Enable SSE2 compression path to work on MSVC

[TrianglesPCT]

The compile time detection uses the __SSE2__ predefined macro, but this does not exist on MSVC--resulting it that compiler always using scalar path.

On MSVC you can detect SSE support by checking for _M_AMD64, as when targeting x64 it requires SSE2 as a baseline, this patch adds this check.

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[TrianglesPCT]

Switch to unaligned load

[Cyan4973]

Thanks @TrianglesPCT ,

did you attempt to measure performance differences provided by your PR ?

[TrianglesPCT]

Thanks @TrianglesPCT ,

did you attempt to measure performance differences provided by your PR ?

I removed the AVX2 stuff for a later PR

[Cyan4973]

Well, even without AVX2,
this PR is presumed to help performance, because it's supposed to help SSE2 detection ?

[TrianglesPCT]

All it is doing is normalizing MSVC to target the same code path as GCC/Clang when SSE2 is set as a requirement for your compile target. Not adding any new code..

The defined(__SSE2__) check doesn't work on MSVC because that define doesn't exist even if SSE2 is enabled.

If you want specific performance comparison I can do that might be few days until I have time for that.

[terrelln]

If you want specific performance comparison I can do that might be few days until I have time for that.

That would be great! But that doesn't need to block merging this PR. You can easily measure performance with the builtin benchmark tool.

zstd -b5e12 silesia.tar

[ghost]

Will there be a hot fix for v1.5.0?

[wolfpld]

You can easily measure performance with the builtin benchmark tool.

The difference is rather spectacular. Results for 5950X.

Before:

 5#silesia.tar       : 211957760 ->  63806593 (3.322), 111.0 MB/s , 977.5 MB/s
 6#silesia.tar       : 211957760 ->  62980544 (3.365), 107.9 MB/s ,1001.6 MB/s
 7#silesia.tar       : 211957760 ->  61482185 (3.447),  73.1 MB/s ,1055.9 MB/s
 8#silesia.tar       : 211957760 ->  60914308 (3.480),  57.2 MB/s ,1076.1 MB/s
 9#silesia.tar       : 211957760 ->  59928587 (3.537),  52.1 MB/s ,1100.2 MB/s
10#silesia.tar       : 211957760 ->  59296205 (3.575),  50.3 MB/s ,1103.6 MB/s
11#silesia.tar       : 211957760 ->  59152928 (3.583),  47.7 MB/s ,1106.8 MB/s
12#silesia.tar       : 211957760 ->  58640204 (3.615),  30.6 MB/s ,1123.8 MB/s

After:

 5#silesia.tar       : 211957760 ->  63806593 (3.322), 160.8 MB/s , 980.0 MB/s
 6#silesia.tar       : 211957760 ->  62980544 (3.365), 153.3 MB/s ,1004.7 MB/s
 7#silesia.tar       : 211957760 ->  61482185 (3.447), 111.9 MB/s ,1056.3 MB/s
 8#silesia.tar       : 211957760 ->  60914308 (3.480),  90.9 MB/s ,1079.5 MB/s
 9#silesia.tar       : 211957760 ->  59928587 (3.537),  74.7 MB/s ,1101.9 MB/s
10#silesia.tar       : 211957760 ->  59296205 (3.575),  71.3 MB/s ,1107.0 MB/s
11#silesia.tar       : 211957760 ->  59152928 (3.583),  65.0 MB/s ,1113.2 MB/s
12#silesia.tar       : 211957760 ->  58640204 (3.615),  51.3 MB/s ,1129.6 MB/s

[senhuang42]

This is a great fix, thanks for the contribution!