diff --git a/llvm/include/llvm/IR/ConstantRange.h b/llvm/include/llvm/IR/ConstantRange.h
--- a/llvm/include/llvm/IR/ConstantRange.h
+++ b/llvm/include/llvm/IR/ConstantRange.h
@@ -92,6 +92,9 @@
   /// unsigned domain.
   static ConstantRange fromKnownBits(const KnownBits &Known, bool IsSigned);
 
+  /// Get the known bits valid for the given range.
+  KnownBits toKnownBits() const;
+
   /// Produce the smallest range such that all values that may satisfy the given
   /// predicate with any value contained within Other is contained in the
   /// returned range.  Formally, this returns a superset of
diff --git a/llvm/include/llvm/Support/KnownBits.h b/llvm/include/llvm/Support/KnownBits.h
--- a/llvm/include/llvm/Support/KnownBits.h
+++ b/llvm/include/llvm/Support/KnownBits.h
@@ -35,6 +35,12 @@
   /// Create a known bits object of BitWidth bits initialized to unknown.
   KnownBits(unsigned BitWidth) : Zero(BitWidth, 0), One(BitWidth, 0) {}
 
+  /// Return true if this KnownBits is equal to another KnownBits.
+  bool operator==(const KnownBits &CR) const {
+    return Zero == CR.Zero && One == CR.One;
+  }
+  bool operator!=(const KnownBits &KB) const { return !operator==(KB); }
+
   /// Get the bit width of this value.
   unsigned getBitWidth() const {
     assert(Zero.getBitWidth() == One.getBitWidth() &&
@@ -209,8 +215,19 @@
   /// Compute known bits resulting from adding LHS and RHS.
   static KnownBits computeForAddSub(bool Add, bool NSW, const KnownBits &LHS,
                                     KnownBits RHS);
+
+  /// Print out the bounds to a stream.
+  void print(raw_ostream &OS) const;
+
+  /// Allow printing from a debugger easily.
+  void dump() const;
 };
 
+inline raw_ostream &operator<<(raw_ostream &OS, const KnownBits &KB) {
+  KB.print(OS);
+  return OS;
+}
+
 } // end namespace llvm
 
 #endif
diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -74,6 +74,42 @@
   return ConstantRange(Lower, Upper + 1);
 }
 
+KnownBits ConstantRange::toKnownBits() const {
+  KnownBits Known(getBitWidth());
+
+  // If the range has no/all members, or has a wrap, then "no known bits"
+  // is as precise as we can get.
+  if (isEmptySet() || isFullSet() || isSignWrappedSet() || isWrappedSet())
+    return Known; // No bits known.
+
+  // We know all bits of a constant.
+  if (const APInt *SingleElement = getSingleElement()) {
+    Known.One = *SingleElement;
+    Known.Zero = ~*SingleElement;
+    return Known;
+  }
+
+  Known.One = getUnsignedMin();
+  Known.Zero = ~getUnsignedMin();
+
+  auto HighestTransientBit = APIntOps::GetPositionOfMostSignificantDifferentBit(
+      getUnsignedMin(), getUnsignedMax());
+  assert(
+      HighestTransientBit.hasValue() &&
+      "Since the constant range does not consist of a single constant, there "
+      "must be some some different bits, so we must have found the threshold.");
+  assert((getBitWidth() - (1 + *HighestTransientBit)) >= 1 &&
+         "If we get here, we know *at least* the (common) sign bit.");
+
+  // We need to claim to not know all low bits up to and including
+  // HighestTransientBit. But since `getUnsignedMin()` was used as baseline,
+  // that bit itself isn't known to be One, so we don't need to unset it as One.
+  Known.One.clearLowBits(*HighestTransientBit);
+  Known.Zero.clearLowBits(1 + *HighestTransientBit);
+
+  return Known;
+}
+
 ConstantRange ConstantRange::makeAllowedICmpRegion(CmpInst::Predicate Pred,
                                                    const ConstantRange &CR) {
   if (CR.isEmptySet())
diff --git a/llvm/lib/Support/KnownBits.cpp b/llvm/lib/Support/KnownBits.cpp
--- a/llvm/lib/Support/KnownBits.cpp
+++ b/llvm/lib/Support/KnownBits.cpp
@@ -12,6 +12,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/KnownBits.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 
@@ -81,3 +83,11 @@
 
   return KnownOut;
 }
+
+void KnownBits::print(raw_ostream &OS) const {
+  OS << "Known-zero: " << Zero << ", Known-one: " << One;
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void KnownBits::dump() const { print(dbgs()); }
+#endif
diff --git a/llvm/unittests/IR/ConstantRangeTest.cpp b/llvm/unittests/IR/ConstantRangeTest.cpp
--- a/llvm/unittests/IR/ConstantRangeTest.cpp
+++ b/llvm/unittests/IR/ConstantRangeTest.cpp
@@ -2121,6 +2121,7 @@
         if (Num.sgt(MaxSigned)) MaxSigned = Num;
       }
 
+      // KB -> CR conversion is precisely identical to brute-force approach.
       ConstantRange UnsignedCR(MinUnsigned, MaxUnsigned + 1);
       ConstantRange SignedCR(MinSigned, MaxSigned + 1);
       EXPECT_EQ(UnsignedCR, ConstantRange::fromKnownBits(Known, false));
@@ -2129,6 +2130,39 @@
   }
 }
 
+TEST_F(ConstantRangeTest, ToKnownBitsExhaustive) {
+  unsigned Bits = 6;
+  KnownBits Known(Bits);
+  EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {
+    if (CR.isEmptySet())
+      return;
+
+    // Acquire precise KnownBits knowledge for a given constant range via the
+    // brute-force approach. That results in conservatively-larger value range.
+    Known.Zero.setAllBits();
+    Known.One.setAllBits();
+    ForeachNumInConstantRange(CR, [&](const APInt &N) {
+      Known.Zero &= ~N;
+      Known.One &= N;
+    });
+    ASSERT_FALSE(Known.hasConflict());
+    // But not every value found in known bits is found in constant range!
+
+    // If we produce constant range from known bits, it may be conservatively
+    // larger than the reference constant range. The reference constant range
+    // must be contained within the new constant range.
+    ConstantRange UnsignedCRFromKB(ConstantRange::fromKnownBits(Known, false));
+    ConstantRange SignedCRFromKB(ConstantRange::fromKnownBits(Known, true));
+    EXPECT_EQ(SignedCRFromKB, UnsignedCRFromKB);
+    EXPECT_TRUE(UnsignedCRFromKB.contains(CR));
+
+    // If we distill constant range into known bits, the result is a precise
+    // match to the known-bits we got via brute-force.
+    KnownBits KBFromCR(CR.toKnownBits());
+    EXPECT_EQ(KBFromCR, Known);
+  });
+}
+
 TEST_F(ConstantRangeTest, Negative) {
   // All elements in an empty set (of which there are none) are both negative
   // and non-negative. Empty & full sets checked explicitly for clarity, but