WebAssembly runtime support

.cargo/config.toml

@@ -0,0 +1,2 @@
+[target.wasm32-unknown-unknown]
+runner = "wasmtime run"

.dockerignore

@@ -0,0 +1,8 @@
+.git*
+target/
+
+*.lock
+*.md
+*.txt
+.dockerignore
+Dockerfile*

Dockerfile.test

@@ -0,0 +1,10 @@
+FROM rustlang/rust:nightly
+
+RUN rustup target add wasm32-unknown-unknown && \
+    cargo install wasmtime-cli
+
+WORKDIR /app
+COPY . .
+
+RUN cargo test
+RUN cargo test --target wasm32-unknown-unknown

src/barriers.rs

@@ -157,6 +157,7 @@
 #[inline(always)]
 pub fn optimization_barrier_u8(mut value: u8) -> u8 {
     unsafe {
+        #[cfg(not(target_arch = "wasm32"))]
         std::arch::asm!(
             // Rust requires us to use every register defined, so we use it inside of a comment.
             "/* optimization_barrier_u8 {unused} */",
@@ -169,6 +170,14 @@ pub fn optimization_barrier_u8(mut value: u8) -> u8 {
             // Since the assembly block is a no-op, we easily uphold all of these invariants.
             options(pure, nomem, nostack, preserves_flags)
         );
+
+        // WebAssembly only supports local class
+        #[cfg(target_arch = "wasm32")]
+        std::arch::asm!(
+            "/* optimization_barrier_u8 {unused} */",
+            unused = inout(local) value,
+            options(pure, nomem, nostack, preserves_flags)
+        );
     }
 
     value

src/lib.rs

@@ -21,6 +21,7 @@
 //! page](https://www.chosenplaintext.ca/open-source/rust-timing-shield/getting-started) for more
 //! information.
 
+#![cfg_attr(target_arch = "wasm32", feature(asm_experimental_arch))]
 #[cfg(test)]
 extern crate quickcheck;