Changed to use table pairs, seems to ever-so-slightly regress.

upb/decode_fast.c

@@ -29,8 +29,8 @@ const char *fastdecode_tag_dispatch(upb_decstate *d, const char *ptr, upb_msg *m
   uint64_t data;
   size_t idx;
   idx = (tag & 0xf8) >> 3;
-  data = table->field_data[idx] ^ tag;
-  return table->field_parser[idx](UPB_PARSE_ARGS);
+  data = table->fasttable[idx].field_data ^ tag;
+  return table->fasttable[idx].field_parser(UPB_PARSE_ARGS);
 }
 
 UPB_FORCEINLINE
@@ -40,7 +40,7 @@ uint32_t fastdecode_load_tag(const char* ptr) {
   return tag;
 }
 
-UPB_FORCEINLINE
+UPB_NOINLINE
 const char *fastdecode_dispatch(upb_decstate *d, const char *ptr, upb_msg *msg,
                                 const upb_msglayout *table, uint64_t hasbits) {
   if (UPB_UNLIKELY(ptr >= d->fastlimit)) {

upb/def.c

@@ -958,7 +958,7 @@ static bool make_layout(const upb_symtab *symtab, const upb_msgdef *m) {
   l->submsgs = submsgs;
 
   for (i = 0; i < 32; i++) {
-    l->field_parser[i] = &fastdecode_generic;
+    l->fasttable[i].field_parser = &fastdecode_generic;
   }
 
   if (upb_msgdef_mapentry(m)) {

upb/msg.h

@@ -54,9 +54,13 @@ typedef const char *_upb_field_parser(struct upb_decstate *d, const char *ptr,
                                       const struct upb_msglayout *table,
                                       uint64_t hasbits, uint64_t data);
 
+typedef struct _upb_table_pair {
+  _upb_field_parser *field_parser;
+  uint64_t field_data;
+} _upb_table_pair;
+
 typedef struct upb_msglayout {
-  _upb_field_parser *field_parser[32];
-  uint64_t field_data[32];
+  _upb_table_pair fasttable[32];
   const struct upb_msglayout *const* submsgs;
   const upb_msglayout_field *fields;
   /* Must be aligned to sizeof(void*).  Doesn't include internal members like

upbc/generator.cc

@@ -965,12 +965,7 @@ void WriteSource(const protobuf::FileDescriptor* file, Output& output) {
     output("const upb_msglayout $0 = {\n", MessageInit(message));
     output("  {\n");
     for (const auto& ent : table) {
-      output("    &$0,\n", ent.first);
-    }
-    output("  },\n");
-    output("  {\n");
-    for (const auto& ent : table) {
-      output("    $0,\n", GetSizeInit(ent.second));
+      output("    {&$0, $1},\n", ent.first, GetSizeInit(ent.second));
     }
     output("  },\n");
     output("  $0,\n", submsgs_array_ref);