rustc: Add flag for enabling GC.

src/rustc/driver/driver.rs

@@ -421,6 +421,7 @@ fn build_session_options(matches: getopts::matches,
         session::unknown_crate
     };
     let static = opt_present(matches, ~"static");
+    let gc = opt_present(matches, ~"gc");
 
     let parse_only = opt_present(matches, ~"parse-only");
     let no_trans = opt_present(matches, ~"no-trans");
@@ -519,6 +520,7 @@ fn build_session_options(matches: getopts::matches,
     let sopts: @session::options =
         @{crate_type: crate_type,
           static: static,
+          gc: gc,
           optimize: opt_level,
           debuginfo: debuginfo,
           extra_debuginfo: extra_debuginfo,

src/rustc/driver/session.rs

@@ -82,6 +82,7 @@ type options =
     // with additional crate configurations during the compile process
     {crate_type: crate_type,
      static: bool,
+     gc: bool,
      optimize: OptLevel,
      debuginfo: bool,
      extra_debuginfo: bool,
@@ -221,6 +222,7 @@ fn basic_options() -> @options {
     @{
         crate_type: session::lib_crate,
         static: false,
+        gc: false,
         optimize: No,
         debuginfo: false,
         extra_debuginfo: false,

src/rustc/middle/trans/base.rs

@@ -4792,6 +4792,13 @@ fn trans_closure(ccx: @crate_ctxt, path: path, decl: ast::fn_decl,
                                   some(body.span));
     create_llargs_for_fn_args(fcx, ty_self, decl.inputs);
 
+    // Set GC for function.
+    if ccx.sess.opts.gc {
+        do str::as_c_str("generic") |strategy| {
+            llvm::LLVMSetGC(fcx.llfn, strategy);
+        }
+    }
+
     // Create the first basic block in the function and keep a handle on it to
     //  pass to finish_fn later.
     let bcx_top = top_scope_block(fcx, body.info());