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use std::env;
fn defined(var: &str) -> bool {
env::var_os(var).is_some()
}
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_x86_32() -> bool {
let arch = &target_components()[0];
arch == "i386" || arch == "i586" || arch == "i686"
}
fn is_armv7() -> bool {
target_components()[0] == "armv7"
}
// Windows targets may be using the MSVC toolchain or the GNU 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.
target_components()[1] == "pc"
&& target_components()[2] == "windows"
&& target_components()[3] == "msvc"
}
fn is_windows_gnu() -> bool {
// Some targets are only two components long, so check in steps.
target_components()[1] == "pc"
&& target_components()[2] == "windows"
&& target_components()[3] == "gnu"
}
fn new_build() -> cc::Build {
let mut build = cc::Build::new();
if !is_windows_msvc() {
build.flag("-std=c11");
}
build
}
const WINDOWS_MSVC_ERROR: &str = r#"
The "c" feature is enabled, but your version of the MSVC C compiler does not
support the "/arch:AVX512" flag. If you are building the "b3sum" or "bao_bin"
crates, you can disable AVX-512 with Cargo's "--no-default-features" flag.
(Note that this also disables other default features like Rayon-based
multithreading, which you can re-enable with "--features=rayon".) Other crates
might or might not support this workaround.
"#;
const GNU_ERROR: &str = r#"
The "c" feature is enabled, but your C compiler does not support the
"-mavx512f" flag. If you are building the "b3sum" or "bao_bin" crates, you can
disable AVX-512 with Cargo's "--no-default-features" flag. (Note that this also
disables other default features like Rayon-based multithreading, which you can
re-enable with "--features=rayon".) Other crates might or might not support
this workaround.
"#;
fn check_for_avx512_compiler_support() {
let build = new_build();
if is_windows_msvc() {
if !build.is_flag_supported("/arch:AVX512").unwrap() {
eprintln!("{}", WINDOWS_MSVC_ERROR.trim());
std::process::exit(1);
}
} else {
if !build.is_flag_supported("-mavx512f").unwrap() {
eprintln!("{}", GNU_ERROR.trim());
std::process::exit(1);
}
}
}
fn main() -> Result<(), Box<dyn std::error::Error>> {
if defined("CARGO_FEATURE_C") {
check_for_avx512_compiler_support();
if is_x86_64() && !defined("CARGO_FEATURE_C_PREFER_INTRINSICS") {
// On 64-bit, use the assembly implementations, unless the
// "c_prefer_intrinsics" feature is enabled.
if is_windows_msvc() {
let mut build = new_build();
build.file("c/blake3_sse41_x86-64_windows_msvc.asm");
build.file("c/blake3_avx2_x86-64_windows_msvc.asm");
build.file("c/blake3_avx512_x86-64_windows_msvc.asm");
build.compile("blake3_asm");
} else if is_windows_gnu() {
let mut build = new_build();
build.file("c/blake3_sse41_x86-64_windows_gnu.S");
build.file("c/blake3_avx2_x86-64_windows_gnu.S");
build.file("c/blake3_avx512_x86-64_windows_gnu.S");
build.compile("blake3_asm");
} else {
// All non-Windows implementations are assumed to support
// Linux-style assembly. These files do contain a small
// explicit workaround for macOS also.
let mut build = new_build();
build.file("c/blake3_sse41_x86-64_unix.S");
build.file("c/blake3_avx2_x86-64_unix.S");
build.file("c/blake3_avx512_x86-64_unix.S");
build.compile("blake3_asm");
}
} else if is_x86_64() || is_x86_32() {
// Assembly implementations are only for 64-bit. On 32-bit, or if
// the "c_prefer_intrinsics" feature is enabled, use the
// intrinsics-based C implementations. These each need to be
// compiled separately, with the corresponding instruction set
// extension explicitly enabled in the compiler.
let mut sse41_build = new_build();
sse41_build.file("c/blake3_sse41.c");
if is_windows_msvc() {
// /arch:SSE2 is the default on x86 and undefined on x86_64:
// https://docs.microsoft.com/en-us/cpp/build/reference/arch-x86
// It also includes SSE4.1 intrisincs:
// https://stackoverflow.com/a/32183222/823869
} else {
sse41_build.flag("-msse4.1");
}
sse41_build.compile("blake3_sse41");
let mut avx2_build = new_build();
avx2_build.file("c/blake3_avx2.c");
if is_windows_msvc() {
avx2_build.flag("/arch:AVX2");
} else {
avx2_build.flag("-mavx2");
}
avx2_build.compile("blake3_avx2");
let mut avx512_build = new_build();
avx512_build.file("c/blake3_avx512.c");
if is_windows_msvc() {
// Note that a lot of versions of MSVC don't support /arch:AVX512,
// and they'll discard it with a warning, hopefully leading to a
// build error.
avx512_build.flag("/arch:AVX512");
} else {
avx512_build.flag("-mavx512f");
avx512_build.flag("-mavx512vl");
}
avx512_build.compile("blake3_avx512");
} else {
// Currently no effect for non-x86 platforms.
}
}
if defined("CARGO_FEATURE_C_NEON") {
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 c_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");
}
// The `cc` crate does not 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")
);
}
Ok(())
}
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