Introduce the wasmtime-explorer crate (#5975)

This implements Godbolt Compiler Explorer-like functionality for Wasmtime and
Cranelift. Given a Wasm module, it compiles the module to native code and then
writes a standalone HTML file that gives a split pane view between the WAT and
ASM disassemblies.

src/bin/wasmtime.rs

@@ -6,7 +6,7 @@
 use anyhow::Result;
 use clap::{ErrorKind, Parser};
 use wasmtime_cli::commands::{
-    CompileCommand, ConfigCommand, RunCommand, SettingsCommand, WastCommand,
+    CompileCommand, ConfigCommand, ExploreCommand, RunCommand, SettingsCommand, WastCommand,
 };
 
 /// Wasmtime WebAssembly Runtime
@@ -35,6 +35,8 @@ enum Wasmtime {
     Config(ConfigCommand),
     /// Compiles a WebAssembly module.
     Compile(CompileCommand),
+    /// Explore the compilation of a WebAssembly module to native code.
+    Explore(ExploreCommand),
     /// Runs a WebAssembly module
     Run(RunCommand),
     /// Displays available Cranelift settings for a target.
@@ -49,6 +51,7 @@ impl Wasmtime {
         match self {
             Self::Config(c) => c.execute(),
             Self::Compile(c) => c.execute(),
+            Self::Explore(c) => c.execute(),
             Self::Run(c) => c.execute(),
             Self::Settings(c) => c.execute(),
             Self::Wast(c) => c.execute(),

src/commands.rs

@@ -2,8 +2,9 @@
 
 mod compile;
 mod config;
+mod explore;
 mod run;
 mod settings;
 mod wast;
 
-pub use self::{compile::*, config::*, run::*, settings::*, wast::*};
+pub use self::{compile::*, config::*, explore::*, run::*, settings::*, wast::*};

src/commands/explore.rs

@@ -0,0 +1,51 @@
+//! The module that implements the `wasmtime explore` command.
+
+use anyhow::{Context, Result};
+use clap::Parser;
+use std::path::PathBuf;
+use wasmtime_cli_flags::CommonOptions;
+
+/// Explore the compilation of a WebAssembly module to native code.
+#[derive(Parser)]
+#[clap(name = "explore")]
+pub struct ExploreCommand {
+    #[clap(flatten)]
+    common: CommonOptions,
+
+    /// The target triple; default is the host triple
+    #[clap(long, value_name = "TARGET")]
+    target: Option<String>,
+
+    /// The path of the WebAssembly module to compile
+    #[clap(required = true, value_name = "MODULE")]
+    module: PathBuf,
+
+    /// The path of the explorer output (derived from the MODULE name if none
+    /// provided)
+    #[clap(short, long)]
+    output: Option<PathBuf>,
+}
+
+impl ExploreCommand {
+    /// Executes the command.
+    pub fn execute(&self) -> Result<()> {
+        self.common.init_logging();
+
+        let config = self.common.config(self.target.as_deref())?;
+
+        let wasm = std::fs::read(&self.module)
+            .with_context(|| format!("failed to read Wasm module: {}", self.module.display()))?;
+
+        let output = self
+            .output
+            .clone()
+            .unwrap_or_else(|| self.module.with_extension("explore.html"));
+        let output_file = std::fs::File::create(&output)
+            .with_context(|| format!("failed to create file: {}", output.display()))?;
+        let mut output_file = std::io::BufWriter::new(output_file);
+
+        wasmtime_explorer::generate(&config, self.target.as_deref(), &wasm, &mut output_file)?;
+        println!("Exploration written to {}", output.display());
+        Ok(())
+    }
+}