diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 724d858a3..0051f5f5e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -86,6 +86,19 @@ jobs:
       - name: dependency tree check
         run: ./ci/dependencies.sh
 
+  # When this job failed, run ci/no_atomic_cas.sh and commit result changes.
+  # TODO(taiki-e): Ideally, this should be automated using a bot that creates
+  #                PR when failed, but there is no bandwidth to implement it
+  #                right now...
+  codegen:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update nightly && rustup default nightly
+      - run: ci/no_atomic_cas.sh
+      - run: git diff --exit-code
+
   # Check formatting.
   rustfmt:
     name: rustfmt
@@ -93,7 +106,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install Rust
-        run: rustup update stable && rustup default stable
+        run: rustup update stable
       - name: rustfmt
         run: ./ci/rustfmt.sh
 
@@ -104,7 +117,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install Rust
-        run: rustup update stable && rustup default stable
+        run: rustup update stable
       - name: clippy
         run: ./ci/clippy.sh
 
@@ -126,7 +139,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Install Rust
-        run: rustup update stable && rustup default stable
+        run: rustup update stable
       - name: loom
         run: ./ci/crossbeam-epoch-loom.sh
 
@@ -154,6 +167,7 @@ jobs:
       - test
       - features
       - dependencies
+      - codegen
       - rustfmt
       - clippy
       - san
diff --git a/Cargo.toml b/Cargo.toml
index 4389b7931..1a490e5ee 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -36,8 +36,9 @@ alloc = ["crossbeam-epoch/alloc", "crossbeam-queue/alloc"]
 
 # Enable to use of unstable functionality.
 # This is disabled by default and requires recent nightly compiler.
-# Note that this is outside of the normal semver guarantees and minor versions
-# of crossbeam may make breaking changes to them at any time.
+#
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 nightly = ["crossbeam-epoch/nightly", "crossbeam-utils/nightly", "crossbeam-queue/nightly"]
 
 [dependencies]
diff --git a/build.rs b/build.rs
new file mode 100644
index 000000000..ad7715cf1
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic_cas.rs");
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let target = match env::var("TARGET") {
+        Ok(target) => target,
+        Err(e) => {
+            println!(
+                "cargo:warning={}: unable to get TARGET environment variable: {}",
+                env!("CARGO_PKG_NAME"),
+                e
+            );
+            return;
+        }
+    };
+
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
+    if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
+        println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+    }
+
+    println!("cargo:rerun-if-changed=no_atomic_cas.rs");
+}
diff --git a/ci/check-features.sh b/ci/check-features.sh
index 1eeddc520..c6901d0b7 100755
--- a/ci/check-features.sh
+++ b/ci/check-features.sh
@@ -22,7 +22,5 @@ else
     rustup target add thumbv7m-none-eabi
     rustup target add thumbv6m-none-eabi
     cargo hack check --all --feature-powerset --no-dev-deps --exclude benchmarks --target thumbv7m-none-eabi --skip std,default
-    # * `--features nightly` is required for enable `cfg_target_has_atomic`.
-    # * `--ignore-unknown-features` - some crates doesn't have 'nightly' feature
-    cargo hack check --all --feature-powerset --no-dev-deps --exclude benchmarks --target thumbv6m-none-eabi --skip std,default --features nightly --ignore-unknown-features
+    cargo hack check --all --feature-powerset --no-dev-deps --exclude benchmarks --target thumbv6m-none-eabi --skip std,default
 fi
diff --git a/ci/no_atomic_cas.sh b/ci/no_atomic_cas.sh
new file mode 100755
index 000000000..40b2f1b90
--- /dev/null
+++ b/ci/no_atomic_cas.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# Update the list of targets that do not support atomic CAS operations.
+#
+# Usage:
+#    ./ci/no_atomic_cas.sh
+
+set -euo pipefail
+IFS=$'\n\t'
+
+cd "$(cd "$(dirname "$0")" && pwd)"/..
+
+file="no_atomic_cas.rs"
+
+{
+    echo "// This file is @generated by $(basename "$0")."
+    echo "// It is not intended for manual editing."
+    echo ""
+    echo "const NO_ATOMIC_CAS_TARGETS: &[&str] = &["
+} >"$file"
+
+for target in $(rustc --print target-list); do
+    res=$(rustc --print target-spec-json -Z unstable-options --target "$target" \
+        | jq -r "select(.\"atomic-cas\" == false)")
+    [[ -z "$res" ]] || echo "    \"$target\"," >>"$file"
+done
+
+echo "];" >>"$file"
diff --git a/crossbeam-channel/Cargo.toml b/crossbeam-channel/Cargo.toml
index 0e048a262..c2812fef4 100644
--- a/crossbeam-channel/Cargo.toml
+++ b/crossbeam-channel/Cargo.toml
@@ -20,6 +20,8 @@ default = ["std"]
 
 # Enable to use APIs that require `std`.
 # This is enabled by default.
+#
+# NOTE: Disabling `std` feature is not supported yet.
 std = ["crossbeam-utils/std"]
 
 [dependencies]
diff --git a/crossbeam-deque/Cargo.toml b/crossbeam-deque/Cargo.toml
index 55e22351b..cba710e74 100644
--- a/crossbeam-deque/Cargo.toml
+++ b/crossbeam-deque/Cargo.toml
@@ -20,6 +20,8 @@ default = ["std"]
 
 # Enable to use APIs that require `std`.
 # This is enabled by default.
+#
+# NOTE: Disabling `std` feature is not supported yet.
 std = ["crossbeam-epoch/std", "crossbeam-utils/std"]
 
 [dependencies]
diff --git a/crossbeam-epoch/Cargo.toml b/crossbeam-epoch/Cargo.toml
index de70ebb87..18154259b 100644
--- a/crossbeam-epoch/Cargo.toml
+++ b/crossbeam-epoch/Cargo.toml
@@ -24,18 +24,21 @@ std = ["alloc", "crossbeam-utils/std", "lazy_static"]
 
 # Enable to use APIs that require `alloc`.
 # This is enabled by default and also enabled if the `std` feature is enabled.
+#
+# NOTE: Disabling both `std` *and* `alloc` features is not supported yet.
 alloc = []
 
 # Enable to use of unstable functionality.
 # This is disabled by default and requires recent nightly compiler.
-# Note that this is outside of the normal semver guarantees and minor versions
-# of crossbeam may make breaking changes to them at any time.
+#
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 nightly = ["crossbeam-utils/nightly", "const_fn"]
 
 # Enable the use of loom for concurrency testing.
 #
-# This configuration option is outside of the normal semver guarantees: minor
-# versions of crossbeam may make breaking changes to it at any time.
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 loom = ["loom-crate", "crossbeam-utils/loom"]
 
 [dependencies]
@@ -45,8 +48,8 @@ memoffset = "0.6"
 
 # Enable the use of loom for concurrency testing.
 #
-# This configuration option is outside of the normal semver guarantees: minor
-# versions of crossbeam may make breaking changes to it at any time.
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 [target.'cfg(crossbeam_loom)'.dependencies]
 loom-crate = { package = "loom", version = "0.5", optional = true }
 
diff --git a/crossbeam-epoch/build.rs b/crossbeam-epoch/build.rs
new file mode 100644
index 000000000..ad7715cf1
--- /dev/null
+++ b/crossbeam-epoch/build.rs
@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic_cas.rs");
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let target = match env::var("TARGET") {
+        Ok(target) => target,
+        Err(e) => {
+            println!(
+                "cargo:warning={}: unable to get TARGET environment variable: {}",
+                env!("CARGO_PKG_NAME"),
+                e
+            );
+            return;
+        }
+    };
+
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
+    if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
+        println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+    }
+
+    println!("cargo:rerun-if-changed=no_atomic_cas.rs");
+}
diff --git a/crossbeam-epoch/no_atomic_cas.rs b/crossbeam-epoch/no_atomic_cas.rs
new file mode 120000
index 000000000..3d7380fad
--- /dev/null
+++ b/crossbeam-epoch/no_atomic_cas.rs
@@ -0,0 +1 @@
+../no_atomic_cas.rs
\ No newline at end of file
diff --git a/crossbeam-epoch/src/lib.rs b/crossbeam-epoch/src/lib.rs
index 81b6b37c9..8dfd5104a 100644
--- a/crossbeam-epoch/src/lib.rs
+++ b/crossbeam-epoch/src/lib.rs
@@ -62,7 +62,6 @@
     unreachable_pub
 )]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "nightly", feature(cfg_target_has_atomic))]
 #![cfg_attr(feature = "nightly", feature(const_fn_trait_bound))]
 
 #[cfg(crossbeam_loom)]
@@ -143,7 +142,7 @@ mod primitive {
             pub(crate) use core::sync::atomic::fence;
             pub(crate) use core::sync::atomic::AtomicUsize;
         }
-        #[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+        #[cfg(not(crossbeam_no_atomic_cas))]
         pub(crate) use alloc::sync::Arc;
     }
 
@@ -154,7 +153,7 @@ mod primitive {
     pub(crate) use lazy_static::lazy_static;
 }
 
-#[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+#[cfg(not(crossbeam_no_atomic_cas))]
 cfg_if! {
     if #[cfg(feature = "alloc")] {
         extern crate alloc;
diff --git a/crossbeam-queue/Cargo.toml b/crossbeam-queue/Cargo.toml
index 622536eb8..b79778d83 100644
--- a/crossbeam-queue/Cargo.toml
+++ b/crossbeam-queue/Cargo.toml
@@ -24,12 +24,17 @@ std = ["alloc", "crossbeam-utils/std"]
 
 # Enable to use APIs that require `alloc`.
 # This is enabled by default and also enabled if the `std` feature is enabled.
+#
+# NOTE: Disabling both `std` *and* `alloc` features is not supported yet.
 alloc = []
 
+# These features are no longer used.
+# TODO: remove in the next major version.
 # Enable to use of unstable functionality.
 # This is disabled by default and requires recent nightly compiler.
-# Note that this is outside of the normal semver guarantees and minor versions
-# of crossbeam may make breaking changes to them at any time.
+#
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 nightly = ["crossbeam-utils/nightly"]
 
 [dependencies]
diff --git a/crossbeam-queue/build.rs b/crossbeam-queue/build.rs
new file mode 100644
index 000000000..ad7715cf1
--- /dev/null
+++ b/crossbeam-queue/build.rs
@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic_cas.rs");
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let target = match env::var("TARGET") {
+        Ok(target) => target,
+        Err(e) => {
+            println!(
+                "cargo:warning={}: unable to get TARGET environment variable: {}",
+                env!("CARGO_PKG_NAME"),
+                e
+            );
+            return;
+        }
+    };
+
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
+    if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
+        println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+    }
+
+    println!("cargo:rerun-if-changed=no_atomic_cas.rs");
+}
diff --git a/crossbeam-queue/no_atomic_cas.rs b/crossbeam-queue/no_atomic_cas.rs
new file mode 120000
index 000000000..3d7380fad
--- /dev/null
+++ b/crossbeam-queue/no_atomic_cas.rs
@@ -0,0 +1 @@
+../no_atomic_cas.rs
\ No newline at end of file
diff --git a/crossbeam-queue/src/lib.rs b/crossbeam-queue/src/lib.rs
index cba6416f6..846d7c2e1 100644
--- a/crossbeam-queue/src/lib.rs
+++ b/crossbeam-queue/src/lib.rs
@@ -19,9 +19,8 @@
     unreachable_pub
 )]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "nightly", feature(cfg_target_has_atomic))]
 
-#[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+#[cfg(not(crossbeam_no_atomic_cas))]
 cfg_if::cfg_if! {
     if #[cfg(feature = "alloc")] {
         extern crate alloc;
diff --git a/crossbeam-skiplist/Cargo.toml b/crossbeam-skiplist/Cargo.toml
index f6c46efaa..beae558d9 100644
--- a/crossbeam-skiplist/Cargo.toml
+++ b/crossbeam-skiplist/Cargo.toml
@@ -24,14 +24,10 @@ std = ["alloc", "crossbeam-epoch/std", "crossbeam-utils/std"]
 
 # Enable to use APIs that require `alloc`.
 # This is enabled by default and also enabled if the `std` feature is enabled.
+#
+# NOTE: Disabling both `std` *and* `alloc` features is not supported yet.
 alloc = ["crossbeam-epoch/alloc"]
 
-# Enable to use of unstable functionality.
-# This is disabled by default and requires recent nightly compiler.
-# Note that this is outside of the normal semver guarantees and minor versions
-# of crossbeam may make breaking changes to them at any time.
-nightly = ["crossbeam-epoch/nightly", "crossbeam-utils/nightly"]
-
 [dependencies]
 cfg-if = "1"
 
diff --git a/crossbeam-skiplist/build.rs b/crossbeam-skiplist/build.rs
new file mode 100644
index 000000000..ad7715cf1
--- /dev/null
+++ b/crossbeam-skiplist/build.rs
@@ -0,0 +1,32 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
+include!("no_atomic_cas.rs");
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let target = match env::var("TARGET") {
+        Ok(target) => target,
+        Err(e) => {
+            println!(
+                "cargo:warning={}: unable to get TARGET environment variable: {}",
+                env!("CARGO_PKG_NAME"),
+                e
+            );
+            return;
+        }
+    };
+
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
+    if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
+        println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+    }
+
+    println!("cargo:rerun-if-changed=no_atomic_cas.rs");
+}
diff --git a/crossbeam-skiplist/no_atomic_cas.rs b/crossbeam-skiplist/no_atomic_cas.rs
new file mode 120000
index 000000000..3d7380fad
--- /dev/null
+++ b/crossbeam-skiplist/no_atomic_cas.rs
@@ -0,0 +1 @@
+../no_atomic_cas.rs
\ No newline at end of file
diff --git a/crossbeam-skiplist/src/lib.rs b/crossbeam-skiplist/src/lib.rs
index 13988fa32..cb5f0462d 100644
--- a/crossbeam-skiplist/src/lib.rs
+++ b/crossbeam-skiplist/src/lib.rs
@@ -242,11 +242,10 @@
     unreachable_pub
 )]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "nightly", feature(cfg_target_has_atomic))]
 
 use cfg_if::cfg_if;
 
-#[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+#[cfg(not(crossbeam_no_atomic_cas))]
 cfg_if! {
     if #[cfg(feature = "alloc")] {
         extern crate alloc;
diff --git a/crossbeam-utils/Cargo.toml b/crossbeam-utils/Cargo.toml
index 4962b7141..212671e59 100644
--- a/crossbeam-utils/Cargo.toml
+++ b/crossbeam-utils/Cargo.toml
@@ -22,10 +22,13 @@ default = ["std"]
 # This is enabled by default.
 std = ["lazy_static"]
 
+# These features are no longer used.
+# TODO: remove in the next major version.
 # Enable to use of unstable functionality.
 # This is disabled by default and requires recent nightly compiler.
-# Note that this is outside of the normal semver guarantees and minor versions
-# of crossbeam may make breaking changes to them at any time.
+#
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 nightly = []
 
 [dependencies]
@@ -34,8 +37,8 @@ lazy_static = { version = "1.4.0", optional = true }
 
 # Enable the use of loom for concurrency testing.
 #
-# This configuration option is outside of the normal semver guarantees: minor
-# versions of crossbeam may make breaking changes to it at any time.
+# NOTE: This feature is outside of the normal semver guarantees and minor or
+# patch versions of crossbeam may make breaking changes to them at any time.
 [target.'cfg(crossbeam_loom)'.dependencies]
 loom = { version = "0.5", optional = true }
 
diff --git a/crossbeam-utils/build.rs b/crossbeam-utils/build.rs
index 3e5102183..a2d5d2b86 100644
--- a/crossbeam-utils/build.rs
+++ b/crossbeam-utils/build.rs
@@ -1,9 +1,35 @@
+#![warn(rust_2018_idioms)]
+
+use std::env;
+
 use autocfg::AutoCfg;
 
+include!("no_atomic_cas.rs");
+
 // The rustc-cfg strings below are *not* public API. Please let us know by
 // opening a GitHub issue if your build environment requires some way to enable
 // these cfgs other than by executing our build script.
 fn main() {
+    let target = match env::var("TARGET") {
+        Ok(target) => target,
+        Err(e) => {
+            println!(
+                "cargo:warning={}: unable to get TARGET environment variable: {}",
+                env!("CARGO_PKG_NAME"),
+                e
+            );
+            return;
+        }
+    };
+
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
+    if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
+        println!("cargo:rustc-cfg=crossbeam_no_atomic_cas");
+    }
+
     let cfg = match AutoCfg::new() {
         Ok(cfg) => cfg,
         Err(e) => {
diff --git a/crossbeam-utils/no_atomic_cas.rs b/crossbeam-utils/no_atomic_cas.rs
new file mode 120000
index 000000000..3d7380fad
--- /dev/null
+++ b/crossbeam-utils/no_atomic_cas.rs
@@ -0,0 +1 @@
+../no_atomic_cas.rs
\ No newline at end of file
diff --git a/crossbeam-utils/src/lib.rs b/crossbeam-utils/src/lib.rs
index 880d37ec6..a533af257 100644
--- a/crossbeam-utils/src/lib.rs
+++ b/crossbeam-utils/src/lib.rs
@@ -38,7 +38,6 @@
     unreachable_pub
 )]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "nightly", feature(cfg_target_has_atomic))]
 
 #[cfg(crossbeam_loom)]
 #[allow(unused_imports)]
@@ -94,7 +93,7 @@ cfg_if! {
     }
 }
 
-#[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+#[cfg(not(crossbeam_no_atomic_cas))]
 pub mod atomic;
 
 mod cache_padded;
diff --git a/no_atomic_cas.rs b/no_atomic_cas.rs
new file mode 100644
index 000000000..0819af1a4
--- /dev/null
+++ b/no_atomic_cas.rs
@@ -0,0 +1,11 @@
+// This file is @generated by no_atomic_cas.sh.
+// It is not intended for manual editing.
+
+const NO_ATOMIC_CAS_TARGETS: &[&str] = &[
+    "avr-unknown-gnu-atmega328",
+    "msp430-none-elf",
+    "riscv32i-unknown-none-elf",
+    "riscv32imc-unknown-none-elf",
+    "thumbv4t-none-eabi",
+    "thumbv6m-none-eabi",
+];
diff --git a/src/lib.rs b/src/lib.rs
index 9d7d37416..6fbf4a051 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -52,9 +52,8 @@
     unreachable_pub
 )]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "nightly", feature(cfg_target_has_atomic))]
 
-#[cfg_attr(feature = "nightly", cfg(target_has_atomic = "ptr"))]
+#[cfg(not(crossbeam_no_atomic_cas))]
 pub use crossbeam_utils::atomic;
 
 pub mod utils {