Adding an --emit-opt-clif CLI option

crates/cranelift/src/builder.rs

@@ -21,6 +21,7 @@ struct Builder {
     linkopts: LinkOptions,
     cache_store: Option<Arc<dyn CacheStore>>,
     clif_dir: Option<path::PathBuf>,
+    opt_clif_dir: Option<path::PathBuf>,
     wmemcheck: bool,
 }
 
@@ -44,6 +45,7 @@ pub fn builder(triple: Option<Triple>) -> Result<Box<dyn CompilerBuilder>> {
         linkopts: LinkOptions::default(),
         cache_store: None,
         clif_dir: None,
+        opt_clif_dir: None,
         wmemcheck: false,
     }))
 }
@@ -58,6 +60,11 @@ impl CompilerBuilder for Builder {
         Ok(())
     }
 
+    fn opt_clif_dir(&mut self, path: &path::Path) -> Result<()> {
+        self.opt_clif_dir = Some(path.to_path_buf());
+        Ok(())
+    }
+
     fn target(&mut self, target: target_lexicon::Triple) -> Result<()> {
         self.inner.target(target)?;
         Ok(())
@@ -97,6 +104,7 @@ impl CompilerBuilder for Builder {
             self.cache_store.clone(),
             self.linkopts.clone(),
             self.clif_dir.clone(),
+            self.opt_clif_dir.clone(),
             self.wmemcheck,
         )))
     }

crates/cranelift/src/compiler.rs

@@ -1,3 +1,4 @@
+use crate::compiler::path::PathBuf;
 use crate::debug::DwarfSectionRelocTarget;
 use crate::func_environ::FuncEnvironment;
 use crate::DEBUG_ASSERT_TRAP_CODE;
@@ -69,6 +70,7 @@ pub struct Compiler {
     linkopts: LinkOptions,
     cache_store: Option<Arc<dyn CacheStore>>,
     clif_dir: Option<path::PathBuf>,
+    opt_clif_dir: Option<path::PathBuf>,
     wmemcheck: bool,
 }
 
@@ -107,6 +109,7 @@ impl Compiler {
         cache_store: Option<Arc<dyn CacheStore>>,
         linkopts: LinkOptions,
         clif_dir: Option<path::PathBuf>,
+        opt_clif_dir: Option<path::PathBuf>,
         wmemcheck: bool,
     ) -> Compiler {
         Compiler {
@@ -116,6 +119,7 @@ impl Compiler {
             linkopts,
             cache_store,
             clif_dir,
+            opt_clif_dir,
             wmemcheck,
         }
     }
@@ -228,7 +232,11 @@ impl wasmtime_environ::Compiler for Compiler {
             write!(output, "{}", context.func.display()).unwrap();
         }
 
-        let (info, func) = compiler.finish_with_info(Some((&body, &self.tunables)))?;
+        let (info, func) = compiler.finish_with_info(
+            Some((&body, &self.tunables)),
+            &self.opt_clif_dir,
+            func_index.as_u32(),
+        )?;
 
         let timing = cranelift_codegen::timing::take_current();
         log::debug!("{:?} translated in {:?}", func_index, timing.total());
@@ -799,21 +807,34 @@ impl FunctionCompiler<'_> {
     }
 
     fn finish(self) -> Result<CompiledFunction, CompileError> {
-        let (info, func) = self.finish_with_info(None)?;
+        let (info, func) = self.finish_with_info(None, &None, 0)?;
         assert!(info.stack_maps.is_empty());
         Ok(func)
     }
 
     fn finish_with_info(
         mut self,
         body_and_tunables: Option<(&FunctionBody<'_>, &Tunables)>,
+        opt_clif_dir: &Option<PathBuf>,
+        func_index: u32,
     ) -> Result<(WasmFunctionInfo, CompiledFunction), CompileError> {
         let context = &mut self.cx.codegen_context;
         let isa = &*self.compiler.isa;
         let (_, _code_buf) =
             compile_maybe_cached(context, isa, self.cx.incremental_cache_ctx.as_mut())?;
         let mut compiled_code = context.take_compiled_code().unwrap();
 
+        if let Some(path) = opt_clif_dir {
+            use std::io::Write;
+
+            let mut path = path.to_path_buf();
+            path.push(format!("wasm_func_{func_index}"));
+            path.set_extension("clif");
+
+            let mut output = std::fs::File::create(path).unwrap();
+            write!(output, "{}", context.func.display()).unwrap();
+        }
+
         // Give wasm functions, user defined code, a "preferred" alignment
         // instead of the minimum alignment as this can help perf in niche
         // situations.

crates/environ/src/compile/mod.rs

@@ -111,6 +111,11 @@ pub trait CompilerBuilder: Send + Sync + fmt::Debug {
         anyhow::bail!("clif output not supported");
     }
 
+    /// Enables optimized clif output in the directory specified.
+    fn opt_clif_dir(&mut self, _path: &path::Path) -> Result<()> {
+        anyhow::bail!("optimized clif output not supported");
+    }
+
     /// Returns the currently configured target triple that compilation will
     /// produce artifacts for.
     fn triple(&self) -> &target_lexicon::Triple;

crates/wasmtime/src/config.rs

@@ -163,6 +163,7 @@ struct CompilerConfig {
     #[cfg(all(feature = "incremental-cache", feature = "cranelift"))]
     cache_store: Option<Arc<dyn CacheStore>>,
     clif_dir: Option<std::path::PathBuf>,
+    opt_clif_dir: Option<std::path::PathBuf>,
     wmemcheck: bool,
 }
 
@@ -177,6 +178,7 @@ impl CompilerConfig {
             #[cfg(all(feature = "incremental-cache", feature = "cranelift"))]
             cache_store: None,
             clif_dir: None,
+            opt_clif_dir: None,
             wmemcheck: false,
         }
     }
@@ -1897,6 +1899,10 @@ impl Config {
             compiler.clif_dir(path)?;
         }
 
+        if let Some(path) = &self.compiler_config.opt_clif_dir {
+            compiler.opt_clif_dir(path)?;
+        }
+
         // If probestack is enabled for a target, Wasmtime will always use the
         // inline strategy which doesn't require us to define a `__probestack`
         // function or similar.
@@ -1999,6 +2005,13 @@ impl Config {
         self
     }
 
+    /// Enables optimized clif output when compiling a WebAssembly module.
+    #[cfg(any(feature = "cranelift", feature = "winch"))]
+    pub fn emit_opt_clif(&mut self, path: &Path) -> &mut Self {
+        self.compiler_config.opt_clif_dir = Some(path.to_path_buf());
+        self
+    }
+
     /// Configures whether, when on macOS, Mach ports are used for exception
     /// handling instead of traditional Unix-based signal handling.
     ///

src/commands/compile.rs

@@ -51,6 +51,10 @@ pub struct CompileCommand {
     #[arg(long = "emit-clif", value_name = "PATH")]
     pub emit_clif: Option<PathBuf>,
 
+    /// The directory path to write optimized clif files into, one clif file per wasm function.
+    #[arg(long = "emit-opt-clif", value_name = "PATH")]
+    pub emit_opt_clif: Option<PathBuf>,
+
     /// The path of the WebAssembly to compile
     #[arg(index = 1, value_name = "MODULE")]
     pub module: PathBuf,
@@ -78,6 +82,21 @@ impl CompileCommand {
             config.emit_clif(&path);
         }
 
+        if let Some(path) = self.emit_opt_clif {
+            if !path.exists() {
+                std::fs::create_dir(&path)?;
+            }
+
+            if !path.is_dir() {
+                bail!(
+                    "the path passed for '--emit-opt-clif' ({}) must be a directory",
+                    path.display()
+                );
+            }
+
+            config.emit_opt_clif(&path);
+        }
+
         let engine = Engine::new(&config)?;
 
         if self.module.file_name().is_none() {