[RFC] Remove the old x86 backend

.github/workflows/main.yml

@@ -328,28 +328,6 @@ jobs:
       env:
         RUST_BACKTRACE: 1
 
-  # Perform all tests (debug mode) for `wasmtime` with the old x86 backend.
-  test_x86:
-    name: Test old x86 backend
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v2
-      with:
-        submodules: true
-    - uses: ./.github/actions/install-rust
-      with:
-        toolchain: stable
-
-    # Install wasm32 targets in order to build various tests throughout the
-    # repo.
-    - run: rustup target add wasm32-wasi
-    - run: rustup target add wasm32-unknown-unknown
-
-    # Run the old x86 backend CI (we will eventually remove this).
-    - run: ./ci/run-tests.sh --features old-x86-backend --locked
-      env:
-        RUST_BACKTRACE: 1
-
   # Build and test the wasi-nn module.
   test_wasi_nn:
     name: Test wasi-nn module

Cargo.toml

@@ -100,9 +100,6 @@ posix-signals-on-macos = ["wasmtime/posix-signals-on-macos"]
 # backend is the default now.
 experimental_x64 = []
 
-# Use the old x86 backend.
-old-x86-backend = ["wasmtime/old-x86-backend"]
-
 [badges]
 maintenance = { status = "actively-developed" }
 

build.rs

@@ -182,11 +182,6 @@ fn write_testsuite_tests(
 fn ignore(testsuite: &str, testname: &str, strategy: &str) -> bool {
     match strategy {
         "Cranelift" => match (testsuite, testname) {
-            // Skip all reference types tests on the old backend. The modern
-            // implementation of reference types uses atomic instructions
-            // for reference counts on `externref`, but the old backend does not
-            // implement atomic instructions.
-            ("reference_types", _) if cfg!(feature = "old-x86-backend") => return true,
             // No simd support yet for s390x.
             ("simd", _) if platform_is_s390x() => return true,
             // No memory64 support yet for s390x.

cranelift/codegen/Cargo.toml

@@ -63,22 +63,17 @@ unwind = ["gimli"]
 # If no ISA targets are explicitly enabled, the ISA target for the host machine is enabled.
 x86 = []
 arm64 = []
-riscv = []
 s390x = []
 arm32 = [] # Work-in-progress codegen backend for ARM.
 
 # Stub feature that does nothing, for Cargo-features compatibility: the new
 # backend is the default now.
 experimental_x64 = []
 
-# Make the old x86 backend the default.
-old-x86-backend = []
-
 # Option to enable all architectures.
 all-arch = [
     "x86",
     "arm64",
-    "riscv",
     "s390x"
 ]