Add regalloc3 as an option for Cranelift's register allocator

Author: Amanieu

Cargo.lock

@@ -611,3 +611,6 @@ debug = "line-tables-only"
 inherits = "release"
 codegen-units = 1
 lto = true
+
+[patch.crates-io]
+regalloc2 = { git = "https://github.com/Amanieu/regalloc2.git", branch = "regalloc3" }

Cargo.toml

@@ -43,7 +43,7 @@ pub(crate) fn define() -> SettingGroup {
             have adequate support for the kinds of allocations required by exception
             handling (https://github.com/bytecodealliance/regalloc2/issues/217).
         "#,
-        vec!["backtracking"],
+        vec!["backtracking", "regalloc3"],
     );
 
     settings.add_enum(

cranelift/codegen/meta/src/shared/settings.rs

@@ -66,6 +66,7 @@ pub fn compile<B: LowerBackend + TargetIsa>(
 
         options.algorithm = match b.flags().regalloc_algorithm() {
             RegallocAlgorithm::Backtracking => Algorithm::Ion,
+            RegallocAlgorithm::Regalloc3 => Algorithm::Regalloc3,
             // Note: single-pass is currently disabled
             // (https://github.com/bytecodealliance/regalloc2/issues/217).
         };

cranelift/codegen/src/machinst/compile.rs

@@ -482,6 +482,7 @@ impl WasmtimeOptionValue for wasmtime::RegallocAlgorithm {
     fn parse(val: Option<&str>) -> Result<Self> {
         match String::parse(val)?.as_str() {
             "backtracking" => Ok(wasmtime::RegallocAlgorithm::Backtracking),
+            "regalloc3" => Ok(wasmtime::RegallocAlgorithm::Regalloc3),
             other => bail!(
                 "unknown regalloc algorithm`{}`, only backtracking,single-pass accepted",
                 other

crates/cli-flags/src/opt.rs

@@ -1296,6 +1296,7 @@ impl Config {
     pub fn cranelift_regalloc_algorithm(&mut self, algo: RegallocAlgorithm) -> &mut Self {
         let val = match algo {
             RegallocAlgorithm::Backtracking => "backtracking",
+            RegallocAlgorithm::Regalloc3 => "regalloc3",
         };
         self.compiler_config
             .settings
@@ -2874,6 +2875,9 @@ pub enum RegallocAlgorithm {
     /// results in better register utilization, producing fewer spills
     /// and moves, but can cause super-linear compile runtime.
     Backtracking,
+
+    /// New experimental register allocator.
+    Regalloc3,
 }
 
 /// Select which profiling technique to support.