Export of internal Abseil changes

--
3a9b4e8e5ecba532db5cc4ac12d12660307ce9fb by Derek Mauro <dmauro@google.com>:

Use the Bazel @platforms repository for platform constraints
Fixes #1000

PiperOrigin-RevId: 390644226

--
b34e4d2f8a86b54bd483ec4c9c3dd781ad2d8b68 by Abseil Team <absl-team@google.com>:

debugging: add some handling for RISC-V

The RISC-V architecture uses a downward growing stack and can host Linux using
ELF files.  Adjust a few sites accordingly to indicate how to handle the RISC-V
architecture.

PiperOrigin-RevId: 390631894

--
5fa3a0961bf3dd0799c048956a0128f7b8113f1e by Samuel Benzaquen <sbenza@google.com>:

Rename the buffer hash function to LowLevelHash.
Although it started as wyhash, it will depart from it so it does not make sense
to keep the name.

PiperOrigin-RevId: 390483506

--
2e7867a2301d58ad4cd5abcaa5fd6f0db973ae7b by Abseil Team <absl-team@google.com>:

This is an internal change.

PiperOrigin-RevId: 390349746
GitOrigin-RevId: 3a9b4e8e5ecba532db5cc4ac12d12660307ce9fb
Change-Id: I322c3762552a2107e6c6b108c25c01e5efa8aecd

CMake/AbseilDll.cmake

@@ -124,8 +124,8 @@ set(ABSL_INTERNAL_DLL_FILES
   "hash/internal/hash.h"
   "hash/internal/hash.cc"
   "hash/internal/spy_hash_state.h"
-  "hash/internal/wyhash.h"
-  "hash/internal/wyhash.cc"
+  "hash/internal/low_level_hash.h"
+  "hash/internal/low_level_hash.cc"
   "memory/memory.h"
   "meta/type_traits.h"
   "numeric/bits.h"

WORKSPACE

@@ -42,3 +42,11 @@ http_archive(
     strip_prefix = "rules_cc-daf6ace7cfeacd6a83e9ff2ed659f416537b6c74",
     urls = ["https://github.com/bazelbuild/rules_cc/archive/daf6ace7cfeacd6a83e9ff2ed659f416537b6c74.zip"],
 )
+
+# Bazel platform rules.
+http_archive(
+    name = "platforms",
+    sha256 = "b601beaf841244de5c5a50d2b2eddd34839788000fa1be4260ce6603ca0d8eb7",
+    strip_prefix = "platforms-98939346da932eef0b54cf808622f5bb0928f00b",
+    urls = ["https://github.com/bazelbuild/platforms/archive/98939346da932eef0b54cf808622f5bb0928f00b.zip"],
+)

absl/BUILD.bazel

@@ -44,14 +44,14 @@ config_setting(
 config_setting(
     name = "osx",
     constraint_values = [
-        "@bazel_tools//platforms:osx",
+        "@platforms//os:osx",
     ],
 )
 
 config_setting(
     name = "ios",
     constraint_values = [
-        "@bazel_tools//platforms:ios",
+        "@platforms//os:ios",
     ],
 )
 

absl/debugging/internal/stack_consumption.cc

@@ -43,7 +43,7 @@ namespace {
 // unspecified. Therefore, instead we hardcode the direction of the
 // stack on platforms we know about.
 #if defined(__i386__) || defined(__x86_64__) || defined(__ppc__) || \
-    defined(__aarch64__)
+    defined(__aarch64__) || defined(__riscv)
 constexpr bool kStackGrowsDown = true;
 #else
 #error Need to define kStackGrowsDown

absl/debugging/internal/stack_consumption.h

@@ -26,7 +26,7 @@
 #error ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION cannot be set directly
 #elif !defined(__APPLE__) && !defined(_WIN32) &&                     \
     (defined(__i386__) || defined(__x86_64__) || defined(__ppc__) || \
-     defined(__aarch64__))
+     defined(__aarch64__) || defined(__riscv))
 #define ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION 1
 
 namespace absl {

absl/debugging/internal/symbolize.h

@@ -28,8 +28,8 @@
 
 #ifdef ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE
 #error ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE cannot be directly set
-#elif defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__) && \
-    !defined(__asmjs__) && !defined(__wasm__)
+#elif defined(__ELF__) && defined(__GLIBC__) && !defined(__native_client__) \
+      && !defined(__asmjs__) && !defined(__wasm__)
 #define ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE 1
 
 #include <elf.h>

absl/hash/BUILD.bazel

@@ -37,7 +37,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":city",
-        ":wyhash",
+        ":low_level_hash",
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:endian",
@@ -143,9 +143,9 @@ cc_test(
 )
 
 cc_library(
-    name = "wyhash",
-    srcs = ["internal/wyhash.cc"],
-    hdrs = ["internal/wyhash.h"],
+    name = "low_level_hash",
+    srcs = ["internal/low_level_hash.cc"],
+    hdrs = ["internal/low_level_hash.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
@@ -157,13 +157,13 @@ cc_library(
 )
 
 cc_test(
-    name = "wyhash_test",
-    srcs = ["internal/wyhash_test.cc"],
+    name = "low_level_hash_test",
+    srcs = ["internal/low_level_hash_test.cc"],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     visibility = ["//visibility:private"],
     deps = [
-        ":wyhash",
+        ":low_level_hash",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
     ],

absl/hash/CMakeLists.txt

@@ -36,7 +36,7 @@ absl_cc_library(
     absl::optional
     absl::variant
     absl::utility
-    absl::wyhash
+    absl::low_level_hash
   PUBLIC
 )
 
@@ -118,11 +118,11 @@ absl_cc_test(
 
 absl_cc_library(
   NAME
-    wyhash
+    low_level_hash
   HDRS
-    "internal/wyhash.h"
+    "internal/low_level_hash.h"
   SRCS
-    "internal/wyhash.cc"
+    "internal/low_level_hash.cc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   DEPS
@@ -133,13 +133,13 @@ absl_cc_library(
 
 absl_cc_test(
   NAME
-    wyhash_test
+    low_level_hash_test
   SRCS
-    "internal/wyhash_test.cc"
+    "internal/low_level_hash_test.cc"
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
-    absl::wyhash
+    absl::low_level_hash
     absl::strings
     GTest::gmock_main
 )

absl/hash/internal/hash.cc

@@ -46,21 +46,22 @@ uint64_t MixingHashState::CombineLargeContiguousImpl64(
 
 ABSL_CONST_INIT const void* const MixingHashState::kSeed = &kSeed;
 
-// The salt array used by Wyhash. This array is NOT the mechanism used to make
-// absl::Hash non-deterministic between program invocations.  See `Seed()` for
-// that mechanism.
+// The salt array used by LowLevelHash. This array is NOT the mechanism used to
+// make absl::Hash non-deterministic between program invocations.  See `Seed()`
+// for that mechanism.
 //
 // Any random values are fine. These values are just digits from the decimal
 // part of pi.
 // https://en.wikipedia.org/wiki/Nothing-up-my-sleeve_number
-constexpr uint64_t kWyhashSalt[5] = {
+constexpr uint64_t kHashSalt[5] = {
     uint64_t{0x243F6A8885A308D3}, uint64_t{0x13198A2E03707344},
     uint64_t{0xA4093822299F31D0}, uint64_t{0x082EFA98EC4E6C89},
     uint64_t{0x452821E638D01377},
 };
 
-uint64_t MixingHashState::WyhashImpl(const unsigned char* data, size_t len) {
-  return Wyhash(data, len, Seed(), kWyhashSalt);
+uint64_t MixingHashState::LowLevelHashImpl(const unsigned char* data,
+                                           size_t len) {
+  return LowLevelHash(data, len, Seed(), kHashSalt);
 }
 
 }  // namespace hash_internal

absl/hash/internal/hash.h

@@ -42,7 +42,7 @@
 #include "absl/base/internal/unaligned_access.h"
 #include "absl/base/port.h"
 #include "absl/container/fixed_array.h"
-#include "absl/hash/internal/wyhash.h"
+#include "absl/hash/internal/low_level_hash.h"
 #include "absl/meta/type_traits.h"
 #include "absl/numeric/int128.h"
 #include "absl/strings/string_view.h"
@@ -874,14 +874,14 @@ class ABSL_DLL MixingHashState : public HashStateBase<MixingHashState> {
     return static_cast<uint64_t>(m ^ (m >> (sizeof(m) * 8 / 2)));
   }
 
-  // An extern to avoid bloat on a direct call to Wyhash() with fixed values for
-  // both the seed and salt parameters.
-  static uint64_t WyhashImpl(const unsigned char* data, size_t len);
+  // An extern to avoid bloat on a direct call to LowLevelHash() with fixed
+  // values for both the seed and salt parameters.
+  static uint64_t LowLevelHashImpl(const unsigned char* data, size_t len);
 
   ABSL_ATTRIBUTE_ALWAYS_INLINE static uint64_t Hash64(const unsigned char* data,
                                                       size_t len) {
 #ifdef ABSL_HAVE_INTRINSIC_INT128
-    return WyhashImpl(data, len);
+    return LowLevelHashImpl(data, len);
 #else
     return absl::hash_internal::CityHash64(reinterpret_cast<const char*>(data), len);
 #endif
@@ -945,8 +945,8 @@ inline uint64_t MixingHashState::CombineContiguousImpl(
 inline uint64_t MixingHashState::CombineContiguousImpl(
     uint64_t state, const unsigned char* first, size_t len,
     std::integral_constant<int, 8> /* sizeof_size_t */) {
-  // For large values we use Wyhash or CityHash depending on the platform, for
-  // small ones we just use a multiplicative hash.
+  // For large values we use LowLevelHash or CityHash depending on the platform,
+  // for small ones we just use a multiplicative hash.
   uint64_t v;
   if (len > 16) {
     if (ABSL_PREDICT_FALSE(len > PiecewiseChunkSize())) {

absl/hash/internal/wyhash.cc → absl/hash/internal/low_level_hash.cc

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/hash/internal/wyhash.h"
+#include "absl/hash/internal/low_level_hash.h"
 
 #include "absl/base/internal/unaligned_access.h"
 #include "absl/numeric/int128.h"
@@ -21,14 +21,14 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace hash_internal {
 
-static uint64_t WyhashMix(uint64_t v0, uint64_t v1) {
+static uint64_t Mix(uint64_t v0, uint64_t v1) {
   absl::uint128 p = v0;
   p *= v1;
   return absl::Uint128Low64(p) ^ absl::Uint128High64(p);
 }
 
-uint64_t Wyhash(const void* data, size_t len, uint64_t seed,
-                const uint64_t salt[]) {
+uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed,
+                      const uint64_t salt[]) {
   const uint8_t* ptr = static_cast<const uint8_t*>(data);
   uint64_t starting_length = static_cast<uint64_t>(len);
   uint64_t current_state = seed ^ salt[0];
@@ -49,12 +49,12 @@ uint64_t Wyhash(const void* data, size_t len, uint64_t seed,
       uint64_t g = absl::base_internal::UnalignedLoad64(ptr + 48);
       uint64_t h = absl::base_internal::UnalignedLoad64(ptr + 56);
 
-      uint64_t cs0 = WyhashMix(a ^ salt[1], b ^ current_state);
-      uint64_t cs1 = WyhashMix(c ^ salt[2], d ^ current_state);
+      uint64_t cs0 = Mix(a ^ salt[1], b ^ current_state);
+      uint64_t cs1 = Mix(c ^ salt[2], d ^ current_state);
       current_state = (cs0 ^ cs1);
 
-      uint64_t ds0 = WyhashMix(e ^ salt[3], f ^ duplicated_state);
-      uint64_t ds1 = WyhashMix(g ^ salt[4], h ^ duplicated_state);
+      uint64_t ds0 = Mix(e ^ salt[3], f ^ duplicated_state);
+      uint64_t ds1 = Mix(g ^ salt[4], h ^ duplicated_state);
       duplicated_state = (ds0 ^ ds1);
 
       ptr += 64;
@@ -70,7 +70,7 @@ uint64_t Wyhash(const void* data, size_t len, uint64_t seed,
     uint64_t a = absl::base_internal::UnalignedLoad64(ptr);
     uint64_t b = absl::base_internal::UnalignedLoad64(ptr + 8);
 
-    current_state = WyhashMix(a ^ salt[1], b ^ current_state);
+    current_state = Mix(a ^ salt[1], b ^ current_state);
 
     ptr += 16;
     len -= 16;
@@ -101,9 +101,9 @@ uint64_t Wyhash(const void* data, size_t len, uint64_t seed,
     b = 0;
   }
 
-  uint64_t w = WyhashMix(a ^ salt[1], b ^ current_state);
+  uint64_t w = Mix(a ^ salt[1], b ^ current_state);
   uint64_t z = salt[1] ^ starting_length;
-  return WyhashMix(w, z);
+  return Mix(w, z);
 }
 
 }  // namespace hash_internal

absl/hash/internal/wyhash.h → absl/hash/internal/low_level_hash.h

@@ -12,16 +12,18 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 //
-// This file provides the Google-internal implementation of the Wyhash
-// algorithm.
+// This file provides the Google-internal implementation of LowLevelHash.
 //
-// Wyhash is a fast hash function for hash tables, the fastest we've currently
-// (late 2020) found that passes the SMHasher tests. The algorithm relies on
-// intrinsic 128-bit multiplication for speed. This is not meant to be secure -
-// just fast.
+// LowLevelHash is a fast hash function for hash tables, the fastest we've
+// currently (late 2020) found that passes the SMHasher tests. The algorithm
+// relies on intrinsic 128-bit multiplication for speed. This is not meant to be
+// secure - just fast.
+//
+// It is closely based on a version of wyhash, but does not maintain or
+// guarantee future compatibility with it.
 
-#ifndef ABSL_HASH_INTERNAL_WYHASH_H_
-#define ABSL_HASH_INTERNAL_WYHASH_H_
+#ifndef ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_
+#define ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_
 
 #include <stdint.h>
 #include <stdlib.h>
@@ -38,11 +40,11 @@ namespace hash_internal {
 // To allow all hashable types (including string_view and Span) to depend on
 // this algorithm, we keep the API low-level, with as few dependencies as
 // possible.
-uint64_t Wyhash(const void* data, size_t len, uint64_t seed,
-                const uint64_t salt[5]);
+uint64_t LowLevelHash(const void* data, size_t len, uint64_t seed,
+                      const uint64_t salt[5]);
 
 }  // namespace hash_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
 
-#endif  // ABSL_HASH_INTERNAL_WYHASH_H_
+#endif  // ABSL_HASH_INTERNAL_LOW_LEVEL_HASH_H_