Use BitOperations in more callsites (CoreCLR)

[grant-d]

Some more missed optimizations from previous PRs.

cc @tannergooding, @jkotas

[grant-d]

I ran the following unit to ensure that these methods are in fact equivalent:

        [Fact]
        public static void Foo()
        {
            for (int i = 0; i < 32; i++)
            {
                uint n = 11u << i; // 0x1011, to make it more interesting

                int expected = BitOps.PopCount(n); // new
                int actual = bitcount(n); // old
                Assert.Equal(expected, actual);

                expected = BitOps.TrailingZeroCount(n); // new
                actual = bitindex(n); // old
                Assert.Equal(expected, actual);
            }
        }

        // Original source

        static int[] nibblebits = { 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4 };
        private static int bitcount(uint n)
        {
            int count = 0;
            for (; n != 0; n = n >> 4)
                count += nibblebits[n & 0x0f];
            return count;
        }
        private static int bitindex(uint n)
        {
            //Debug.Assert(bitcount(n) == 1);
            int idx = 0;
            while ((n & (1 << idx)) == 0)
                idx++;
            return idx;
        }

[grant-d]

Note that this assert is already taken care of in the preceding if statement at the callsite

[grant-d]

This looks like this is just a constant, val = 4; ?

public static SessionMask All
{
    get { return new SessionMask(MASK); }
}

internal const uint MASK = 0x0fU; // 0000_1111

internal struct SessionMask
{
    private uint m_mask;

    public SessionMask(uint mask = 0)
    { m_mask = mask & MASK; }
…
}

[grant-d]

@dotnet-bot test OSX10.12 x64 Checked Innerloop Build and Test please
@dotnet-bot test Windows_NT x64 Checked CoreFX Tests please
@dotnet-bot test Windows_NT x64 Release CoreFX Tests please

[jkotas]

Thanks! Could you please copy the EventProvider.cs file to CoreFX and make sure that build -framework netfx builds fine? I think this will need downlevel implementations of these new operations in the StubEnvironment to make corefx build with this.

[jkotas]

@grant-d I have pushed a portable implementations of PopCount and TrailingZeroCount to your branch, so that this lands in CoreFX without needing further adjustments. Could you please review them?

[grant-d]

Thanks for doing that @jkotas. It have reviewed and it looks good. Maybe there's an opportunity in a later PR to optimize that loop.
LGTM

[grant-d]

@dotnet-bot test Windows_NT x64 Checked CoreFX Tests please