Show function names in explore tool instead of only function indices (#8639)

* Implement runtime::Module::function_locations_with_names()

Map the iterator returned by Module::function_locations() to another
one that returns a 3-tuple containing the function name, the offset,
and the length of each function defined in this particular module.

* Show function names in "explore" instead of just the indices

* Address review: Change iterator format

* Address review: use the new iterator struct

* Address review comments

Cargo.lock

@@ -3683,6 +3683,7 @@ dependencies = [
  "target-lexicon",
  "wasmprinter",
  "wasmtime",
+ "wasmtime-environ",
 ]
 
 [[package]]

crates/explorer/Cargo.toml

@@ -20,3 +20,4 @@ serde_json = { workspace = true }
 target-lexicon = { workspace = true, features = ['std'] }
 wasmprinter = { workspace = true }
 wasmtime = { workspace = true, features = ["cranelift", "runtime"] }
+wasmtime-environ = { workspace = true }

crates/explorer/src/index.js

@@ -191,12 +191,16 @@ const renderInst = (mnemonic, operands) => {
 
 // Render the ASM.
 
-let nthFunc = 0;
 for (const func of state.asm.functions) {
   const funcElem = document.createElement("div");
 
   const funcHeader = document.createElement("h3");
-  funcHeader.textContent = `Defined Function ${nthFunc}`;
+  let func_name =
+    func.name === null ? `function[${func.func_index}]` : func.name;
+  let demangled_name =
+    func.demangled_name !== null ? func.demangled_name : func_name;
+  funcHeader.textContent = `Disassembly of function <${demangled_name}>:`;
+  funcHeader.title = `Function ${func.func_index}: ${func_name}`;
   funcElem.appendChild(funcHeader);
 
   const bodyElem = document.createElement("pre");
@@ -216,7 +220,6 @@ for (const func of state.asm.functions) {
   funcElem.appendChild(bodyElem);
 
   asmElem.appendChild(funcElem);
-  nthFunc++;
 }
 
 // Render the WAT.

crates/explorer/src/lib.rs

@@ -2,6 +2,7 @@ use anyhow::Result;
 use capstone::arch::BuildsCapstone;
 use serde_derive::Serialize;
 use std::{io::Write, str::FromStr};
+use wasmtime_environ::demangle_function_name;
 
 pub fn generate(
     config: &wasmtime::Config,
@@ -83,6 +84,9 @@ struct AnnotatedAsm {
 
 #[derive(Serialize, Debug)]
 struct AnnotatedFunction {
+    func_index: u32,
+    name: Option<String>,
+    demangled_name: Option<String>,
     instructions: Vec<AnnotatedInstruction>,
 }
 
@@ -129,10 +133,9 @@ fn annotate_asm(
     };
 
     let functions = module
-        .function_locations()
-        .into_iter()
-        .map(|(start, len)| {
-            let body = &text[start..][..len];
+        .functions()
+        .map(|function| {
+            let body = &text[function.offset..][..function.len];
 
             let mut cs = match target.architecture {
                 target_lexicon::Architecture::Aarch64(_) => capstone::Capstone::new()
@@ -165,13 +168,13 @@ fn annotate_asm(
             cs.set_skipdata(true).unwrap();
 
             let instructions = cs
-                .disasm_all(body, start as u64)
+                .disasm_all(body, function.offset as u64)
                 .map_err(|e| anyhow::anyhow!("{e}"))?;
             let instructions = instructions
                 .iter()
                 .map(|inst| {
                     let address = u32::try_from(inst.address()).unwrap();
-                    let wasm_offset = wasm_offset_for_address(start, address);
+                    let wasm_offset = wasm_offset_for_address(function.offset, address);
                     Ok(AnnotatedInstruction {
                         wasm_offset,
                         address,
@@ -181,7 +184,24 @@ fn annotate_asm(
                     })
                 })
                 .collect::<Result<Vec<_>>>()?;
-            Ok(AnnotatedFunction { instructions })
+
+            let demangled_name = if let Some(name) = &function.name {
+                let mut demangled = String::new();
+                if demangle_function_name(&mut demangled, &name).is_ok() {
+                    Some(demangled)
+                } else {
+                    None
+                }
+            } else {
+                None
+            };
+
+            Ok(AnnotatedFunction {
+                func_index: function.index.as_u32(),
+                name: function.name,
+                demangled_name,
+                instructions,
+            })
         })
         .collect::<Result<Vec<_>>>()?;
 

crates/wasmtime/src/runtime/module.rs

@@ -1017,13 +1017,21 @@ impl Module {
         self.code_object().code_memory().text()
     }
 
-    /// Get the locations of functions in this module's `.text` section.
-    ///
-    /// Each function's location is a (`.text` section offset, length) pair.
-    pub fn function_locations<'a>(&'a self) -> impl ExactSizeIterator<Item = (usize, usize)> + 'a {
-        self.compiled_module().finished_functions().map(|(f, _)| {
-            let loc = self.compiled_module().func_loc(f);
-            (loc.start as usize, loc.length as usize)
+    /// Get information about functions in this module's `.text` section: their
+    /// index, name, and offset+length.
+    ///
+    /// Results are yielded in a ModuleFunction struct.
+    pub fn functions<'a>(&'a self) -> impl ExactSizeIterator<Item = ModuleFunction> + 'a {
+        let module = self.compiled_module();
+        module.finished_functions().map(|(idx, _)| {
+            let loc = module.func_loc(idx);
+            let idx = module.module().func_index(idx);
+            ModuleFunction {
+                index: idx,
+                name: module.func_name(idx).map(|n| n.to_string()),
+                offset: loc.start as usize,
+                len: loc.length as usize,
+            }
         })
     }
 
@@ -1032,6 +1040,14 @@ impl Module {
     }
 }
 
+/// Describes a function for a given module.
+pub struct ModuleFunction {
+    pub index: wasmtime_environ::FuncIndex,
+    pub name: Option<String>,
+    pub offset: usize,
+    pub len: usize,
+}
+
 impl ModuleInner {
     fn memory_images(&self) -> Result<Option<&ModuleMemoryImages>> {
         let images = self