Index: lib/Transforms/Utils/SimplifyIndVar.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyIndVar.cpp
+++ lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -38,6 +38,9 @@
 STATISTIC(
     NumSimplifiedSDiv,
     "Number of IV signed division operations converted to unsigned division");
+STATISTIC(
+    NumSimplifiedSRem,
+    "Number of IV signed remainder operations converted to unsigned remainder");
 STATISTIC(NumElimCmp     , "Number of IV comparisons eliminated");
 
 namespace {
@@ -76,9 +79,10 @@
     bool eliminateOverflowIntrinsic(CallInst *CI);
     bool eliminateIVUser(Instruction *UseInst, Instruction *IVOperand);
     void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
-    void eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
+    bool eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
                               bool IsSigned);
     bool eliminateSDiv(BinaryOperator *SDiv);
+    bool eliminateSRem(BinaryOperator *SRem);
     bool strengthenOverflowingOperation(BinaryOperator *OBO, Value *IVOperand);
   };
 }
@@ -296,15 +300,40 @@
   return false;
 }
 
+bool SimplifyIndvar::eliminateSRem(BinaryOperator *SRem) {
+  // Get the SCEVs for the ICmp operands.
+  auto *N = SE->getSCEV(SRem->getOperand(0));
+  auto *D = SE->getSCEV(SRem->getOperand(1));
+
+  // Simplify unnecessary loops away.
+  const Loop *L = LI->getLoopFor(SRem->getParent());
+  N = SE->getSCEVAtScope(N, L);
+  D = SE->getSCEVAtScope(D, L);
+
+  // Replace sdiv by udiv if both of the operands are non-negative
+  if (SE->isKnownNonNegative(N) && SE->isKnownNonNegative(D)) {
+    auto *URem = BinaryOperator::Create(
+        BinaryOperator::URem, SRem->getOperand(0), SRem->getOperand(1),
+        SRem->getName() + ".urem", SRem);
+    SRem->replaceAllUsesWith(URem);
+    DEBUG(dbgs() << "INDVARS: Simplified srem: " << *SRem << '\n');
+    ++NumSimplifiedSRem;
+    Changed = true;
+    DeadInsts.push_back(SRem);
+    return true;
+  }
+
+  return false;
+}
+
 /// SimplifyIVUsers helper for eliminating useless
 /// remainder operations operating on an induction variable.
-void SimplifyIndvar::eliminateIVRemainder(BinaryOperator *Rem,
-                                      Value *IVOperand,
-                                      bool IsSigned) {
+bool SimplifyIndvar::eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
+                                          bool IsSigned) {
   // We're only interested in the case where we know something about
   // the numerator.
   if (IVOperand != Rem->getOperand(0))
-    return;
+    return false;
 
   // Get the SCEVs for the ICmp operands.
   const SCEV *S = SE->getSCEV(Rem->getOperand(0));
@@ -324,12 +353,12 @@
     // (i+1) % n  -->  (i+1)==n?0:(i+1)  if i is in [0,n).
     const SCEV *LessOne = SE->getMinusSCEV(S, SE->getOne(S->getType()));
     if (IsSigned && !SE->isKnownNonNegative(LessOne))
-      return;
+      return false;
 
     if (!SE->isKnownPredicate(IsSigned ?
                               ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
                               LessOne, X))
-      return;
+      return false;
 
     ICmpInst *ICmp = new ICmpInst(Rem, ICmpInst::ICMP_EQ,
                                   Rem->getOperand(0), Rem->getOperand(1));
@@ -344,6 +373,7 @@
   ++NumElimRem;
   Changed = true;
   DeadInsts.emplace_back(Rem);
+  return true;
 }
 
 bool SimplifyIndvar::eliminateOverflowIntrinsic(CallInst *CI) {
@@ -460,7 +490,8 @@
   if (BinaryOperator *Bin = dyn_cast<BinaryOperator>(UseInst)) {
     bool IsSRem = Bin->getOpcode() == Instruction::SRem;
     if (IsSRem || Bin->getOpcode() == Instruction::URem) {
-      eliminateIVRemainder(Bin, IVOperand, IsSRem);
+      if (!eliminateIVRemainder(Bin, IVOperand, IsSRem) && IsSRem)
+        eliminateSRem(Bin);
       return true;
     }
 
Index: test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
===================================================================
--- /dev/null
+++ test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
@@ -0,0 +1,109 @@
+; RUN: opt < %s -indvars -S | FileCheck %s
+
+define void @test0(i32* %a) {
+; CHECK-LABEL: @test0(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %rem = srem i32 %i.01, 2
+; CHECK-NOT: srem
+; CHECK:     urem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test2(i32* %a, i32 %d) {
+; CHECK-LABEL: @test2(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %mul = mul nsw i32 %i.01, 64
+  %rem = srem i32 %mul, %d
+; CHECK-NOT: urem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test3(i32* %a) {
+; CHECK-LABEL: @test3(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %rem = srem i32 2048, %i.01
+; CHECK:     urem
+; CHECK-NOT: srem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test4(i32* %a) {
+; CHECK-LABEL: @test4(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %mul = mul nsw i32 %i.01, 64
+  %rem = srem i32 %mul, 8
+; CHECK:     urem
+; CHECK-NOT: srem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test5(i32* %a) {
+; CHECK-LABEL: @test5(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %mul = mul nsw i32 %i.01, 64
+  %rem = srem i32 %mul, 6
+; CHECK:     urem
+; CHECK-NOT: srem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+