Use portable-atomic instead of atomic-polyfill (google#123)

crates/interpreter/CHANGELOG.md

@@ -4,7 +4,7 @@
 
 ### Minor
 
-- Use `atomic-polyfill` to support RV32IMC
+- Use `portable-atomic` to support RV32IMC
 
 ### Patch
 

crates/interpreter/Cargo.toml

@@ -12,11 +12,11 @@ keywords = ["embedded", "framework", "no-std", "wasm"]
 categories = ["embedded", "no-std", "wasm"]
 
 [dependencies]
-atomic-polyfill = "1.0.2"
 libm = { version = "0.2.6", optional = true }
 lru = { version = "0.10.0", optional = true }
 num_enum = { version = "0.6.0", default-features = false }
 paste = "1.0.12"
+portable-atomic = { version = "1.2.0", default-features = false }
 
 [dev-dependencies]
 lazy_static = "1.4.0"

crates/interpreter/src/id.rs

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use atomic_polyfill::{AtomicUsize, Ordering};
+use portable_atomic::{AtomicUsize, Ordering};
 
 /// Returns numbers from 1 to u32::MAX (inclusive).
 pub struct UniqueId {

crates/interpreter/src/lib.rs

@@ -89,6 +89,20 @@
 //! }
 //! # }
 //! ```
+//!
+//! # Atomic support
+//!
+//! This crate uses atomic operations and relies on the `portable-atomic` crate to support
+//! architectures without atomic operations. Depending on your architecture, you may need one of the
+//! following:
+//!
+//! - Enable the `portable-atomic/critical-section` feature (possibly adding a direct dependency on
+//! `portable-atomic`).
+//!
+//! - Set the `--cfg=portable_atomic_unsafe_assume_single_core` rustc flag.
+//!
+//! You can find more information in the `portable-atomic`
+//! [documentation](https://docs.rs/portable-atomic/latest/portable_atomic).
 
 #![cfg_attr(not(feature = "debug"), no_std)]
 #![cfg_attr(not(feature = "toctou"), feature(slice_split_at_unchecked))]

crates/interpreter/test.sh

@@ -17,7 +17,10 @@ set -ex
 
 cargo check
 cargo check --target=thumbv7em-none-eabi
-cargo check --target=riscv32imc-unknown-none-elf
+cargo check --target=riscv32imc-unknown-none-elf \
+  --features=portable-atomic/critical-section
+RUSTFLAGS=--cfg=portable_atomic_unsafe_assume_single_core \
+  cargo check --target=riscv32imc-unknown-none-elf
 cargo fmt -- --check
 cargo clippy -- --deny=warnings
 [ -e ../../third_party/WebAssembly/spec/.git ] || git submodule update --init