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use std::env;
fn main() {
enable_simd_optimizations();
enable_libc();
}
// This adds various simd cfgs if this compiler and target support it.
//
// This can be disabled with RUSTFLAGS="--cfg memchr_disable_auto_simd", but
// this is generally only intended for testing.
//
// On targets which don't feature SSE2, this is disabled, as LLVM wouln't know
// how to work with SSE2 operands. Enabling SSE4.2 and AVX on SSE2-only targets
// is not a problem. In that case, the fastest option will be chosen at
// runtime.
fn enable_simd_optimizations() {
if is_env_set("CARGO_CFG_MEMCHR_DISABLE_AUTO_SIMD") {
return;
}
let arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
match &arch[..] {
"x86_64" => {
if !target_has_feature("sse2") {
return;
}
println!("cargo:rustc-cfg=memchr_runtime_simd");
println!("cargo:rustc-cfg=memchr_runtime_sse2");
println!("cargo:rustc-cfg=memchr_runtime_sse42");
println!("cargo:rustc-cfg=memchr_runtime_avx");
}
"wasm32" | "wasm64" => {
if !target_has_feature("simd128") {
return;
}
println!("cargo:rustc-cfg=memchr_runtime_simd");
println!("cargo:rustc-cfg=memchr_runtime_wasm128");
}
_ => {}
}
}
// This adds a `memchr_libc` cfg if and only if libc can be used, if no other
// better option is available.
//
// This could be performed in the source code, but it's simpler to do it once
// here and consolidate it into one cfg knob.
//
// Basically, we use libc only if its enabled and if we aren't targeting a
// known bad platform. For example, wasm32 doesn't have a libc and the
// performance of memchr on Windows is seemingly worse than the fallback
// implementation.
fn enable_libc() {
const NO_ARCH: &'static [&'static str] = &["wasm32", "windows"];
const NO_ENV: &'static [&'static str] = &["sgx"];
if !is_feature_set("LIBC") {
return;
}
let arch = match env::var("CARGO_CFG_TARGET_ARCH") {
Err(_) => return,
Ok(arch) => arch,
};
let env = match env::var("CARGO_CFG_TARGET_ENV") {
Err(_) => return,
Ok(env) => env,
};
if NO_ARCH.contains(&&*arch) || NO_ENV.contains(&&*env) {
return;
}
println!("cargo:rustc-cfg=memchr_libc");
}
fn is_feature_set(name: &str) -> bool {
is_env_set(&format!("CARGO_FEATURE_{}", name))
}
fn is_env_set(name: &str) -> bool {
env::var_os(name).is_some()
}
fn target_has_feature(feature: &str) -> bool {
env::var("CARGO_CFG_TARGET_FEATURE")
.map(|features| features.contains(feature))
.unwrap_or(false)
}
|
