diff --git a/ci/dox.sh b/ci/dox.sh
index e70a32b2db..3e507b4563 100755
--- a/ci/dox.sh
+++ b/ci/dox.sh
@@ -22,9 +22,6 @@ dox() {
   rm -rf "target/doc/${arch}"
   mkdir "target/doc/${arch}"
 
-  export RUSTFLAGS="--cfg core_arch_docs"
-  export RUSTDOCFLAGS="--cfg core_arch_docs"
-
   cargo build --verbose --target "${target}" --manifest-path crates/core_arch/Cargo.toml
   cargo build --verbose --target "${target}" --manifest-path crates/std_detect/Cargo.toml
 
@@ -32,16 +29,14 @@ dox() {
           -o "target/doc/${arch}" crates/core_arch/src/lib.rs \
           --edition=2018 \
           --crate-name core_arch \
-          --library-path "target/${target}/debug/deps" \
-          --cfg core_arch_docs
+          --library-path "target/${target}/debug/deps"
   rustdoc --verbose --target "${target}" \
           -o "target/doc/${arch}" crates/std_detect/src/lib.rs \
           --edition=2018 \
           --crate-name std_detect \
           --library-path "target/${target}/debug/deps" \
           --extern cfg_if="$(ls target/"${target}"/debug/deps/libcfg_if-*.rlib)" \
-          --extern libc="$(ls target/"${target}"/debug/deps/liblibc-*.rlib)" \
-          --cfg core_arch_docs
+          --extern libc="$(ls target/"${target}"/debug/deps/liblibc-*.rlib)"
 }
 
 dox i686 i686-unknown-linux-gnu
diff --git a/crates/core_arch/Cargo.toml b/crates/core_arch/Cargo.toml
index 14b5479d19..e2b332af2b 100644
--- a/crates/core_arch/Cargo.toml
+++ b/crates/core_arch/Cargo.toml
@@ -13,7 +13,6 @@ readme = "README.md"
 keywords = ["core", "simd", "arch", "intrinsics"]
 categories = ["hardware-support", "no-std"]
 license = "MIT OR Apache-2.0"
-build = "build.rs"
 edition = "2018"
 
 [badges]
diff --git a/crates/core_arch/build.rs b/crates/core_arch/build.rs
deleted file mode 100644
index 4d65e9ddc3..0000000000
--- a/crates/core_arch/build.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-fn main() {
-    println!("cargo:rustc-cfg=core_arch_docs");
-}
diff --git a/crates/core_arch/src/arm/v7.rs b/crates/core_arch/src/arm/v7.rs
index e7507f9b95..59beaf722b 100644
--- a/crates/core_arch/src/arm/v7.rs
+++ b/crates/core_arch/src/arm/v7.rs
@@ -76,7 +76,6 @@ mod tests {
     }
 
     #[test]
-    #[cfg(dont_compile_me)] // FIXME need to add `v7` upstream in rustc
     fn _rbit_u32() {
         unsafe {
             assert_eq!(