test: Add floating-point utils

test/unittests/CMakeLists.txt

@@ -17,6 +17,7 @@ target_sources(
     execute_floating_point_test.cpp
     execute_numeric_test.cpp
     execute_test.cpp
+    floating_point_utils_test.cpp
     instantiate_test.cpp
     leb128_test.cpp
     module_test.cpp

test/unittests/floating_point_utils_test.cpp

@@ -0,0 +1,106 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#include <gtest/gtest.h>
+#include <test/utils/floating_point_utils.hpp>
+
+using namespace fizzy::test;
+
+TEST(floating_point_utils, double_as_uint64)
+{
+    using Limits = std::numeric_limits<double>;
+
+    EXPECT_EQ(as_uint64(0.0), 0x0000000000000000);
+    EXPECT_EQ(as_uint64(-0.0), 0x8000000000000000);
+    EXPECT_EQ(as_uint64(Limits::infinity()), 0x7FF'0000000000000);
+    EXPECT_EQ(as_uint64(-Limits::infinity()), 0xFFF'0000000000000);
+    EXPECT_EQ(as_uint64(Limits::max()), 0x7FE'FFFFFFFFFFFFF);
+    EXPECT_EQ(as_uint64(-Limits::max()), 0xFFE'FFFFFFFFFFFFF);
+    EXPECT_EQ(as_uint64(Limits::min()), 0x001'0000000000000);
+    EXPECT_EQ(as_uint64(-Limits::min()), 0x801'0000000000000);
+    EXPECT_EQ(as_uint64(Limits::denorm_min()), 0x000'0000000000001);
+    EXPECT_EQ(as_uint64(-Limits::denorm_min()), 0x800'0000000000001);
+    EXPECT_EQ(as_uint64(1.0), 0x3FF'0000000000000);
+    EXPECT_EQ(as_uint64(-1.0), 0xBFF'0000000000000);
+    EXPECT_EQ(as_uint64(std::nextafter(1.0, 0.0)), 0x3FE'FFFFFFFFFFFFF);
+    EXPECT_EQ(as_uint64(std::nextafter(-1.0, 0.0)), 0xBFE'FFFFFFFFFFFFF);
+    EXPECT_EQ(as_uint64(Limits::quiet_NaN()), 0x7FF'8000000000000);
+    EXPECT_EQ(as_uint64(-Limits::quiet_NaN()), 0xFFF'8000000000000);
+}
+
+TEST(floating_point_utils, float_as_uint64)
+{
+    using Limits = std::numeric_limits<float>;
+
+    EXPECT_EQ(as_uint64(0.0f), 0x00000000);
+    EXPECT_EQ(as_uint64(-0.0f), 0x80000000);
+    EXPECT_EQ(as_uint64(Limits::infinity()), 0x7F800000);
+    EXPECT_EQ(as_uint64(-Limits::infinity()), 0xFF800000);
+    EXPECT_EQ(as_uint64(Limits::max()), 0x7F7FFFFF);
+    EXPECT_EQ(as_uint64(-Limits::max()), 0xFF7FFFFF);
+    EXPECT_EQ(as_uint64(Limits::min()), 0x00800000);
+    EXPECT_EQ(as_uint64(-Limits::min()), 0x80800000);
+    EXPECT_EQ(as_uint64(Limits::denorm_min()), 0x00000001);
+    EXPECT_EQ(as_uint64(-Limits::denorm_min()), 0x80000001);
+    EXPECT_EQ(as_uint64(1.0f), 0x3F800000);
+    EXPECT_EQ(as_uint64(-1.0f), 0xBF800000);
+    EXPECT_EQ(as_uint64(std::nextafter(1.0f, 0.0f)), 0x3F7FFFFF);
+    EXPECT_EQ(as_uint64(std::nextafter(-1.0f, 0.0f)), 0xBF7FFFFF);
+    EXPECT_EQ(as_uint64(Limits::quiet_NaN()), 0x7FC00000);
+    EXPECT_EQ(as_uint64(-Limits::quiet_NaN()), 0xFFC00000);
+}
+
+TEST(floating_point_utils, double_nan_payload)
+{
+    using Limits = std::numeric_limits<double>;
+    constexpr auto qnan = Limits::quiet_NaN();
+
+    EXPECT_EQ(get_nan_payload(0.0), 0);
+    EXPECT_EQ(get_nan_payload(Limits::signaling_NaN()), 0x4000000000000);
+    EXPECT_EQ(get_nan_payload(qnan), 0x8000000000000);  // Wasm canonical nan.
+    EXPECT_EQ(get_nan_payload(qnan + 1.0), 0x8000000000000);
+    EXPECT_EQ(get_nan_payload(Limits::infinity() - Limits::infinity()), 0x8000000000000);
+}
+
+TEST(floating_point_utils, float_nan_payload)
+{
+    using Limits = std::numeric_limits<float>;
+    constexpr auto qnan = Limits::quiet_NaN();
+
+    EXPECT_EQ(get_nan_payload(0.0f), 0);
+    EXPECT_EQ(get_nan_payload(Limits::signaling_NaN()), 0x200000);
+    EXPECT_EQ(get_nan_payload(qnan), 0x400000);  // Wasm canonical nan.
+    EXPECT_EQ(get_nan_payload(qnan + 1.0f), 0x400000);
+    EXPECT_EQ(get_nan_payload(Limits::infinity() - Limits::infinity()), 0x400000);
+}
+
+TEST(floating_point_utils, double_nan)
+{
+    EXPECT_TRUE(std::isnan(nan<double>()));
+    EXPECT_TRUE(std::isnan(nan<double>(1)));
+    EXPECT_TRUE(std::isnan(nan<double>(0xdeadbeef)));
+    EXPECT_TRUE(std::isnan(nan<double>(0xdeadbeefbeeef)));
+    EXPECT_FALSE(std::isnan(nan<double>(0)));
+
+    EXPECT_EQ(get_nan_payload(nan<double>()), FPUtils<double>::CanonicalNaNPayload);
+
+    EXPECT_EQ(as_uint64(nan<double>()), 0x7FF'8000000000000);
+    EXPECT_EQ(as_uint64(nan<double>(0xdeadbeef)), 0x7FF'00000deadbeef);
+    EXPECT_EQ(as_uint64(nan<double>(0xdeadbeefbeeef)), 0x7FF'deadbeefbeeef);
+}
+
+TEST(floating_point_utils, float_nan)
+{
+    EXPECT_TRUE(std::isnan(nan<float>()));
+    EXPECT_TRUE(std::isnan(nan<float>(1)));
+    EXPECT_TRUE(std::isnan(nan<float>(0x7fffff)));
+    EXPECT_TRUE(std::isnan(nan<float>(0x400001)));
+    EXPECT_FALSE(std::isnan(nan<float>(0)));
+
+    EXPECT_EQ(get_nan_payload(nan<float>()), FPUtils<float>::CanonicalNaNPayload);
+
+    EXPECT_EQ(as_uint64(nan<float>()), 0x7FC00000);
+    EXPECT_EQ(as_uint64(nan<float>(0x7fffff)), 0x7FFFFFFF);
+    EXPECT_EQ(as_uint64(nan<float>(0x400001)), 0x7FC00001);
+}

test/utils/CMakeLists.txt

@@ -15,6 +15,7 @@ target_sources(
     asserts.hpp
     execute_helpers.hpp
     fizzy_engine.cpp
+    floating_point_utils.hpp
     hex.cpp
     hex.hpp
     leb128_encode.cpp

test/utils/floating_point_utils.hpp

@@ -0,0 +1,69 @@
+// Fizzy: A fast WebAssembly interpreter
+// Copyright 2020 The Fizzy Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include <cmath>
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+
+namespace fizzy::test
+{
+template <typename T, typename = std::enable_if<std::is_floating_point_v<T>>>
+struct FPUtils
+{
+    using Limits = std::numeric_limits<T>;
+
+    static constexpr auto NumMantissaBits = Limits::digits - 1;
+    static constexpr auto MantissaMask = (uint64_t{1} << NumMantissaBits) - 1;
+
+    static constexpr auto CanonicalNaNPayload = uint64_t{1} << (NumMantissaBits - 1);
+};
+
+template <typename T, typename = std::enable_if<std::is_floating_point_v<T>>>
+uint64_t as_uint64(T value) noexcept
+{
+    constexpr auto num_bytes = sizeof(T);
+    uint8_t bytes[num_bytes];
+    __builtin_memcpy(bytes, &value, num_bytes);
+
+    uint64_t u = 0;
+    for (size_t i = 0; i < num_bytes; ++i)
+        u |= uint64_t{bytes[i]} << (i * 8);  // little-endian
+    return u;
+}
+
+template <typename T, typename = std::enable_if<std::is_floating_point_v<T>>>
+T from_uint64(uint64_t value) noexcept
+{
+    constexpr auto num_bytes = sizeof(T);
+    uint8_t bytes[num_bytes];
+
+    for (size_t i = 0; i < num_bytes; ++i)
+        bytes[i] = static_cast<uint8_t>(value >> (i * 8));  // little-endian
+
+    T result;
+    __builtin_memcpy(&result, bytes, num_bytes);
+    return result;
+}
+
+template <typename T, typename = std::enable_if<std::is_floating_point_v<T>>>
+uint64_t get_nan_payload(T value) noexcept
+{
+    if (!std::isnan(value))
+        return 0;  // NaN payload is never 0.
+
+    return as_uint64(value) & FPUtils<T>::MantissaMask;
+}
+
+template <typename T, typename = std::enable_if<std::is_floating_point_v<T>>>
+T nan(uint64_t payload = FPUtils<T>::CanonicalNaNPayload) noexcept
+{
+    using Utils = FPUtils<T>;
+    const auto nan_exponent = (uint64_t{Utils::Limits::max_exponent} << 1) - 1;
+    return from_uint64<T>(
+        ((nan_exponent << Utils::NumMantissaBits)) | (payload & Utils::MantissaMask));
+}
+}  // namespace fizzy::test