mirror of
https://github.com/openharmony/third_party_rust_memchr.git
synced 2026-07-01 08:14:31 -04:00
Alex Crichton
c28170ec18
This commit adds simd acceleration support to the `memmem` module. This is added with the freshly-stabilized support from rust-lang/rust#86204. This mostly just cribs off the generic simd support for 128-bit types built for sse, copying bits and pieces of code here and there. Some refactoring happened internally to help reduce duplication where possible. I ran some initial benchmarks with the `memmem/krate/*` regex and a hacked up single-threaded version of criterion. Some [initial comparisons][compare] using Wasmtime as a runtime do indeed show a lot of improvements, but there are indeed some slowdowns as well. [compare]: https://gist.github.com/alexcrichton/6a72e682e7b6d505ade605359fbe3f2d PR #84
89 lines
2.7 KiB
Rust
89 lines
2.7 KiB
Rust
use std::env;
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fn main() {
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enable_simd_optimizations();
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enable_libc();
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}
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// This adds various simd cfgs if this compiler and target support it.
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//
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// This can be disabled with RUSTFLAGS="--cfg memchr_disable_auto_simd", but
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// this is generally only intended for testing.
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//
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// On targets which don't feature SSE2, this is disabled, as LLVM wouln't know
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// how to work with SSE2 operands. Enabling SSE4.2 and AVX on SSE2-only targets
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// is not a problem. In that case, the fastest option will be chosen at
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// runtime.
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fn enable_simd_optimizations() {
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if is_env_set("CARGO_CFG_MEMCHR_DISABLE_AUTO_SIMD") {
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return;
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}
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let arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
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match &arch[..] {
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"x86_64" => {
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if !target_has_feature("sse2") {
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return;
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}
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println!("cargo:rustc-cfg=memchr_runtime_simd");
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println!("cargo:rustc-cfg=memchr_runtime_sse2");
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println!("cargo:rustc-cfg=memchr_runtime_sse42");
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println!("cargo:rustc-cfg=memchr_runtime_avx");
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}
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"wasm32" | "wasm64" => {
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if !target_has_feature("simd128") {
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return;
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}
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println!("cargo:rustc-cfg=memchr_runtime_simd");
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println!("cargo:rustc-cfg=memchr_runtime_wasm128");
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}
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_ => {}
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}
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}
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// This adds a `memchr_libc` cfg if and only if libc can be used, if no other
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// better option is available.
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//
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// This could be performed in the source code, but it's simpler to do it once
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// here and consolidate it into one cfg knob.
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//
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// Basically, we use libc only if its enabled and if we aren't targeting a
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// known bad platform. For example, wasm32 doesn't have a libc and the
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// performance of memchr on Windows is seemingly worse than the fallback
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// implementation.
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fn enable_libc() {
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const NO_ARCH: &'static [&'static str] = &["wasm32", "windows"];
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const NO_ENV: &'static [&'static str] = &["sgx"];
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if !is_feature_set("LIBC") {
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return;
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}
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let arch = match env::var("CARGO_CFG_TARGET_ARCH") {
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Err(_) => return,
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Ok(arch) => arch,
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};
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let env = match env::var("CARGO_CFG_TARGET_ENV") {
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Err(_) => return,
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Ok(env) => env,
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};
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if NO_ARCH.contains(&&*arch) || NO_ENV.contains(&&*env) {
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return;
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}
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println!("cargo:rustc-cfg=memchr_libc");
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}
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fn is_feature_set(name: &str) -> bool {
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is_env_set(&format!("CARGO_FEATURE_{}", name))
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}
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fn is_env_set(name: &str) -> bool {
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env::var_os(name).is_some()
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}
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fn target_has_feature(feature: &str) -> bool {
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env::var("CARGO_CFG_TARGET_FEATURE")
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.map(|features| features.contains(feature))
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.unwrap_or(false)
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}
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