Optimize TDP table generation:

- For enums that are already defined in a sequential manner, use the existing info from the descriptor.
 - For other enums use a bit set to find unique values instead of a vector+sort+unique. Much less work to do so, and we can use stack for it instead of heap most of the time.

PiperOrigin-RevId: 623613446

src/google/protobuf/BUILD.bazel

@@ -626,6 +626,7 @@ cc_library(
         "@com_google_absl//absl/base:core_headers",
         "@com_google_absl//absl/base:dynamic_annotations",
         "@com_google_absl//absl/container:btree",
+        "@com_google_absl//absl/container:fixed_array",
         "@com_google_absl//absl/container:flat_hash_map",
         "@com_google_absl//absl/container:flat_hash_set",
         "@com_google_absl//absl/functional:any_invocable",

src/google/protobuf/descriptor.h

@@ -284,6 +284,8 @@ class PROTOBUF_EXPORT InternalFeatureHelper {
 
 PROTOBUF_EXPORT absl::string_view ShortEditionName(Edition edition);
 
+bool IsEnumFullySequential(const EnumDescriptor* enum_desc);
+
 }  // namespace internal
 
 // Provide an Abseil formatter for edition names.
@@ -1387,6 +1389,7 @@ class PROTOBUF_EXPORT EnumDescriptor : private internal::SymbolBase {
 
  private:
   friend class Symbol;
+  friend bool internal::IsEnumFullySequential(const EnumDescriptor* enum_desc);
   typedef EnumOptions OptionsType;
 
   // Allows access to GetLocationPath for annotations.
@@ -2797,6 +2800,10 @@ inline const FileDescriptor* FileDescriptor::weak_dependency(int index) const {
 
 namespace internal {
 
+inline bool IsEnumFullySequential(const EnumDescriptor* enum_desc) {
+  return enum_desc->sequential_value_limit_ == enum_desc->value_count() - 1;
+}
+
 // FieldRange(desc) provides an iterable range for the fields of a
 // descriptor type, appropriate for range-for loops.
 

src/google/protobuf/generated_message_tctable_gen.cc

@@ -15,6 +15,7 @@
 #include <utility>
 #include <vector>
 
+#include "absl/container/fixed_array.h"
 #include "absl/log/absl_check.h"
 #include "absl/numeric/bits.h"
 #include "absl/strings/str_cat.h"
@@ -44,31 +45,71 @@ bool TreatEnumAsInt(const FieldDescriptor* field) {
           field->containing_type()->map_value() == field);
 }
 
-bool GetEnumValidationRange(const EnumDescriptor* enum_type, int16_t& start,
+bool SetEnumValidationRange(int start_value, int64_t size_value, int16_t& start,
                             uint16_t& size) {
-  ABSL_CHECK_GT(enum_type->value_count(), 0) << enum_type->DebugString();
+  if (static_cast<int16_t>(start_value) != start_value) {
+    return false;
+  }
 
-  // Check if the enum values are a single, contiguous range.
-  std::vector<int> enum_values;
-  for (int i = 0, N = static_cast<int>(enum_type->value_count()); i < N; ++i) {
-    enum_values.push_back(enum_type->value(i)->number());
-  }
-  auto values_begin = enum_values.begin();
-  auto values_end = enum_values.end();
-  std::sort(values_begin, values_end);
-  enum_values.erase(std::unique(values_begin, values_end), values_end);
-
-  if (std::numeric_limits<int16_t>::min() <= enum_values[0] &&
-      enum_values[0] <= std::numeric_limits<int16_t>::max() &&
-      enum_values.size() <= std::numeric_limits<uint16_t>::max() &&
-      static_cast<int>(enum_values[0] + enum_values.size() - 1) ==
-          enum_values.back()) {
-    start = static_cast<int16_t>(enum_values[0]);
-    size = static_cast<uint16_t>(enum_values.size());
-    return true;
-  } else {
+  if (static_cast<uint16_t>(size_value) != size_value) {
+    return false;
+  }
+
+  start = start_value;
+  size = size_value;
+  return true;
+}
+
+bool GetEnumValidationRangeSlow(const EnumDescriptor* enum_type, int16_t& start,
+                                uint16_t& size) {
+  const auto val = [&](int index) { return enum_type->value(index)->number(); };
+  int min = val(0);
+  int max = min;
+
+  for (int i = 1, N = static_cast<int>(enum_type->value_count()); i < N; ++i) {
+    min = std::min(min, val(i));
+    max = std::max(max, val(i));
+  }
+
+  // int64 because max-min can overflow int.
+  int64_t range = static_cast<int64_t>(max) - static_cast<int64_t>(min) + 1;
+
+  if (enum_type->value_count() < range) {
+    // There are not enough values to fill the range. Exit early.
     return false;
   }
+
+  if (!SetEnumValidationRange(min, range, start, size)) {
+    // Don't even bother on checking for a dense range if we can't represent the
+    // min/max in the output.
+    return false;
+  }
+
+  absl::FixedArray<uint64_t> array((range + 63) / 64);
+  array.fill(0);
+
+  int unique_count = 0;
+  for (int i = 0, N = static_cast<int>(enum_type->value_count()); i < N; ++i) {
+    size_t index = val(i) - min;
+    uint64_t& v = array[index / 64];
+    size_t bit_pos = index % 64;
+    unique_count += (v & (uint64_t{1} << bit_pos)) == 0;
+    v |= uint64_t{1} << bit_pos;
+  }
+
+  return unique_count == range;
+}
+
+bool GetEnumValidationRange(const EnumDescriptor* enum_type, int16_t& start,
+                            uint16_t& size) {
+  if (!IsEnumFullySequential(enum_type)) {
+    // Maybe the labels are not sequential in declaration order, but the values
+    // could still be a dense range. Try the slower approach.
+    return GetEnumValidationRangeSlow(enum_type, start, size);
+  }
+
+  return SetEnumValidationRange(enum_type->value(0)->number(),
+                                enum_type->value_count(), start, size);
 }
 
 enum class EnumRangeInfo {