go 1.5 already includes the SSE42 updateCastagnoli() function about crc32

[klauspost]

I am not sure what you mean. I have adjusted the documentation, since it is carryless multiplication your CPU must support, not only SSE 4.2.

[wscott]

For example I added some tests like this:

func BenchmarkCCrc1KB(b *testing.B) {
    benchmark(b, New(MakeTable(Castagnoli)), 1024)
}

func BenchmarkCStdCrc1KB(b *testing.B) {
    benchmark(b, crc32.New(crc32.MakeTable(Castagnoli)), 1024)
}

And found that for Castagnoli the std library was the same speed. And looking I see it already included that support. https://golang.org/src/hash/crc32/crc32_amd64.s

I assumed that you wrote all of the assembly files and the std library just copied part of them. Now I am guessing they always had the fast Castagnoli version and you extended it to include the SSE code for the IEEE crc as well.

[klauspost]

Yes, I started this as a copy of the standard library.

This is the current "tip" version, which includes my code: https://tip.golang.org/src/hash/crc32/crc32_amd64.s

[wscott]

BTW another optimization that I notice isn't included is that the slicingBy8 optimization can still be used in the Castagnoli case.

[klauspost]

Oh yes, that might be nice for other platforms.

[klauspost]

Added in PR #5