Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1408,7 +1408,15 @@
     }
   }
 
-  return nullptr;
+  if (II.getMetadata(LLVMContext::MD_range))
+    return nullptr;
+
+  Metadata *LowAndHigh[] = {
+      ConstantAsMetadata::get(ConstantInt::get(IT, DefiniteZeros)),
+      ConstantAsMetadata::get(ConstantInt::get(IT, PossibleZeros + 1))};
+  II.setMetadata(LLVMContext::MD_range,
+                 MDNode::get(II.getContext(), LowAndHigh));
+  return ⅈ
 }
 
 // TODO: If the x86 backend knew how to convert a bool vector mask back to an
Index: test/Transforms/InstCombine/intrinsics.ll
===================================================================
--- test/Transforms/InstCombine/intrinsics.ll
+++ test/Transforms/InstCombine/intrinsics.ll
@@ -283,10 +283,7 @@
 
 define i1 @cttz_knownbits(i32 %arg) {
 ; CHECK-LABEL: @cttz_knownbits(
-; CHECK-NEXT:    [[OR:%.*]] = or i32 [[ARG:%.*]], 4
-; CHECK-NEXT:    [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true) #0
-; CHECK-NEXT:    [[RES:%.*]] = icmp eq i32 [[CNT]], 4
-; CHECK-NEXT:    ret i1 [[RES]]
+; CHECK-NEXT:    ret i1 false
 ;
   %or = or i32 %arg, 4
   %cnt = call i32 @llvm.cttz.i32(i32 %or, i1 true) nounwind readnone
@@ -306,10 +303,7 @@
 
 define i1 @ctlz_knownbits(i8 %arg) {
 ; CHECK-LABEL: @ctlz_knownbits(
-; CHECK-NEXT:    [[OR:%.*]] = or i8 [[ARG:%.*]], 32
-; CHECK-NEXT:    [[CNT:%.*]] = call i8 @llvm.ctlz.i8(i8 [[OR]], i1 true) #0
-; CHECK-NEXT:    [[RES:%.*]] = icmp eq i8 [[CNT]], 4
-; CHECK-NEXT:    ret i1 [[RES]]
+; CHECK-NEXT:    ret i1 false
 ;
   %or = or i8 %arg, 32
   %cnt = call i8 @llvm.ctlz.i8(i8 %or, i1 true) nounwind readnone
@@ -405,13 +399,14 @@
 }
 
 define i32 @cttz_make_undef(i32 %a) {
+; CHECK-LABEL: @cttz_make_undef(
+; CHECK-NEXT:    [[OR:%.*]] = or i32 [[A:%.*]], 8
+; CHECK-NEXT:    [[CTTZ:%.*]] = tail call i32 @llvm.cttz.i32(i32 [[OR]], i1 true), !range !1
+; CHECK-NEXT:    ret i32 [[CTTZ]]
+;
   %or = or i32 %a, 8
   %cttz = tail call i32 @llvm.cttz.i32(i32 %or, i1 false)
   ret i32 %cttz
-; CHECK-LABEL: @cttz_make_undef(
-; CHECK-NEXT: %or = or i32 %a, 8
-; CHECK-NEXT: %cttz = tail call i32 @llvm.cttz.i32(i32 %or, i1 true)
-; CHECK-NEXT: ret i32 %cttz
 }
 
 define i32 @ctlz_select(i32 %Value) nounwind {