Switch default to new x86_64 backend.

.github/workflows/main.yml

@@ -286,7 +286,7 @@ jobs:
     # Test debug (DWARF) related functionality on new backend.
     - run: |
         sudo apt-get update && sudo apt-get install -y gdb lldb
-        cargo test --features experimental_x64 test_debug_dwarf -- --ignored --test-threads 1 --test debug::
+        cargo test test_debug_dwarf -- --ignored --test-threads 1 --test debug::
       if: matrix.os == 'ubuntu-latest'
       env:
         RUST_BACKTRACE: 1
@@ -309,10 +309,9 @@ jobs:
       env:
         RUST_BACKTRACE: 1
 
-  # Perform all tests (debug mode) for `wasmtime` with the experimental x64
-  # backend.
+  # Perform all tests (debug mode) for `wasmtime` with the old x86 backend.
   test_x64:
-    name: Test x64 new backend
+    name: Test old x86 backend
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v2
@@ -328,38 +327,8 @@ jobs:
     - run: rustup target add wasm32-wasi
     - run: rustup target add wasm32-unknown-unknown
 
-    # Run the x64 CI script.
-    - run: ./ci/run-experimental-x64-ci.sh
-      env:
-        RUST_BACKTRACE: 1
-
-  # Perform tests on the new x64 backend on Windows as well.
-  test_x64_win:
-    name: Test x64 new backend on Windows
-    runs-on: windows-latest
-    steps:
-    - uses: actions/checkout@v2
-      with:
-        submodules: true
-    - uses: ./.github/actions/install-rust
-    - uses: ./.github/actions/define-llvm-env
-
-    - name: Install libclang
-      # Note: libclang is pre-installed on the macOS and linux images.
-      if: matrix.os == 'windows-latest'
-      run: |
-        curl https://releases.llvm.org/9.0.0/LLVM-9.0.0-win64.exe -o llvm-installer.exe
-        7z x llvm-installer.exe -oC:/llvm-binary
-        echo LIBCLANG_PATH=C:/llvm-binary/bin/libclang.dll >> $GITHUB_ENV
-        echo C:/llvm-binary/bin >> $GITHUB_PATH
-
-    # 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 x64 CI script.
-    - run: ./ci/run-experimental-x64-ci.sh
+    # Run the old x86 backend CI (we will eventually remove this).
+    - run: ./ci/run-old-x86-ci.sh
       env:
         RUST_BACKTRACE: 1
 

Cargo.toml

@@ -93,9 +93,12 @@ wasi-nn = ["wasmtime-wasi-nn"]
 uffd = ["wasmtime/uffd"]
 all-arch = ["wasmtime/all-arch"]
 
-# Try the experimental, work-in-progress new x86_64 backend. This is not stable
-# as of June 2020.
-experimental_x64 = ["wasmtime-jit/experimental_x64"]
+# Stub feature that does nothing, for Cargo-features compatibility: the new
+# backend is the default now.
+experimental_x64 = []
+
+# Use the old x86 backend.
+old-x86-backend = ["wasmtime-jit/old-x86-backend"]
 
 [badges]
 maintenance = { status = "actively-developed" }

build.rs

@@ -155,11 +155,8 @@ fn write_testsuite_tests(
     let testname = extract_name(path);
 
     writeln!(out, "#[test]")?;
-    if experimental_x64_should_panic(testsuite, &testname, strategy) {
-        writeln!(
-            out,
-            r#"#[cfg_attr(feature = "experimental_x64", should_panic)]"#
-        )?;
+    if x64_should_panic(testsuite, &testname, strategy) {
+        writeln!(out, r#"#[should_panic]"#)?;
     } else if ignore(testsuite, &testname, strategy) {
         writeln!(out, "#[ignore]")?;
     } else if pooling {
@@ -186,10 +183,10 @@ fn write_testsuite_tests(
     Ok(())
 }
 
-/// For experimental_x64 backend features that are not supported yet, mark tests as panicking, so
+/// For x64 backend features that are not supported yet, mark tests as panicking, so
 /// they stop "passing" once the features are properly implemented.
-fn experimental_x64_should_panic(testsuite: &str, testname: &str, strategy: &str) -> bool {
-    if !cfg!(feature = "experimental_x64") || strategy != "Cranelift" {
+fn x64_should_panic(testsuite: &str, testname: &str, strategy: &str) -> bool {
+    if !platform_is_x64() || strategy != "Cranelift" {
         return false;
     }
 
@@ -222,12 +219,11 @@ fn ignore(testsuite: &str, testname: &str, strategy: &str) -> bool {
             _ => (),
         },
         "Cranelift" => match (testsuite, testname) {
-            // TODO(#1886): Ignore reference types tests if this isn't x64,
-            // because Cranelift only supports reference types on x64.
-            ("reference_types", _) => {
-                return env::var("CARGO_CFG_TARGET_ARCH").unwrap() != "x86_64";
+            ("simd", _) if cfg!(feature = "old-x86-backend") => return true, // skip all SIMD tests on old backend.
+            // These are only implemented on x64.
+            ("simd", "simd_i64x2_arith2") | ("simd", "simd_boolean") => {
+                return !platform_is_x64() || cfg!(feature = "old-x86-backend")
             }
-
             // These are new instructions that are not really implemented in any backend.
             ("simd", "simd_i8x16_arith2")
             | ("simd", "simd_conversions")
@@ -240,26 +236,14 @@ fn ignore(testsuite: &str, testname: &str, strategy: &str) -> bool {
             | ("simd", "simd_i64x2_extmul_i32x4")
             | ("simd", "simd_int_to_int_extend") => return true,
 
-            // These are only implemented on x64.
-            ("simd", "simd_i64x2_arith2") | ("simd", "simd_boolean") => {
-                return !cfg!(feature = "experimental_x64")
-            }
-
-            // These are only implemented on aarch64 and x64.
-            ("simd", "simd_i64x2_cmp")
-            | ("simd", "simd_f32x4_pmin_pmax")
-            | ("simd", "simd_f64x2_pmin_pmax")
-            | ("simd", "simd_f32x4_rounding")
-            | ("simd", "simd_f64x2_rounding")
-            | ("simd", "simd_i32x4_dot_i16x8") => {
-                return !(cfg!(feature = "experimental_x64")
-                    || env::var("CARGO_CFG_TARGET_ARCH").unwrap() == "aarch64")
-            }
-
             _ => {}
         },
         _ => panic!("unrecognized strategy"),
     }
 
     false
 }
+
+fn platform_is_x64() -> bool {
+    env::var("CARGO_CFG_TARGET_ARCH").unwrap() == "x86_64"
+}

ci/run-experimental-x64-ci.sh → ci/run-old-x86-ci.sh

@@ -3,7 +3,7 @@
 cargo test \
             --locked \
             --features test-programs/test_programs \
-            --features experimental_x64 \
+            --features old-x86-backend \
             --all \
             --exclude wasmtime-lightbeam \
             --exclude wasmtime-wasi-nn \

cranelift/Cargo.toml

@@ -50,7 +50,6 @@ default = ["disas", "wasm", "cranelift-codegen/all-arch", "peepmatic-souper", "s
 disas = ["capstone"]
 enable-peepmatic = ["cranelift-codegen/enable-peepmatic", "cranelift-filetests/enable-peepmatic"]
 wasm = ["wat", "cranelift-wasm"]
-experimental_x64 = ["cranelift-codegen/x64", "cranelift-filetests/experimental_x64", "cranelift-reader/experimental_x64"]
 experimental_arm32 = ["cranelift-codegen/arm32", "cranelift-filetests/experimental_arm32"]
 souper-harvest = ["cranelift-codegen/souper-harvest", "rayon"]
 all-arch = ["cranelift-codegen/all-arch"]

cranelift/codegen/Cargo.toml

@@ -63,9 +63,15 @@ unwind = ["gimli"]
 x86 = []
 arm64 = []
 riscv = []
-x64 = [] # New work-in-progress codegen backend for x86_64 based on the new isel.
 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",

cranelift/codegen/src/isa/mod.rs

@@ -74,16 +74,15 @@ use thiserror::Error;
 #[cfg(feature = "riscv")]
 mod riscv;
 
-// N.B.: the old x86-64 backend (`x86`) and the new one (`x64`) can both be
-// included; if the new backend is included, then it is the default backend
-// returned for an x86-64 triple, but a specific option can request the old
-// backend. It is important to have the ability to instantiate *both* backends
-// in the same build so that we can do things like differential fuzzing between
-// backends, or perhaps offer a runtime configuration flag in the future.
+// N.B.: the old x86-64 backend (`x86`) and the new one (`x64`) are both
+// included whenever building with x86 support. The new backend is the default,
+// but the old can be requested with `BackendVariant::Legacy`. However, if this
+// crate is built with the `old-x86-backend` feature, then the old backend is
+// default instead.
 #[cfg(feature = "x86")]
 mod x86;
 
-#[cfg(feature = "x64")]
+#[cfg(feature = "x86")]
 mod x64;
 
 #[cfg(feature = "arm32")]
@@ -122,7 +121,7 @@ macro_rules! isa_builder {
 /// The "variant" for a given target. On one platform (x86-64), we have two
 /// backends, the "old" and "new" one; the new one is the default if included
 /// in the build configuration and not otherwise specified.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Debug)]
 pub enum BackendVariant {
     /// Any backend available.
     Any,
@@ -149,13 +148,13 @@ pub fn lookup_variant(triple: Triple, variant: BackendVariant) -> Result<Builder
             isa_builder!(x86, (feature = "x86"), triple)
         }
         (Architecture::X86_64, BackendVariant::MachInst) => {
-            isa_builder!(x64, (feature = "x64"), triple)
+            isa_builder!(x64, (feature = "x86"), triple)
         }
-        #[cfg(feature = "x64")]
+        #[cfg(not(feature = "old-x86-backend"))]
         (Architecture::X86_64, BackendVariant::Any) => {
-            isa_builder!(x64, (feature = "x64"), triple)
+            isa_builder!(x64, (feature = "x86"), triple)
         }
-        #[cfg(not(feature = "x64"))]
+        #[cfg(feature = "old-x86-backend")]
         (Architecture::X86_64, BackendVariant::Any) => {
             isa_builder!(x86, (feature = "x86"), triple)
         }
@@ -277,7 +276,13 @@ pub trait TargetIsa: fmt::Display + Send + Sync {
     /// Get the ISA-dependent flag values that were used to make this trait object.
     fn isa_flags(&self) -> Vec<settings::Value>;
 
-    /// Hashes all flags, both ISA-independent and ISA-dependent, into the specified hasher.
+    /// Get the variant of this ISA (Legacy or MachInst).
+    fn variant(&self) -> BackendVariant {
+        BackendVariant::Legacy
+    }
+
+    /// Hashes all flags, both ISA-independent and ISA-specific, into the
+    /// specified hasher.
     fn hash_all_flags(&self, hasher: &mut dyn Hasher);
 
     /// Get the default calling convention of this target.

cranelift/codegen/src/isa/unwind/winx64.rs

@@ -8,9 +8,7 @@ use log::warn;
 #[cfg(feature = "enable-serde")]
 use serde::{Deserialize, Serialize};
 
-#[cfg(feature = "x64")]
 use crate::binemit::CodeOffset;
-#[cfg(feature = "x64")]
 use crate::isa::unwind::UnwindInst;
 
 /// Maximum (inclusive) size of a "small" stack allocation
@@ -334,10 +332,8 @@ impl UnwindInfo {
     }
 }
 
-#[cfg(feature = "x64")]
 const UNWIND_RBP_REG: u8 = 5;
 
-#[cfg(feature = "x64")]
 pub(crate) fn create_unwind_info_from_insts<MR: RegisterMapper<regalloc::Reg>>(
     insts: &[(CodeOffset, UnwindInst)],
 ) -> CodegenResult<UnwindInfo> {

cranelift/codegen/src/isa/x64/inst/unwind/systemv.rs

@@ -109,6 +109,7 @@ mod tests {
     use target_lexicon::triple;
 
     #[test]
+    #[cfg_attr(feature = "old-x86-backend", ignore)]
     fn test_simple_func() {
         let isa = lookup(triple!("x86_64"))
             .expect("expect x86 ISA")
@@ -151,6 +152,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg_attr(feature = "old-x86-backend", ignore)]
     fn test_multi_return_func() {
         let isa = lookup(triple!("x86_64"))
             .expect("expect x86 ISA")

cranelift/codegen/src/machinst/adapter.rs

@@ -2,7 +2,9 @@
 
 use crate::binemit;
 use crate::ir;
-use crate::isa::{EncInfo, Encoding, Encodings, Legalize, RegClass, RegInfo, TargetIsa};
+use crate::isa::{
+    BackendVariant, EncInfo, Encoding, Encodings, Legalize, RegClass, RegInfo, TargetIsa,
+};
 use crate::machinst::*;
 use crate::regalloc::RegisterSet;
 use crate::settings::{self, Flags};
@@ -62,6 +64,10 @@ impl TargetIsa for TargetIsaAdapter {
         self.backend.isa_flags()
     }
 
+    fn variant(&self) -> BackendVariant {
+        BackendVariant::MachInst
+    }
+
     fn hash_all_flags(&self, hasher: &mut dyn Hasher) {
         self.backend.hash_all_flags(hasher);
     }

cranelift/filetests/Cargo.toml

@@ -30,4 +30,3 @@ anyhow = "1.0.32"
 [features]
 enable-peepmatic = []
 experimental_arm32 = []
-experimental_x64 = []

cranelift/filetests/filetests/isa/x64/amode-opt.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %amode_add(i64, i64) -> i64 {
 block0(v0: i64, v1: i64):

cranelift/filetests/filetests/isa/x64/b1.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %f0(b1, i32, i32) -> i32 {
 ; check:  pushq   %rbp

cranelift/filetests/filetests/isa/x64/basic.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %f(i32, i32) -> i32 {
 block0(v0: i32, v1: i32):

cranelift/filetests/filetests/isa/x64/bitops-i128-run.clif

@@ -1,6 +1,5 @@
 test run
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %ctz(i64, i64) -> i8 {
 block0(v0: i64, v1: i64):

cranelift/filetests/filetests/isa/x64/bitrev-i128-run.clif

@@ -1,6 +1,5 @@
 test run
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %reverse_bits_zero() -> b1 {
 block0:

cranelift/filetests/filetests/isa/x64/branches.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %f0(i32, i32) -> i32 {
 block0(v0: i32, v1: i32):

cranelift/filetests/filetests/isa/x64/clz-lzcnt.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64 has_lzcnt
-feature "experimental_x64"
+target x86_64 machinst has_lzcnt
 
 function %clz(i64) -> i64 {
 block0(v0: i64):

cranelift/filetests/filetests/isa/x64/cmp-mem-bug.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %f0(i64, i64) -> i64, i64 {
 block0(v0: i64, v1: i64):

cranelift/filetests/filetests/isa/x64/ctz-bmi1.clif

@@ -1,6 +1,5 @@
 test compile
-target x86_64 has_bmi1
-feature "experimental_x64"
+target x86_64 machinst has_bmi1
 
 function %ctz(i64) -> i64 {
 block0(v0: i64):

cranelift/filetests/filetests/isa/x64/div-checks-run.clif

@@ -1,7 +1,6 @@
 test run
 set avoid_div_traps=false
-target x86_64
-feature "experimental_x64"
+target x86_64 machinst
 
 function %f0(i32, i32) -> i32 {
 block0(v0: i32, v1: i32):