Migrating code to object (from faerie) (#1848)

* Using the "object" library everywhere in wasmtime.
* scroll_derive

src/commands/wasm2obj.rs

@@ -5,6 +5,7 @@ use crate::{init_file_per_thread_logger, pick_compilation_strategy, CommonOption
 use anyhow::{anyhow, Context as _, Result};
 use std::{
     fs::File,
+    io::Write,
     path::{Path, PathBuf},
     str::FromStr,
 };
@@ -75,13 +76,13 @@ impl WasmToObjCommand {
             self.common.enable_simd,
             self.common.opt_level(),
             self.common.debug_info,
-            self.output.clone(),
             &cache_config,
         )?;
 
-        // FIXME: Make the format a parameter.
-        let file = File::create(Path::new(&self.output)).context("failed to create object file")?;
-        obj.write(file).context("failed to write object file")?;
+        let mut file =
+            File::create(Path::new(&self.output)).context("failed to create object file")?;
+        file.write_all(&obj.write()?)
+            .context("failed to write object file")?;
 
         Ok(())
     }

src/obj.rs

@@ -1,5 +1,5 @@
 use anyhow::{anyhow, bail, Context as _, Result};
-use faerie::Artifact;
+use object::write::Object;
 use target_lexicon::Triple;
 use wasmtime::Strategy;
 use wasmtime_debug::{emit_dwarf, read_debuginfo, write_debugsections};
@@ -21,9 +21,8 @@ pub fn compile_to_obj(
     enable_simd: bool,
     opt_level: wasmtime::OptLevel,
     debug_info: bool,
-    artifact_name: String,
     cache_config: &CacheConfig,
-) -> Result<Artifact> {
+) -> Result<Object> {
     let isa_builder = match target {
         Some(target) => native::lookup(target.clone())?,
         None => native::builder(),
@@ -51,7 +50,7 @@ pub fn compile_to_obj(
 
     let isa = isa_builder.finish(settings::Flags::new(flag_builder));
 
-    let mut obj = Artifact::new(isa.triple().clone(), artifact_name);
+    let mut obj = Object::new(isa.triple().binary_format, isa.triple().architecture);
 
     // TODO: Expose the tunables as command-line flags.
     let mut tunables = Tunables::default();