deps: cherry-pick c736883 from upstream V8

Original commit message:

    Optionally use halfsiphash for integer hashing.

    Change-Id: Ibd14f7b3fe78635675c76ae864112e3a3a7bc701
    Reviewed-on: https://chromium-review.googlesource.com/c/1382463
    Commit-Queue: Yang Guo <yangguo@chromium.org>
    Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#58674}

Refs: https://github.com/v8/v8/commit/c736883ed4e3ff92d1fd5a60497cec5311df9a25

4 files changed, 221 insertions, 0 deletions

diff --git a/deps/v8/src/third_party/siphash/LICENSE b/deps/v8/src/third_party/siphash/LICENSE
new file mode 100644
index 0000000000..670154e353
--- /dev/null
+++ b/deps/v8/src/third_party/siphash/LICENSE
@@ -0,0 +1,116 @@
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diff --git a/deps/v8/src/third_party/siphash/halfsiphash.cc b/deps/v8/src/third_party/siphash/halfsiphash.cc
new file mode 100644
index 0000000000..d3730c4819
--- /dev/null
+++ b/deps/v8/src/third_party/siphash/halfsiphash.cc
@@ -0,0 +1,83 @@
+/*
+ * SipHash reference C implementation
+ *
+ * Copyright (c) 2016 Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
+ *
+ * To the extent possible under law, the author(s) have dedicated all
+ * copyright and related and neighboring rights to this software to the public
+ * domain worldwide. This software is distributed without any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication along
+ * with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+/*
+ * Originally taken from https://github.com/veorq/SipHash/
+ * Altered to match V8's use case.
+ */
+
+#include <stdint.h>
+
+#include "src/base/logging.h"
+#include "src/base/v8-fallthrough.h"
+
+#define ROTL(x, b) (uint32_t)(((x) << (b)) | ((x) >> (32 - (b))))
+
+#define SIPROUND       \
+  do {                 \
+    v0 += v1;          \
+    v1 = ROTL(v1, 5);  \
+    v1 ^= v0;          \
+    v0 = ROTL(v0, 16); \
+    v2 += v3;          \
+    v3 = ROTL(v3, 8);  \
+    v3 ^= v2;          \
+    v0 += v3;          \
+    v3 = ROTL(v3, 7);  \
+    v3 ^= v0;          \
+    v2 += v1;          \
+    v1 = ROTL(v1, 13); \
+    v1 ^= v2;          \
+    v2 = ROTL(v2, 16); \
+  } while (0)
+
+// Simplified half-siphash-2-4 implementation for 4 byte input.
+uint32_t halfsiphash(const uint32_t value, const uint64_t seed) {
+  uint32_t v0 = 0;
+  uint32_t v1 = 0;
+  uint32_t v2 = 0x6c796765;
+  uint32_t v3 = 0x74656462;
+  uint32_t k[2];
+  memcpy(k, &seed, sizeof(seed));
+  uint32_t b = 4 << 24;
+  v3 ^= k[1];
+  v2 ^= k[0];
+  v1 ^= k[1];
+  v0 ^= k[0];
+
+  v3 ^= value;
+
+  // 2 c-rounds
+  SIPROUND;
+  SIPROUND;
+
+  v0 ^= value;
+  v3 ^= b;
+
+  // 2 c-rounds
+  SIPROUND;
+  SIPROUND;
+
+  v0 ^= b;
+  v2 ^= 0xff;
+
+  // 4 d-rounds
+  SIPROUND;
+  SIPROUND;
+  SIPROUND;
+  SIPROUND;
+
+  b = v1 ^ v3;
+  return b;
+}
diff --git a/deps/v8/src/third_party/siphash/halfsiphash.h b/deps/v8/src/third_party/siphash/halfsiphash.h
new file mode 100644
index 0000000000..7b55115774
--- /dev/null
+++ b/deps/v8/src/third_party/siphash/halfsiphash.h
@@ -0,0 +1,17 @@
+/*
+ * SipHash reference C implementation
+ *
+ * Copyright (c) 2016 Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
+ *
+ * To the extent possible under law, the author(s) have dedicated all
+ * copyright and related and neighboring rights to this software to the public
+ * domain worldwide. This software is distributed without any warranty.
+ *
+ * You should have received a copy of the CC0 Public Domain Dedication along
+ * with this software. If not, see
+ * <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#include <cstdint>
+
+uint32_t halfsiphash(const uint32_t value, const uint64_t seed);
diff --git a/deps/v8/src/utils.h b/deps/v8/src/utils.h
index 90a1227a2b..51c22ffd70 100644
--- a/deps/v8/src/utils.h
+++ b/deps/v8/src/utils.h
@@ -22,6 +22,7 @@
 #include "src/base/platform/platform.h"
 #include "src/base/v8-fallthrough.h"
 #include "src/globals.h"
+#include "src/third_party/siphash/halfsiphash.h"
 #include "src/vector.h"
 
 #if defined(V8_OS_AIX)
@@ -513,7 +514,11 @@ inline uint32_t ComputeLongHash(uint64_t key) {
 }
 
 inline uint32_t ComputeSeededHash(uint32_t key, uint64_t seed) {
+#ifdef V8_USE_SIPHASH
+  return halfsiphash(key, seed);
+#else
   return ComputeLongHash(static_cast<uint64_t>(key) ^ seed);
+#endif  // V8_USE_SIPHASH
 }
 
 inline uint32_t ComputePointerHash(void* ptr) {