Index: llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ llvm/trunk/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -35,6 +35,9 @@
 STATISTIC(NumElimIdentity, "Number of IV identities eliminated");
 STATISTIC(NumElimOperand,  "Number of IV operands folded into a use");
 STATISTIC(NumElimRem     , "Number of IV remainder operations eliminated");
+STATISTIC(
+    NumSimplifiedSDiv,
+    "Number of IV signed division operations converted to unsigned division");
 STATISTIC(NumElimCmp     , "Number of IV comparisons eliminated");
 
 namespace {
@@ -75,6 +78,7 @@
     void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
     void eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
                               bool IsSigned);
+    bool eliminateSDiv(BinaryOperator *SDiv);
     bool strengthenOverflowingOperation(BinaryOperator *OBO, Value *IVOperand);
   };
 }
@@ -265,6 +269,33 @@
   Changed = true;
 }
 
+bool SimplifyIndvar::eliminateSDiv(BinaryOperator *SDiv) {
+  // Get the SCEVs for the ICmp operands.
+  auto *N = SE->getSCEV(SDiv->getOperand(0));
+  auto *D = SE->getSCEV(SDiv->getOperand(1));
+
+  // Simplify unnecessary loops away.
+  const Loop *L = LI->getLoopFor(SDiv->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 *UDiv = BinaryOperator::Create(
+        BinaryOperator::UDiv, SDiv->getOperand(0), SDiv->getOperand(1),
+        SDiv->getName() + ".udiv", SDiv);
+    UDiv->setIsExact(SDiv->isExact());
+    SDiv->replaceAllUsesWith(UDiv);
+    DEBUG(dbgs() << "INDVARS: Simplified sdiv: " << *SDiv << '\n');
+    ++NumSimplifiedSDiv;
+    Changed = true;
+    DeadInsts.push_back(SDiv);
+    return true;
+  }
+
+  return false;
+}
+
 /// SimplifyIVUsers helper for eliminating useless
 /// remainder operations operating on an induction variable.
 void SimplifyIndvar::eliminateIVRemainder(BinaryOperator *Rem,
@@ -426,12 +457,15 @@
     eliminateIVComparison(ICmp, IVOperand);
     return true;
   }
-  if (BinaryOperator *Rem = dyn_cast<BinaryOperator>(UseInst)) {
-    bool IsSigned = Rem->getOpcode() == Instruction::SRem;
-    if (IsSigned || Rem->getOpcode() == Instruction::URem) {
-      eliminateIVRemainder(Rem, IVOperand, IsSigned);
+  if (BinaryOperator *Bin = dyn_cast<BinaryOperator>(UseInst)) {
+    bool IsSRem = Bin->getOpcode() == Instruction::SRem;
+    if (IsSRem || Bin->getOpcode() == Instruction::URem) {
+      eliminateIVRemainder(Bin, IVOperand, IsSRem);
       return true;
     }
+
+    if (Bin->getOpcode() == Instruction::SDiv)
+      return eliminateSDiv(Bin);
   }
 
   if (auto *CI = dyn_cast<CallInst>(UseInst))
Index: llvm/trunk/test/Transforms/IndVarSimplify/replace-sdiv-by-udiv.ll
===================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/replace-sdiv-by-udiv.ll
+++ llvm/trunk/test/Transforms/IndVarSimplify/replace-sdiv-by-udiv.ll
@@ -0,0 +1,130 @@
+; 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 ]
+  %div = sdiv i32 %i.01, 2
+; CHECK-NOT: sdiv
+; CHECK:     udiv
+  %idxprom = sext i32 %div 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 @test1(i32* %a) {
+; CHECK-LABEL: @test1(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %div = sdiv exact i32 %i.01, 2
+; CHECK-NOT: sdiv
+; CHECK:     udiv exact
+  %idxprom = sext i32 %div 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
+  %div = sdiv i32 %mul, %d
+; CHECK-NOT: udiv
+  %idxprom = sext i32 %div 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 ]
+  %div = sdiv i32 2048, %i.01
+; CHECK:     udiv
+; CHECK-NOT: sdiv
+  %idxprom = sext i32 %div 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
+  %div = sdiv i32 %mul, 8
+; CHECK:     udiv
+; CHECK-NOT: sdiv
+  %idxprom = sext i32 %div 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
+  %div = sdiv i32 %mul, 6
+; CHECK:     udiv
+; CHECK-NOT: sdiv
+  %idxprom = sext i32 %div 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
+}
+