diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6565,7 +6565,12 @@
              i = ++BasicBlock::iterator(I),
              UI = BasicBlock::iterator(dyn_cast<Instruction>(Use));
          i != UI; ++i)
-      if (i == I->getParent()->end() || i->mayHaveSideEffects())
+      if (i == I->getParent()->end() ||
+          // Explicitly check for and ignore llvm.assume intrinsics, which are
+          // marked as accessing InaccessibleMemOnly in order to maintain
+          // control dependencies, and therefore not detected as side effect
+          // free.
+          (i->mayHaveSideEffects() && !isa<AssumeInst>(i)))
         return false;
 
     // Look through GEPs. A load from a GEP derived from NULL is still undefined
diff --git a/llvm/test/Transforms/PhaseOrdering/d83507-knowledge-retention-bug.ll b/llvm/test/Transforms/PhaseOrdering/d83507-knowledge-retention-bug.ll
--- a/llvm/test/Transforms/PhaseOrdering/d83507-knowledge-retention-bug.ll
+++ b/llvm/test/Transforms/PhaseOrdering/d83507-knowledge-retention-bug.ll
@@ -1,15 +1,15 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -O1                   -enable-knowledge-retention -S < %s  | FileCheck %s
-; RUN: opt -passes='default<O1>' -enable-knowledge-retention -S < %s  | FileCheck %s
+; RUN: opt -loop-rotate -instcombine -enable-knowledge-retention -S < %s  | FileCheck %s
+; RUN: opt -passes='loop(loop-rotate),instcombine' -enable-knowledge-retention -S < %s  | FileCheck %s
 
 %0 = type { %0* }
 
 define %0* @f1() local_unnamed_addr {
 ; CHECK-LABEL: @f1(
 ; CHECK-NEXT:  bb:
-; CHECK-NEXT:    br label [[BB3:%.*]]
+; CHECK:         br label [[BB3:%.*]]
 ; CHECK:       bb3:
-; CHECK-NEXT:    [[I1:%.*]] = phi %0* [ [[I5:%.*]], [[BB3]] ], [ undef, [[BB:%.*]] ]
+; CHECK-NEXT:    [[I1:%.*]] = phi %0* [ undef, [[BB:%.*]] ], [ [[I5:%.*]], [[BB3]] ]
 ; CHECK-NEXT:    call void @llvm.assume(i1 true) [ "nonnull"(%0* [[I1]]) ]
 ; CHECK-NEXT:    [[I4:%.*]] = getelementptr inbounds [[TMP0:%.*]], %0* [[I1]], i64 0, i32 0
 ; CHECK-NEXT:    [[I5]] = load %0*, %0** [[I4]], align 8
diff --git a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
--- a/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
+++ b/llvm/test/Transforms/SimplifyCFG/UnreachableEliminate.ll
@@ -84,6 +84,41 @@
   ret void
 }
 
+declare void @llvm.assume(i1)
+declare i1 @llvm.type.test(i8*, metadata) nounwind readnone
+
+;; Same as the above test but make sure the unreachable control flow is still
+;; removed in the presence of a type test / assume sequence.
+
+define void @test5_type_test_assume(i1 %cond, i8* %ptr, [3 x i8*]* %vtable) {
+; CHECK-LABEL: @test5_type_test_assume(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = xor i1 [[COND:%.*]], true
+; CHECK-NEXT:    call void @llvm.assume(i1 [[TMP0]])
+; CHECK-NEXT:    [[VTABLE:%.*]] = bitcast [3 x i8*]* %vtable to i8*
+; CHECK-NEXT:    [[P:%.*]] = call i1 @llvm.type.test(i8* [[VTABLE]], metadata !"foo")
+; CHECK-NEXT:    tail call void @llvm.assume(i1 [[P]])
+; CHECK-NEXT:    store i8 2, i8* [[PTR:%.*]], align 8
+; CHECK-NEXT:    ret void
+;
+entry:
+  br i1 %cond, label %bb1, label %bb3
+
+bb3:
+  br label %bb2
+
+bb1:
+  br label %bb2
+
+bb2:
+  %ptr.2 = phi i8* [ %ptr, %bb3 ], [ null, %bb1 ]
+  %vtablei8 = bitcast [3 x i8*]* %vtable to i8*
+  %p = call i1 @llvm.type.test(i8* %vtablei8, metadata !"foo")
+  tail call void @llvm.assume(i1 %p)
+  store i8 2, i8* %ptr.2, align 8
+  ret void
+}
+
 define void @test5_no_null_opt(i1 %cond, i8* %ptr) #0 {
 ; CHECK-LABEL: @test5_no_null_opt(
 ; CHECK-NEXT:  entry: