Index: llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
+++ llvm/trunk/include/llvm/Analysis/ScalarEvolution.h
@@ -1378,6 +1378,9 @@
   /// Helper function called from createNodeForPHI.
   const SCEV *createAddRecFromPHI(PHINode *PN);
 
+  /// Evaluate ICmpInst to a constant node for special patterns.
+  const SCEV *evaluateForICmp(ICmpInst *IC);
+
   /// A helper function for createAddRecFromPHI to handle simple cases.
   const SCEV *createSimpleAffineAddRec(PHINode *PN, Value *BEValueV,
                                             Value *StartValueV);
Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -4756,11 +4756,26 @@
           Ops.push_back(Add->getOperand(i));
       const SCEV *Accum = getAddExpr(Ops);
 
+      bool InvariantF = isLoopInvariant(Accum, L);
+
+      if (!InvariantF && Accum->getSCEVType() == scZeroExtend) {
+        const SCEV *Op = dyn_cast<SCEVZeroExtendExpr>(Accum)->getOperand();
+        const SCEVUnknown *Un = dyn_cast<SCEVUnknown>(Op);
+        if (Un && Un->getValue() && isa<Instruction>(Un->getValue()) &&
+            dyn_cast<Instruction>(Un->getValue())->getOpcode() ==
+                Instruction::ICmp) {
+          const SCEV *ICmpSC = evaluateForICmp(cast<ICmpInst>(Un->getValue()));
+          bool IsConstSC = ICmpSC->getSCEVType() == scConstant;
+          Accum =
+              IsConstSC ? getZeroExtendExpr(ICmpSC, Accum->getType()) : Accum;
+          InvariantF = IsConstSC ? true : false;
+        }
+      }
+
       // This is not a valid addrec if the step amount is varying each
       // loop iteration, but is not itself an addrec in this loop.
-      if (isLoopInvariant(Accum, L) ||
-          (isa<SCEVAddRecExpr>(Accum) &&
-           cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
+      if (InvariantF || (isa<SCEVAddRecExpr>(Accum) &&
+                         cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
         SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
 
         if (auto BO = MatchBinaryOp(BEValueV, DT)) {
@@ -6443,6 +6458,30 @@
   }
 }
 
+
+const SCEV *ScalarEvolution::evaluateForICmp(ICmpInst *IC) {
+  BasicBlock *Latch = nullptr;
+  const Loop *L = LI.getLoopFor(IC->getParent());
+
+  // If compare instruction is same or inverse of the compare in the
+  // branch of the loop latch, then return a constant evolution
+  // node. This shall facilitate computations of loop exit counts
+  // in cases where compare appears in the evolution chain of induction
+  // variables.
+  if (L && (Latch = L->getLoopLatch())) {
+    BranchInst *BI = dyn_cast<BranchInst>(Latch->getTerminator());
+    if (BI && BI->isConditional() && BI->getCondition() == IC) {
+      if (BI->getSuccessor(0) != L->getHeader())
+        return getZero(Type::getInt1Ty(getContext()));
+      else
+        return getOne(Type::getInt1Ty(getContext()));
+    }
+  }
+
+  return getUnknown(IC);
+}
+
+
 void ScalarEvolution::forgetValue(Value *V) {
   Instruction *I = dyn_cast<Instruction>(V);
   if (!I) return;
Index: llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ llvm/trunk/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2973,8 +2973,11 @@
       // Ignore users that are part of a SCEV expression. This way we only
       // consider leaf IV Users. This effectively rediscovers a portion of
       // IVUsers analysis but in program order this time.
-      if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
-        continue;
+      if (SE.isSCEVable(I.getType())) {
+        const SCEV *SI = SE.getSCEV(&I);
+        if (!isa<SCEVUnknown>(SI) && !isa<SCEVConstant>(SI))
+          continue;
+      }
 
       // Remove this instruction from any NearUsers set it may be in.
       for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
Index: llvm/trunk/test/Analysis/ScalarEvolution/pr34538.ll
===================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/pr34538.ll
+++ llvm/trunk/test/Analysis/ScalarEvolution/pr34538.ll
@@ -0,0 +1,19 @@
+; RUN: opt -S -scalar-evolution -loop-deletion -simplifycfg -analyze < %s | FileCheck %s --check-prefix=CHECK-ANALYSIS
+
+define i32 @foo() local_unnamed_addr #0 {
+; CHECK-ANALYSIS: Loop %do.body: backedge-taken count is 10000
+; CHECK-ANALYSIS: Loop %do.body: max backedge-taken count is 10000
+; CHECK-ANALYSIS: Loop %do.body: Predicated backedge-taken count is 10000
+entry:
+  br label %do.body
+
+do.body:                                          ; preds = %do.body, %entry
+  %start.0 = phi i32 [ 0, %entry ], [ %inc.start.0, %do.body ]
+  %cmp = icmp slt i32 %start.0, 10000
+  %inc = zext i1 %cmp to i32
+  %inc.start.0 = add nsw i32 %start.0, %inc
+  br i1 %cmp, label %do.body, label %do.end
+
+do.end:                                           ; preds = %do.body
+  ret i32 0
+}