diff --git a/BUILD b/BUILD
index 3789b98f42..1276714b9c 100644
--- a/BUILD
+++ b/BUILD
@@ -38,7 +38,7 @@ config_setting(
 
 upb_fasttable_enabled(
     name = "fasttable_enabled",
-    build_setting_default = True,
+    build_setting_default = False,
     visibility = ["//visibility:public"],
 )
 
diff --git a/cmake/google/protobuf/descriptor.upb.c b/cmake/google/protobuf/descriptor.upb.c
index c54304aa50..7225c146ff 100644
--- a/cmake/google/protobuf/descriptor.upb.c
+++ b/cmake/google/protobuf/descriptor.upb.c
@@ -23,10 +23,8 @@ static const upb_msglayout_field google_protobuf_FileDescriptorSet__fields[1] =
 const upb_msglayout google_protobuf_FileDescriptorSet_msginit = {
   &google_protobuf_FileDescriptorSet_submsgs[0],
   &google_protobuf_FileDescriptorSet__fields[0],
-  UPB_SIZE(8, 8), 1, false, 8,
+  UPB_SIZE(8, 8), 1, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000000003f00000a, &upb_prm_1bt_max192b},
   },
 };
 
@@ -57,24 +55,8 @@ static const upb_msglayout_field google_protobuf_FileDescriptorProto__fields[12]
 const upb_msglayout google_protobuf_FileDescriptorProto_msginit = {
   &google_protobuf_FileDescriptorProto_submsgs[0],
   &google_protobuf_FileDescriptorProto__fields[0],
-  UPB_SIZE(64, 128), 12, false, 120,
+  UPB_SIZE(64, 128), 12, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x0018000002000012, &upb_pss_1bt},
-    {0x004800003f00001a, &upb_prs_1bt},
-    {0x005000003f000022, &upb_prm_1bt_max128b},
-    {0x005800003f01002a, &upb_prm_1bt_max128b},
-    {0x006000003f040032, &upb_prm_1bt_max64b},
-    {0x006800003f02003a, &upb_prm_1bt_max128b},
-    {0x0038000003030042, &upb_psm_1bt_max256b},
-    {0x004000000405004a, &upb_psm_1bt_max64b},
-    {0x007000003f000050, &upb_prv4_1bt},
-    {0x007800003f000058, &upb_prv4_1bt},
-    {0x0028000005000062, &upb_pss_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -104,24 +86,8 @@ static const upb_msglayout_field google_protobuf_DescriptorProto__fields[10] = {
 const upb_msglayout google_protobuf_DescriptorProto_msginit = {
   &google_protobuf_DescriptorProto_submsgs[0],
   &google_protobuf_DescriptorProto__fields[0],
-  UPB_SIZE(48, 96), 10, false, 120,
+  UPB_SIZE(48, 96), 10, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x002000003f040012, &upb_prm_1bt_max128b},
-    {0x002800003f00001a, &upb_prm_1bt_max128b},
-    {0x003000003f030022, &upb_prm_1bt_max128b},
-    {0x003800003f01002a, &upb_prm_1bt_max64b},
-    {0x004000003f040032, &upb_prm_1bt_max128b},
-    {0x001800000205003a, &upb_psm_1bt_max64b},
-    {0x004800003f060042, &upb_prm_1bt_max64b},
-    {0x005000003f02004a, &upb_prm_1bt_max64b},
-    {0x005800003f000052, &upb_prs_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -138,12 +104,8 @@ static const upb_msglayout_field google_protobuf_DescriptorProto_ExtensionRange_
 const upb_msglayout google_protobuf_DescriptorProto_ExtensionRange_msginit = {
   &google_protobuf_DescriptorProto_ExtensionRange_submsgs[0],
   &google_protobuf_DescriptorProto_ExtensionRange__fields[0],
-  UPB_SIZE(16, 24), 3, false, 24,
+  UPB_SIZE(16, 24), 3, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0004000001000008, &upb_psv4_1bt},
-    {0x0008000002000010, &upb_psv4_1bt},
-    {0x001000000300001a, &upb_psm_1bt_max64b},
   },
 };
 
@@ -155,12 +117,8 @@ static const upb_msglayout_field google_protobuf_DescriptorProto_ReservedRange__
 const upb_msglayout google_protobuf_DescriptorProto_ReservedRange_msginit = {
   NULL,
   &google_protobuf_DescriptorProto_ReservedRange__fields[0],
-  UPB_SIZE(16, 16), 2, false, 24,
+  UPB_SIZE(16, 16), 2, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0004000001000008, &upb_psv4_1bt},
-    {0x0008000002000010, &upb_psv4_1bt},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -175,40 +133,8 @@ static const upb_msglayout_field google_protobuf_ExtensionRangeOptions__fields[1
 const upb_msglayout google_protobuf_ExtensionRangeOptions_msginit = {
   &google_protobuf_ExtensionRangeOptions_submsgs[0],
   &google_protobuf_ExtensionRangeOptions__fields[0],
-  UPB_SIZE(8, 8), 1, false, 248,
+  UPB_SIZE(8, 8), 1, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000000003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -233,40 +159,8 @@ static const upb_msglayout_field google_protobuf_FieldDescriptorProto__fields[11
 const upb_msglayout google_protobuf_FieldDescriptorProto_msginit = {
   &google_protobuf_FieldDescriptorProto_submsgs[0],
   &google_protobuf_FieldDescriptorProto__fields[0],
-  UPB_SIZE(72, 112), 11, false, 248,
+  UPB_SIZE(72, 112), 11, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x001800000100000a, &upb_pss_1bt},
-    {0x0028000002000012, &upb_pss_1bt},
-    {0x000c000003000018, &upb_psv4_1bt},
-    {0x0004000004000020, &upb_psv4_1bt},
-    {0x0008000005000028, &upb_psv4_1bt},
-    {0x0038000006000032, &upb_pss_1bt},
-    {0x004800000700003a, &upb_pss_1bt},
-    {0x0068000008000042, &upb_psm_1bt_max64b},
-    {0x0010000009000048, &upb_psv4_1bt},
-    {0x005800000a000052, &upb_pss_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x001400000b000188, &upb_psb1_2bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -282,12 +176,8 @@ static const upb_msglayout_field google_protobuf_OneofDescriptorProto__fields[2]
 const upb_msglayout google_protobuf_OneofDescriptorProto_msginit = {
   &google_protobuf_OneofDescriptorProto_submsgs[0],
   &google_protobuf_OneofDescriptorProto__fields[0],
-  UPB_SIZE(16, 32), 2, false, 24,
+  UPB_SIZE(16, 32), 2, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x0018000002000012, &upb_psm_1bt_max64b},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -308,16 +198,8 @@ static const upb_msglayout_field google_protobuf_EnumDescriptorProto__fields[5]
 const upb_msglayout google_protobuf_EnumDescriptorProto_msginit = {
   &google_protobuf_EnumDescriptorProto_submsgs[0],
   &google_protobuf_EnumDescriptorProto__fields[0],
-  UPB_SIZE(32, 64), 5, false, 56,
+  UPB_SIZE(32, 64), 5, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x002000003f020012, &upb_prm_1bt_max64b},
-    {0x001800000201001a, &upb_psm_1bt_max64b},
-    {0x002800003f000022, &upb_prm_1bt_max64b},
-    {0x003000003f00002a, &upb_prs_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -329,12 +211,8 @@ static const upb_msglayout_field google_protobuf_EnumDescriptorProto_EnumReserve
 const upb_msglayout google_protobuf_EnumDescriptorProto_EnumReservedRange_msginit = {
   NULL,
   &google_protobuf_EnumDescriptorProto_EnumReservedRange__fields[0],
-  UPB_SIZE(16, 16), 2, false, 24,
+  UPB_SIZE(16, 16), 2, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0004000001000008, &upb_psv4_1bt},
-    {0x0008000002000010, &upb_psv4_1bt},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -351,12 +229,8 @@ static const upb_msglayout_field google_protobuf_EnumValueDescriptorProto__field
 const upb_msglayout google_protobuf_EnumValueDescriptorProto_msginit = {
   &google_protobuf_EnumValueDescriptorProto_submsgs[0],
   &google_protobuf_EnumValueDescriptorProto__fields[0],
-  UPB_SIZE(24, 32), 3, false, 24,
+  UPB_SIZE(24, 32), 3, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x0004000002000010, &upb_psv4_1bt},
-    {0x001800000300001a, &upb_psm_1bt_max64b},
   },
 };
 
@@ -374,12 +248,8 @@ static const upb_msglayout_field google_protobuf_ServiceDescriptorProto__fields[
 const upb_msglayout google_protobuf_ServiceDescriptorProto_msginit = {
   &google_protobuf_ServiceDescriptorProto_submsgs[0],
   &google_protobuf_ServiceDescriptorProto__fields[0],
-  UPB_SIZE(24, 48), 3, false, 24,
+  UPB_SIZE(24, 48), 3, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x002000003f000012, &upb_prm_1bt_max128b},
-    {0x001800000201001a, &upb_psm_1bt_max64b},
   },
 };
 
@@ -399,16 +269,8 @@ static const upb_msglayout_field google_protobuf_MethodDescriptorProto__fields[6
 const upb_msglayout google_protobuf_MethodDescriptorProto_msginit = {
   &google_protobuf_MethodDescriptorProto_submsgs[0],
   &google_protobuf_MethodDescriptorProto__fields[0],
-  UPB_SIZE(32, 64), 6, false, 56,
+  UPB_SIZE(32, 64), 6, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x0018000002000012, &upb_pss_1bt},
-    {0x002800000300001a, &upb_pss_1bt},
-    {0x0038000004000022, &upb_psm_1bt_max64b},
-    {0x0001000005000028, &upb_psb1_1bt},
-    {0x0002000006000030, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -443,40 +305,8 @@ static const upb_msglayout_field google_protobuf_FileOptions__fields[21] = {
 const upb_msglayout google_protobuf_FileOptions_msginit = {
   &google_protobuf_FileOptions_submsgs[0],
   &google_protobuf_FileOptions__fields[0],
-  UPB_SIZE(104, 192), 21, false, 248,
+  UPB_SIZE(104, 192), 21, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x001800000100000a, &upb_pss_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0028000002000042, &upb_pss_1bt},
-    {0x0004000003000048, &upb_psv4_1bt},
-    {0x0008000004000050, &upb_psb1_1bt},
-    {0x003800000500005a, &upb_pss_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0009000006000180, &upb_psb1_2bt},
-    {0x000a000007000188, &upb_psb1_2bt},
-    {0x000b000008000190, &upb_psb1_2bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000c0000090001a0, &upb_psb1_2bt},
-    {0x005800000e0002aa, &upb_pss_2bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000d00000a0001b8, &upb_psb1_2bt},
-    {0x00780000100002c2, &upb_pss_2bt},
-    {0x00880000110002ca, &upb_pss_2bt},
-    {0x00100000120002d0, &upb_psb1_2bt},
-    {0x000e00000b0001d8, &upb_psb1_2bt},
-    {0x00980000130002e2, &upb_pss_2bt},
-    {0x00a80000140002ea, &upb_pss_2bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000f00000c0001f8, &upb_psb1_2bt},
   },
 };
 
@@ -495,40 +325,8 @@ static const upb_msglayout_field google_protobuf_MessageOptions__fields[5] = {
 const upb_msglayout google_protobuf_MessageOptions_msginit = {
   &google_protobuf_MessageOptions_submsgs[0],
   &google_protobuf_MessageOptions__fields[0],
-  UPB_SIZE(16, 16), 5, false, 248,
+  UPB_SIZE(16, 16), 5, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0001000001000008, &upb_psb1_1bt},
-    {0x0002000002000010, &upb_psb1_1bt},
-    {0x0003000003000018, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0004000004000038, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -549,40 +347,8 @@ static const upb_msglayout_field google_protobuf_FieldOptions__fields[7] = {
 const upb_msglayout google_protobuf_FieldOptions_msginit = {
   &google_protobuf_FieldOptions_submsgs[0],
   &google_protobuf_FieldOptions__fields[0],
-  UPB_SIZE(24, 24), 7, false, 248,
+  UPB_SIZE(24, 24), 7, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0004000001000008, &upb_psv4_1bt},
-    {0x000c000002000010, &upb_psb1_1bt},
-    {0x000d000003000018, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000e000004000028, &upb_psb1_1bt},
-    {0x0008000005000030, &upb_psv4_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000f000006000050, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x001000003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -597,40 +363,8 @@ static const upb_msglayout_field google_protobuf_OneofOptions__fields[1] = {
 const upb_msglayout google_protobuf_OneofOptions_msginit = {
   &google_protobuf_OneofOptions_submsgs[0],
   &google_protobuf_OneofOptions__fields[0],
-  UPB_SIZE(8, 8), 1, false, 248,
+  UPB_SIZE(8, 8), 1, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000000003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -647,40 +381,8 @@ static const upb_msglayout_field google_protobuf_EnumOptions__fields[3] = {
 const upb_msglayout google_protobuf_EnumOptions_msginit = {
   &google_protobuf_EnumOptions_submsgs[0],
   &google_protobuf_EnumOptions__fields[0],
-  UPB_SIZE(8, 16), 3, false, 248,
+  UPB_SIZE(8, 16), 3, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0001000001000010, &upb_psb1_1bt},
-    {0x0002000002000018, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -696,40 +398,8 @@ static const upb_msglayout_field google_protobuf_EnumValueOptions__fields[2] = {
 const upb_msglayout google_protobuf_EnumValueOptions_msginit = {
   &google_protobuf_EnumValueOptions_submsgs[0],
   &google_protobuf_EnumValueOptions__fields[0],
-  UPB_SIZE(8, 16), 2, false, 248,
+  UPB_SIZE(8, 16), 2, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0001000001000008, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -745,40 +415,8 @@ static const upb_msglayout_field google_protobuf_ServiceOptions__fields[2] = {
 const upb_msglayout google_protobuf_ServiceOptions_msginit = {
   &google_protobuf_ServiceOptions_submsgs[0],
   &google_protobuf_ServiceOptions__fields[0],
-  UPB_SIZE(8, 16), 2, false, 248,
+  UPB_SIZE(8, 16), 2, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0001000001000288, &upb_psb1_2bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -795,40 +433,8 @@ static const upb_msglayout_field google_protobuf_MethodOptions__fields[3] = {
 const upb_msglayout google_protobuf_MethodOptions_msginit = {
   &google_protobuf_MethodOptions_submsgs[0],
   &google_protobuf_MethodOptions__fields[0],
-  UPB_SIZE(16, 24), 3, false, 248,
+  UPB_SIZE(16, 24), 3, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0008000001000288, &upb_psb1_2bt},
-    {0x0004000002000290, &upb_psv4_2bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x001000003f003eba, &upb_prm_2bt_max128b},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -849,24 +455,8 @@ static const upb_msglayout_field google_protobuf_UninterpretedOption__fields[7]
 const upb_msglayout google_protobuf_UninterpretedOption_msginit = {
   &google_protobuf_UninterpretedOption_submsgs[0],
   &google_protobuf_UninterpretedOption__fields[0],
-  UPB_SIZE(64, 96), 7, false, 120,
+  UPB_SIZE(64, 96), 7, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x005000003f000012, &upb_prm_1bt_max64b},
-    {0x002000000100001a, &upb_pss_1bt},
-    {0x0008000002000020, &upb_psv8_1bt},
-    {0x0010000003000028, &upb_psv8_1bt},
-    {0x0018000004000031, &upb_psf8_1bt},
-    {0x003000000500003a, &upb_pss_1bt},
-    {0x0040000006000042, &upb_pss_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -878,12 +468,8 @@ static const upb_msglayout_field google_protobuf_UninterpretedOption_NamePart__f
 const upb_msglayout google_protobuf_UninterpretedOption_NamePart_msginit = {
   NULL,
   &google_protobuf_UninterpretedOption_NamePart__fields[0],
-  UPB_SIZE(16, 32), 2, false, 24,
+  UPB_SIZE(16, 32), 2, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000800000100000a, &upb_pss_1bt},
-    {0x0001000002000010, &upb_psb1_1bt},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -898,10 +484,8 @@ static const upb_msglayout_field google_protobuf_SourceCodeInfo__fields[1] = {
 const upb_msglayout google_protobuf_SourceCodeInfo_msginit = {
   &google_protobuf_SourceCodeInfo_submsgs[0],
   &google_protobuf_SourceCodeInfo__fields[0],
-  UPB_SIZE(8, 8), 1, false, 8,
+  UPB_SIZE(8, 8), 1, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000000003f00000a, &upb_prm_1bt_max128b},
   },
 };
 
@@ -916,16 +500,8 @@ static const upb_msglayout_field google_protobuf_SourceCodeInfo_Location__fields
 const upb_msglayout google_protobuf_SourceCodeInfo_Location_msginit = {
   NULL,
   &google_protobuf_SourceCodeInfo_Location__fields[0],
-  UPB_SIZE(32, 64), 5, false, 56,
+  UPB_SIZE(32, 64), 5, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x002800003f00000a, &upb_ppv4_1bt},
-    {0x003000003f000012, &upb_ppv4_1bt},
-    {0x000800000100001a, &upb_pss_1bt},
-    {0x0018000002000022, &upb_pss_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x003800003f000032, &upb_prs_1bt},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
@@ -940,10 +516,8 @@ static const upb_msglayout_field google_protobuf_GeneratedCodeInfo__fields[1] =
 const upb_msglayout google_protobuf_GeneratedCodeInfo_msginit = {
   &google_protobuf_GeneratedCodeInfo_submsgs[0],
   &google_protobuf_GeneratedCodeInfo__fields[0],
-  UPB_SIZE(8, 8), 1, false, 8,
+  UPB_SIZE(8, 8), 1, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x000000003f00000a, &upb_prm_1bt_max64b},
   },
 };
 
@@ -957,16 +531,8 @@ static const upb_msglayout_field google_protobuf_GeneratedCodeInfo_Annotation__f
 const upb_msglayout google_protobuf_GeneratedCodeInfo_Annotation_msginit = {
   NULL,
   &google_protobuf_GeneratedCodeInfo_Annotation__fields[0],
-  UPB_SIZE(24, 48), 4, false, 56,
+  UPB_SIZE(24, 48), 4, false, 255,
   {
-    {0x0000000000000000, &fastdecode_generic},
-    {0x002000003f00000a, &upb_ppv4_1bt},
-    {0x0010000001000012, &upb_pss_1bt},
-    {0x0004000002000018, &upb_psv4_1bt},
-    {0x0008000003000020, &upb_psv4_1bt},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
-    {0x0000000000000000, &fastdecode_generic},
   },
 };
 
diff --git a/kokoro/ubuntu/build.sh b/kokoro/ubuntu/build.sh
index 1b1089097e..2dacffec6d 100644
--- a/kokoro/ubuntu/build.sh
+++ b/kokoro/ubuntu/build.sh
@@ -11,15 +11,25 @@ fi
 echo PATH=$PATH
 ls -l `which cmake`
 cmake --version
-echo CC=${CC:-cc}
-${CC:-cc} --version
 
 # Log the bazel path and version.
 which bazel
 bazel version
 
 cd $(dirname $0)/../..
-bazel test --test_output=errors ...
+
+if which gcc; then
+  gcc --version
+  bazel test --test_output=errors ...
+  # The checked-in code is with fasttable not enabled.
+  bazel test --test_output=errors ... --//:fasttable_enabled=true -- -cmake:test_generated_files
+fi
+
+if which clang; then
+  CC=clang bazel test --test_output=errors ...
+  # The checked-in code is with fasttable not enabled.
+  CC=clang bazel test --test_output=errors ... --//:fasttable_enabled=true -- -cmake:test_generated_files
+fi
 
 if [[ $(uname) = "Linux" ]]; then
   # Verify the ASAN build.  Have to exclude test_conformance_upb as protobuf
diff --git a/upb/decode.int.h b/upb/decode.int.h
index 41303531d7..8cd09bbf46 100644
--- a/upb/decode.int.h
+++ b/upb/decode.int.h
@@ -99,7 +99,7 @@ const char *fastdecode_tagdispatch(upb_decstate *d, const char *ptr,
   uint8_t mask = table;
   uint64_t data;
   size_t idx = tag & mask;
-  __builtin_assume((idx & 7) == 0);
+  UPB_ASSUME((idx & 7) == 0);
   idx >>= 3;
   data = table_p->fasttable[idx].field_data ^ tag;
   return table_p->fasttable[idx].field_parser(d, ptr, msg, table, hasbits, data);
diff --git a/upb/decode_fast.c b/upb/decode_fast.c
index 8170b4929f..cb30317dbb 100644
--- a/upb/decode_fast.c
+++ b/upb/decode_fast.c
@@ -47,8 +47,9 @@ static const char *fastdecode_isdonefallback(upb_decstate *d, const char *ptr,
 }
 
 UPB_FORCEINLINE
-const char *fastdecode_dispatch(upb_decstate *d, const char *ptr, upb_msg *msg,
-                                intptr_t table, uint64_t hasbits) {
+static const char *fastdecode_dispatch(upb_decstate *d, const char *ptr,
+                                       upb_msg *msg, intptr_t table,
+                                       uint64_t hasbits) {
   if (UPB_UNLIKELY(ptr >= d->limit_ptr)) {
     int overrun = ptr - d->end;
     if (UPB_LIKELY(overrun == d->limit)) {
@@ -331,7 +332,7 @@ static const char *fastdecode_varint64(const char *ptr, uint64_t *val) {
     *val += (byte - 1) << 63;
   }
 done:
-  __builtin_assume(ptr != NULL);
+  UPB_ASSUME(ptr != NULL);
   return ptr;
 }
 
@@ -872,7 +873,7 @@ static const char *fastdecode_tosubmsg(upb_decstate *d, const char *ptr,
                                        void *ctx) {
   fastdecode_submsgdata *submsg = ctx;
   ptr = fastdecode_dispatch(d, ptr, submsg->msg, submsg->table, 0);
-  __builtin_assume(ptr != NULL);
+  UPB_ASSUME(ptr != NULL);
   return ptr;
 }
 
diff --git a/upb/msg.h b/upb/msg.h
index f0f55ffd7b..4f4185ffde 100644
--- a/upb/msg.h
+++ b/upb/msg.h
@@ -68,8 +68,8 @@ typedef struct upb_msglayout {
   bool extendable;
   uint8_t table_mask;
 #if __STDC_VERSION__ >= 199901L
-  // To constant-initialize the tables of variable length, we need a flexible
-  // array member, and we need to compile in C99 mode.
+  /* To constant-initialize the tables of variable length, we need a flexible
+   * array member, and we need to compile in C99 mode. */
   _upb_fasttable_entry fasttable[];
 #else
   _upb_fasttable_entry fasttable[1];