1use std::env; 2 3fn main() { 4 enable_simd_optimizations(); 5 enable_libc(); 6} 7 8// This adds various simd cfgs if this compiler and target support it. 9// 10// This can be disabled with RUSTFLAGS="--cfg memchr_disable_auto_simd", but 11// this is generally only intended for testing. 12// 13// On targets which don't feature SSE2, this is disabled, as LLVM wouln't know 14// how to work with SSE2 operands. Enabling SSE4.2 and AVX on SSE2-only targets 15// is not a problem. In that case, the fastest option will be chosen at 16// runtime. 17fn enable_simd_optimizations() { 18 if is_env_set("CARGO_CFG_MEMCHR_DISABLE_AUTO_SIMD") { 19 return; 20 } 21 let arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap(); 22 match &arch[..] { 23 "x86_64" => { 24 if !target_has_feature("sse2") { 25 return; 26 } 27 println!("cargo:rustc-cfg=memchr_runtime_simd"); 28 println!("cargo:rustc-cfg=memchr_runtime_sse2"); 29 println!("cargo:rustc-cfg=memchr_runtime_sse42"); 30 println!("cargo:rustc-cfg=memchr_runtime_avx"); 31 } 32 "wasm32" | "wasm64" => { 33 if !target_has_feature("simd128") { 34 return; 35 } 36 println!("cargo:rustc-cfg=memchr_runtime_simd"); 37 println!("cargo:rustc-cfg=memchr_runtime_wasm128"); 38 } 39 _ => {} 40 } 41} 42 43// This adds a `memchr_libc` cfg if and only if libc can be used, if no other 44// better option is available. 45// 46// This could be performed in the source code, but it's simpler to do it once 47// here and consolidate it into one cfg knob. 48// 49// Basically, we use libc only if its enabled and if we aren't targeting a 50// known bad platform. For example, wasm32 doesn't have a libc and the 51// performance of memchr on Windows is seemingly worse than the fallback 52// implementation. 53fn enable_libc() { 54 const NO_ARCH: &'static [&'static str] = &["wasm32", "windows"]; 55 const NO_ENV: &'static [&'static str] = &["sgx"]; 56 57 if !is_feature_set("LIBC") { 58 return; 59 } 60 61 let arch = match env::var("CARGO_CFG_TARGET_ARCH") { 62 Err(_) => return, 63 Ok(arch) => arch, 64 }; 65 let env = match env::var("CARGO_CFG_TARGET_ENV") { 66 Err(_) => return, 67 Ok(env) => env, 68 }; 69 if NO_ARCH.contains(&&*arch) || NO_ENV.contains(&&*env) { 70 return; 71 } 72 73 println!("cargo:rustc-cfg=memchr_libc"); 74} 75 76fn is_feature_set(name: &str) -> bool { 77 is_env_set(&format!("CARGO_FEATURE_{}", name)) 78} 79 80fn is_env_set(name: &str) -> bool { 81 env::var_os(name).is_some() 82} 83 84fn target_has_feature(feature: &str) -> bool { 85 env::var("CARGO_CFG_TARGET_FEATURE") 86 .map(|features| features.contains(feature)) 87 .unwrap_or(false) 88} 89