[ Storage Feature Request] enable rust-rocksdb compile with sse4.2 for fast computer crc32 hash

[nkysg]

https://github.com/rust-rocksdb/rust-rocksdb/pull/526 the build.rs show this

        config.flag_if_supported("-msse2");
        }
        if target_features.contains(&"sse4.1") {
            config.flag_if_supported("-msse4.1");
        }
        if target_features.contains(&"sse4.2") {
            config.flag_if_supported("-msse4.2");
            config.define("HAVE_SSE42", Some("1"));
        }

we can add this compile flags

[nkysg]

On my macos run this cmd rustc --print=cfg, it output this

debug_assertions
target_arch="x86_64"
target_endian="little"
target_env=""
target_family="unix"
target_feature="fxsr"
target_feature="sse"
target_feature="sse2"
target_feature="sse3"
target_feature="ssse3"
target_os="macos"
target_pointer_width="64"
target_vendor="apple"
unix

but i run this cmd sysctl -a | grep machdep.cpu | grep features it output

machdep.cpu.features: FPU VME DE PSE TSC MSR PAE MCE CX8 APIC SEP MTRR PGE MCA CMOV PAT PSE36 CLFSH DS ACPI MMX FXSR SSE SSE2 SS HTT TM PBE SSE3 PCLMULQDQ DTES64 MON DSCPL VMX EST TM2 SSSE3 FMA CX16 TPR PDCM SSE4.1 SSE4.2 x2APIC MOVBE POPCNT AES PCID XSAVE OSXSAVE SEGLIM64 TSCTMR AVX1.0 RDRAND F16C

why rustc --print=cfg does not show SSE4.2 I thought this is rustc bug. I found a artcile Possible issue detecting SSE4.2 support - help this artcile say I must use rustc --print=cfg -C target-cpu=native it output

debug_assertions
target_arch="x86_64"
target_endian="little"
target_env=""
target_family="unix"
target_feature="aes"
target_feature="avx"
target_feature="avx2"
target_feature="bmi1"
target_feature="bmi2"
target_feature="fma"
target_feature="fxsr"
target_feature="lzcnt"
target_feature="pclmulqdq"
target_feature="popcnt"
target_feature="rdrand"
target_feature="rdseed"
target_feature="sha"
target_feature="sse"
target_feature="sse2"
target_feature="sse3"
target_feature="sse4.1"
target_feature="sse4.2"
target_feature="ssse3"
target_feature="xsave"
target_feature="xsavec"
target_feature="xsaveopt"
target_feature="xsaves"
target_os="macos"
target_pointer_width="64"
target_vendor="apple"
unix

satisfy

config.flag_if_supported("-msse2");
        }
        if target_features.contains(&"sse4.1") {
            config.flag_if_supported("-msse4.1");
        }
        if target_features.contains(&"sse4.2") {
            config.flag_if_supported("-msse4.2");
            config.define("HAVE_SSE42", Some("1"));
        }

May be use this cmd RUSTFLAGS="-C target-cpu=native" cargo build --release OK? but this https://stackoverflow.com/questions/67444134/rust-target-cpu-native-gets-slower-simd-execution show that it may be have bug

[templexxx]

This bug seems to have been fixed @nkysg SSE42 is pretty old. It's really hard to find a X86-64 CPU which doesn't support SSE4.2. We could add this feature manually if there is still a bug.

[nkysg]

This bug seems to have been fixed @nkysg SSE42 is pretty old. It's really hard to find a X86-64 CPU which doesn't support SSE4.2. We could add this feature manually if there is still a bug.

Yes, I think you are right. We can try do it。@templexxx