diff --git a/compiler/rustc_mir_dataflow/src/value_analysis.rs b/compiler/rustc_mir_dataflow/src/value_analysis.rs
index 64e45083fc0..5fe768f8310 100644
--- a/compiler/rustc_mir_dataflow/src/value_analysis.rs
+++ b/compiler/rustc_mir_dataflow/src/value_analysis.rs
@@ -146,10 +146,7 @@ pub trait ValueAnalysis<'tcx> {
             Rvalue::CopyForDeref(place) => {
                 self.handle_operand(&Operand::Copy(*place), state).into()
             }
-            _ => {
-                // FIXME: Check that other Rvalues really have no side-effect.
-                ValueOrPlaceOrRef::Unknown
-            }
+            _ => ValueOrPlaceOrRef::Unknown,
         }
     }
 
@@ -200,7 +197,20 @@ pub trait ValueAnalysis<'tcx> {
         self.super_terminator(terminator, state)
     }
 
-    fn super_terminator(&self, _terminator: &Terminator<'tcx>, _state: &mut State<Self::Value>) {}
+    fn super_terminator(&self, terminator: &Terminator<'tcx>, _state: &mut State<Self::Value>) {
+        match &terminator.kind {
+            TerminatorKind::Call { .. } | TerminatorKind::InlineAsm { .. } => {
+                // Effect is applied by `handle_call_return`.
+            }
+            TerminatorKind::DropAndReplace { .. } | TerminatorKind::Yield { .. } => {
+                // They would have an effect, but are not allowed in this phase.
+                bug!("encountered disallowed terminator");
+            }
+            _ => {
+                // The other terminators can be ignored.
+            }
+        }
+    }
 
     fn handle_call_return(
         &self,
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index f461514716e..c80ff3dd3ec 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
@@ -35,7 +35,6 @@ impl<'tcx> MirPass<'tcx> for DataflowConstProp {
     }
 }
 
-// FIXME: Consider support for discriminants, mutable references, arrays and slices.
 struct ConstAnalysis<'tcx> {
     map: Map,
     tcx: TyCtxt<'tcx>,