Export of internal Abseil changes.

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4e224c85c3730398919fc5195cb1fc7a752e6e4f by Mark Barolak <mbar@google.com>:

Update some references to "StringPiece" to say "string_view" instead.

PiperOrigin-RevId: 219693697

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6bdc925a3db5e97f1f8a404bdfda2e47e48f7b9a by Abseil Team <absl-team@google.com>:

Disable weak symbols for the Windows backend of LLVM, since they are currently buggy. See https://bugs.llvm.org/show_bug.cgi?id=37598 for more information.

PiperOrigin-RevId: 219676493

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5823f495036181191f435efa4c45d60ca3160145 by Derek Mauro <dmauro@google.com>:

Don't use the SSE2 implementation of container_internal::Group
with -funsigned-char under GCC.

This is a workaround for https://github.com/abseil/abseil-cpp/issues/209.

_mm_cmpgt_epi8 is broken under GCC with -funsigned-char.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87853

PiperOrigin-RevId: 219666066
GitOrigin-RevId: 4e224c85c3730398919fc5195cb1fc7a752e6e4f
Change-Id: I2f115d0256576cf476ae73a9464c21d4106a2a56

absl/base/attributes.h

@@ -155,7 +155,12 @@
 // ABSL_ATTRIBUTE_WEAK
 //
 // Tags a function as weak for the purposes of compilation and linking.
-#if ABSL_HAVE_ATTRIBUTE(weak) || (defined(__GNUC__) && !defined(__clang__))
+// Weak attributes currently do not work properly in LLVM's Windows backend,
+// so disable them there. See https://bugs.llvm.org/show_bug.cgi?id=37598
+// for futher information.
+#if (ABSL_HAVE_ATTRIBUTE(weak) || \
+     (defined(__GNUC__) && !defined(__clang__))) && \
+    !(defined(__llvm__) && defined(_WIN32))
 #undef ABSL_ATTRIBUTE_WEAK
 #define ABSL_ATTRIBUTE_WEAK __attribute__((weak))
 #define ABSL_HAVE_ATTRIBUTE_WEAK 1
@@ -296,13 +301,13 @@
 
 // ABSL_HAVE_ATTRIBUTE_SECTION
 //
-// Indicates whether labeled sections are supported. Labeled sections are not
-// supported on Darwin/iOS.
+// Indicates whether labeled sections are supported. Weak symbol support is
+// a prerequisite. Labeled sections are not supported on Darwin/iOS.
 #ifdef ABSL_HAVE_ATTRIBUTE_SECTION
 #error ABSL_HAVE_ATTRIBUTE_SECTION cannot be directly set
 #elif (ABSL_HAVE_ATTRIBUTE(section) ||                \
        (defined(__GNUC__) && !defined(__clang__))) && \
-    !defined(__APPLE__)
+    !defined(__APPLE__) && ABSL_HAVE_ATTRIBUTE_WEAK
 #define ABSL_HAVE_ATTRIBUTE_SECTION 1
 
 // ABSL_ATTRIBUTE_SECTION

absl/container/internal/raw_hash_set.h

@@ -337,10 +337,10 @@ inline bool IsDeleted(ctrl_t c) { return c == kDeleted; }
 inline bool IsEmptyOrDeleted(ctrl_t c) { return c < kSentinel; }
 
 #if SWISSTABLE_HAVE_SSE2
-struct Group {
+struct GroupSse2Impl {
   static constexpr size_t kWidth = 16;  // the number of slots per group
 
-  explicit Group(const ctrl_t* pos) {
+  explicit GroupSse2Impl(const ctrl_t* pos) {
     ctrl = _mm_loadu_si128(reinterpret_cast<const __m128i*>(pos));
   }
 
@@ -390,11 +390,13 @@ struct Group {
 
   __m128i ctrl;
 };
-#else
-struct Group {
+#endif  // SWISSTABLE_HAVE_SSE2
+
+struct GroupPortableImpl {
   static constexpr size_t kWidth = 8;
 
-  explicit Group(const ctrl_t* pos) : ctrl(little_endian::Load64(pos)) {}
+  explicit GroupPortableImpl(const ctrl_t* pos)
+      : ctrl(little_endian::Load64(pos)) {}
 
   BitMask<uint64_t, kWidth, 3> Match(h2_t hash) const {
     // For the technique, see:
@@ -441,12 +443,24 @@ struct Group {
 
   uint64_t ctrl;
 };
-#endif  // SWISSTABLE_HAVE_SSE2
+
+#if SWISSTABLE_HAVE_SSE2 && defined(__GNUC__) && !defined(__clang__)
+// https://github.com/abseil/abseil-cpp/issues/209
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87853
+// _mm_cmpgt_epi8 is broken under GCC with -funsigned-char
+// Work around this by using the portable implementation of Group
+// when using -funsigned-char under GCC.
+using Group = std::conditional<std::is_signed<char>::value, GroupSse2Impl,
+                               GroupPortableImpl>::type;
+#elif SWISSTABLE_HAVE_SSE2
+using Group = GroupSse2Impl;
+#else
+using Group = GroupPortableImpl;
+#endif
 
 template <class Policy, class Hash, class Eq, class Alloc>
 class raw_hash_set;
 
-
 inline bool IsValidCapacity(size_t n) {
   return ((n + 1) & n) == 0 && n >= Group::kWidth - 1;
 }

absl/container/internal/raw_hash_set_test.cc

@@ -130,8 +130,8 @@ TEST(Group, EmptyGroup) {
   for (h2_t h = 0; h != 128; ++h) EXPECT_FALSE(Group{EmptyGroup()}.Match(h));
 }
 
-#if SWISSTABLE_HAVE_SSE2
 TEST(Group, Match) {
+  if (Group::kWidth == 16) {
     ctrl_t group[] = {kEmpty, 1, kDeleted, 3, kEmpty, 5, kSentinel, 7,
                       7,      5, 3,        1, 1,      1, 1,         1};
     EXPECT_THAT(Group{group}.Match(0), ElementsAre());
@@ -139,36 +139,41 @@ TEST(Group, Match) {
     EXPECT_THAT(Group{group}.Match(3), ElementsAre(3, 10));
     EXPECT_THAT(Group{group}.Match(5), ElementsAre(5, 9));
     EXPECT_THAT(Group{group}.Match(7), ElementsAre(7, 8));
-}
-
-TEST(Group, MatchEmpty) {
-  ctrl_t group[] = {kEmpty, 1, kDeleted, 3, kEmpty, 5, kSentinel, 7,
-                    7,      5, 3,        1, 1,      1, 1,         1};
-  EXPECT_THAT(Group{group}.MatchEmpty(), ElementsAre(0, 4));
-}
-
-TEST(Group, MatchEmptyOrDeleted) {
-  ctrl_t group[] = {kEmpty, 1, kDeleted, 3, kEmpty, 5, kSentinel, 7,
-                    7,      5, 3,        1, 1,      1, 1,         1};
-  EXPECT_THAT(Group{group}.MatchEmptyOrDeleted(), ElementsAre(0, 2, 4));
-}
-#else
-TEST(Group, Match) {
+  } else if (Group::kWidth == 8) {
     ctrl_t group[] = {kEmpty, 1, 2, kDeleted, 2, 1, kSentinel, 1};
     EXPECT_THAT(Group{group}.Match(0), ElementsAre());
     EXPECT_THAT(Group{group}.Match(1), ElementsAre(1, 5, 7));
     EXPECT_THAT(Group{group}.Match(2), ElementsAre(2, 4));
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
 }
+
 TEST(Group, MatchEmpty) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {kEmpty, 1, kDeleted, 3, kEmpty, 5, kSentinel, 7,
+                      7,      5, 3,        1, 1,      1, 1,         1};
+    EXPECT_THAT(Group{group}.MatchEmpty(), ElementsAre(0, 4));
+  } else if (Group::kWidth == 8) {
     ctrl_t group[] = {kEmpty, 1, 2, kDeleted, 2, 1, kSentinel, 1};
     EXPECT_THAT(Group{group}.MatchEmpty(), ElementsAre(0));
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
 }
 
 TEST(Group, MatchEmptyOrDeleted) {
+  if (Group::kWidth == 16) {
+    ctrl_t group[] = {kEmpty, 1, kDeleted, 3, kEmpty, 5, kSentinel, 7,
+                      7,      5, 3,        1, 1,      1, 1,         1};
+    EXPECT_THAT(Group{group}.MatchEmptyOrDeleted(), ElementsAre(0, 2, 4));
+  } else if (Group::kWidth == 8) {
     ctrl_t group[] = {kEmpty, 1, 2, kDeleted, 2, 1, kSentinel, 1};
     EXPECT_THAT(Group{group}.MatchEmptyOrDeleted(), ElementsAre(0, 3));
+  } else {
+    FAIL() << "No test coverage for Group::kWidth==" << Group::kWidth;
+  }
 }
-#endif
 
 TEST(Batch, DropDeletes) {
   constexpr size_t kCapacity = 63;

absl/strings/str_cat.cc

@@ -80,7 +80,7 @@ AlphaNum::AlphaNum(Dec dec) {
 // StrCat()
 //    This merges the given strings or integers, with no delimiter.  This
 //    is designed to be the fastest possible way to construct a string out
-//    of a mix of raw C strings, StringPieces, strings, and integer values.
+//    of a mix of raw C strings, string_views, strings, and integer values.
 // ----------------------------------------------------------------------
 
 // Append is merely a version of memcpy that returns the address of the byte

absl/strings/str_split_benchmark.cc

@@ -35,16 +35,16 @@ std::string MakeTestString(int desired_length) {
   return test;
 }
 
-void BM_Split2StringPiece(benchmark::State& state) {
+void BM_Split2StringView(benchmark::State& state) {
   std::string test = MakeTestString(state.range(0));
   for (auto _ : state) {
     std::vector<absl::string_view> result = absl::StrSplit(test, ';');
     benchmark::DoNotOptimize(result);
   }
 }
-BENCHMARK_RANGE(BM_Split2StringPiece, 0, 1 << 20);
+BENCHMARK_RANGE(BM_Split2StringView, 0, 1 << 20);
 
-void BM_Split2StringPieceLifted(benchmark::State& state) {
+void BM_Split2StringViewLifted(benchmark::State& state) {
   std::string test = MakeTestString(state.range(0));
   std::vector<absl::string_view> result;
   for (auto _ : state) {
@@ -52,7 +52,7 @@ void BM_Split2StringPieceLifted(benchmark::State& state) {
   }
   benchmark::DoNotOptimize(result);
 }
-BENCHMARK_RANGE(BM_Split2StringPieceLifted, 0, 1 << 20);
+BENCHMARK_RANGE(BM_Split2StringViewLifted, 0, 1 << 20);
 
 void BM_Split2String(benchmark::State& state) {
   std::string test = MakeTestString(state.range(0));