Index: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -4189,6 +4189,7 @@
           Builder.CreateAssumption(Builder.CreateNot(Cond));
           Builder.CreateBr(BI->getSuccessor(1));
           EraseTerminatorAndDCECond(BI);
+          Changed = true;
         } else if (BI->getSuccessor(1) == BB) {
           Builder.CreateAssumption(Cond);
           Builder.CreateBr(BI->getSuccessor(0));
Index: llvm/trunk/test/Transforms/SimplifyCFG/invalidate-dom.ll
===================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/invalidate-dom.ll
+++ llvm/trunk/test/Transforms/SimplifyCFG/invalidate-dom.ll
@@ -0,0 +1,90 @@
+; RUN: opt -aa-pipeline=default -passes="default<O2>" -disable-output %s
+; REQUIRES: asserts
+; PR42272
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@b = external global i32, align 4
+@f = external global i32, align 4
+@g = external global i32, align 4
+
+define i32* @a(i32 %h) #0 {
+entry:
+  %h.addr = alloca i32, align 4
+  store i32 %h, i32* %h.addr, align 4
+  %tmp0 = load i32, i32* %h.addr, align 4
+  switch i32 %tmp0, label %sw.default [
+    i32 4, label %sw.bb
+    i32 3, label %sw.bb1
+    i32 2, label %sw.bb3
+  ]
+
+sw.bb:                                            ; preds = %entry
+  %call = call i32 (...) @c()
+  unreachable
+
+sw.bb1:                                           ; preds = %entry
+  %call2 = call i32 (...) @c()
+  unreachable
+
+sw.bb3:                                           ; preds = %entry
+  %call4 = call i32 (...) @c()
+  %conv = sext i32 %call4 to i64
+  %tmp1 = inttoptr i64 %conv to i32*
+  ret i32* %tmp1
+
+sw.default:                                       ; preds = %entry
+  unreachable
+}
+
+define i32 @m() #1 {
+entry:
+  %call = call i32 @j()
+  %call1 = call i32 @j()
+  ret i32 undef
+}
+
+define internal i32 @j() #0 {
+entry:
+  %i = alloca i32, align 4
+  store i32 0, i32* %i, align 4
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %tmp0 = load i32, i32* %i, align 4
+  %tmp1 = load i32, i32* @f, align 4
+  %cmp = icmp ult i32 %tmp0, %tmp1
+  br i1 %cmp, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond
+  %tmp2 = load i32, i32* @f, align 4
+  %call3 = call i32* @a(i32 %tmp2)
+  ret i32 undef
+
+for.body:                                         ; preds = %for.cond
+  %call = call i32 (...) @c()
+  %call1 = call i32 (...) @c()
+  %call2 = call i32 (...) @c()
+  %tmp3 = load i32, i32* @b, align 4
+  %tmp4 = load i32, i32* @g, align 4
+  %sub = sub nsw i32 %tmp4, %tmp3
+  store i32 %sub, i32* @g, align 4
+  %tmp5 = load i32, i32* %i, align 4
+  %inc = add i32 %tmp5, 1
+  store i32 %inc, i32* %i, align 4
+  br label %for.cond
+}
+
+declare i32 @c(...) #0
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #2
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #2
+
+attributes #0 = { "use-soft-float"="false" }
+attributes #1 = { "target-cpu"="x86-64" }
+attributes #2 = { argmemonly nounwind }
+