Export of internal Abseil changes.

--
821196cfb2a3b943ffdc4c9e75daec92d7ffb28b by Abseil Team <absl-team@google.com>:

Performance improvements

PiperOrigin-RevId: 212668992

--
704858e2e767016bad27d53eec01d9d48e546b23 by Abseil Team <absl-team@google.com>:

Low-level Portability enchancements for Abseil Mutex on WebAssembly.

Emscripten Pthreads do not use signals, so remove use of pthread_sigmask or
other async-signal-safe related handling code.

PiperOrigin-RevId: 212527958

--
be3e38cb4d493b755132d20c8c2d1a51e45d5449 by Jon Cohen <cohenjon@google.com>:

Internal change.

PiperOrigin-RevId: 212523797
GitOrigin-RevId: 821196cfb2a3b943ffdc4c9e75daec92d7ffb28b
Change-Id: I5694e23e4e09364a15dd6fc4e2e3f15e38835687

absl/base/internal/low_level_alloc.cc

@@ -401,16 +401,20 @@ bool LowLevelAlloc::DeleteArena(Arena *arena) {
     ABSL_RAW_CHECK(munmap_result != 0,
                    "LowLevelAlloc::DeleteArena: VitualFree failed");
 #else
+#ifndef ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
     if ((arena->flags & LowLevelAlloc::kAsyncSignalSafe) == 0) {
       munmap_result = munmap(region, size);
     } else {
       munmap_result = base_internal::DirectMunmap(region, size);
     }
+#else
+    munmap_result = munmap(region, size);
+#endif  // ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
     if (munmap_result != 0) {
       ABSL_RAW_LOG(FATAL, "LowLevelAlloc::DeleteArena: munmap failed: %d",
                    errno);
     }
-#endif
+#endif  // _WIN32
   }
   section.Leave();
   arena->~Arena();
@@ -545,6 +549,7 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
                                MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
       ABSL_RAW_CHECK(new_pages != nullptr, "VirtualAlloc failed");
 #else
+#ifndef ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
       if ((arena->flags & LowLevelAlloc::kAsyncSignalSafe) != 0) {
         new_pages = base_internal::DirectMmap(nullptr, new_pages_size,
             PROT_WRITE|PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
@@ -552,10 +557,15 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
         new_pages = mmap(nullptr, new_pages_size, PROT_WRITE | PROT_READ,
                          MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
       }
+#else
+      new_pages = mmap(nullptr, new_pages_size, PROT_WRITE | PROT_READ,
+                       MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+#endif  // ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
       if (new_pages == MAP_FAILED) {
         ABSL_RAW_LOG(FATAL, "mmap error: %d", errno);
       }
-#endif
+
+#endif  // _WIN32
       arena->mu.Lock();
       s = reinterpret_cast<AllocList *>(new_pages);
       s->header.size = new_pages_size;

absl/base/internal/low_level_alloc.h

@@ -39,10 +39,13 @@
 #define ABSL_LOW_LEVEL_ALLOC_MISSING 1
 #endif
 
-// Using LowLevelAlloc with kAsyncSignalSafe isn't supported on Windows.
+// Using LowLevelAlloc with kAsyncSignalSafe isn't supported on Windows or
+// asm.js / WebAssembly.
+// See https://kripken.github.io/emscripten-site/docs/porting/pthreads.html
+// for more information.
 #ifdef ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING
 #error ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING cannot be directly set
-#elif defined(_WIN32)
+#elif defined(_WIN32) || defined(__asmjs__) || defined(__wasm__)
 #define ABSL_LOW_LEVEL_ALLOC_ASYNC_SIGNAL_SAFE_MISSING 1
 #endif
 

absl/base/internal/thread_identity.cc

@@ -68,6 +68,14 @@ void SetCurrentThreadIdentity(
   // NOTE: Not async-safe.  But can be open-coded.
   absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,
                   reclaimer);
+
+#ifdef __EMSCRIPTEN__
+  // Emscripten PThread implementation does not support signals.
+  // See https://kripken.github.io/emscripten-site/docs/porting/pthreads.html
+  // for more information.
+  pthread_setspecific(thread_identity_pthread_key,
+                      reinterpret_cast<void*>(identity));
+#else
   // We must mask signals around the call to setspecific as with current glibc,
   // a concurrent getspecific (needed for GetCurrentThreadIdentityIfPresent())
   // may zero our value.
@@ -81,6 +89,8 @@ void SetCurrentThreadIdentity(
   pthread_setspecific(thread_identity_pthread_key,
                       reinterpret_cast<void*>(identity));
   pthread_sigmask(SIG_SETMASK, &curr_signals, nullptr);
+#endif  // !__EMSCRIPTEN__
+
 #elif ABSL_THREAD_IDENTITY_MODE == ABSL_THREAD_IDENTITY_MODE_USE_TLS
   // NOTE: Not async-safe.  But can be open-coded.
   absl::call_once(init_thread_identity_key_once, AllocateThreadIdentityKey,

absl/memory/memory_test.cc

@@ -149,7 +149,6 @@ TEST(Make_UniqueTest, NotAmbiguousWithStdMakeUnique) {
 }
 
 #if 0
-// TODO(billydonahue): Make a proper NC test.
 // These tests shouldn't compile.
 TEST(MakeUniqueTestNC, AcceptMoveOnlyLvalue) {
   auto m = MoveOnly();

absl/strings/internal/str_format/bind.h

@@ -186,7 +186,7 @@ class StreamedWrapper {
  private:
   template <typename S>
   friend ConvertResult<Conv::s> FormatConvertImpl(const StreamedWrapper<S>& v,
-                                                  const ConversionSpec& conv,
+                                                  ConversionSpec conv,
                                                   FormatSinkImpl* out);
   const T& v_;
 };

absl/strings/internal/str_format/extension.h

@@ -18,6 +18,7 @@
 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_EXTENSION_H_
 
 #include <limits.h>
+#include <cstddef>
 #include <cstring>
 #include <ostream>
 
@@ -307,7 +308,12 @@ class ConversionSpec {
  public:
   Flags flags() const { return flags_; }
   LengthMod length_mod() const { return length_mod_; }
-  ConversionChar conv() const { return conv_; }
+  ConversionChar conv() const {
+    // Keep this field first in the struct . It generates better code when
+    // accessing it when ConversionSpec is passed by value in registers.
+    static_assert(offsetof(ConversionSpec, conv_) == 0, "");
+    return conv_;
+  }
 
   // Returns the specified width. If width is unspecfied, it returns a negative
   // value.
@@ -324,9 +330,9 @@ class ConversionSpec {
   void set_left(bool b) { flags_.left = b; }
 
  private:
+  ConversionChar conv_;
   Flags flags_;
   LengthMod length_mod_;
-  ConversionChar conv_;
   int width_;
   int precision_;
 };

absl/strings/str_format_test.cc

@@ -601,3 +601,39 @@ TEST_F(ParsedFormatTest, RegressionMixPositional) {
 
 }  // namespace
 }  // namespace absl
+
+// Some codegen thunks that we can use to easily dump the generated assembly for
+// different StrFormat calls.
+
+inline std::string CodegenAbslStrFormatInt(int i) {
+  return absl::StrFormat("%d", i);
+}
+
+inline std::string CodegenAbslStrFormatIntStringInt64(int i, const std::string& s,
+                                                 int64_t i64) {
+  return absl::StrFormat("%d %s %d", i, s, i64);
+}
+
+inline void CodegenAbslStrAppendFormatInt(std::string* out, int i) {
+  absl::StrAppendFormat(out, "%d", i);
+}
+
+inline void CodegenAbslStrAppendFormatIntStringInt64(std::string* out, int i,
+                                                     const std::string& s,
+                                                     int64_t i64) {
+  absl::StrAppendFormat(out, "%d %s %d", i, s, i64);
+}
+
+auto absl_internal_str_format_force_codegen_funcs = std::make_tuple(
+    CodegenAbslStrFormatInt, CodegenAbslStrFormatIntStringInt64,
+    CodegenAbslStrAppendFormatInt, CodegenAbslStrAppendFormatIntStringInt64);
+
+bool absl_internal_str_format_force_codegen_always_false;
+// Force the compiler to generate the functions by making it look like we
+// escape the function pointers.
+// It can't statically know that
+// absl_internal_str_format_force_codegen_always_false is not changed by someone
+// else.
+bool absl_internal_str_format_force_codegen =
+    absl_internal_str_format_force_codegen_always_false &&
+    printf("%p", &absl_internal_str_format_force_codegen_funcs) == 0;