Reorganize upb file structure

This change moves almost everything in the `upb/` directory up one level, so
that for example `upb/upb/generated_code_support.h` becomes just
`upb/generated_code_support.h`. The only exceptions I made to this were that I
left `upb/cmake` and `upb/BUILD` where they are, mostly because that avoids
conflict with other files and the current locations seem reasonable for now.

The `python/` directory is a little bit of a challenge because we had to merge
the existing directory there with `upb/python/`. I made `upb/python/BUILD` into
the BUILD file for the merged directory, and it effectively loads the contents
of the other BUILD file via `python/build_targets.bzl`, but I plan to clean
this up soon.

PiperOrigin-RevId: 568651768
diff --git a/benchmarks/benchmark.cc b/benchmarks/benchmark.cc
new file mode 100644
index 0000000..a2e2cc2
--- /dev/null
+++ b/benchmarks/benchmark.cc
@@ -0,0 +1,390 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2023 Google LLC.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google LLC nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <benchmark/benchmark.h>
+
+#include <string.h>
+
+#include <vector>
+
+#include "google/ads/googleads/v13/services/google_ads_service.upbdefs.h"
+#include "google/protobuf/descriptor.pb.h"
+#include "absl/container/flat_hash_set.h"
+#include "google/protobuf/dynamic_message.h"
+#include "benchmarks/descriptor.pb.h"
+#include "benchmarks/descriptor.upb.h"
+#include "benchmarks/descriptor.upbdefs.h"
+#include "benchmarks/descriptor_sv.pb.h"
+#include "upb/base/internal/log2.h"
+#include "upb/mem/arena.h"
+#include "upb/reflection/def.hpp"
+
+upb_StringView descriptor = benchmarks_descriptor_proto_upbdefinit.descriptor;
+namespace protobuf = ::google::protobuf;
+
+// A buffer big enough to parse descriptor.proto without going to heap.
+// We use 64-bit ints here to force alignment.
+int64_t buf[8191];
+
+void CollectFileDescriptors(
+    const _upb_DefPool_Init* file,
+    std::vector<upb_StringView>& serialized_files,
+    absl::flat_hash_set<const _upb_DefPool_Init*>& seen) {
+  if (!seen.insert(file).second) return;
+  for (_upb_DefPool_Init** deps = file->deps; *deps; deps++) {
+    CollectFileDescriptors(*deps, serialized_files, seen);
+  }
+  serialized_files.push_back(file->descriptor);
+}
+
+static void BM_ArenaOneAlloc(benchmark::State& state) {
+  for (auto _ : state) {
+    upb_Arena* arena = upb_Arena_New();
+    upb_Arena_Malloc(arena, 1);
+    upb_Arena_Free(arena);
+  }
+}
+BENCHMARK(BM_ArenaOneAlloc);
+
+static void BM_ArenaInitialBlockOneAlloc(benchmark::State& state) {
+  for (auto _ : state) {
+    upb_Arena* arena = upb_Arena_Init(buf, sizeof(buf), nullptr);
+    upb_Arena_Malloc(arena, 1);
+    upb_Arena_Free(arena);
+  }
+}
+BENCHMARK(BM_ArenaInitialBlockOneAlloc);
+
+static void BM_ArenaFuseUnbalanced(benchmark::State& state) {
+  std::vector<upb_Arena*> arenas(state.range(0));
+  size_t n = 0;
+  for (auto _ : state) {
+    for (auto& arena : arenas) {
+      arena = upb_Arena_New();
+    }
+    for (auto& arena : arenas) {
+      upb_Arena_Fuse(arenas[0], arena);
+    }
+    for (auto& arena : arenas) {
+      upb_Arena_Free(arena);
+    }
+    n += arenas.size();
+  }
+  state.SetItemsProcessed(n);
+}
+BENCHMARK(BM_ArenaFuseUnbalanced)->Range(2, 128);
+
+static void BM_ArenaFuseBalanced(benchmark::State& state) {
+  std::vector<upb_Arena*> arenas(state.range(0));
+  size_t n = 0;
+
+  for (auto _ : state) {
+    for (auto& arena : arenas) {
+      arena = upb_Arena_New();
+    }
+
+    // Perform a series of fuses that keeps the halves balanced.
+    size_t max = upb_Log2Ceiling(arenas.size());
+    for (size_t n = 0; n <= max; n++) {
+      size_t step = 1 << n;
+      for (size_t i = 0; i + step < arenas.size(); i += (step * 2)) {
+        upb_Arena_Fuse(arenas[i], arenas[i + step]);
+      }
+    }
+
+    for (auto& arena : arenas) {
+      upb_Arena_Free(arena);
+    }
+    n += arenas.size();
+  }
+  state.SetItemsProcessed(n);
+}
+BENCHMARK(BM_ArenaFuseBalanced)->Range(2, 128);
+
+enum LoadDescriptorMode {
+  NoLayout,
+  WithLayout,
+};
+
+// This function is mostly copied from upb/def.c, but it is modified to avoid
+// passing in the pre-generated mini-tables, in order to force upb to compute
+// them dynamically.  Generally you would never want to do this, but we want to
+// simulate the cost we would pay if we were loading these types purely from
+// descriptors, with no mini-tales available.
+bool LoadDefInit_BuildLayout(upb_DefPool* s, const _upb_DefPool_Init* init,
+                             size_t* bytes) {
+  _upb_DefPool_Init** deps = init->deps;
+  google_protobuf_FileDescriptorProto* file;
+  upb_Arena* arena;
+  upb_Status status;
+
+  upb_Status_Clear(&status);
+
+  if (upb_DefPool_FindFileByName(s, init->filename)) {
+    return true;
+  }
+
+  arena = upb_Arena_New();
+
+  for (; *deps; deps++) {
+    if (!LoadDefInit_BuildLayout(s, *deps, bytes)) goto err;
+  }
+
+  file = google_protobuf_FileDescriptorProto_parse_ex(
+      init->descriptor.data, init->descriptor.size, nullptr,
+      kUpb_DecodeOption_AliasString, arena);
+  *bytes += init->descriptor.size;
+
+  if (!file) {
+    upb_Status_SetErrorFormat(
+        &status,
+        "Failed to parse compiled-in descriptor for file '%s'. This should "
+        "never happen.",
+        init->filename);
+    goto err;
+  }
+
+  // KEY DIFFERENCE: Here we pass in only the descriptor, and not the
+  // pre-generated minitables.
+  if (!upb_DefPool_AddFile(s, file, &status)) {
+    goto err;
+  }
+
+  upb_Arena_Free(arena);
+  return true;
+
+err:
+  fprintf(stderr,
+          "Error loading compiled-in descriptor for file '%s' (this should "
+          "never happen): %s\n",
+          init->filename, upb_Status_ErrorMessage(&status));
+  exit(1);
+}
+
+template <LoadDescriptorMode Mode>
+static void BM_LoadAdsDescriptor_Upb(benchmark::State& state) {
+  size_t bytes_per_iter = 0;
+  for (auto _ : state) {
+    upb::DefPool defpool;
+    if (Mode == NoLayout) {
+      google_ads_googleads_v13_services_SearchGoogleAdsRequest_getmsgdef(
+          defpool.ptr());
+      bytes_per_iter = _upb_DefPool_BytesLoaded(defpool.ptr());
+    } else {
+      bytes_per_iter = 0;
+      LoadDefInit_BuildLayout(
+          defpool.ptr(),
+          &google_ads_googleads_v13_services_google_ads_service_proto_upbdefinit,
+          &bytes_per_iter);
+    }
+  }
+  state.SetBytesProcessed(state.iterations() * bytes_per_iter);
+}
+BENCHMARK_TEMPLATE(BM_LoadAdsDescriptor_Upb, NoLayout);
+BENCHMARK_TEMPLATE(BM_LoadAdsDescriptor_Upb, WithLayout);
+
+template <LoadDescriptorMode Mode>
+static void BM_LoadAdsDescriptor_Proto2(benchmark::State& state) {
+  extern _upb_DefPool_Init
+      google_ads_googleads_v13_services_google_ads_service_proto_upbdefinit;
+  std::vector<upb_StringView> serialized_files;
+  absl::flat_hash_set<const _upb_DefPool_Init*> seen_files;
+  CollectFileDescriptors(
+      &google_ads_googleads_v13_services_google_ads_service_proto_upbdefinit,
+      serialized_files, seen_files);
+  size_t bytes_per_iter = 0;
+  for (auto _ : state) {
+    bytes_per_iter = 0;
+    protobuf::Arena arena;
+    protobuf::DescriptorPool pool;
+    for (auto file : serialized_files) {
+      absl::string_view input(file.data, file.size);
+      auto proto =
+          protobuf::Arena::CreateMessage<protobuf::FileDescriptorProto>(&arena);
+      bool ok = proto->ParseFrom<protobuf::MessageLite::kMergePartial>(input) &&
+                pool.BuildFile(*proto) != nullptr;
+      if (!ok) {
+        printf("Failed to add file.\n");
+        exit(1);
+      }
+      bytes_per_iter += input.size();
+    }
+
+    if (Mode == WithLayout) {
+      protobuf::DynamicMessageFactory factory;
+      const protobuf::Descriptor* d = pool.FindMessageTypeByName(
+          "google.ads.googleads.v13.services.SearchGoogleAdsResponse");
+      if (!d) {
+        printf("Failed to find descriptor.\n");
+        exit(1);
+      }
+      factory.GetPrototype(d);
+    }
+  }
+  state.SetBytesProcessed(state.iterations() * bytes_per_iter);
+}
+BENCHMARK_TEMPLATE(BM_LoadAdsDescriptor_Proto2, NoLayout);
+BENCHMARK_TEMPLATE(BM_LoadAdsDescriptor_Proto2, WithLayout);
+
+enum CopyStrings {
+  Copy,
+  Alias,
+};
+
+enum ArenaMode {
+  NoArena,
+  UseArena,
+  InitBlock,
+};
+
+template <ArenaMode AMode, CopyStrings Copy>
+static void BM_Parse_Upb_FileDesc(benchmark::State& state) {
+  for (auto _ : state) {
+    upb_Arena* arena;
+    if (AMode == InitBlock) {
+      arena = upb_Arena_Init(buf, sizeof(buf), nullptr);
+    } else {
+      arena = upb_Arena_New();
+    }
+    upb_benchmark_FileDescriptorProto* set =
+        upb_benchmark_FileDescriptorProto_parse_ex(
+            descriptor.data, descriptor.size, nullptr,
+            Copy == Alias ? kUpb_DecodeOption_AliasString : 0, arena);
+    if (!set) {
+      printf("Failed to parse.\n");
+      exit(1);
+    }
+    upb_Arena_Free(arena);
+  }
+  state.SetBytesProcessed(state.iterations() * descriptor.size);
+}
+BENCHMARK_TEMPLATE(BM_Parse_Upb_FileDesc, UseArena, Copy);
+BENCHMARK_TEMPLATE(BM_Parse_Upb_FileDesc, UseArena, Alias);
+BENCHMARK_TEMPLATE(BM_Parse_Upb_FileDesc, InitBlock, Copy);
+BENCHMARK_TEMPLATE(BM_Parse_Upb_FileDesc, InitBlock, Alias);
+
+template <ArenaMode AMode, class P>
+struct Proto2Factory;
+
+template <class P>
+struct Proto2Factory<NoArena, P> {
+ public:
+  P* GetProto() { return &proto; }
+
+ private:
+  P proto;
+};
+
+template <class P>
+struct Proto2Factory<UseArena, P> {
+ public:
+  P* GetProto() { return protobuf::Arena::CreateMessage<P>(&arena); }
+
+ private:
+  protobuf::Arena arena;
+};
+
+template <class P>
+struct Proto2Factory<InitBlock, P> {
+ public:
+  Proto2Factory() : arena(GetOptions()) {}
+  P* GetProto() { return protobuf::Arena::CreateMessage<P>(&arena); }
+
+ private:
+  protobuf::ArenaOptions GetOptions() {
+    protobuf::ArenaOptions opts;
+    opts.initial_block = (char*)buf;
+    opts.initial_block_size = sizeof(buf);
+    return opts;
+  }
+
+  protobuf::Arena arena;
+};
+
+using FileDesc = ::upb_benchmark::FileDescriptorProto;
+using FileDescSV = ::upb_benchmark::sv::FileDescriptorProto;
+
+template <class P, ArenaMode AMode, CopyStrings kCopy>
+void BM_Parse_Proto2(benchmark::State& state) {
+  constexpr protobuf::MessageLite::ParseFlags kParseFlags =
+      kCopy == Copy
+          ? protobuf::MessageLite::ParseFlags::kMergePartial
+          : protobuf::MessageLite::ParseFlags::kMergePartialWithAliasing;
+  for (auto _ : state) {
+    Proto2Factory<AMode, P> proto_factory;
+    auto proto = proto_factory.GetProto();
+    absl::string_view input(descriptor.data, descriptor.size);
+    bool ok = proto->template ParseFrom<kParseFlags>(input);
+    if (!ok) {
+      printf("Failed to parse.\n");
+      exit(1);
+    }
+  }
+  state.SetBytesProcessed(state.iterations() * descriptor.size);
+}
+BENCHMARK_TEMPLATE(BM_Parse_Proto2, FileDesc, NoArena, Copy);
+BENCHMARK_TEMPLATE(BM_Parse_Proto2, FileDesc, UseArena, Copy);
+BENCHMARK_TEMPLATE(BM_Parse_Proto2, FileDesc, InitBlock, Copy);
+BENCHMARK_TEMPLATE(BM_Parse_Proto2, FileDescSV, InitBlock, Alias);
+
+static void BM_SerializeDescriptor_Proto2(benchmark::State& state) {
+  upb_benchmark::FileDescriptorProto proto;
+  proto.ParseFromArray(descriptor.data, descriptor.size);
+  for (auto _ : state) {
+    proto.SerializePartialToArray(buf, sizeof(buf));
+  }
+  state.SetBytesProcessed(state.iterations() * descriptor.size);
+}
+BENCHMARK(BM_SerializeDescriptor_Proto2);
+
+static void BM_SerializeDescriptor_Upb(benchmark::State& state) {
+  int64_t total = 0;
+  upb_Arena* arena = upb_Arena_New();
+  upb_benchmark_FileDescriptorProto* set =
+      upb_benchmark_FileDescriptorProto_parse(descriptor.data, descriptor.size,
+                                              arena);
+  if (!set) {
+    printf("Failed to parse.\n");
+    exit(1);
+  }
+  for (auto _ : state) {
+    upb_Arena* enc_arena = upb_Arena_Init(buf, sizeof(buf), nullptr);
+    size_t size;
+    char* data =
+        upb_benchmark_FileDescriptorProto_serialize(set, enc_arena, &size);
+    if (!data) {
+      printf("Failed to serialize.\n");
+      exit(1);
+    }
+    total += size;
+  }
+  state.SetBytesProcessed(total);
+}
+BENCHMARK(BM_SerializeDescriptor_Upb);