--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lldb/source/Utility/ConstString.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,339 @@
+//===-- ConstString.cpp ---------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "lldb/Utility/ConstString.h"
+
+#include "lldb/Utility/Stream.h"
+
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/iterator.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/DJB.h"
+#include "llvm/Support/FormatProviders.h"
+#include "llvm/Support/RWMutex.h"
+#include "llvm/Support/Threading.h"
+
+#include <array>
+#include <utility>
+
+#include <inttypes.h>
+#include <stdint.h>
+#include <string.h>
+
+using namespace lldb_private;
+
+class Pool {
+public:
+  /// The default BumpPtrAllocatorImpl slab size.
+  static const size_t AllocatorSlabSize = 4096;
+  static const size_t SizeThreshold = AllocatorSlabSize;
+  /// Every Pool has its own allocator which receives an equal share of
+  /// the ConstString allocations. This means that when allocating many
+  /// ConstStrings, every allocator sees only its small share of allocations and
+  /// assumes LLDB only allocated a small amount of memory so far. In reality
+  /// LLDB allocated a total memory that is N times as large as what the
+  /// allocator sees (where N is the number of string pools). This causes that
+  /// the BumpPtrAllocator continues a long time to allocate memory in small
+  /// chunks which only makes sense when allocating a small amount of memory
+  /// (which is true from the perspective of a single allocator). On some
+  /// systems doing all these small memory allocations causes LLDB to spend
+  /// a lot of time in malloc, so we need to force all these allocators to
+  /// behave like one allocator in terms of scaling their memory allocations
+  /// with increased demand. To do this we set the growth delay for each single
+  /// allocator to a rate so that our pool of allocators scales their memory
+  /// allocations similar to a single BumpPtrAllocatorImpl.
+  ///
+  /// Currently we have 256 string pools and the normal growth delay of the
+  /// BumpPtrAllocatorImpl is 128 (i.e., the memory allocation size increases
+  /// every 128 full chunks), so by changing the delay to 1 we get a
+  /// total growth delay in our allocator collection of 256/1 = 256. This is
+  /// still only half as fast as a normal allocator but we can't go any faster
+  /// without decreasing the number of string pools.
+  static const size_t AllocatorGrowthDelay = 1;
+  typedef llvm::BumpPtrAllocatorImpl<llvm::MallocAllocator, AllocatorSlabSize,
+                                     SizeThreshold, AllocatorGrowthDelay>
+      Allocator;
+  typedef const char *StringPoolValueType;
+  typedef llvm::StringMap<StringPoolValueType, Allocator> StringPool;
+  typedef llvm::StringMapEntry<StringPoolValueType> StringPoolEntryType;
+
+  static StringPoolEntryType &
+  GetStringMapEntryFromKeyData(const char *keyData) {
+    return StringPoolEntryType::GetStringMapEntryFromKeyData(keyData);
+  }
+
+  static size_t GetConstCStringLength(const char *ccstr) {
+    if (ccstr != nullptr) {
+      // Since the entry is read only, and we derive the entry entirely from
+      // the pointer, we don't need the lock.
+      const StringPoolEntryType &entry = GetStringMapEntryFromKeyData(ccstr);
+      return entry.getKey().size();
+    }
+    return 0;
+  }
+
+  StringPoolValueType GetMangledCounterpart(const char *ccstr) const {
+    if (ccstr != nullptr) {
+      const uint8_t h = hash(llvm::StringRef(ccstr));
+      llvm::sys::SmartScopedReader<false> rlock(m_string_pools[h].m_mutex);
+      return GetStringMapEntryFromKeyData(ccstr).getValue();
+    }
+    return nullptr;
+  }
+
+  const char *GetConstCString(const char *cstr) {
+    if (cstr != nullptr)
+      return GetConstCStringWithLength(cstr, strlen(cstr));
+    return nullptr;
+  }
+
+  const char *GetConstCStringWithLength(const char *cstr, size_t cstr_len) {
+    if (cstr != nullptr)
+      return GetConstCStringWithStringRef(llvm::StringRef(cstr, cstr_len));
+    return nullptr;
+  }
+
+  const char *GetConstCStringWithStringRef(const llvm::StringRef &string_ref) {
+    if (string_ref.data()) {
+      const uint8_t h = hash(string_ref);
+
+      {
+        llvm::sys::SmartScopedReader<false> rlock(m_string_pools[h].m_mutex);
+        auto it = m_string_pools[h].m_string_map.find(string_ref);
+        if (it != m_string_pools[h].m_string_map.end())
+          return it->getKeyData();
+      }
+
+      llvm::sys::SmartScopedWriter<false> wlock(m_string_pools[h].m_mutex);
+      StringPoolEntryType &entry =
+          *m_string_pools[h]
+               .m_string_map.insert(std::make_pair(string_ref, nullptr))
+               .first;
+      return entry.getKeyData();
+    }
+    return nullptr;
+  }
+
+  const char *
+  GetConstCStringAndSetMangledCounterPart(llvm::StringRef demangled,
+                                          const char *mangled_ccstr) {
+    const char *demangled_ccstr = nullptr;
+
+    {
+      const uint8_t h = hash(demangled);
+      llvm::sys::SmartScopedWriter<false> wlock(m_string_pools[h].m_mutex);
+
+      // Make or update string pool entry with the mangled counterpart
+      StringPool &map = m_string_pools[h].m_string_map;
+      StringPoolEntryType &entry = *map.try_emplace(demangled).first;
+
+      entry.second = mangled_ccstr;
+
+      // Extract the const version of the demangled_cstr
+      demangled_ccstr = entry.getKeyData();
+    }
+
+    {
+      // Now assign the demangled const string as the counterpart of the
+      // mangled const string...
+      const uint8_t h = hash(llvm::StringRef(mangled_ccstr));
+      llvm::sys::SmartScopedWriter<false> wlock(m_string_pools[h].m_mutex);
+      GetStringMapEntryFromKeyData(mangled_ccstr).setValue(demangled_ccstr);
+    }
+
+    // Return the constant demangled C string
+    return demangled_ccstr;
+  }
+
+  const char *GetConstTrimmedCStringWithLength(const char *cstr,
+                                               size_t cstr_len) {
+    if (cstr != nullptr) {
+      const size_t trimmed_len = strnlen(cstr, cstr_len);
+      return GetConstCStringWithLength(cstr, trimmed_len);
+    }
+    return nullptr;
+  }
+
+  // Return the size in bytes that this object and any items in its collection
+  // of uniqued strings + data count values takes in memory.
+  size_t MemorySize() const {
+    size_t mem_size = sizeof(Pool);
+    for (const auto &pool : m_string_pools) {
+      llvm::sys::SmartScopedReader<false> rlock(pool.m_mutex);
+      for (const auto &entry : pool.m_string_map)
+        mem_size += sizeof(StringPoolEntryType) + entry.getKey().size();
+    }
+    return mem_size;
+  }
+
+protected:
+  uint8_t hash(const llvm::StringRef &s) const {
+    uint32_t h = llvm::djbHash(s);
+    return ((h >> 24) ^ (h >> 16) ^ (h >> 8) ^ h) & 0xff;
+  }
+
+  struct PoolEntry {
+    mutable llvm::sys::SmartRWMutex<false> m_mutex;
+    StringPool m_string_map;
+  };
+
+  std::array<PoolEntry, 256> m_string_pools;
+};
+
+// Frameworks and dylibs aren't supposed to have global C++ initializers so we
+// hide the string pool in a static function so that it will get initialized on
+// the first call to this static function.
+//
+// Note, for now we make the string pool a pointer to the pool, because we
+// can't guarantee that some objects won't get destroyed after the global
+// destructor chain is run, and trying to make sure no destructors touch
+// ConstStrings is difficult.  So we leak the pool instead.
+static Pool &StringPool() {
+  static llvm::once_flag g_pool_initialization_flag;
+  static Pool *g_string_pool = nullptr;
+
+  llvm::call_once(g_pool_initialization_flag,
+                 []() { g_string_pool = new Pool(); });
+
+  return *g_string_pool;
+}
+
+ConstString::ConstString(const char *cstr)
+    : m_string(StringPool().GetConstCString(cstr)) {}
+
+ConstString::ConstString(const char *cstr, size_t cstr_len)
+    : m_string(StringPool().GetConstCStringWithLength(cstr, cstr_len)) {}
+
+ConstString::ConstString(const llvm::StringRef &s)
+    : m_string(StringPool().GetConstCStringWithStringRef(s)) {}
+
+bool ConstString::operator<(ConstString rhs) const {
+  if (m_string == rhs.m_string)
+    return false;
+
+  llvm::StringRef lhs_string_ref(GetStringRef());
+  llvm::StringRef rhs_string_ref(rhs.GetStringRef());
+
+  // If both have valid C strings, then return the comparison
+  if (lhs_string_ref.data() && rhs_string_ref.data())
+    return lhs_string_ref < rhs_string_ref;
+
+  // Else one of them was nullptr, so if LHS is nullptr then it is less than
+  return lhs_string_ref.data() == nullptr;
+}
+
+Stream &lldb_private::operator<<(Stream &s, ConstString str) {
+  const char *cstr = str.GetCString();
+  if (cstr != nullptr)
+    s << cstr;
+
+  return s;
+}
+
+size_t ConstString::GetLength() const {
+  return Pool::GetConstCStringLength(m_string);
+}
+
+bool ConstString::Equals(ConstString lhs, ConstString rhs,
+                         const bool case_sensitive) {
+  if (lhs.m_string == rhs.m_string)
+    return true;
+
+  // Since the pointers weren't equal, and identical ConstStrings always have
+  // identical pointers, the result must be false for case sensitive equality
+  // test.
+  if (case_sensitive)
+    return false;
+
+  // perform case insensitive equality test
+  llvm::StringRef lhs_string_ref(lhs.GetStringRef());
+  llvm::StringRef rhs_string_ref(rhs.GetStringRef());
+  return lhs_string_ref.equals_lower(rhs_string_ref);
+}
+
+int ConstString::Compare(ConstString lhs, ConstString rhs,
+                         const bool case_sensitive) {
+  // If the iterators are the same, this is the same string
+  const char *lhs_cstr = lhs.m_string;
+  const char *rhs_cstr = rhs.m_string;
+  if (lhs_cstr == rhs_cstr)
+    return 0;
+  if (lhs_cstr && rhs_cstr) {
+    llvm::StringRef lhs_string_ref(lhs.GetStringRef());
+    llvm::StringRef rhs_string_ref(rhs.GetStringRef());
+
+    if (case_sensitive) {
+      return lhs_string_ref.compare(rhs_string_ref);
+    } else {
+      return lhs_string_ref.compare_lower(rhs_string_ref);
+    }
+  }
+
+  if (lhs_cstr)
+    return +1; // LHS isn't nullptr but RHS is
+  else
+    return -1; // LHS is nullptr but RHS isn't
+}
+
+void ConstString::Dump(Stream *s, const char *fail_value) const {
+  if (s != nullptr) {
+    const char *cstr = AsCString(fail_value);
+    if (cstr != nullptr)
+      s->PutCString(cstr);
+  }
+}
+
+void ConstString::DumpDebug(Stream *s) const {
+  const char *cstr = GetCString();
+  size_t cstr_len = GetLength();
+  // Only print the parens if we have a non-nullptr string
+  const char *parens = cstr ? "\"" : "";
+  s->Printf("%*p: ConstString, string = %s%s%s, length = %" PRIu64,
+            static_cast<int>(sizeof(void *) * 2),
+            static_cast<const void *>(this), parens, cstr, parens,
+            static_cast<uint64_t>(cstr_len));
+}
+
+void ConstString::SetCString(const char *cstr) {
+  m_string = StringPool().GetConstCString(cstr);
+}
+
+void ConstString::SetString(const llvm::StringRef &s) {
+  m_string = StringPool().GetConstCStringWithLength(s.data(), s.size());
+}
+
+void ConstString::SetStringWithMangledCounterpart(llvm::StringRef demangled,
+                                                   ConstString mangled) {
+  m_string = StringPool().GetConstCStringAndSetMangledCounterPart(
+      demangled, mangled.m_string);
+}
+
+bool ConstString::GetMangledCounterpart(ConstString &counterpart) const {
+  counterpart.m_string = StringPool().GetMangledCounterpart(m_string);
+  return (bool)counterpart;
+}
+
+void ConstString::SetCStringWithLength(const char *cstr, size_t cstr_len) {
+  m_string = StringPool().GetConstCStringWithLength(cstr, cstr_len);
+}
+
+void ConstString::SetTrimmedCStringWithLength(const char *cstr,
+                                              size_t cstr_len) {
+  m_string = StringPool().GetConstTrimmedCStringWithLength(cstr, cstr_len);
+}
+
+size_t ConstString::StaticMemorySize() {
+  // Get the size of the static string pool
+  return StringPool().MemorySize();
+}
+
+void llvm::format_provider<ConstString>::format(const ConstString &CS,
+                                                llvm::raw_ostream &OS,
+                                                llvm::StringRef Options) {
+  format_provider<StringRef>::format(CS.GetStringRef(), OS, Options);
+}