upb/text_encode.c
+++ b/upb/text_encode.c
@@ -17,6 +17,7 @@ typedef struct {
   int indent_depth;
   int options;
   const upb_symtab *ext_pool;
+  _upb_mapsorter sorter;
 } txtenc;
 
 static void txtenc_msg(txtenc *e, const upb_msg *msg, const upb_msgdef *m);
@@ -187,6 +188,25 @@ static void txtenc_array(txtenc *e, const upb_array *arr,
   }
 }
 
+static void txtenc_mapentry(txtenc *e, upb_msgval key, upb_msgval val,
+                            const upb_fielddef *f) {
+  const upb_msgdef *entry = upb_fielddef_msgsubdef(f);
+  const upb_fielddef *key_f = upb_msgdef_field(entry, 0);
+  const upb_fielddef *val_f = upb_msgdef_field(entry, 1);
+  txtenc_indent(e);
+  txtenc_printf(e, "%s: {", upb_fielddef_name(f));
+  txtenc_endfield(e);
+  e->indent_depth++;
+
+  txtenc_field(e, key, key_f);
+  txtenc_field(e, val, val_f);
+
+  e->indent_depth--;
+  txtenc_indent(e);
+  txtenc_putstr(e, "}");
+  txtenc_endfield(e);
+}
+
 /*
  * Maps print as messages of key/value, etc.
  *
@@ -200,27 +220,28 @@ static void txtenc_array(txtenc *e, const upb_array *arr,
  *    }
  */
 static void txtenc_map(txtenc *e, const upb_map *map, const upb_fielddef *f) {
-  const upb_msgdef *entry = upb_fielddef_msgsubdef(f);
-  const upb_fielddef *key_f = upb_msgdef_itof(entry, 1);
-  const upb_fielddef *val_f = upb_msgdef_itof(entry, 2);
-  size_t iter = UPB_MAP_BEGIN;
-
-  while (upb_mapiter_next(map, &iter)) {
-    upb_msgval key = upb_mapiter_key(map, iter);
-    upb_msgval val = upb_mapiter_value(map, iter);
-
-    txtenc_indent(e);
-    txtenc_printf(e, "%s: {", upb_fielddef_name(f));
-    txtenc_endfield(e);
-    e->indent_depth++;
-
-    txtenc_field(e, key, key_f);
-    txtenc_field(e, val, val_f);
-
-    e->indent_depth--;
-    txtenc_indent(e);
-    txtenc_putstr(e, "}");
-    txtenc_endfield(e);
+  if (e->options & UPB_TXTENC_NOSORT) {
+    size_t iter = UPB_MAP_BEGIN;
+    while (upb_mapiter_next(map, &iter)) {
+      upb_msgval key = upb_mapiter_key(map, iter);
+      upb_msgval val = upb_mapiter_value(map, iter);
+      txtenc_mapentry(e, key, val, f);
+    }
+  } else {
+    const upb_msgdef *entry = upb_fielddef_msgsubdef(f);
+    const upb_fielddef *key_f = upb_msgdef_field(entry, 0);
+    _upb_sortedmap sorted;
+    upb_map_entry ent;
+
+    _upb_mapsorter_pushmap(&e->sorter, upb_fielddef_descriptortype(key_f), map,
+                           &sorted);
+    while (_upb_sortedmap_next(&e->sorter, map, &sorted, &ent)) {
+      upb_msgval key, val;
+      memcpy(&key, &ent.k, sizeof(key));
+      memcpy(&val, &ent.v, sizeof(val));
+      txtenc_mapentry(e, key, val, f);
+    }
+    _upb_mapsorter_popmap(&e->sorter, &sorted);
   }
 }
 
@@ -392,7 +413,9 @@ size_t upb_text_encode(const upb_msg *msg, const upb_msgdef *m,
   e.indent_depth = 0;
   e.options = options;
   e.ext_pool = ext_pool;
+  _upb_mapsorter_init(&e.sorter);
 
   txtenc_msg(&e, msg, m);
+  _upb_mapsorter_destroy(&e.sorter);
   return txtenc_nullz(&e, size);
 }
diff --git a/upb/text_encode.h b/upb/text_encode.h
index 1a0003cb31..4ad3d1c4d7 100644
--- a/upb/text_encode.h
+++ b/upb/text_encode.h
@@ -13,7 +13,10 @@ enum {
   UPB_TXTENC_SINGLELINE = 1,
 
   /* When set, unknown fields are not printed. */
-  UPB_TXTENC_SKIPUNKNOWN = 2
+  UPB_TXTENC_SKIPUNKNOWN = 2,
+
+  /* When set, maps are *not* sorted (this avoids allocating tmp mem). */
+  UPB_TXTENC_NOSORT = 4
 };
 
 /* Encodes the given |msg| to text format.  The message's reflection is given in
diff --git a/upb/upb.h b/upb/upb.h
index 7e7309dc45..11c0e4dc99 100644
--- a/upb/upb.h
+++ b/upb/upb.h
@@ -324,6 +324,10 @@ UPB_INLINE int _upb_lg2ceil(int x) {
 #endif
 }
 
+UPB_INLINE int _upb_lg2ceilsize(int x) {
+  return 1 << _upb_lg2ceil(x);
+}
+
 #include "upb/port_undef.inc"
 
 #ifdef __cplusplus