Remove the lightbeam backend (#3390)

This commit removes the Lightbeam backend from Wasmtime as per [RFC 14].
This backend hasn't received maintenance in quite some time, and as [RFC
14] indicates this doesn't meet the threshold for keeping the code
in-tree, so this commit removes it.

A fast "baseline" compiler may still be added in the future. The
addition of such a backend should be in line with [RFC 14], though, with
the principles we now have for stable releases of Wasmtime. I'll close
out Lightbeam-related issues once this is merged.

[RFC 14]: bytecodealliance/rfcs#14

.github/workflows/main.yml

@@ -131,7 +131,6 @@ jobs:
     # Check some feature combinations of the `wasmtime` crate
     - run: cargo check -p wasmtime --no-default-features
     - run: cargo check -p wasmtime --no-default-features --features wat
-    - run: cargo check -p wasmtime --no-default-features --features lightbeam
     - run: cargo check -p wasmtime --no-default-features --features jitdump
     - run: cargo check -p wasmtime --no-default-features --features vtune
     - run: cargo check -p wasmtime --no-default-features --features cache
@@ -307,7 +306,7 @@ jobs:
         RUST_BACKTRACE: 1
       if: matrix.target == ''
 
-    # Build and test all features except for lightbeam
+    # Build and test all features
     - run: ./ci/run-tests.sh --locked
       env:
         RUST_BACKTRACE: 1
@@ -329,16 +328,6 @@ jobs:
       env:
         RUST_BACKTRACE: 1
 
-    # Build and test lightbeam. Note that
-    # Lightbeam tests fail right now, but we don't want to block on that.
-    - run: cargo build --package lightbeam
-      if: matrix.target != 'aarch64-unknown-linux-gnu' && matrix.target != 's390x-unknown-linux-gnu'
-    - run: cargo test --package lightbeam
-      if: matrix.target != 'aarch64-unknown-linux-gnu' && matrix.target != 's390x-unknown-linux-gnu'
-      continue-on-error: true
-      env:
-        RUST_BACKTRACE: 1
-
   # Perform all tests (debug mode) for `wasmtime` with the old x86 backend.
   test_x86:
     name: Test old x86 backend

Cargo.toml

@@ -75,21 +75,19 @@ members = [
   "cranelift",
   "crates/bench-api",
   "crates/c-api",
-  "crates/lightbeam/wasmtime",
   "crates/misc/run-examples",
   "examples/fib-debug/wasm",
   "examples/wasi/wasm",
   "examples/tokio/wasm",
   "fuzz",
 ]
 exclude = [
-  'crates/wasi-common/WASI/tools/witx-cli', 
+  'crates/wasi-common/WASI/tools/witx-cli',
   'docs/rust_wasi_markdown_parser'
   ]
 
 [features]
 default = ["jitdump", "wasmtime/wat", "wasmtime/parallel-compilation", "wasi-nn"]
-lightbeam = ["wasmtime/lightbeam"]
 jitdump = ["wasmtime/jitdump"]
 vtune = ["wasmtime/vtune"]
 wasi-crypto = ["wasmtime-wasi-crypto"]

README.md

@@ -70,8 +70,8 @@ Hello, world!
   quickly generate high-quality machine code at runtime.
 
 * **Configurable**. Whether you need to precompile your wasm ahead of time,
-  generate code blazingly fast with Lightbeam, or interpret it at runtime,
-  Wasmtime has you covered for all your wasm-executing needs.
+  or interpret it at runtime, Wasmtime has you covered for all your
+  wasm-executing needs.
 
 * **WASI**. Wasmtime supports a rich set of APIs for interacting with the host
   environment through the [WASI standard](https://wasi.dev).

build.rs

@@ -17,11 +17,7 @@ fn main() -> anyhow::Result<()> {
     );
     let mut out = String::new();
 
-    for strategy in &[
-        "Cranelift",
-        #[cfg(feature = "lightbeam")]
-        "Lightbeam",
-    ] {
+    for strategy in &["Cranelift"] {
         writeln!(out, "#[cfg(test)]")?;
         writeln!(out, "#[allow(non_snake_case)]")?;
         writeln!(out, "mod {} {{", strategy)?;
@@ -185,14 +181,6 @@ fn write_testsuite_tests(
 /// Ignore tests that aren't supported yet.
 fn ignore(testsuite: &str, testname: &str, strategy: &str) -> bool {
     match strategy {
-        #[cfg(feature = "lightbeam")]
-        "Lightbeam" => match (testsuite, testname) {
-            ("simd", _) => return true,
-            ("multi_value", _) => return true,
-            ("reference_types", _) => return true,
-            ("bulk_memory_operations", _) => return true,
-            _ => (),
-        },
         "Cranelift" => match (testsuite, testname) {
             // Skip all reference types tests on the old backend. The modern
             // implementation of reference types uses atomic instructions

ci/run-tests.sh

@@ -3,7 +3,6 @@
 cargo test \
     --features "test-programs/test_programs" \
     --workspace \
-    --exclude '*lightbeam*' \
     --exclude 'wasmtime-wasi-*' \
     --exclude 'peepmatic*' \
     --exclude wasi-crypto \

cranelift/codegen/src/isa/x64/inst/emit_tests.rs

@@ -8,8 +8,8 @@
 //!
 //! cd to the top of your wasmtime tree, then:
 //! RUST_BACKTRACE=1 cargo test --features test-programs/test_programs \
-//!   --features experimental_x64 --all --exclude peepmatic --exclude lightbeam \
-//!   --exclude wasmtime-lightbeam --exclude peepmatic-automata --exclude peepmatic-fuzzing \
+//!   --features experimental_x64 --all --exclude peepmatic \
+//!   --exclude peepmatic-automata --exclude peepmatic-fuzzing \
 //!   --exclude peepmatic-macro --exclude wasmtime-wasi-nn -- isa::x64::inst::emit_tests::test_x64_emit
 
 use super::*;

crates/c-api/Cargo.toml

@@ -34,7 +34,6 @@ cap-std = { version = "0.19.1", optional = true }
 
 [features]
 default = ['jitdump', 'wat', 'wasi', 'cache']
-lightbeam = ["wasmtime/lightbeam"]
 jitdump = ["wasmtime/jitdump"]
 cache = ["wasmtime/cache"]
 wasi = ['wasi-common', 'wasi-cap-std-sync', 'wasmtime-wasi', 'cap-std']

crates/c-api/include/wasmtime/config.h

@@ -26,19 +26,13 @@ typedef uint8_t wasmtime_strategy_t;
  * The default value is #WASMTIME_STRATEGY_AUTO.
  */
 enum wasmtime_strategy_enum { // Strategy
-  /// Wasmtime will automatically determine whether to use Cranelift or
-  /// Lightbeam, and currently it will always pick Cranelift. This default may
-  /// change over time though.
+  /// Automatically picks the compilation backend, currently always defaulting
+  /// to Cranelift.
   WASMTIME_STRATEGY_AUTO,
 
-  /// Indicates that Cranelift will unconditionally use Cranelift to compile
+  /// Indicates that Wasmtime will unconditionally use Cranelift to compile
   /// WebAssembly code.
   WASMTIME_STRATEGY_CRANELIFT,
-
-  /// Indicates that Cranelift will unconditionally use Lightbeam to compile
-  /// WebAssembly code. Note that Lightbeam isn't always enabled at compile
-  /// time, and if that's the case an error will be returned.
-  WASMTIME_STRATEGY_LIGHTBEAM,
 };
 
 /**

crates/c-api/src/config.rs

@@ -20,7 +20,6 @@ wasmtime_c_api_macros::declare_own!(wasm_config_t);
 pub enum wasmtime_strategy_t {
     WASMTIME_STRATEGY_AUTO,
     WASMTIME_STRATEGY_CRANELIFT,
-    WASMTIME_STRATEGY_LIGHTBEAM,
 }
 
 #[repr(u8)]
@@ -114,7 +113,6 @@ pub extern "C" fn wasmtime_config_strategy_set(
     let result = c.config.strategy(match strategy {
         WASMTIME_STRATEGY_AUTO => Strategy::Auto,
         WASMTIME_STRATEGY_CRANELIFT => Strategy::Cranelift,
-        WASMTIME_STRATEGY_LIGHTBEAM => Strategy::Lightbeam,
     });
     handle_result(result, |_cfg| {})
 }