Export of internal Abseil changes

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4ff721439234e91caf6f7b772e5f554e7dd423c8 by Benjamin Barenblat <bbaren@google.com>:

Remove endian-sensitivity from hash slow path

Prior to this commit, the Abseil hash fast path was endian-agnostic, but
the slow path assumed a little-endian platform. Change the slow path to
be endian-correct, ensuring that values produced by the fast and slow
paths are equal even on big-endian systems.

PiperOrigin-RevId: 355424258

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7f4fe1aa4de46ad0a2ef19fa9c061fc12a7391ed by Abseil Team <absl-team@google.com>:

Directly store CordzInfo in the InlineData data contents of InlineRep

This greatly reduces the cost of coping and moving cords. Especially the move constructor and move assignment are now back to lean loads and stores without needing any CordzInfo lookups for tracked cords.

PiperOrigin-RevId: 355409161

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3ca4ca84ed6d98f1e383ffd8d12c28876e905bb3 by Abseil Team <absl-team@google.com>:

Add #include <unordered_map>

PiperOrigin-RevId: 355386114

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30b0ffad0621971b3135148fcc9e183b0dd2a6bb by Abseil Team <absl-team@google.com>:

Optimize Cord copy constructor

This change avoids double stores of the Cord copy constructor from the zero init of the InlineData / InlineRep contents followed by the assignment and inlines the copy constructor.

PiperOrigin-RevId: 355287939

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0c043fa7b6e41ca7cefc5edc1e17ad46223e4e77 by CJ Johnson <johnsoncj@google.com>:

Now that the absl::Cleanup example returns absl::Status, since we decided on absl::FailedPreconditionError, the precondition should be a positive statement and then the check should be failure to adhere to that positive statement

PiperOrigin-RevId: 355216923

--
9ed922ca5d28fe8790ec6bc0837cf39fbcc92896 by Gennadiy Rozental <rogeeff@google.com>:

Do not set mvsc linker flags for clang-cl (fixes #874)

Import of https://github.com/abseil/abseil-cpp/pull/891

PiperOrigin-RevId: 355199380
GitOrigin-RevId: 4ff721439234e91caf6f7b772e5f554e7dd423c8
Change-Id: I3d9d2383549720d7a91f9108dfcd979ad6632fce

3 files changed, 42 insertions, 11 deletions

diff --git a/absl/hash/BUILD.bazel b/absl/hash/BUILD.bazel
index 90c6c8a8..4b2c220f 100644
--- a/absl/hash/BUILD.bazel
+++ b/absl/hash/BUILD.bazel
@@ -38,6 +38,7 @@ cc_library(
     deps = [
         ":city",
         ":wyhash",
+        "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:endian",
         "//absl/container:fixed_array",
diff --git a/absl/hash/CMakeLists.txt b/absl/hash/CMakeLists.txt
index 6d198775..b43bfa54 100644
--- a/absl/hash/CMakeLists.txt
+++ b/absl/hash/CMakeLists.txt
@@ -26,6 +26,7 @@ absl_cc_library(
     ${ABSL_DEFAULT_COPTS}
     DEPS
     absl::city
+    absl::config
     absl::core_headers
     absl::endian
     absl::fixed_array
diff --git a/absl/hash/internal/hash.h b/absl/hash/internal/hash.h
index eb3471d8..7fb0af0b 100644
--- a/absl/hash/internal/hash.h
+++ b/absl/hash/internal/hash.h
@@ -38,7 +38,8 @@
 #include <utility>
 #include <vector>
 
-#include "absl/base/internal/endian.h"
+#include "absl/base/config.h"
+#include "absl/base/internal/unaligned_access.h"
 #include "absl/base/port.h"
 #include "absl/container/fixed_array.h"
 #include "absl/hash/internal/wyhash.h"
@@ -804,26 +805,54 @@ class ABSL_DLL HashState : public HashStateBase<HashState> {
                                                size_t len);
 
   // Reads 9 to 16 bytes from p.
-  // The first 8 bytes are in .first, the rest (zero padded) bytes are in
-  // .second.
+  // The least significant 8 bytes are in .first, the rest (zero padded) bytes
+  // are in .second.
   static std::pair<uint64_t, uint64_t> Read9To16(const unsigned char* p,
                                                  size_t len) {
-    uint64_t high = little_endian::Load64(p + len - 8);
-    return {little_endian::Load64(p), high >> (128 - len * 8)};
+    uint64_t low_mem = absl::base_internal::UnalignedLoad64(p);
+    uint64_t high_mem = absl::base_internal::UnalignedLoad64(p + len - 8);
+#ifdef ABSL_IS_LITTLE_ENDIAN
+    uint64_t most_significant = high_mem;
+    uint64_t least_significant = low_mem;
+#else
+    uint64_t most_significant = low_mem;
+    uint64_t least_significant = high_mem;
+#endif
+    return {least_significant, most_significant >> (128 - len * 8)};
   }
 
   // Reads 4 to 8 bytes from p. Zero pads to fill uint64_t.
   static uint64_t Read4To8(const unsigned char* p, size_t len) {
-    return (static_cast<uint64_t>(little_endian::Load32(p + len - 4))
-            << (len - 4) * 8) |
-           little_endian::Load32(p);
+    uint32_t low_mem = absl::base_internal::UnalignedLoad32(p);
+    uint32_t high_mem = absl::base_internal::UnalignedLoad32(p + len - 4);
+#ifdef ABSL_IS_LITTLE_ENDIAN
+    uint32_t most_significant = high_mem;
+    uint32_t least_significant = low_mem;
+#else
+    uint32_t most_significant = low_mem;
+    uint32_t least_significant = high_mem;
+#endif
+    return (static_cast<uint64_t>(most_significant) << (len - 4) * 8) |
+           least_significant;
   }
 
   // Reads 1 to 3 bytes from p. Zero pads to fill uint32_t.
   static uint32_t Read1To3(const unsigned char* p, size_t len) {
-    return static_cast<uint32_t>((p[0]) |                         //
-                                 (p[len / 2] << (len / 2 * 8)) |  //
-                                 (p[len - 1] << ((len - 1) * 8)));
+    unsigned char mem0 = p[0];
+    unsigned char mem1 = p[len / 2];
+    unsigned char mem2 = p[len - 1];
+#ifdef ABSL_IS_LITTLE_ENDIAN
+    unsigned char significant2 = mem2;
+    unsigned char significant1 = mem1;
+    unsigned char significant0 = mem0;
+#else
+    unsigned char significant2 = mem0;
+    unsigned char significant1 = mem1;
+    unsigned char significant0 = mem2;
+#endif
+    return static_cast<uint32_t>(significant0 |                     //
+                                 (significant1 << (len / 2 * 8)) |  //
+                                 (significant2 << ((len - 1) * 8)));
   }
 
   ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Mix(uint64_t state, uint64_t v) {