src/tests/unittests/MathTests.cpp

// Copyright 2017 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <gtest/gtest.h>

#include "common/Math.h"

// Tests for ScanForward
TEST(Math, ScanForward) {
    // Test extrema
    ASSERT_EQ(ScanForward(1), 0);
    ASSERT_EQ(ScanForward(0x80000000), 31);

    // Test with more than one bit set.
    ASSERT_EQ(ScanForward(256), 8);
    ASSERT_EQ(ScanForward(256 + 32), 5);
    ASSERT_EQ(ScanForward(1024 + 256 + 32), 5);
}

// Tests for Log2
TEST(Math, Log2) {
    // Test extrema
    ASSERT_EQ(Log2(1), 0);
    ASSERT_EQ(Log2(0xFFFFFFFF), 31);

    // Test boundary between two logs
    ASSERT_EQ(Log2(0x80000000), 31);
    ASSERT_EQ(Log2(0x7FFFFFFF), 30);

    ASSERT_EQ(Log2(16), 4);
    ASSERT_EQ(Log2(15), 3);
}

// Tests for IsPowerOfTwo
TEST(Math, IsPowerOfTwo) {
    ASSERT_TRUE(IsPowerOfTwo(1));
    ASSERT_TRUE(IsPowerOfTwo(2));
    ASSERT_FALSE(IsPowerOfTwo(3));

    ASSERT_TRUE(IsPowerOfTwo(0x8000000));
    ASSERT_FALSE(IsPowerOfTwo(0x8000400));
}

// Tests for AlignPtr
TEST(Math, AlignPtr) {
    constexpr size_t kTestAlignment = 8;

    char buffer[kTestAlignment * 4];

    for (size_t i = 0; i < 2 * kTestAlignment; ++i) {
        char* unaligned = &buffer[i];
        char* aligned = AlignPtr(unaligned, kTestAlignment);

        ASSERT_GE(aligned - unaligned, 0);
        ASSERT_LT(static_cast<size_t>(aligned - unaligned), kTestAlignment);
        ASSERT_EQ(reinterpret_cast<uintptr_t>(aligned) & (kTestAlignment -1), 0);
    }
}

// Tests for Align
TEST(Math, Align) {
    // 0 aligns to 0
    ASSERT_EQ(Align(0, 4), 0);
    ASSERT_EQ(Align(0, 256), 0);
    ASSERT_EQ(Align(0, 512), 0);

    // Multiples align to self
    ASSERT_EQ(Align(8, 8), 8);
    ASSERT_EQ(Align(16, 8), 16);
    ASSERT_EQ(Align(24, 8), 24);
    ASSERT_EQ(Align(256, 256), 256);
    ASSERT_EQ(Align(512, 256), 512);
    ASSERT_EQ(Align(768, 256), 768);

    // Alignment with 1 is self
    for (uint32_t i = 0; i < 128; ++i) {
        ASSERT_EQ(Align(i, 1), i);
    }

    // Everything in the range (align, 2*align] aligns to 2*align
    for (uint32_t i = 1; i <= 64; ++i) {
        ASSERT_EQ(Align(64 + i, 64), 128);
    }
}

// Tests for IsPtrAligned
TEST(Math, IsPtrAligned) {
    constexpr size_t kTestAlignment = 8;

    char buffer[kTestAlignment * 4];

    for (size_t i = 0; i < 2 * kTestAlignment; ++i) {
        char* unaligned = &buffer[i];
        char* aligned = AlignPtr(unaligned, kTestAlignment);

        ASSERT_EQ(IsPtrAligned(unaligned, kTestAlignment), unaligned == aligned);
    }
}

// Tests for IsAligned
TEST(Math, IsAligned) {
    // 0 is aligned
    ASSERT_TRUE(IsAligned(0, 4));
    ASSERT_TRUE(IsAligned(0, 256));
    ASSERT_TRUE(IsAligned(0, 512));

    // Multiples are aligned
    ASSERT_TRUE(IsAligned(8, 8));
    ASSERT_TRUE(IsAligned(16, 8));
    ASSERT_TRUE(IsAligned(24, 8));
    ASSERT_TRUE(IsAligned(256, 256));
    ASSERT_TRUE(IsAligned(512, 256));
    ASSERT_TRUE(IsAligned(768, 256));

    // Alignment with 1 is always aligned
    for (uint32_t i = 0; i < 128; ++i) {
        ASSERT_TRUE(IsAligned(i, 1));
    }

    // Everything in the range (align, 2*align) is not aligned
    for (uint32_t i = 1; i < 64; ++i) {
        ASSERT_FALSE(IsAligned(64 + i, 64));
    }
}