Clone all MIR bodies

Author: saethlin

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -166,6 +166,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     let llfn = cx.get_fn(instance);
 
     let mir = cx.tcx().instance_mir(instance.def);
+    drop(std::hint::black_box(mir.clone()));
 
     let fn_abi = cx.fn_abi_of_instance(instance, ty::List::empty());
     debug!("fn_abi: {:?}", fn_abi);