Added #defines UPB_ENABLE_FASTTABLE and UPB_TRY_ENABLE_FASTTABLE.

These control whether fasttable decoding is on.

BUILD

@@ -7,8 +7,8 @@ load(
     "//bazel:upb_proto_library.bzl",
     "upb_fasttable_enabled",
     "upb_proto_library",
-    "upb_proto_reflection_library",
     "upb_proto_library_copts",
+    "upb_proto_reflection_library",
 )
 
 # copybara:strip_for_google3_begin
@@ -37,6 +37,11 @@ upb_fasttable_enabled(
     visibility = ["//visibility:public"],
 )
 
+config_setting(
+    name = "fasttable_enabled_setting",
+    flag_values = {"//:fasttable_enabled": "true"},
+)
+
 upb_proto_library_copts(
     name = "upb_proto_library_copts__for_generated_code_only_do_not_use",
     copts = UPB_DEFAULT_COPTS,

bazel/build_defs.bzl

@@ -16,6 +16,7 @@ UPB_DEFAULT_CPPOPTS = select({
 
 UPB_DEFAULT_COPTS = select({
     "//:windows": [],
+    "//:fasttable_enabled_setting": ["-std=gnu99", "-DUPB_ENABLE_FASTTABLE"],
     "//conditions:default": [
         # copybara:strip_for_google3_begin
         "-std=c99",

bazel/upb_proto_library.bzl

@@ -126,7 +126,7 @@ def fasttable_enabled_impl(ctx):
 
 upb_fasttable_enabled = rule(
     implementation = fasttable_enabled_impl,
-    build_setting = config.bool(flag = True)
+    build_setting = config.bool(flag = True),
 )
 
 # Dummy rule to expose select() copts to aspects  ##############################
@@ -285,7 +285,7 @@ _upb_proto_library_aspect = aspect(
             "//:upb",
         ]),
         "_ext": attr.string(default = ".upb"),
-        "_fasttable_enabled": attr.label(default = "//:fasttable_enabled")
+        "_fasttable_enabled": attr.label(default = "//:fasttable_enabled"),
     }),
     implementation = _upb_proto_library_aspect_impl,
     provides = [
@@ -344,7 +344,7 @@ _upb_proto_reflection_library_aspect = aspect(
             ],
         ),
         "_ext": attr.string(default = ".upbdefs"),
-        "_fasttable_enabled": attr.label(default = "//:fasttable_enabled")
+        "_fasttable_enabled": attr.label(default = "//:fasttable_enabled"),
     }),
     implementation = _upb_proto_reflection_library_aspect_impl,
     provides = [

cmake/build_defs.bzl

@@ -1,4 +1,3 @@
-
 def generated_file_staleness_test(name, outs, generated_pattern):
     """Tests that checked-in file(s) match the contents of generated file(s).
 

upb/bindings/lua/lua_proto_library.bzl

@@ -1,4 +1,3 @@
-
 load("@bazel_skylib//lib:paths.bzl", "paths")
 
 # Generic support code #########################################################
@@ -12,6 +11,7 @@ def _get_real_short_path(file):
     if short_path.startswith("../"):
         second_slash = short_path.index("/", 3)
         short_path = short_path[second_slash + 1:]
+
     # Sometimes it has another few prefixes like:
     #   _virtual_imports/any_proto/google/protobuf/any.proto
     # We want just google/protobuf/any.proto.
@@ -65,7 +65,8 @@ def _lua_proto_rule_impl(ctx):
     return [
         DefaultInfo(
             files = files,
-            data_runfiles = ctx.runfiles(files = files.to_list())),
+            data_runfiles = ctx.runfiles(files = files.to_list()),
+        ),
     ]
 
 def _lua_proto_library_aspect_impl(target, ctx):

upb/decode.c

@@ -535,14 +535,15 @@ static const char *decode_tomsg(upb_decstate *d, const char *ptr, upb_msg *msg,
 UPB_FORCEINLINE
 static bool decode_tryfastdispatch(upb_decstate *d, const char **ptr,
                                    upb_msg *msg, const upb_msglayout *layout) {
+#if UPB_FASTTABLE
   if (layout && layout->table_mask != (unsigned char)-1) {
     uint16_t tag = fastdecode_loadtag(*ptr);
     intptr_t table = decode_totable(layout);
     *ptr = fastdecode_tagdispatch(d, *ptr, msg, table, 0, tag);
     return true;
-  } else {
-    return false;
   }
+#endif
+  return false;
 }
 
 UPB_NOINLINE

upb/decode_fast.c

@@ -15,6 +15,8 @@
 /* Must be last. */
 #include "upb/port_def.inc"
 
+#if UPB_FASTTABLE
+
 // The standard set of arguments passed to each parsing function.
 // Thanks to x86-64 calling conventions, these will stay in registers.
 #define UPB_PARSE_PARAMS                                          \
@@ -969,3 +971,5 @@ TAGBYTES(r)
 #undef TAGBYTES
 #undef SIZES
 #undef F
+
+#endif  /* UPB_FASTTABLE */

upb/port_def.inc

@@ -125,6 +125,43 @@
 #define UPB_UNREACHABLE() do { assert(0); } while(0)
 #endif
 
+/* Configure whether fasttable is switched on or not. *************************/
+
+#if defined(__x86_64__) && defined(__GNUC__)
+#define UPB_FASTTABLE_SUPPORTED 1
+#else
+#define UPB_FASTTABLE_SUPPORTED 0
+#endif
+
+/* define UPB_ENABLE_FASTTABLE to force fast table support.
+ * This is useful when we want to ensure we are really getting fasttable,
+ * for example for testing or benchmarking. */
+#if defined(UPB_ENABLE_FASTTABLE)
+#if !UPB_FASTTABLE_SUPPORTED
+#error fasttable is x86-64 + Clang/GCC only
+#endif
+#define UPB_FASTTABLE 1
+/* Define UPB_TRY_ENABLE_FASTTABLE to use fasttable if possible.
+ * This is useful for releasing code that might be used on multiple platforms,
+ * for example the PHP or Ruby C extensions. */
+#elif defined(UPB_TRY_ENABLE_FASTTABLE)
+#define UPB_FASTTABLE UPB_FASTTABLE_SUPPORTED
+#else
+#define UPB_FASTTABLE 0
+#endif
+
+/* UPB_FASTTABLE_INIT() allows protos compiled for fasttable to gracefully
+ * degrade to non-fasttable if we are using UPB_TRY_ENABLE_FASTTABLE. */
+#if !UPB_FASTTABLE && defined(UPB_TRY_ENABLE_FASTTABLE)
+#define UPB_FASTTABLE_INIT(...)
+#else
+#define UPB_FASTTABLE_INIT(...) __VA_ARGS__
+#endif
+
+#undef UPB_FASTTABLE_SUPPORTED
+
+/* ASAN poisoning (for arena) *************************************************/
+
 #if defined(__SANITIZE_ADDRESS__)
 #define UPB_ASAN 1
 #ifdef __cplusplus

upbc/generator.cc

@@ -1037,12 +1037,12 @@ void WriteSource(const protobuf::FileDescriptor* file, Output& output,
            table_mask
     );
     if (!table.empty()) {
-      output("  {\n");
+      output("  UPB_FASTTABLE_INIT({\n");
       for (const auto& ent : table) {
         output("    {0x$1, &$0},\n", ent.first,
                absl::StrCat(absl::Hex(ent.second, absl::kZeroPad16)));
       }
-      output("  },\n");
+      output("  }),\n");
     }
     output("};\n\n");
   }