diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ead2a6f..599ea56 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,8 +17,7 @@ jobs:
       - simd
       - check_x86
       - aarch64
-      - msrv_x64
-      - msrv_aarch64
+      - msrv
       - miri
       - clippy_check
     steps:
@@ -44,7 +43,7 @@ jobs:
 
     runs-on: ${{ matrix.os }}
     env:
-      CARGO_CFG_HTTPARSE_DISABLE_SIMD: 1
+      RUSTFLAGS: --cfg httparse_disable_simd
 
     steps:
       - name: Checkout
@@ -76,14 +75,10 @@ jobs:
           - nightly
 
         target_feature:
+          - "" # runtime detection
           - "+sse4.2"
           - "+avx2"
           - "+sse4.2,+avx2"
-
-        disable_compiletime:
-          - 0
-          - 1
-
     steps:
       - name: Checkout
         uses: actions/checkout@v5
@@ -96,7 +91,6 @@ jobs:
       - name: Test
         env:
           RUSTFLAGS: -C target_feature=${{ matrix.target_feature }}
-          CARGO_CFG_HTTPARSE_DISABLE_SIMD_COMPILETIME: ${{ matrix.disable_compiletime }}
         run: cargo test
 
   check_x86:
@@ -113,48 +107,26 @@ jobs:
 
       - name: Test without SIMD
         env:
-          CARGO_CFG_HTTPARSE_DISABLE_SIMD_COMPILETIME: 1
+          RUSTFLAGS: --cfg httparse_disable_simd
         run: cargo test --target i686-unknown-linux-musl
 
       - name: Test
         run: cargo test --target i686-unknown-linux-musl
 
-  msrv_x64:
-    name: msrv (x64)
+  msrv:
+    name: msrv
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v5
 
       - name: Install Rust
-        uses: dtolnay/rust-toolchain@1.47.0
+        uses: dtolnay/rust-toolchain@1.59.0
 
-      # Only build, dev-dependencies don't compile on 1.47.0
+      # Only build, dev-dependencies don't compile on 1.59.0
       - name: Build
         run: cargo build
 
-  # This tests that aarch64 gracefully fallbacks to SWAR if neon_intrinsics aren't available (<1.59)
-  msrv_aarch64:
-    name: msrv (aarch64)
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v5
-
-      - name: Install cross-compiling dependencies
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y gcc-aarch64-linux-gnu
-
-      - name: Setup Rust
-        uses: dtolnay/rust-toolchain@1.47.0
-        with:
-          target: aarch64-unknown-linux-gnu
-
-      # Only build, dev-dependencies don't compile on 1.47.0
-      - name: Build
-        run: cargo build --target aarch64-unknown-linux-gnu
-
   clippy_check:
     runs-on: ubuntu-latest
     steps:
diff --git a/.github/workflows/cibench.yml b/.github/workflows/cibench.yml
index 647b91a..323e5d4 100644
--- a/.github/workflows/cibench.yml
+++ b/.github/workflows/cibench.yml
@@ -5,12 +5,13 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
-  RUSTFLAGS: "-C target-cpu=native"
 
 jobs:
   benchmark:
     name: Run benchmarks
     runs-on: ubuntu-latest
+    env:
+      RUSTFLAGS: "-C target-cpu=native"
     steps:
       - uses: actions/checkout@v5
         with:
@@ -41,7 +42,17 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        feature: [swar, sse42, avx2]
+        include:
+          - feature: runtime
+            rustflags: ""
+          - feature: swar
+            rustflags: "--cfg httparse_disable_simd"
+          - feature: sse4.2
+            rustflags: "-C target-feature=+sse4.2"
+          - feature: avx2
+            rustflags: "-C target-feature=+avx2"
+    env:
+      RUSTFLAGS: ${{ matrix.rustflags }}
     steps:
       - uses: actions/checkout@v5
         with:
@@ -57,17 +68,11 @@ jobs:
         run: |
           git checkout master
           cargo bench --bench parse -- --save-baseline master-${{ matrix.feature }}
-        env:
-          CARGO_CFG_HTTPARSE_DISABLE_SIMD: ${{ matrix.feature == 'swar' && '1' || '0' }}
-          RUSTFLAGS: ${{ matrix.feature != 'swar' && format('-C target-feature=+{0}', matrix.feature) || '' }}
 
       - name: Run benchmarks (PR)
         run: |
           git checkout ${{ github.event.pull_request.head.sha }}
           cargo bench --bench parse -- --save-baseline pr-${{ github.event.pull_request.number }}-${{ github.event.pull_request.head.sha }}-${{ matrix.feature }}
-        env:
-          CARGO_CFG_HTTPARSE_DISABLE_SIMD: ${{ matrix.feature == 'swar' && '1' || '0' }}
-          RUSTFLAGS: ${{ matrix.feature != 'swar' && format('-C target-feature=+{0}', matrix.feature) || '' }}
 
       - name: Compare benchmarks
         run: |
@@ -78,7 +83,13 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        feature: [swar, neon]
+        include:
+          - feature: swar
+            rustflags: "--cfg httparse_disable_simd"
+          - feature: neon
+            rustflags: "-C target-feature=+neon"
+    env:
+      RUSTFLAGS: ${{ matrix.rustflags }}
     steps:
       - uses: actions/checkout@v5
         with:
@@ -94,17 +105,11 @@ jobs:
         run: |
           git checkout master
           cargo bench --bench parse -- --save-baseline master-aarch64-${{ matrix.feature }}
-        env:
-          CARGO_CFG_HTTPARSE_DISABLE_SIMD: ${{ matrix.feature == 'swar' && '1' || '0' }}
-          RUSTFLAGS: ${{ matrix.feature == 'neon' && '-C target-feature=+neon' || '' }}
 
       - name: Run benchmarks (PR)
         run: |
           git checkout ${{ github.event.pull_request.head.sha }}
           cargo bench --bench parse -- --save-baseline pr-${{ github.event.pull_request.number }}-${{ github.event.pull_request.head.sha }}-aarch64-${{ matrix.feature }}
-        env:
-          CARGO_CFG_HTTPARSE_DISABLE_SIMD: ${{ matrix.feature == 'swar' && '1' || '0' }}
-          RUSTFLAGS: ${{ matrix.feature == 'neon' && '-C target-feature=+neon' || '' }}
 
       - name: Compare benchmarks
         run: |
diff --git a/Cargo.toml b/Cargo.toml
index 6cc7d42..7d60497 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,8 +9,8 @@ documentation = "https://docs.rs/httparse"
 readme = "README.md"
 keywords = ["http", "parser", "no_std"]
 categories = ["network-programming", "no-std", "parser-implementations", "web-programming"]
-edition = "2018"
-build = "build.rs"
+edition = "2021"
+rust-version = "1.59"
 
 [features]
 default = ["std"]
@@ -34,8 +34,5 @@ opt-level = 3
 
 [lints.rust]
 unexpected_cfgs = { level = "warn", check-cfg = [
-    'cfg(httparse_simd)',
-    'cfg(httparse_simd_target_feature_avx2)',
-    'cfg(httparse_simd_target_feature_sse42)',
-    'cfg(httparse_simd_neon_intrinsics)',
+    'cfg(httparse_disable_simd)',
 ] }
diff --git a/build.rs b/build.rs
deleted file mode 100644
index 6c45358..0000000
--- a/build.rs
+++ /dev/null
@@ -1,133 +0,0 @@
-use std::env;
-use std::ffi::OsString;
-use std::process::Command;
-
-fn main() {
-    // We check rustc version to enable features beyond MSRV, such as:
-    // - 1.59 => neon_intrinsics
-    let rustc = env::var_os("RUSTC").unwrap_or(OsString::from("rustc"));
-    let output = Command::new(rustc)
-        .arg("--version")
-        .output()
-        .expect("failed to check 'rustc --version'")
-        .stdout;
-
-    let raw_version = String::from_utf8(output)
-        .expect("rustc version output should be utf-8");
-    
-    let version = match Version::parse(&raw_version) {
-        Ok(version) => version,
-        Err(err) => {
-            println!("cargo:warning=failed to parse `rustc --version`: {}", err);
-            return;
-        }
-    };
-
-    enable_new_features(version);
-}
-
-fn enable_new_features(version: Version) {
-    enable_simd(version);
-}
-
-fn enable_simd(version: Version) {
-    if env::var_os("CARGO_FEATURE_STD").is_none() {
-        println!("cargo:warning=building for no_std disables httparse SIMD");
-        return;
-    }
-    if env::var_os("CARGO_CFG_MIRI").is_some() {
-        println!("cargo:warning=building for Miri disables httparse SIMD");
-        return;
-    }
-
-    let env_disable = "CARGO_CFG_HTTPARSE_DISABLE_SIMD";
-    if var_is(env_disable, "1") {
-        println!("cargo:warning=detected {} environment variable, disabling SIMD", env_disable);
-        return;
-    }
-
-    // 1.59.0 is the first version to support neon_intrinsics
-    if version >= Version(1, 59, 0) {
-        println!("cargo:rustc-cfg=httparse_simd_neon_intrinsics");
-    }
-
-    println!("cargo:rustc-cfg=httparse_simd");
-
-    // cfg(target_feature) isn't stable yet, but CARGO_CFG_TARGET_FEATURE has
-    // a list... We aren't doing anything unsafe, since the is_x86_feature_detected
-    // macro still checks in the actual lib, BUT!
-    //
-    // By peeking at the list here, we can change up slightly how we do feature
-    // detection in the lib. If our features aren't in the feature list, we
-    // stick with a cached runtime detection strategy.
-    //
-    // But if the features *are* in the list, we benefit from removing our cache,
-    // since the compiler will eliminate several branches with its internal
-    // cfg(target_feature) usage.
-
-
-    let env_runtime_only = "CARGO_CFG_HTTPARSE_DISABLE_SIMD_COMPILETIME";
-    if var_is(env_runtime_only, "1") {
-        println!("cargo:warning=detected {} environment variable, using runtime SIMD detection only", env_runtime_only);
-        return;
-    }
-    let feature_list = match env::var_os("CARGO_CFG_TARGET_FEATURE") {
-        Some(var) => match var.into_string() {
-            Ok(s) => s,
-            Err(_) => {
-                println!("cargo:warning=CARGO_CFG_TARGET_FEATURE was not valid utf-8");
-                return;
-            },
-        },
-        None => {
-            println!("cargo:warning=CARGO_CFG_TARGET_FEATURE was not set");
-            return
-        },
-    };
-    
-    let features = feature_list.split(',').map(|s| s.trim());
-    if features.clone().any(|f| f == "sse4.2") {
-        println!("cargo:rustc-cfg=httparse_simd_target_feature_sse42");
-    }
-    if features.clone().any(|f| f == "avx2") {
-        println!("cargo:rustc-cfg=httparse_simd_target_feature_avx2");
-    }
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, PartialOrd)]
-struct Version (u32, u32, u32);
-
-impl Version {
-    fn parse(s: &str) -> Result<Version, String> {
-        let s = match s.strip_prefix("rustc ") {
-            Some(s) => s,
-            None => return Err(format!("unrecognized version string: {}", s)),
-        };
-
-        let mut iter = s
-            .split('.')
-            .take(3)
-            .map(|s| match s.find(|c: char| !c.is_ascii_digit()) {
-                Some(end) => &s[..end],
-                None => s,
-            })
-            .map(|s| s.parse::<u32>().map_err(|e| e.to_string()));
-    
-        if iter.clone().count() != 3 {
-            return Err(format!("not enough version parts: {:?}", s));
-        }
-        
-        let major = iter.next().unwrap()?;
-        let minor = iter.next().unwrap()?;
-        let patch = iter.next().unwrap()?;
-
-        Ok(Version(major, minor, patch))
-    }
-}
-
-fn var_is(key: &str, val: &str) -> bool {
-    match env::var(key) {
-        Ok(v) => v == val,
-        Err(_) => false,
-    }
-}
diff --git a/clippy.toml b/clippy.toml
deleted file mode 100644
index 7846a3e..0000000
--- a/clippy.toml
+++ /dev/null
@@ -1 +0,0 @@
-msrv = "1.47"
diff --git a/src/macros.rs b/src/macros.rs
index 751f60b..50ab156 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -10,10 +10,10 @@ macro_rules! next {
 }
 
 macro_rules! expect {
-    ($bytes:ident.next() == $pat:pat => $ret:expr) => {
+    ($bytes:ident.next() == $pat:pat_param => $ret:expr) => {
         expect!(next!($bytes) => $pat |? $ret)
     };
-    ($e:expr => $pat:pat |? $ret:expr) => {
+    ($e:expr => $pat:pat_param |? $ret:expr) => {
         match $e {
             v@$pat => v,
             _ => return $ret
@@ -31,7 +31,7 @@ macro_rules! complete {
 }
 
 macro_rules! byte_map {
-    ($($p:pat)|+) => {{
+    ($($p:pat_param)|+) => {{
         const fn make_map() -> [bool; 256] {
             let mut ret = [false; 256];
             let mut i = 0;
diff --git a/src/simd/mod.rs b/src/simd/mod.rs
index 0e4493a..39e61ce 100644
--- a/src/simd/mod.rs
+++ b/src/simd/mod.rs
@@ -1,21 +1,24 @@
 mod swar;
 
-#[cfg(not(all(
-    httparse_simd,
-    any(
+#[cfg(any(
+    httparse_disable_simd,
+    miri,
+    not(feature = "std"),
+    not(any(
         target_arch = "x86",
         target_arch = "x86_64",
         all(
             target_arch = "aarch64",
-            httparse_simd_neon_intrinsics,
+            target_feature = "neon",
         )
-    ),
-)))]
+    ))
+))]
 pub use self::swar::*;
 
 #[cfg(all(
-    httparse_simd,
-    not(httparse_simd_target_feature_avx2),
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
+    not(target_feature = "avx2"),
     any(
         target_arch = "x86",
         target_arch = "x86_64",
@@ -24,10 +27,11 @@ pub use self::swar::*;
 mod sse42;
 
 #[cfg(all(
-    httparse_simd,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
     any(
-        httparse_simd_target_feature_avx2,
-        not(httparse_simd_target_feature_sse42),
+        target_feature = "avx2",
+        not(target_feature = "sse4.2"),
     ),
     any(
         target_arch = "x86",
@@ -37,10 +41,11 @@ mod sse42;
 mod avx2;
 
 #[cfg(all(
-    httparse_simd,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
     not(any(
-        httparse_simd_target_feature_sse42,
-        httparse_simd_target_feature_avx2,
+        target_feature = "sse4.2",
+        target_feature = "avx2",
     )),
     any(
         target_arch = "x86",
@@ -50,10 +55,11 @@ mod avx2;
 mod runtime;
 
 #[cfg(all(
-    httparse_simd,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
     not(any(
-        httparse_simd_target_feature_sse42,
-        httparse_simd_target_feature_avx2,
+        target_feature = "sse4.2",
+        target_feature = "avx2",
     )),
     any(
         target_arch = "x86",
@@ -63,9 +69,10 @@ mod runtime;
 pub use self::runtime::*;
 
 #[cfg(all(
-    httparse_simd,
-    httparse_simd_target_feature_sse42,
-    not(httparse_simd_target_feature_avx2),
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
+    target_feature = "sse4.2",
+    not(target_feature = "avx2"),
     any(
         target_arch = "x86",
         target_arch = "x86_64",
@@ -79,21 +86,20 @@ mod sse42_compile_time {
 
     #[inline(always)]
     pub fn match_uri_vectored(b: &mut crate::iter::Bytes<'_>) {
-        // SAFETY: calls are guarded by a compile time feature check
-        unsafe { crate::simd::sse42::match_uri_vectored(b) }
+        unsafe { super::sse42::match_uri_vectored(b) }
     }
-    
+
     #[inline(always)]
     pub fn match_header_value_vectored(b: &mut crate::iter::Bytes<'_>) {
-        // SAFETY: calls are guarded by a compile time feature check
-        unsafe { crate::simd::sse42::match_header_value_vectored(b) }
+        unsafe { super::sse42::match_header_value_vectored(b) }
     }
 }
 
 #[cfg(all(
-    httparse_simd,
-    httparse_simd_target_feature_sse42,
-    not(httparse_simd_target_feature_avx2),
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
+    target_feature = "sse4.2",
+    not(target_feature = "avx2"),
     any(
         target_arch = "x86",
         target_arch = "x86_64",
@@ -102,8 +108,9 @@ mod sse42_compile_time {
 pub use self::sse42_compile_time::*;
 
 #[cfg(all(
-    httparse_simd,
-    httparse_simd_target_feature_avx2,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
+    target_feature = "avx2",
     any(
         target_arch = "x86",
         target_arch = "x86_64",
@@ -117,20 +124,19 @@ mod avx2_compile_time {
 
     #[inline(always)]
     pub fn match_uri_vectored(b: &mut crate::iter::Bytes<'_>) {
-        // SAFETY: calls are guarded by a compile time feature check
-        unsafe { crate::simd::avx2::match_uri_vectored(b) }
+        unsafe { super::avx2::match_uri_vectored(b) }
     }
-    
+
     #[inline(always)]
     pub fn match_header_value_vectored(b: &mut crate::iter::Bytes<'_>) {
-        // SAFETY: calls are guarded by a compile time feature check
-        unsafe { crate::simd::avx2::match_header_value_vectored(b) }
+        unsafe { super::avx2::match_header_value_vectored(b) }
     }
 }
 
 #[cfg(all(
-    httparse_simd,
-    httparse_simd_target_feature_avx2,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
+    target_feature = "avx2",
     any(
         target_arch = "x86",
         target_arch = "x86_64",
@@ -139,15 +145,17 @@ mod avx2_compile_time {
 pub use self::avx2_compile_time::*;
 
 #[cfg(all(
-    httparse_simd,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
     target_arch = "aarch64",
-    httparse_simd_neon_intrinsics,
+    target_feature = "neon",
 ))]
 mod neon;
 
 #[cfg(all(
-    httparse_simd,
+    not(any(httparse_disable_simd, miri)),
+    feature = "std",
     target_arch = "aarch64",
-    httparse_simd_neon_intrinsics,
+    target_feature = "neon",
 ))]
 pub use self::neon::*;