vendor/memchr/build.rs

   1 use std::env;
   2
   3 fn main() {
   4     enable_simd_optimizations();
   5     enable_libc();
   6 }
   7
   8 // This adds various simd cfgs if this compiler supports it.
   9 //
  10 // This can be disabled with RUSTFLAGS="--cfg memchr_disable_auto_simd", but
  11 // this is generally only intended for testing.
  12 fn enable_simd_optimizations() {
  13     if is_env_set("CARGO_CFG_MEMCHR_DISABLE_AUTO_SIMD") {
  14         return;
  15     }
  16     println!("cargo:rustc-cfg=memchr_runtime_simd");
  17     println!("cargo:rustc-cfg=memchr_runtime_sse2");
  18     println!("cargo:rustc-cfg=memchr_runtime_sse42");
  19     println!("cargo:rustc-cfg=memchr_runtime_avx");
  20 }
  21
  22 // This adds a `memchr_libc` cfg if and only if libc can be used, if no other
  23 // better option is available.
  24 //
  25 // This could be performed in the source code, but it's simpler to do it once
  26 // here and consolidate it into one cfg knob.
  27 //
  28 // Basically, we use libc only if its enabled and if we aren't targeting a
  29 // known bad platform. For example, wasm32 doesn't have a libc and the
  30 // performance of memchr on Windows is seemingly worse than the fallback
  31 // implementation.
  32 fn enable_libc() {
  33     const NO_ARCH: &'static [&'static str] = &["wasm32", "windows"];
  34     const NO_ENV: &'static [&'static str] = &["sgx"];
  35
  36     if !is_feature_set("LIBC") {
  37         return;
  38     }
  39
  40     let arch = match env::var("CARGO_CFG_TARGET_ARCH") {
  41         Err(_) => return,
  42         Ok(arch) => arch,
  43     };
  44     let env = match env::var("CARGO_CFG_TARGET_ENV") {
  45         Err(_) => return,
  46         Ok(env) => env,
  47     };
  48     if NO_ARCH.contains(&&*arch) || NO_ENV.contains(&&*env) {
  49         return;
  50     }
  51
  52     println!("cargo:rustc-cfg=memchr_libc");
  53 }
  54
  55 fn is_feature_set(name: &str) -> bool {
  56     is_env_set(&format!("CARGO_FEATURE_{}", name))
  57 }
  58
  59 fn is_env_set(name: &str) -> bool {
  60     env::var_os(name).is_some()
  61 }