Use worse MIR for incr comp

Author: saethlin

compiler/rustc_codegen_ssa/src/base.rs

@@ -416,7 +416,7 @@ pub(crate) fn codegen_instance<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>>(
     // release builds.
     info!("codegen_instance({})", instance);
 
-    mir::codegen_mir::<Bx>(cx, instance);
+    mir::lower_mir::<Bx>(cx, instance);
 }
 
 /// Creates the `main` function which will initialize the rust runtime and call

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -159,7 +159,7 @@ impl<'tcx, V: CodegenObject> LocalRef<'tcx, V> {
 ///////////////////////////////////////////////////////////////////////////
 
 #[instrument(level = "debug", skip(cx))]
-pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
+pub fn lower_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     cx: &'a Bx::CodegenCx,
     instance: Instance<'tcx>,
 ) {

compiler/rustc_middle/src/ty/mod.rs

@@ -1718,6 +1718,14 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
+    pub fn codegen_mir(self, instance: ty::Instance<'tcx>) -> &'tcx Body<'tcx> {
+        if self.sess.opts.incremental == None {
+            self.build_codegen_mir(instance)
+        } else {
+            self.instance_mir(instance.def)
+        }
+    }
+
     /// Returns the possibly-auto-generated MIR of a [`ty::InstanceKind`].
     #[instrument(skip(self), level = "debug")]
     pub fn instance_mir(self, instance: ty::InstanceKind<'tcx>) -> &'tcx Body<'tcx> {