From 005ba9342ca28d0f049a77832b9db7e2cc1ce35d Mon Sep 17 00:00:00 2001
From: Cathal Mullan <contact@cathal.dev>
Date: Fri, 7 Nov 2025 19:48:36 +0000
Subject: [PATCH] Simplify runtime SIMD detection

---
 src/simd/runtime.rs | 50 +++++++++++----------------------------------
 1 file changed, 12 insertions(+), 38 deletions(-)

diff --git a/src/simd/runtime.rs b/src/simd/runtime.rs
index c523a92..3b9f64e 100644
--- a/src/simd/runtime.rs
+++ b/src/simd/runtime.rs
@@ -1,34 +1,4 @@
-use std::sync::atomic::{AtomicU8, Ordering};
 use crate::iter::Bytes;
-use super::avx2;
-use super::sse42;
-
-const AVX2: u8 = 1;
-const SSE42: u8 = 2;
-const NOP: u8 = 3;
-
-fn detect_runtime_feature() -> u8 {
-    if is_x86_feature_detected!("avx2") {
-        AVX2
-    } else if is_x86_feature_detected!("sse4.2") {
-        SSE42
-    } else {
-        NOP
-    }
-}
-
-static RUNTIME_FEATURE: AtomicU8 = AtomicU8::new(0);
-
-#[inline]
-fn get_runtime_feature() -> u8 {
-    let mut feature = RUNTIME_FEATURE.load(Ordering::Relaxed);
-    if feature == 0 {
-        feature = detect_runtime_feature();
-        RUNTIME_FEATURE.store(feature, Ordering::Relaxed);
-    }
-
-    feature
-}
 
 pub fn match_header_name_vectored(bytes: &mut Bytes) {
     super::swar::match_header_name_vectored(bytes);
@@ -37,10 +7,12 @@ pub fn match_header_name_vectored(bytes: &mut Bytes) {
 pub fn match_uri_vectored(bytes: &mut Bytes) {
     // SAFETY: calls are guarded by a feature check
     unsafe {
-        match get_runtime_feature() {
-            AVX2 => avx2::match_uri_vectored(bytes),
-            SSE42 => sse42::match_uri_vectored(bytes),
-            _ /* NOP */ => super::swar::match_uri_vectored(bytes),
+        if is_x86_feature_detected!("avx2") {
+            super::avx2::match_uri_vectored(bytes)
+        } else if is_x86_feature_detected!("sse4.2") {
+            super::sse42::match_uri_vectored(bytes)
+        } else {
+            super::swar::match_uri_vectored(bytes)
         }
     }
 }
@@ -48,10 +20,12 @@ pub fn match_uri_vectored(bytes: &mut Bytes) {
 pub fn match_header_value_vectored(bytes: &mut Bytes) {
     // SAFETY: calls are guarded by a feature check
     unsafe {
-        match get_runtime_feature() {
-            AVX2 => avx2::match_header_value_vectored(bytes),
-            SSE42 => sse42::match_header_value_vectored(bytes),
-            _ /* NOP */ => super::swar::match_header_value_vectored(bytes),
+        if is_x86_feature_detected!("avx2") {
+            super::avx2::match_header_value_vectored(bytes)
+        } else if is_x86_feature_detected!("sse4.2") {
+            super::sse42::match_header_value_vectored(bytes)
+        } else {
+            super::swar::match_header_value_vectored(bytes)
         }
     }
 }