diff --git a/build.sh b/build.sh
index 20f88163283..82e613ff1c6 100755
--- a/build.sh
+++ b/build.sh
@@ -23,6 +23,8 @@ extract_data() {
 RUSTC="rustc -Zcodegen-backend=$(pwd)/target/debug/librustc_codegen_cranelift.$dylib_ext -L crate=target/out --out-dir target/out"
 
 rm -r target/out
+mkdir -p target/out/mir
+mkdir -p target/out/clif
 
 SHOULD_CODEGEN=1 $RUSTC examples/mini_core.rs --crate-name mini_core --crate-type lib &&
 extract_data libmini_core.rlib mini_core.o &&
@@ -39,4 +41,3 @@ gcc target/out/mini_core.o target/out/mini_core_hello_world.o -o target/out/mini
 
 $RUSTC target/libcore/src/libcore/lib.rs --color=always --crate-type lib -Cincremental=target/incremental 2>&1 | (head -n 20; echo "===="; tail -n 1000)
 cat target/libcore/log.txt | sort | uniq -c | grep -v "rval unsize move" | grep -v "rval len"
-
diff --git a/src/abi.rs b/src/abi.rs
index f230e07125c..7e19a4fba4f 100644
--- a/src/abi.rs
+++ b/src/abi.rs
@@ -242,7 +242,6 @@ pub fn codegen_fn_prelude<'a, 'tcx: 'a>(
     start_ebb: Ebb,
 ) {
     let ssa_analyzed = crate::analyze::analyze(fx);
-    fx.tcx.sess.warn(&format!("ssa {:?}", ssa_analyzed));
 
     match fx.self_sig().abi {
         Abi::Rust | Abi::RustCall => {}
@@ -301,6 +300,9 @@ pub fn codegen_fn_prelude<'a, 'tcx: 'a>(
 
     fx.bcx.switch_to_block(start_ebb);
 
+    fx.top_nop = Some(fx.bcx.ins().nop());
+    fx.add_global_comment(format!("ssa {:?}", ssa_analyzed));
+
     match output_pass_mode {
         PassMode::NoPass => {
             let null = fx.bcx.ins().iconst(types::I64, 0);
diff --git a/src/base.rs b/src/base.rs
index 48a59a154b6..c3034164de0 100644
--- a/src/base.rs
+++ b/src/base.rs
@@ -1,5 +1,14 @@
 use crate::prelude::*;
 
+struct PrintOnPanic(String);
+impl Drop for PrintOnPanic {
+    fn drop(&mut self) {
+        if ::std::thread::panicking() {
+            println!("{}", self.0);
+        }
+    }
+}
+
 pub fn trans_mono_item<'a, 'tcx: 'a>(cx: &mut CodegenCx<'a, 'tcx>, mono_item: MonoItem<'tcx>) {
     let tcx = cx.tcx;
     let context = &mut cx.context;
@@ -12,11 +21,9 @@ pub fn trans_mono_item<'a, 'tcx: 'a>(cx: &mut CodegenCx<'a, 'tcx>, mono_item: Mo
             } => {
                 let mut mir = ::std::io::Cursor::new(Vec::new());
                 ::rustc_mir::util::write_mir_pretty(tcx, Some(def_id), &mut mir).unwrap();
-                tcx.sess.warn(&format!(
-                    "{:?}:\n\n{}",
-                    inst,
-                    String::from_utf8_lossy(&mir.into_inner())
-                ));
+                let mir_file_name = "target/out/mir/".to_string() + &format!("{:?}", def_id).replace('/', "@");
+                ::std::fs::write(mir_file_name, mir.into_inner()).unwrap();
+                let _print_guard = PrintOnPanic(format!("{:?}", inst));
 
                 let res = each_module!(cx, |(ccx, m)| trans_fn(tcx, *m, ccx, context, inst));
                 if let Some(func_id) = res.jit {
@@ -84,6 +91,8 @@ fn trans_fn<'a, 'tcx: 'a>(
         local_map: HashMap::new(),
         comments: HashMap::new(),
         constants,
+
+        top_nop: None,
     };
 
     // Step 6. Codegen function
@@ -96,7 +105,8 @@ fn trans_fn<'a, 'tcx: 'a>(
     let mut writer = crate::pretty_clif::CommentWriter(fx.comments);
     let mut cton = String::new();
     ::cranelift::codegen::write::decorate_function(&mut writer, &mut cton, &func, None).unwrap();
-    tcx.sess.warn(&cton);
+    let clif_file_name = "target/out/clif/".to_string() + &tcx.symbol_name(instance).as_str();
+    ::std::fs::write(clif_file_name, cton.as_bytes()).unwrap();
 
     // Step 8. Verify function
     verify_func(tcx, writer, &func);
@@ -235,7 +245,7 @@ fn trans_stmt<'a, 'tcx: 'a>(
     cur_ebb: Ebb,
     stmt: &Statement<'tcx>,
 ) {
-    fx.tcx.sess.warn(&format!("stmt {:?}", stmt));
+    let _print_guard = PrintOnPanic(format!("stmt {:?}", stmt));
 
     let inst = fx.bcx.func.layout.last_inst(cur_ebb).unwrap();
     fx.add_comment(inst, format!("{:?}", stmt));
diff --git a/src/common.rs b/src/common.rs
index 02cfc1b2e74..d18b6bf43b2 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -361,6 +361,9 @@ pub struct FunctionCx<'a, 'tcx: 'a, B: Backend + 'a> {
     pub local_map: HashMap<Local, CPlace<'tcx>>,
     pub comments: HashMap<Inst, String>,
     pub constants: &'a mut crate::constant::ConstantCx,
+
+    /// add_global_comment inserts a comment here
+    pub top_nop: Option<Inst>,
 }
 
 impl<'a, 'tcx: 'a, B: Backend + 'a> fmt::Debug for FunctionCx<'a, 'tcx, B> {
diff --git a/src/pretty_clif.rs b/src/pretty_clif.rs
index d872a70b0fe..c6cc521f90d 100644
--- a/src/pretty_clif.rs
+++ b/src/pretty_clif.rs
@@ -35,6 +35,10 @@ impl FuncWriter for CommentWriter {
 }
 
 impl<'a, 'tcx: 'a, B: Backend + 'a> FunctionCx<'a, 'tcx, B> {
+    pub fn add_global_comment<'s, S: Into<Cow<'s, str>>>(&mut self, comment: S) {
+        self.add_comment(self.top_nop.expect("fx.top_nop not yet set"), comment)
+    }
+
     pub fn add_comment<'s, S: Into<Cow<'s, str>>>(&mut self, inst: Inst, comment: S) {
         use std::collections::hash_map::Entry;
         match self.comments.entry(inst) {