Index: include/llvm/Analysis/ValueLattice.h
===================================================================
--- /dev/null
+++ include/llvm/Analysis/ValueLattice.h
@@ -0,0 +1,266 @@
+//===- ValueLattice.h - Value constraint analysis ---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_VALUELATTICE_H
+#define LLVM_ANALYSIS_VALUELATTICE_H
+
+#include "llvm/IR/ConstantRange.h"
+#include "llvm/IR/Constants.h"
+//
+//===----------------------------------------------------------------------===//
+//                               LVILatticeVal
+//===----------------------------------------------------------------------===//
+
+/// This class represents lattice values for constants.
+///
+/// FIXME: This is basically just for bringup, this can be made a lot more rich
+/// in the future.
+///
+
+namespace llvm {
+class LVILatticeVal {
+  enum LVILatticeValueTy {
+    /// This Value has no known value yet.  As a result, this implies the
+    /// producing instruction is dead.  Caution: We use this as the starting
+    /// state in our local meet rules.  In this usage, it's taken to mean
+    /// "nothing known yet".
+    undefined,
+
+    /// This Value has a specific constant value.  (For constant integers,
+    /// constantrange is used instead.  Integer typed constantexprs can appear
+    /// as constant.)
+    constant,
+
+    /// This Value is known to not have the specified value.  (For constant
+    /// integers, constantrange is used instead.  As above, integer typed
+    /// constantexprs can appear here.)
+    notconstant,
+
+    /// The Value falls within this range. (Used only for integer typed values.)
+    constantrange,
+
+    /// We can not precisely model the dynamic values this value might take.
+    overdefined
+  };
+
+  /// Val: This stores the current lattice value along with the Constant* for
+  /// the constant if this is a 'constant' or 'notconstant' value.
+  LVILatticeValueTy Tag;
+  Constant *Val;
+  ConstantRange Range;
+
+public:
+  LVILatticeVal() : Tag(undefined), Val(nullptr), Range(1, true) {}
+
+  static LVILatticeVal get(Constant *C) {
+    LVILatticeVal Res;
+    if (!isa<UndefValue>(C))
+      Res.markConstant(C);
+    return Res;
+  }
+  static LVILatticeVal getNot(Constant *C) {
+    LVILatticeVal Res;
+    if (!isa<UndefValue>(C))
+      Res.markNotConstant(C);
+    return Res;
+  }
+  static LVILatticeVal getRange(ConstantRange CR) {
+    LVILatticeVal Res;
+    Res.markConstantRange(std::move(CR));
+    return Res;
+  }
+  static LVILatticeVal getOverdefined() {
+    LVILatticeVal Res;
+    Res.markOverdefined();
+    return Res;
+  }
+
+  bool isUndefined() const     { return Tag == undefined; }
+  bool isConstant() const      { return Tag == constant; }
+  bool isNotConstant() const   { return Tag == notconstant; }
+  bool isConstantRange() const { return Tag == constantrange; }
+  bool isOverdefined() const   { return Tag == overdefined; }
+
+  Constant *getConstant() const {
+    assert(isConstant() && "Cannot get the constant of a non-constant!");
+    return Val;
+  }
+
+  Constant *getNotConstant() const {
+    assert(isNotConstant() && "Cannot get the constant of a non-notconstant!");
+    return Val;
+  }
+
+  const ConstantRange &getConstantRange() const {
+    assert(isConstantRange() &&
+           "Cannot get the constant-range of a non-constant-range!");
+    return Range;
+  }
+
+  Optional<APInt> asConstantInteger() const {
+    if (isConstant() && isa<ConstantInt>(Val)) {
+      return cast<ConstantInt>(Val)->getValue();
+    } else if (isConstantRange() && Range.isSingleElement()) {
+      return *Range.getSingleElement();
+    }
+    return None;
+  }
+
+private:
+  void markOverdefined() {
+    if (isOverdefined())
+      return;
+    Tag = overdefined;
+  }
+
+  void markConstant(Constant *V) {
+    assert(V && "Marking constant with NULL");
+    if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
+      markConstantRange(ConstantRange(CI->getValue()));
+      return;
+    }
+    if (isa<UndefValue>(V))
+      return;
+
+    assert((!isConstant() || getConstant() == V) &&
+           "Marking constant with different value");
+    assert(isUndefined());
+    Tag = constant;
+    Val = V;
+  }
+
+  void markNotConstant(Constant *V) {
+    assert(V && "Marking constant with NULL");
+    if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
+      markConstantRange(ConstantRange(CI->getValue()+1, CI->getValue()));
+      return;
+    }
+    if (isa<UndefValue>(V))
+      return;
+
+    assert((!isConstant() || getConstant() != V) &&
+           "Marking constant !constant with same value");
+    assert((!isNotConstant() || getNotConstant() == V) &&
+           "Marking !constant with different value");
+    assert(isUndefined() || isConstant());
+    Tag = notconstant;
+    Val = V;
+  }
+
+  void markConstantRange(ConstantRange NewR) {
+    if (isConstantRange()) {
+      if (NewR.isEmptySet())
+        markOverdefined();
+      else {
+        Range = std::move(NewR);
+      }
+      return;
+    }
+
+    assert(isUndefined());
+    if (NewR.isEmptySet())
+      markOverdefined();
+    else {
+      Tag = constantrange;
+      Range = std::move(NewR);
+    }
+  }
+
+public:
+
+  /// Merge the specified lattice value into this one, updating this
+  /// one and returning true if anything changed.
+  bool mergeIn(const LVILatticeVal &RHS, const DataLayout &DL) {
+    if (RHS.isUndefined() || isOverdefined())
+      return false;
+    if (RHS.isOverdefined()) {
+      markOverdefined();
+      return true;
+    }
+
+    if (isUndefined()) {
+      *this = RHS;
+      return !RHS.isUndefined();
+    }
+
+    if (isConstant()) {
+      if (RHS.isConstant() && Val == RHS.Val)
+          return false;
+      markOverdefined();
+      return true;
+    }
+
+    if (isNotConstant()) {
+      if (RHS.isNotConstant() && Val == RHS.Val)
+          return false;
+      markOverdefined();
+      return true;
+    }
+
+    assert(isConstantRange() && "New LVILattice type?");
+    if (!RHS.isConstantRange()) {
+      // We can get here if we've encountered a constantexpr of integer type
+      // and merge it with a constantrange.
+      markOverdefined();
+      return true;
+    }
+    ConstantRange NewR = Range.unionWith(RHS.getConstantRange());
+    if (NewR.isFullSet())
+      markOverdefined();
+    else
+      markConstantRange(std::move(NewR));
+    return true;
+  }
+
+  ConstantInt *getConstantInt() const {
+    assert(isConstant() && isa<ConstantInt>(getConstant()) &&
+           "No integer constant");
+    return cast<ConstantInt>(getConstant());
+  }
+
+  bool satisfiesPredicate(CmpInst::Predicate Pred,
+                          const LVILatticeVal &Other) const {
+    // TODO: share with LVI getPredicateResult.
+    // Integer constants are represented as ConstantRanges with single
+    // elements.
+    if (!isConstantRange() || !Other.isConstantRange())
+      return false;
+
+    const auto &CR = getConstantRange();
+    const auto &OtherCR = Other.getConstantRange();
+    switch (Pred) {
+    case CmpInst::ICMP_NE:
+      return CR.intersectWith(OtherCR).isEmptySet();
+    case CmpInst::ICMP_EQ:
+      return CR.isSingleElement() && OtherCR.isSingleElement() &&
+             CR == OtherCR;
+    default:
+      return ConstantRange::makeSatisfyingICmpRegion(Pred, OtherCR).contains(CR);
+    }
+  }
+};
+
+raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val)
+    LLVM_ATTRIBUTE_USED;
+raw_ostream &operator<<(raw_ostream &OS, const LVILatticeVal &Val) {
+  if (Val.isUndefined())
+    return OS << "undefined";
+  if (Val.isOverdefined())
+    return OS << "overdefined";
+
+  if (Val.isNotConstant())
+    return OS << "notconstant<" << *Val.getNotConstant() << '>';
+  if (Val.isConstantRange())
+    return OS << "constantrange<" << Val.getConstantRange().getLower() << ", "
+              << Val.getConstantRange().getUpper() << '>';
+  return OS << "constant<" << *Val.getConstant() << '>';
+}
+
+}  // end namespace llvm
+#endif