rustc: Compress bytecode files in rlibs

These are only ever used with LTO, so there's no need for reading them to be
speedy.

Author: alexcrichton

src/librustc/back/link.rs

@@ -34,6 +34,7 @@ use std::run;
 use std::str;
 use std::io;
 use std::io::fs;
+use flate;
 use serialize::hex::ToHex;
 use extra::tempfile::TempDir;
 use syntax::abi;
@@ -942,6 +943,15 @@ fn link_rlib(sess: Session,
             // For LTO purposes, the bytecode of this library is also inserted
             // into the archive.
             let bc = obj_filename.with_extension("bc");
+            match fs::File::open(&bc).read_to_end().and_then(|data| {
+                fs::File::create(&bc).write(flate::deflate_bytes(data))
+            }) {
+                Ok(()) => {}
+                Err(e) => {
+                    sess.err(format!("failed to compress bytecode: {}", e));
+                    sess.abort_if_errors()
+                }
+            }
             a.add_file(&bc, false);
             if !sess.opts.cg.save_temps &&
                !sess.opts.output_types.contains(&OutputTypeBitcode) {

src/librustc/back/lto.rs

@@ -16,6 +16,7 @@ use metadata::cstore;
 use util::common::time;
 
 use std::libc;
+use flate;
 
 pub fn run(sess: session::Session, llmod: ModuleRef,
            tm: TargetMachineRef, reachable: &[~str]) {
@@ -55,6 +56,8 @@ pub fn run(sess: session::Session, llmod: ModuleRef,
         let bc = time(sess.time_passes(), format!("read {}.bc", name), (), |_|
                       archive.read(format!("{}.bc", name)));
         let bc = bc.expect("missing bytecode in archive!");
+        let bc = time(sess.time_passes(), format!("inflate {}.bc", name), (), |_|
+                      flate::inflate_bytes(bc));
         let ptr = bc.as_ptr();
         debug!("linking {}", name);
         time(sess.time_passes(), format!("ll link {}", name), (), |()| unsafe {