the revive-explorer utility (#364)

A maintainable and more precise version of what was a hacky but useful
script, exploring the compilers YUL lowering unit.

It analyzes a given shared objects from the debug dump and outputs:
- The count of each YUL statement translated.
- A per YUL statement break-down of bytecode size contributed per.
- Estimated `yul-phaser` cost parameters.

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/explorer/src/dwarfdump.rs

@@ -0,0 +1,59 @@
+//! The `llvm-dwarfdump` utility helper library.
+
+use std::{
+    path::{Path, PathBuf},
+    process::{Command, Stdio},
+};
+
+pub static EXECUTABLE: &str = "llvm-dwarfdump";
+pub static DEBUG_LINES_ARGUMENTS: [&str; 1] = ["--debug-line"];
+pub static SOURCE_FILE_ARGUMENTS: [&str; 1] = ["--show-sources"];
+
+/// Calls the `llvm-dwarfdump` tool to extract debug line information
+/// from the shared object at `path`. Returns the output.
+///
+/// Provide `Some(dwarfdump_exectuable)` to override the default executable.
+pub fn debug_lines(
+    shared_object: &Path,
+    dwarfdump_executable: &Option<PathBuf>,
+) -> anyhow::Result<String> {
+    dwarfdump(shared_object, dwarfdump_executable, &DEBUG_LINES_ARGUMENTS)
+}
+
+/// Calls the `llvm-dwarfdump` tool to extract the source file name.
+/// Returns the source file path.
+///
+/// Provide `Some(dwarfdump_exectuable)` to override the default executable.
+pub fn source_file(
+    shared_object: &Path,
+    dwarfdump_executable: &Option<PathBuf>,
+) -> anyhow::Result<PathBuf> {
+    let output = dwarfdump(shared_object, dwarfdump_executable, &SOURCE_FILE_ARGUMENTS)?;
+    Ok(output.trim().into())
+}
+
+/// The internal `llvm-dwarfdump` helper function.
+fn dwarfdump(
+    shared_object: &Path,
+    dwarfdump_executable: &Option<PathBuf>,
+    arguments: &[&str],
+) -> anyhow::Result<String> {
+    let executable = dwarfdump_executable
+        .to_owned()
+        .unwrap_or_else(|| PathBuf::from(EXECUTABLE));
+
+    let output = Command::new(executable)
+        .args(arguments)
+        .arg(shared_object)
+        .stdin(Stdio::null())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()?
+        .wait_with_output()?;
+
+    if !output.status.success() {
+        anyhow::bail!(String::from_utf8_lossy(&output.stderr).to_string());
+    }
+
+    Ok(String::from_utf8_lossy(&output.stdout).to_string())
+}