diff --git a/Cargo.toml b/Cargo.toml
index 33d5c06b..49e6d253 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -83,3 +83,12 @@ panic = 'abort'
 
 [profile.dev]
 panic = 'abort'
+
+[lints.rust]
+# Values used during testing
+unexpected_cfgs = { level = "warn", check-cfg = [
+  'cfg(feature, values("arch"))',
+  'cfg(feature, values("force-soft-floats"))',
+  'cfg(feature, values("unstable-float"))',
+  'cfg(feature, values("unstable-intrinsics"))',
+] }
diff --git a/build.rs b/build.rs
index 22ec9e4d..6e44207a 100644
--- a/build.rs
+++ b/build.rs
@@ -14,12 +14,9 @@ fn main() {
     configure_check_cfg();
     configure_f16_f128(&target);
 
-    println!("cargo:compiler-rt={}", cwd.join("compiler-rt").display());
+    configure_libm(&target);
 
-    // Activate libm's unstable features to make full use of Nightly.
-    println!("cargo::rustc-check-cfg=cfg(feature, values(\"unstable\", \"force-soft-floats\"))");
-    println!("cargo:rustc-cfg=feature=\"unstable\"");
-    println!("cargo:rustc-cfg=feature=\"force-soft-floats\"");
+    println!("cargo:compiler-rt={}", cwd.join("compiler-rt").display());
 
     // Emscripten's runtime includes all the builtins
     if target.os == "emscripten" {
@@ -104,6 +101,47 @@ fn main() {
     }
 }
 
+/// Run configuration for `libm` since it is included directly.
+///
+/// Much of this is copied from `libm/configure.rs`.
+fn configure_libm(target: &Target) {
+    println!("cargo:rustc-cfg=intrinsics_enabled");
+    println!("cargo:rustc-cfg=arch_enabled");
+    println!("cargo:rustc-cfg=optimizations_enabled");
+
+    // Always use intrinsics
+    println!("cargo:rustc-cfg=intrinsics_enabled");
+
+    //
+    if cfg!(feature = "no-asm") {
+        println!("cargo:rustc-cfg=feature=\"force-soft-floats\"");
+    } else {
+        println!("cargo:rustc-cfg=arch_enabled");
+    }
+
+    println!("cargo:rustc-check-cfg=cfg(optimizations_enabled)");
+    if target.opt_level >= 2 {
+        println!("cargo:rustc-cfg=optimizations_enabled");
+    }
+
+    // Config shorthands
+    println!("cargo:rustc-check-cfg=cfg(x86_no_sse)");
+    if target.arch == "x86" && !target.features.iter().any(|f| f == "sse") {
+        // Shorthand to detect i586 targets
+        println!("cargo:rustc-cfg=x86_no_sse");
+    }
+
+    println!(
+        "cargo:rustc-env=CFG_CARGO_FEATURES={:?}",
+        target.cargo_features
+    );
+    println!("cargo:rustc-env=CFG_OPT_LEVEL={}", target.opt_level);
+    println!("cargo:rustc-env=CFG_TARGET_FEATURES={:?}", target.features);
+
+    // Activate libm's unstable features to make full use of Nightly.
+    println!("cargo:rustc-cfg=feature=\"unstable-intrinsics\"");
+}
+
 fn aarch64_symbol(ordering: Ordering) -> &'static str {
     match ordering {
         Ordering::Relaxed => "relax",
diff --git a/configure.rs b/configure.rs
index e20c717e..6cfbe11c 100644
--- a/configure.rs
+++ b/configure.rs
@@ -6,6 +6,8 @@ use std::env;
 #[allow(dead_code)]
 pub struct Target {
     pub triple: String,
+    pub opt_level: u8,
+    pub cargo_features: Vec<String>,
     pub os: String,
     pub arch: String,
     pub vendor: String,
@@ -22,10 +24,16 @@ impl Target {
             "big" => false,
             x => panic!("unknown endian {x}"),
         };
+        let cargo_features = env::vars()
+            .filter_map(|(name, _value)| name.strip_prefix("CARGO_FEATURE_").map(ToOwned::to_owned))
+            .map(|s| s.to_lowercase().replace("_", "-"))
+            .collect();
 
         Self {
             triple: env::var("TARGET").unwrap(),
             os: env::var("CARGO_CFG_TARGET_OS").unwrap(),
+            opt_level: env::var("OPT_LEVEL").unwrap().parse().unwrap(),
+            cargo_features,
             arch: env::var("CARGO_CFG_TARGET_ARCH").unwrap(),
             vendor: env::var("CARGO_CFG_TARGET_VENDOR").unwrap(),
             env: env::var("CARGO_CFG_TARGET_ENV").unwrap(),
diff --git a/libm b/libm
index f4e5b38a..9d043c56 160000
--- a/libm
+++ b/libm
@@ -1 +1 @@
-Subproject commit f4e5b38aee0e0c592a82ed45b21cd068c9b6c89a
+Subproject commit 9d043c563e213661e87ff87a746bd98f39e81b7a
diff --git a/src/math.rs b/src/math.rs
index 477dfe36..da208239 100644
--- a/src/math.rs
+++ b/src/math.rs
@@ -1,3 +1,4 @@
+#[rustfmt::skip]
 #[allow(dead_code)]
 #[allow(unused_imports)]
 #[allow(clippy::all)]