1 files changed, 103 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/xorshift128plus-inl.h b/third_party/jpeg-xl/lib/jxl/xorshift128plus-inl.h
new file mode 100644
index 0000000000..a473d591f2
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+++ b/third_party/jpeg-xl/lib/jxl/xorshift128plus-inl.h
@@ -0,0 +1,103 @@
+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Fast but weak random generator.
+
+#if defined(LIB_JXL_XORSHIFT128PLUS_INL_H_) == defined(HWY_TARGET_TOGGLE)
+#ifdef LIB_JXL_XORSHIFT128PLUS_INL_H_
+#undef LIB_JXL_XORSHIFT128PLUS_INL_H_
+#else
+#define LIB_JXL_XORSHIFT128PLUS_INL_H_
+#endif
+
+#include <stddef.h>
+
+#include <hwy/highway.h>
+HWY_BEFORE_NAMESPACE();
+namespace jxl {
+namespace HWY_NAMESPACE {
+namespace {
+
+// These templates are not found via ADL.
+using hwy::HWY_NAMESPACE::Add;
+using hwy::HWY_NAMESPACE::ShiftLeft;
+using hwy::HWY_NAMESPACE::ShiftRight;
+using hwy::HWY_NAMESPACE::Xor;
+
+// Adapted from https://github.com/vpxyz/xorshift/blob/master/xorshift128plus/
+// (MIT-license)
+class Xorshift128Plus {
+ public:
+  // 8 independent generators (= single iteration for AVX-512)
+  enum { N = 8 };
+
+  explicit HWY_MAYBE_UNUSED Xorshift128Plus(const uint64_t seed) {
+    // Init state using SplitMix64 generator
+    s0_[0] = SplitMix64(seed + 0x9E3779B97F4A7C15ull);
+    s1_[0] = SplitMix64(s0_[0]);
+    for (size_t i = 1; i < N; ++i) {
+      s0_[i] = SplitMix64(s1_[i - 1]);
+      s1_[i] = SplitMix64(s0_[i]);
+    }
+  }
+
+  HWY_MAYBE_UNUSED Xorshift128Plus(const uint32_t seed1, const uint32_t seed2,
+                                   const uint32_t seed3, const uint32_t seed4) {
+    // Init state using SplitMix64 generator
+    s0_[0] = SplitMix64(((static_cast<uint64_t>(seed1) << 32) + seed2) +
+                        0x9E3779B97F4A7C15ull);
+    s1_[0] = SplitMix64(((static_cast<uint64_t>(seed3) << 32) + seed4) +
+                        0x9E3779B97F4A7C15ull);
+    for (size_t i = 1; i < N; ++i) {
+      s0_[i] = SplitMix64(s0_[i - 1]);
+      s1_[i] = SplitMix64(s1_[i - 1]);
+    }
+  }
+
+  HWY_INLINE HWY_MAYBE_UNUSED void Fill(uint64_t* HWY_RESTRICT random_bits) {
+#if HWY_CAP_INTEGER64
+    const HWY_FULL(uint64_t) d;
+    for (size_t i = 0; i < N; i += Lanes(d)) {
+      auto s1 = Load(d, s0_ + i);
+      const auto s0 = Load(d, s1_ + i);
+      const auto bits = Add(s1, s0);  // b, c
+      Store(s0, d, s0_ + i);
+      s1 = Xor(s1, ShiftLeft<23>(s1));
+      Store(bits, d, random_bits + i);
+      s1 = Xor(s1, Xor(s0, Xor(ShiftRight<18>(s1), ShiftRight<5>(s0))));
+      Store(s1, d, s1_ + i);
+    }
+#else
+    for (size_t i = 0; i < N; ++i) {
+      auto s1 = s0_[i];
+      const auto s0 = s1_[i];
+      const auto bits = s1 + s0;  // b, c
+      s0_[i] = s0;
+      s1 ^= s1 << 23;
+      random_bits[i] = bits;
+      s1 ^= s0 ^ (s1 >> 18) ^ (s0 >> 5);
+      s1_[i] = s1;
+    }
+#endif
+  }
+
+ private:
+  static uint64_t SplitMix64(uint64_t z) {
+    z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9ull;
+    z = (z ^ (z >> 27)) * 0x94D049BB133111EBull;
+    return z ^ (z >> 31);
+  }
+
+  HWY_ALIGN uint64_t s0_[N];
+  HWY_ALIGN uint64_t s1_[N];
+};
+
+}  // namespace
+// NOLINTNEXTLINE(google-readability-namespace-comments)
+}  // namespace HWY_NAMESPACE
+}  // namespace jxl
+HWY_AFTER_NAMESPACE();
+
+#endif  // LIB_JXL_XORSHIFT128PLUS_INL_H_