Index: lib/Transforms/Scalar/SCCP.cpp
===================================================================
--- lib/Transforms/Scalar/SCCP.cpp
+++ lib/Transforms/Scalar/SCCP.cpp
@@ -25,6 +25,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/ValueLattice.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/CallSite.h"
@@ -52,6 +53,8 @@
 STATISTIC(IPNumInstRemoved, "Number of instructions removed by IPSCCP");
 STATISTIC(IPNumArgsElimed ,"Number of arguments constant propagated by IPSCCP");
 STATISTIC(IPNumGlobalConst, "Number of globals found to be constant by IPSCCP");
+STATISTIC(IPNumRangeInfoUsed, "Number of times constant range info was used by"
+                              "IPSCCP");
 
 namespace {
 /// LatticeVal class - This class represents the different lattice values that
@@ -153,6 +156,14 @@
     Val.setInt(forcedconstant);
     Val.setPointer(V);
   }
+
+  LVILatticeVal toLVI() const {
+    if (isOverdefined())
+      return LVILatticeVal::getOverdefined();
+    if (isConstant())
+      return LVILatticeVal::get(getConstant());
+    return LVILatticeVal();
+  }
 };
 } // end anonymous namespace.
 
@@ -169,6 +180,7 @@
   const TargetLibraryInfo *TLI;
   SmallPtrSet<BasicBlock*, 8> BBExecutable; // The BBs that are executable.
   DenseMap<Value*, LatticeVal> ValueState;  // The state each value is in.
+  DenseMap<Value*, LVILatticeVal> ParamState;  // The state each parameter is in.
 
   /// StructValueState - This maintains ValueState for values that have
   /// StructType, for example for formal arguments, calls, insertelement, etc.
@@ -290,10 +302,15 @@
     return StructValues;
   }
 
-  LatticeVal getLatticeValueFor(Value *V) const {
-    DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
-    assert(I != ValueState.end() && "V is not in valuemap!");
-    return I->second;
+  LVILatticeVal getLatticeValueFor(Value *V) {
+    if (ParamState.count(V) == 0) {
+      DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
+      assert(I != ValueState.end() &&
+             "V not found in ValueState nor Paramstate map!");
+      ParamState[V] = I->second.toLVI();
+    }
+
+    return ParamState[V];
   }
 
   /// getTrackedRetVals - Get the inferred return value map.
@@ -426,6 +443,15 @@
     return LV;
   }
 
+  LVILatticeVal &getParamState(Value *V) {
+    assert(!V->getType()->isStructTy() && "Should use getStructValueState");
+
+    if (ParamState.count(V) == 0)
+      ParamState[V] = getValueState(V).toLVI();
+
+    return ParamState[V];
+  }
+
   /// getStructValueState - Return the LatticeVal object that corresponds to the
   /// value/field pair.  This function handles the case when the value hasn't
   /// been seen yet by properly seeding constants etc.
@@ -1162,6 +1188,9 @@
           mergeInValue(getStructValueState(&*AI, i), &*AI, CallArg);
         }
       } else {
+        // Most other parts of the Solver still only use the simpler value
+        // lattice, so we propagate changes for parameters to both lattices.
+        getParamState(&*AI).mergeIn(getValueState(*CAI).toLVI(), DL);
         mergeInValue(&*AI, getValueState(*CAI));
       }
     }
@@ -1557,6 +1586,41 @@
   return false;
 }
 
+static bool tryToReplaceWithConstantRange(SCCPSolver &Solver, Value *V) {
+  bool Changed = false;
+  if (!V->getType()->isIntegerTy())
+    return false;
+
+  const LVILatticeVal &IV = Solver.getLatticeValueFor(V);
+  if (IV.isOverdefined())
+    return false;
+
+  if (V->getType()->isIntegerTy() &&
+      (IV.isConstantRange())) {
+    for (auto &Use : V->uses()) {
+      if (auto *Icmp = dyn_cast<ICmpInst>(Use.getUser())) {
+        auto A = Solver.getLatticeValueFor(Icmp->getOperand(0));
+        auto B = Solver.getLatticeValueFor(Icmp->getOperand(1));
+        Constant *C = nullptr;
+        if (A.satisfiesPredicate(Icmp->getPredicate(), B))
+          C = ConstantInt::getTrue(Icmp->getType());
+        else if(A.satisfiesPredicate(Icmp->getInversePredicate(), B))
+          C = ConstantInt::getFalse(Icmp->getType());
+
+        if (C) {
+          Icmp->replaceAllUsesWith(C);
+          DEBUG(dbgs() << "Replacing " << *Icmp << " with " << *C
+                       << ", because of range information " << A << " " << B
+                       << "\n");
+          Icmp->eraseFromParent();
+          Changed = true;
+        }
+      }
+    }
+  }
+  return Changed;
+}
+
 static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) {
   Constant *Const = nullptr;
   if (V->getType()->isStructTy()) {
@@ -1573,10 +1637,20 @@
     }
     Const = ConstantStruct::get(ST, ConstVals);
   } else {
-    LatticeVal IV = Solver.getLatticeValueFor(V);
+    const LVILatticeVal &IV = Solver.getLatticeValueFor(V);
     if (IV.isOverdefined())
       return false;
-    Const = IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType());
+
+    if (IV.isConstantRange()) {
+      if(IV.getConstantRange().isSingleElement())
+        Const = ConstantInt::get(V->getType(),
+                                 IV.asConstantInteger().getValue());
+      else
+        return false;
+    } else
+      Const = IV.isConstant() ? IV.getConstant() :
+                                UndefValue::get(V->getType());
+
   }
   assert(Const && "Constant is nullptr here!");
   DEBUG(dbgs() << "  Constant: " << *Const << " = " << *V << '\n');
@@ -1816,12 +1890,17 @@
     if (F.isDeclaration())
       continue;
 
-    if (Solver.isBlockExecutable(&F.front()))
+    if (Solver.isBlockExecutable(&F.front())) {
       for (Function::arg_iterator AI = F.arg_begin(), E = F.arg_end(); AI != E;
-           ++AI)
+           ++AI) {
         if (!AI->use_empty() && tryToReplaceWithConstant(Solver, &*AI))
           ++IPNumArgsElimed;
 
+        if (!AI->use_empty() && tryToReplaceWithConstantRange(Solver, &*AI))
+          ++IPNumRangeInfoUsed;
+      }
+    }
+
     for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
       if (!Solver.isBlockExecutable(&*BB)) {
         DEBUG(dbgs() << "  BasicBlock Dead:" << *BB);
Index: test/Transforms/SCCP/ip-constan-ranges.ll
===================================================================
--- /dev/null
+++ test/Transforms/SCCP/ip-constan-ranges.ll
@@ -0,0 +1,117 @@
+; RUN: opt < %s -ipsccp -S | FileCheck %s
+
+; Constant range for %a is [1, 48) and for %b is [301, 1000)
+; CHECK-LABEL: f1
+; CHECK-NOT: icmp
+; CHECK: %a.1 = select i1 false, i32 1, i32 2
+; CHECK: %b.1 = select i1 true, i32 1, i32 2
+; CHECK: %a.2 = select i1 false, i32 1, i32 2
+; CHECK: %b.2 = select i1 true, i32 1, i32 2
+define internal i32 @f1(i32 %a, i32 %b) {
+entry:
+  %cmp.a = icmp sgt i32 %a, 300
+  %cmp.b = icmp sgt i32 %b, 300
+  %cmp.a2 = icmp ugt i32 %a, 300
+  %cmp.b2 = icmp ugt i32 %b, 300
+
+  %a.1 = select i1 %cmp.a, i32 1, i32 2
+  %b.1 = select i1 %cmp.b, i32 1, i32 2
+  %a.2 = select i1 %cmp.a2, i32 1, i32 2
+  %b.2 = select i1 %cmp.b2, i32 1, i32 2
+  %res1 = add i32 %a.1, %b.1
+  %res2 = add i32 %a.2, %b.2
+  %res3 = add i32 %res1, %res2
+  ret i32 %res3
+}
+
+; Constant range for %x is [47, 302)
+; CHECK-LABEL: f2
+; CHECK: %cmp = icmp sgt i32 %x, 300
+; CHECK: %res1 = select i1 %cmp, i32 1, i32 2
+; CHECK-NEXT: %res2 = select i1 true, i32 3, i32 4
+; CHECK-NEXT: %res3 = select i1 true, i32 5, i32 6
+; CHECK-NEXT: %res4 = select i1 %cmp4, i32 3, i32 4
+; CHECK-NEXT: %res5 = select i1 true, i32 5, i32 6
+define internal i32 @f2(i32 %x) {
+entry:
+  %cmp = icmp sgt i32 %x, 300
+  %cmp2 = icmp ne i32 %x, 10
+  %cmp3 = icmp sge i32 %x, 47
+  %cmp4 = icmp ugt i32 %x, 300
+  %cmp5 = icmp uge i32 %x, 47
+  %res1 = select i1 %cmp, i32 1, i32 2
+  %res2 = select i1 %cmp2, i32 3, i32 4
+  %res3 = select i1 %cmp3, i32 5, i32 6
+  %res4 = select i1 %cmp4, i32 3, i32 4
+  %res5 = select i1 %cmp5, i32 5, i32 6
+
+  %res6 = add i32 %res1, %res2
+  %res7 = add i32 %res3, %res4
+  %res = add i32 %res6, %res5
+  ret i32 %res
+}
+
+define i32 @caller1() {
+entry:
+  %call1 = tail call i32 @f1(i32 1, i32 301)
+  %call2 = tail call i32 @f1(i32 47, i32 999)
+  %call3 = tail call i32 @f2(i32 47)
+  %call4 = tail call i32 @f2(i32 301)
+  %res = add nsw i32 %call1, %call2
+  %res.1 = add nsw i32 %res, %call3
+  %res.2 = add nsw i32 %res.1, %call4
+  ret i32 %res.2
+}
+
+; x is overdefined, because constant ranges are only used for parameter
+; values.
+; CHECK-LABEL: f3
+; CHECK: %cmp = icmp sgt i32 %x, 300
+; CHECK: %res = select i1 %cmp, i32 1, i32 2
+; CHECK: ret i32 %res
+define internal i32 @f3(i32 %x) {
+entry:
+  %cmp = icmp sgt i32 %x, 300
+  %res = select i1 %cmp, i32 1, i32 2
+  ret i32 %res
+}
+
+; The phi node could be converted in a ConstantRange.
+define i32 @caller2(i1 %cmp) {
+entry:
+  br i1 %cmp, label %if.true, label %end
+
+if.true:
+  br label %end
+
+end:
+  %res = phi i32 [ 0, %entry], [ 1, %if.true ]
+  %call1 = tail call i32 @f3(i32 %res)
+  ret i32 %call1
+}
+
+; CHECK-LABEL: f4
+; CHECK: %cmp = icmp sgt i32 %x, 300
+; CHECK: %res = select i1 %cmp, i32 1, i32 2
+; CHECK: ret i32 %res
+define internal i32 @f4(i32 %x) {
+entry:
+  %cmp = icmp sgt i32 %x, 300
+  %res = select i1 %cmp, i32 1, i32 2
+  ret i32 %res
+}
+
+; ICmp could introduce bounds on ConstantRanges.
+define i32 @caller3(i32 %x) {
+entry:
+  %cmp = icmp sgt i32 %x, 300
+  br i1 %cmp, label %if.true, label %end
+
+if.true:
+  %x.1 = tail call i32 @f4(i32 %x)
+  br label %end
+
+end:
+  %res = phi i32 [ 0, %entry], [ %x.1, %if.true ]
+  ret i32 %res
+}