use std::env;fn defined(var: &str) -> bool {    println!("cargo:rerun-if-env-changed={}", var);    env::var_os(var).is_some()}fn is_pure() -> bool {    defined("CARGO_FEATURE_PURE")}fn should_prefer_intrinsics() -> bool {    defined("CARGO_FEATURE_PREFER_INTRINSICS")}fn is_neon() -> bool {    defined("CARGO_FEATURE_NEON")}fn is_no_neon() -> bool {    defined("CARGO_FEATURE_NO_NEON")}fn is_wasm32_simd() -> bool {    defined("CARGO_FEATURE_WASM32_SIMD")}fn is_ci() -> bool {    defined("BLAKE3_CI")}fn warn(warning: &str) {    assert!(!warning.contains("\n"));    println!("cargo:warning={}", warning);    if is_ci() {        println!("cargo:warning=Warnings in CI are treated as errors. Build failed.");        std::process::exit(1);    }}fn target_components() -> Vec<String> {    let target = env::var("TARGET").unwrap();    target.split("-").map(|s| s.to_string()).collect()}fn is_x86_64() -> bool {    target_components()[0] == "x86_64"}fn is_windows_target() -> bool {    env::var("CARGO_CFG_TARGET_OS").unwrap() == "windows"}fn use_msvc_asm() -> bool {    const MSVC_NAMES: &[&str] = &["", "cl", "cl.exe"];    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();    let target_env = env::var("CARGO_CFG_TARGET_ENV").unwrap_or_default();    let target_windows_msvc = target_os == "windows" && target_env == "msvc";    let host_triple = env::var("HOST").unwrap_or_default();    let target_triple = env::var("TARGET").unwrap_or_default();    let cross_compiling = host_triple != target_triple;    let cc = env::var("CC").unwrap_or_default().to_ascii_lowercase();    if !target_windows_msvc {        // We are not building for Windows with the MSVC toolchain.        false    } else if !cross_compiling && MSVC_NAMES.contains(&&*cc) {        // We are building on Windows with the MSVC toolchain (and not cross-compiling for another architecture or target).        true    } else {        // We are cross-compiling to Windows with the MSVC toolchain.        let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap_or_default();        let target_vendor = env::var("CARGO_CFG_TARGET_VENDOR").unwrap_or_default();        let cc = env::var(format!("CC_{target_arch}_{target_vendor}_windows_msvc"))            .unwrap_or_default()            .to_ascii_lowercase();        // Check if we are using the MSVC compiler.        MSVC_NAMES.contains(&&*cc)    }}fn is_x86_32() -> bool {    let arch = &target_components()[0];    arch == "i386" || arch == "i586" || arch == "i686"}fn is_arm() -> bool {    is_armv7() || is_aarch64() || target_components()[0] == "arm"}fn is_aarch64() -> bool {    target_components()[0] == "aarch64"}fn is_armv7() -> bool {    target_components()[0] == "armv7"}fn is_wasm32() -> bool {    target_components()[0] == "wasm32"}fn endianness() -> String {    let endianness = env::var("CARGO_CFG_TARGET_ENDIAN").unwrap();    assert!(endianness == "little" || endianness == "big");    endianness}fn is_little_endian() -> bool {    endianness() == "little"}fn is_big_endian() -> bool {    endianness() == "big"}// Windows targets may be using the MSVC toolchain or the MinGW toolchain. The// right compiler flags to use depend on the toolchain. (And we don't want to// use flag_if_supported, because we don't want features to be silently// disabled by old compilers.)fn is_windows_msvc() -> bool {    // Some targets are only two components long, so check in steps.    let second_component = &target_components()[1];    (second_component == "pc" || second_component == "win7")        && target_components()[2] == "windows"        && target_components()[3] == "msvc"}// MinGW toolchain uses 2 different targets depending on the main compiler.// Target for a general MinGW toolchain ends with `-gnu` (GCC is used as C// compiler). Target for a LLVM-MinGW toolchain (Clang is used as C compiler)// ends with `-gnullvm`.fn is_windows_gnu() -> bool {    // Some targets are only two components long, so check in steps.    let second_component = &target_components()[1];    (second_component == "pc" || second_component == "win7")        && target_components()[2] == "windows"        && target_components()[3] != "msvc"}fn new_build() -> cc::Build {    let mut build = cc::Build::new();    if !is_windows_msvc() {        build.flag("-std=c11");    }    // Do NOT trigger a rebuild any time the env changes (e.g. $PATH).    // This prevents all downstream crates from being rebuilt when `cargo check`    // or `cargo build` are run in different environments, like Rust Analyzer    // vs. in the terminal vs. in a Git pre-commit hook.    build.emit_rerun_if_env_changed(false);    build}#[derive(PartialEq)]enum CCompilerSupport {    NoCompiler,    NoAVX512,    YesAVX512,}use CCompilerSupport::*;fn c_compiler_support() -> CCompilerSupport {    let build = new_build();    let flags_checked;    let support_result: Result<bool, _> = if is_windows_msvc() {        flags_checked = "/arch:AVX512";        build.is_flag_supported("/arch:AVX512")    } else {        // Check for both of the flags we use. If -mavx512f works, then -mavx512vl        // will probably always work too, but we might as well be thorough.        flags_checked = "-mavx512f and -mavx512vl";        match build.is_flag_supported("-mavx512f") {            Ok(true) => build.is_flag_supported("-mavx512vl"),            false_or_error => false_or_error,        }    };    match support_result {        Ok(true) => YesAVX512,        Ok(false) => {            warn(&format!(                "The C compiler {:?} does not support {}.",                build.get_compiler().path(),                flags_checked,            ));            NoAVX512        }        Err(e) => {            println!("{:?}", e);            warn(&format!(                "No C compiler {:?} detected.",                build.get_compiler().path()            ));            NoCompiler        }    }}fn build_sse2_sse41_avx2_rust_intrinsics() {    // No C code to compile here. Set the cfg flags that enable the Rust SSE2,    // SSE4.1, and AVX2 intrinsics modules. The regular Cargo build will compile    // them.    println!("cargo:rustc-cfg=blake3_sse2_rust");    println!("cargo:rustc-cfg=blake3_sse41_rust");    println!("cargo:rustc-cfg=blake3_avx2_rust");}fn build_sse2_sse41_avx2_assembly() {    // Build the assembly implementations for SSE4.1 and AVX2. This is    // preferred, but it only supports x86_64.    assert!(is_x86_64());    println!("cargo:rustc-cfg=blake3_sse2_ffi");    println!("cargo:rustc-cfg=blake3_sse41_ffi");    println!("cargo:rustc-cfg=blake3_avx2_ffi");    let mut build = new_build();    if is_windows_target() {        if use_msvc_asm() {            build.file("c/blake3_sse2_x86-64_windows_msvc.asm");            build.file("c/blake3_sse41_x86-64_windows_msvc.asm");            build.file("c/blake3_avx2_x86-64_windows_msvc.asm");        } else {            build.file("c/blake3_sse2_x86-64_windows_gnu.S");            build.file("c/blake3_sse41_x86-64_windows_gnu.S");            build.file("c/blake3_avx2_x86-64_windows_gnu.S");        }    } else {        // All non-Windows implementations are assumed to support        // Linux-style assembly. These files do contain a small        // explicit workaround for macOS also.        build.file("c/blake3_sse2_x86-64_unix.S");        build.file("c/blake3_sse41_x86-64_unix.S");        build.file("c/blake3_avx2_x86-64_unix.S");    }    build.compile("blake3_sse2_sse41_avx2_assembly");}fn build_avx512_c_intrinsics() {    // This is required on 32-bit x86 targets, since the assembly    // implementation doesn't support those.    println!("cargo:rustc-cfg=blake3_avx512_ffi");    let mut build = new_build();    build.file("c/blake3_avx512.c");    if is_windows_msvc() {        build.flag("/arch:AVX512");    } else {        build.flag("-mavx512f");        build.flag("-mavx512vl");    }    if is_windows_gnu() {        // Workaround for https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65782.        build.flag("-fno-asynchronous-unwind-tables");    }    build.compile("blake3_avx512_intrinsics");}fn build_avx512_assembly() {    // Build the assembly implementation for AVX-512. This is preferred, but it    // only supports x86_64.    assert!(is_x86_64());    println!("cargo:rustc-cfg=blake3_avx512_ffi");    let mut build = new_build();    let mut is_msvc = false;    if is_windows_target() {        if use_msvc_asm() {            build.file("c/blake3_avx512_x86-64_windows_msvc.asm");            is_msvc = true;        } else {            build.file("c/blake3_avx512_x86-64_windows_gnu.S");        }    } else {        build.file("c/blake3_avx512_x86-64_unix.S");    }    // Older versions of Clang require these flags, even for assembly. See    // https://github.com/BLAKE3-team/BLAKE3/issues/79.    if !is_msvc {        build.flag("-mavx512f");        build.flag("-mavx512vl");    }    build.compile("blake3_avx512_assembly");}fn build_neon_c_intrinsics() {    let mut build = new_build();    // Note that blake3_neon.c normally depends on the blake3_portable.c    // for the single-instance compression function, but we expose    // portable.rs over FFI instead. See ffi_neon.rs.    build.file("c/blake3_neon.c");    // ARMv7 platforms that support NEON generally need the following    // flags. AArch64 supports NEON by default and does not support -mpfu.    if is_armv7() {        build.flag("-mfpu=neon-vfpv4");        build.flag("-mfloat-abi=hard");    }    build.compile("blake3_neon");}fn build_wasm32_simd() {    assert!(is_wasm32());    // No C code to compile here. Set the cfg flags that enable the Wasm SIMD.    // The regular Cargo build will compile it.    println!("cargo:rustc-cfg=blake3_wasm32_simd");}fn main() -> Result<(), Box<dyn std::error::Error>> {    // If CFLAGS is set, make sure LTO is disabled by appending -fno-lto. (We can't do this with    // .flag() later on, because CFLAGS takes precedence.) Any mismatch between the C compiler and    // the Rust linker can cause linker errors in our C intrinsice implementations if LTO is    // enabled. See https://github.com/BLAKE3-team/BLAKE3/issues/550.    if !is_windows_msvc() {        if let Some(mut flags) = env::var_os("CFLAGS") {            flags.push(" -fno-lto");            // SAFETY: This build script is single-threaded.            unsafe {                env::set_var("CFLAGS", flags);            }        }    }    // As of Rust 1.80, unrecognized config names are warnings. Give Cargo all of our config names.    let all_cfgs = [        "blake3_sse2_ffi",        "blake3_sse2_rust",        "blake3_sse41_ffi",        "blake3_sse41_rust",        "blake3_avx2_ffi",        "blake3_avx2_rust",        "blake3_avx512_ffi",        "blake3_neon",        "blake3_wasm32_simd",    ];    for cfg_name in all_cfgs {        // TODO: Switch this whole file to the new :: syntax when our MSRV reaches 1.77.        // https://doc.rust-lang.org/cargo/reference/build-scripts.html#outputs-of-the-build-script        println!("cargo:rustc-check-cfg=cfg({cfg_name}, values(none()))");    }    if is_pure() && is_neon() {        panic!("It doesn't make sense to enable both \"pure\" and \"neon\".");    }    if is_no_neon() && is_neon() {        panic!("It doesn't make sense to enable both \"no_neon\" and \"neon\".");    }    if is_x86_64() || is_x86_32() {        let support = c_compiler_support();        if is_x86_32() || should_prefer_intrinsics() || is_pure() || support == NoCompiler {            build_sse2_sse41_avx2_rust_intrinsics();        } else {            // We assume that all C compilers can assemble SSE4.1 and AVX2. We            // don't explicitly check for support.            build_sse2_sse41_avx2_assembly();        }        if is_pure() || support == NoCompiler || support == NoAVX512 {            // The binary will not include any AVX-512 code.        } else if is_x86_32() || should_prefer_intrinsics() {            build_avx512_c_intrinsics();        } else {            build_avx512_assembly();        }    }    if is_neon() && is_big_endian() {        panic!("The NEON implementation doesn't support big-endian ARM.")    }    if (is_arm() && is_neon())        || (!is_no_neon() && !is_pure() && is_aarch64() && is_little_endian())    {        println!("cargo:rustc-cfg=blake3_neon");        build_neon_c_intrinsics();    }    if is_wasm32() && is_wasm32_simd() {        build_wasm32_simd();    }    // The `cc` crate doesn't automatically emit rerun-if directives for the    // environment variables it supports, in particular for $CC. We expect to    // do a lot of benchmarking across different compilers, so we explicitly    // add the variables that we're likely to need.    println!("cargo:rerun-if-env-changed=CC");    println!("cargo:rerun-if-env-changed=CFLAGS");    // Ditto for source files, though these shouldn't change as often.    for file in std::fs::read_dir("c")? {        println!(            "cargo:rerun-if-changed={}",            file?.path().to_str().expect("utf-8")        );    }    // When compiling with clang-cl for windows, it adds .asm files to the root    // which we need to delete so cargo doesn't get angry    if is_windows_target() && !use_msvc_asm() {        let _ = std::fs::remove_file("blake3_avx2_x86-64_windows_gnu.asm");        let _ = std::fs::remove_file("blake3_avx512_x86-64_windows_gnu.asm");        let _ = std::fs::remove_file("blake3_sse2_x86-64_windows_gnu.asm");        let _ = std::fs::remove_file("blake3_sse41_x86-64_windows_gnu.asm");    }    Ok(())}