Index: llvm/lib/Analysis/MustExecute.cpp
===================================================================
--- llvm/lib/Analysis/MustExecute.cpp
+++ llvm/lib/Analysis/MustExecute.cpp
@@ -203,6 +203,11 @@
     // Predecessor block may throw, so it has a side exit.
     if (blockMayThrow(Pred))
       return false;
+
+    // BB dominates Pred, so if Pred runs, BB must run.
+    if (DT->dominates(BB, Pred))
+      continue;
+
     for (auto *Succ : successors(Pred))
       if (CheckedSuccessors.insert(Succ).second &&
           Succ != BB && !Predecessors.count(Succ))
Index: llvm/test/Analysis/MustExecute/loop-header.ll
===================================================================
--- llvm/test/Analysis/MustExecute/loop-header.ll
+++ llvm/test/Analysis/MustExecute/loop-header.ll
@@ -83,17 +83,15 @@
   ret i1 false
 }
 
-; FIXME: everything in inner loop header should be must execute
-; for outer as well
 define i1 @nested_no_throw(i32* noalias %p, i32 %high) {
 ; CHECK-LABEL: @nested_no_throw
 ; CHECK-LABEL: loop:                                             ; preds = %next
 ; CHECK:         %iv = phi i32 [ 0, %entry ], [ %iv.next, %next ]	; (mustexec in: loop)
 ; CHECK:         br label %inner_loop	; (mustexec in: loop)
 ; CHECK-LABEL: inner_loop:
-; CHECK:         %v = load i32, i32* %p	; (mustexec in: inner_loop)
-; CHECK:         %inner.test = icmp eq i32 %v, 0	; (mustexec in: inner_loop)
-; CHECK:         br i1 %inner.test, label %inner_loop, label %next	; (mustexec in: inner_loop)
+; CHECK:         %v = load i32, i32* %p	; (mustexec in 2 loops: inner_loop, loop)
+; CHECK:         %inner.test = icmp eq i32 %v, 0	; (mustexec in 2 loops: inner_loop, loop)
+; CHECK:         br i1 %inner.test, label %inner_loop, label %next	; (mustexec in 2 loops: inner_loop, loop)
 ; CHECK-LABEL: next:
 ; CHECK:         %iv.next = add nuw nsw i32 %iv, 1 ; (mustexec in: loop)
 ; CHECK:         %exit.test = icmp slt i32 %iv, %high ; (mustexec in: loop)