diff --git a/include/llvm/Support/KnownBits.h b/include/llvm/Support/KnownBits.h
index 1d926bd3041..d92037bb66c 100644
--- a/include/llvm/Support/KnownBits.h
+++ b/include/llvm/Support/KnownBits.h
@@ -122,39 +122,48 @@ public:
     return ~Zero;
   }
 
-  /// Truncate the underlying known Zero and One bits. This is equivalent
-  /// to truncating the value we're tracking.
+  /// Return known bits for a truncation of the value we're tracking.
   KnownBits trunc(unsigned BitWidth) const {
     return KnownBits(Zero.trunc(BitWidth), One.trunc(BitWidth));
   }
 
-  /// Extends the underlying known Zero and One bits.
-  /// By setting ExtendedBitsAreKnownZero=true this will be equivalent to
-  /// zero extending the value we're tracking.
-  /// With ExtendedBitsAreKnownZero=false the extended bits are set to unknown.
-  KnownBits zext(unsigned BitWidth, bool ExtendedBitsAreKnownZero) const {
+  /// Return known bits for an "any" extension of the value we're tracking,
+  /// where we don't know anything about the extended bits.
+  KnownBits anyext(unsigned BitWidth) const {
+    return KnownBits(Zero.zext(BitWidth), One.zext(BitWidth));
+  }
+
+  /// Return known bits for a zero extension of the value we're tracking.
+  KnownBits zext(unsigned BitWidth) const {
     unsigned OldBitWidth = getBitWidth();
     APInt NewZero = Zero.zext(BitWidth);
-    if (ExtendedBitsAreKnownZero)
-      NewZero.setBitsFrom(OldBitWidth);
+    NewZero.setBitsFrom(OldBitWidth);
     return KnownBits(NewZero, One.zext(BitWidth));
   }
 
-  /// Sign extends the underlying known Zero and One bits. This is equivalent
-  /// to sign extending the value we're tracking.
+  /// Return known bits for a sign extension of the value we're tracking.
   KnownBits sext(unsigned BitWidth) const {
     return KnownBits(Zero.sext(BitWidth), One.sext(BitWidth));
   }
 
-  /// Extends or truncates the underlying known Zero and One bits. When
-  /// extending the extended bits can either be set as known zero (if
-  /// ExtendedBitsAreKnownZero=true) or as unknown (if
-  /// ExtendedBitsAreKnownZero=false).
-  KnownBits zextOrTrunc(unsigned BitWidth,
-                        bool ExtendedBitsAreKnownZero) const {
+  /// Return known bits for an "any" extension or truncation of the value we're
+  /// tracking.
+  KnownBits anyextOrTrunc(unsigned BitWidth) const {
     if (BitWidth > getBitWidth())
-      return zext(BitWidth, ExtendedBitsAreKnownZero);
-    return KnownBits(Zero.zextOrTrunc(BitWidth), One.zextOrTrunc(BitWidth));
+      return anyext(BitWidth);
+    if (BitWidth < getBitWidth())
+      return trunc(BitWidth);
+    return *this;
+  }
+
+  /// Return known bits for a zero extension or truncation of the value we're
+  /// tracking.
+  KnownBits zextOrTrunc(unsigned BitWidth) const {
+    if (BitWidth > getBitWidth())
+      return zext(BitWidth);
+    if (BitWidth < getBitWidth())
+      return trunc(BitWidth);
+    return *this;
   }
 
   /// Return a KnownBits with the extracted bits
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 36a9e7d0988..56c1c514ed8 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -5736,7 +5736,7 @@ ScalarEvolution::getRangeRef(const SCEV *S,
       // For a SCEVUnknown, ask ValueTracking.
       KnownBits Known = computeKnownBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
       if (Known.getBitWidth() != BitWidth)
-        Known = Known.zextOrTrunc(BitWidth, true);
+        Known = Known.zextOrTrunc(BitWidth);
       // If Known does not result in full-set, intersect with it.
       if (Known.getMinValue() != Known.getMaxValue() + 1)
         ConservativeResult = ConservativeResult.intersectWith(
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 3d3c9124215..3a76a699171 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -1254,9 +1254,9 @@ static void computeKnownBitsFromOperator(const Operator *I,
       Q.DL.getTypeSizeInBits(ScalarTy);
 
     assert(SrcBitWidth && "SrcBitWidth can't be zero");
-    Known = Known.zextOrTrunc(SrcBitWidth, false);
+    Known = Known.anyextOrTrunc(SrcBitWidth);
     computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
-    Known = Known.zextOrTrunc(BitWidth, true /* ExtendedBitsAreKnownZero */);
+    Known = Known.zextOrTrunc(BitWidth);
     break;
   }
   case Instruction::BitCast: {
diff --git a/lib/CodeGen/GlobalISel/GISelKnownBits.cpp b/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
index b180efbe6ad..04b29948b5e 100644
--- a/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
+++ b/lib/CodeGen/GlobalISel/GISelKnownBits.cpp
@@ -294,7 +294,7 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
   case TargetOpcode::G_ANYEXT: {
     computeKnownBitsImpl(MI.getOperand(1).getReg(), Known, DemandedElts,
                          Depth + 1);
-    Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
+    Known = Known.zext(BitWidth);
     break;
   }
   case TargetOpcode::G_LOAD: {
@@ -360,9 +360,9 @@ void GISelKnownBits::computeKnownBitsImpl(Register R, KnownBits &Known,
                                ? DL.getIndexSizeInBits(SrcTy.getAddressSpace())
                                : SrcTy.getSizeInBits();
     assert(SrcBitWidth && "SrcBitWidth can't be zero");
-    Known = Known.zextOrTrunc(SrcBitWidth, true);
+    Known = Known.zextOrTrunc(SrcBitWidth);
     computeKnownBitsImpl(SrcReg, Known, DemandedElts, Depth + 1);
-    Known = Known.zextOrTrunc(BitWidth, true);
+    Known = Known.zextOrTrunc(BitWidth);
     if (BitWidth > SrcBitWidth)
       Known.Zero.setBitsFrom(SrcBitWidth);
     break;
diff --git a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 09e4af1b901..a69f1e53428 100644
--- a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -407,7 +407,7 @@ FunctionLoweringInfo::GetLiveOutRegInfo(unsigned Reg, unsigned BitWidth) {
 
   if (BitWidth > LOI->Known.getBitWidth()) {
     LOI->NumSignBits = 1;
-    LOI->Known = LOI->Known.zext(BitWidth, false /* => any extend */);
+    LOI->Known = LOI->Known.anyext(BitWidth);
   }
 
   return LOI;
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 706d3534d70..4c4c58c7afd 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3061,12 +3061,12 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     EVT InVT = Op.getOperand(0).getValueType();
     APInt InDemandedElts = DemandedElts.zextOrSelf(InVT.getVectorNumElements());
     Known = computeKnownBits(Op.getOperand(0), InDemandedElts, Depth + 1);
-    Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
+    Known = Known.zext(BitWidth);
     break;
   }
   case ISD::ZERO_EXTEND: {
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
-    Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
+    Known = Known.zext(BitWidth);
     break;
   }
   case ISD::SIGN_EXTEND_VECTOR_INREG: {
@@ -3089,12 +3089,12 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
     EVT InVT = Op.getOperand(0).getValueType();
     APInt InDemandedElts = DemandedElts.zextOrSelf(InVT.getVectorNumElements());
     Known = computeKnownBits(Op.getOperand(0), InDemandedElts, Depth + 1);
-    Known = Known.zext(BitWidth, false /* ExtendedBitsAreKnownZero */);
+    Known = Known.anyext(BitWidth);
     break;
   }
   case ISD::ANY_EXTEND: {
     Known = computeKnownBits(Op.getOperand(0), DemandedElts, Depth + 1);
-    Known = Known.zext(BitWidth, false /* ExtendedBitsAreKnownZero */);
+    Known = Known.anyext(BitWidth);
     break;
   }
   case ISD::TRUNCATE: {
@@ -3257,7 +3257,7 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
 
     Known = computeKnownBits(InVec, DemandedSrcElts, Depth + 1);
     if (BitWidth > EltBitWidth)
-      Known = Known.zext(BitWidth, false /* => any extend */);
+      Known = Known.anyext(BitWidth);
     break;
   }
   case ISD::INSERT_VECTOR_ELT: {
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index f41bdf09929..9455797310f 100644
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -864,7 +864,7 @@ bool TargetLowering::SimplifyDemandedBits(
     APInt SrcDemandedBits = DemandedBits.zextOrSelf(SrcBitWidth);
     if (SimplifyDemandedBits(Src, SrcDemandedBits, SrcKnown, TLO, Depth + 1))
       return true;
-    Known = SrcKnown.zextOrTrunc(BitWidth, false);
+    Known = SrcKnown.anyextOrTrunc(BitWidth);
     break;
   }
   case ISD::BUILD_VECTOR:
@@ -910,7 +910,7 @@ bool TargetLowering::SimplifyDemandedBits(
     if (SimplifyDemandedBits(Scl, DemandedSclBits, KnownScl, TLO, Depth + 1))
       return true;
 
-    Known = KnownScl.zextOrTrunc(BitWidth, false);
+    Known = KnownScl.anyextOrTrunc(BitWidth);
 
     KnownBits KnownVec;
     if (SimplifyDemandedBits(Vec, DemandedBits, DemandedVecElts, KnownVec, TLO,
@@ -1765,7 +1765,7 @@ bool TargetLowering::SimplifyDemandedBits(
       return true;
     assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     assert(Known.getBitWidth() == InBits && "Src width has changed?");
-    Known = Known.zext(BitWidth, true /* ExtendedBitsAreKnownZero */);
+    Known = Known.zext(BitWidth);
     break;
   }
   case ISD::SIGN_EXTEND:
@@ -1838,7 +1838,7 @@ bool TargetLowering::SimplifyDemandedBits(
       return true;
     assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     assert(Known.getBitWidth() == InBits && "Src width has changed?");
-    Known = Known.zext(BitWidth, false /* => any extend */);
+    Known = Known.anyext(BitWidth);
 
     // Attempt to avoid multi-use ops if we don't need anything from them.
     if (SDValue NewSrc = SimplifyMultipleUseDemandedBits(
@@ -1952,7 +1952,7 @@ bool TargetLowering::SimplifyDemandedBits(
 
     Known = Known2;
     if (BitWidth > EltBitWidth)
-      Known = Known.zext(BitWidth, false /* => any extend */);
+      Known = Known.anyext(BitWidth);
     break;
   }
   case ISD::BITCAST: {
diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index bd82c8f6440..f168eb19e91 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -15853,7 +15853,7 @@ void ARMTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
     if (Op.getOpcode() == ARMISD::VGETLANEs)
       Known = Known.sext(DstSz);
     else {
-      Known = Known.zext(DstSz, true /* extended bits are known zero */);
+      Known = Known.zext(DstSz);
     }
     assert(DstSz == Known.getBitWidth());
     break;
diff --git a/lib/Target/SystemZ/SystemZISelLowering.cpp b/lib/Target/SystemZ/SystemZISelLowering.cpp
index 8cb01709e9e..224b8dde84d 100644
--- a/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -6607,7 +6607,7 @@ SystemZTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
       APInt SrcDemE = getDemandedSrcElements(Op, DemandedElts, 0);
       Known = DAG.computeKnownBits(SrcOp, SrcDemE, Depth + 1);
       if (IsLogical) {
-        Known = Known.zext(BitWidth, true);
+        Known = Known.zext(BitWidth);
       } else
         Known = Known.sext(BitWidth);
       break;
@@ -6636,7 +6636,7 @@ SystemZTargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
   // Known has the width of the source operand(s). Adjust if needed to match
   // the passed bitwidth.
   if (Known.getBitWidth() != BitWidth)
-    Known = Known.zextOrTrunc(BitWidth, false);
+    Known = Known.anyextOrTrunc(BitWidth);
 }
 
 static unsigned computeNumSignBitsBinOp(SDValue Op, const APInt &DemandedElts,
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 1b089540aee..e4639516996 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -32945,7 +32945,7 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
     APInt DemandedElt = APInt::getOneBitSet(SrcVT.getVectorNumElements(),
                                             Op.getConstantOperandVal(1));
     Known = DAG.computeKnownBits(Src, DemandedElt, Depth + 1);
-    Known = Known.zextOrTrunc(BitWidth, false);
+    Known = Known.anyextOrTrunc(BitWidth);
     Known.Zero.setBitsFrom(SrcVT.getScalarSizeInBits());
     break;
   }
@@ -33059,7 +33059,7 @@ void X86TargetLowering::computeKnownBitsForTargetNode(const SDValue Op,
       if ((Shift + Length) <= BitWidth) {
         Known = DAG.computeKnownBits(Op0, Depth + 1);
         Known = Known.extractBits(Length, Shift);
-        Known = Known.zextOrTrunc(BitWidth, true /* ExtBitsAreKnownZero */);
+        Known = Known.zextOrTrunc(BitWidth);
       }
     }
     break;
@@ -36484,7 +36484,7 @@ bool X86TargetLowering::SimplifyDemandedBitsForTargetNode(
         return TLO.CombineTo(
             Op, TLO.DAG.getNode(Opc, SDLoc(Op), VT, V, Op.getOperand(1)));
 
-      Known = KnownVec.zext(BitWidth, true);
+      Known = KnownVec.zext(BitWidth);
       return false;
     }
     break;
diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 3e8764b0111..bf91d99edf2 100644
--- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -396,8 +396,7 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
     if (SimplifyDemandedBits(I, 0, InputDemandedMask, InputKnown, Depth + 1))
       return I;
     assert(InputKnown.getBitWidth() == SrcBitWidth && "Src width changed?");
-    Known = InputKnown.zextOrTrunc(BitWidth,
-                                   true /* ExtendedBitsAreKnownZero */);
+    Known = InputKnown.zextOrTrunc(BitWidth);
     assert(!Known.hasConflict() && "Bits known to be one AND zero?");
     break;
   }