Index: llvm/include/llvm/Analysis/ScalarEvolution.h
===================================================================
--- llvm/include/llvm/Analysis/ScalarEvolution.h
+++ llvm/include/llvm/Analysis/ScalarEvolution.h
@@ -1162,6 +1162,18 @@
   /// Try to apply information from loop guards for \p L to \p Expr.
   const SCEV *applyLoopGuards(const SCEV *Expr, const Loop *L);
 
+  /// Return true if the loop has no abnormal exits. That is, if the loop
+  /// is not infinite, it must exit through an explicit edge in the CFG.
+  /// (As opposed to either a) throwing out of the function or b) entering a
+  /// well defined infinite loop in some callee.)
+  bool loopHasNoAbnormalExits(const Loop *L) {
+    return getLoopProperties(L).HasNoAbnormalExits;
+  }
+
+  /// Return true if this loop is finite by assumption.  That is,
+  /// to be infinite, it must also be undefined.
+  bool loopIsFiniteByAssumption(const Loop *L);
+
 private:
   /// A CallbackVH to arrange for ScalarEvolution to be notified whenever a
   /// Value is deleted.
@@ -1482,14 +1494,6 @@
     return getLoopProperties(L).HasNoSideEffects;
   }
 
-  bool loopHasNoAbnormalExits(const Loop *L) {
-    return getLoopProperties(L).HasNoAbnormalExits;
-  }
-
-  /// Return true if this loop is finite by assumption.  That is,
-  /// to be infinite, it must also be undefined.
-  bool loopIsFiniteByAssumption(const Loop *L);
-
   /// Compute a LoopDisposition value.
   LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
 
Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -36,6 +36,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/iterator_range.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/MemorySSA.h"
@@ -155,6 +156,9 @@
   bool rewriteNonIntegerIVs(Loop *L);
 
   bool simplifyAndExtend(Loop *L, SCEVExpander &Rewriter, LoopInfo *LI);
+  /// Use knowledge about loop finiteness to convert signed to unsigned
+  /// exit conditions where possible.
+  bool canonicalizeExitCondition(Loop *L);
   /// Try to eliminate loop exits based on analyzeable exit counts
   bool optimizeLoopExits(Loop *L, SCEVExpander &Rewriter);
   /// Try to form loop invariant tests for loop exits by changing how many
@@ -1407,6 +1411,55 @@
   return true;
 }
 
+bool IndVarSimplify::canonicalizeExitCondition(Loop *L) {
+  // Note: Conceptually, this should probably live in simplifyAndExtend with
+  // the exit being identified with a bounded use walk, but doing that requires
+  // extending the set of "interesting" IV users to include the icmp, and
+  // doing that regresses results in practice by querying SCEVs before trip
+  // counts which rely on them which results in SCEV caching sub-optimal
+  // answers.
+
+  auto *ExitingBB = L->getExitingBlock();
+  if (!ExitingBB)
+    return false;
+  auto *BI = dyn_cast<BranchInst>(ExitingBB->getTerminator());
+  if (!BI || BI->isUnconditional())
+    return false;;
+
+  auto *ICmp = dyn_cast<ICmpInst>(BI->getCondition());
+  if (!ICmp)
+    return false;
+
+  auto *LHS = dyn_cast<Instruction>(ICmp->getOperand(0));
+  auto *RHS = ICmp->getOperand(1);
+  if (!LHS || !L->isLoopInvariant(RHS))
+    return false;
+
+  // Match (icmp signed-cond zext, RHS)
+  switch (LHS->getOpcode()) {
+  default:
+    return false;
+  case Instruction::ZExt:
+    switch (ICmp->getPredicate()) {
+    default:
+      return false;
+    case ICmpInst::ICMP_SLT:
+    case ICmpInst::ICMP_SLE:
+    case ICmpInst::ICMP_SGT:
+    case ICmpInst::ICMP_SGE:
+      break;
+    };
+  };
+
+  // If the exit might not be taken in a well defined program.
+  if (!SE->loopHasNoAbnormalExits(L) || !SE->loopIsFiniteByAssumption(L))
+    return false;
+  // We have now matched icmp signed-cond zext(X), zext(Y'), and can thus
+  // replace the signed condition with the unsigned version.
+  ICmp->setPredicate(ICmp->getUnsignedPredicate());
+  return true;
+}
+
 bool IndVarSimplify::optimizeLoopExits(Loop *L, SCEVExpander &Rewriter) {
   SmallVector<BasicBlock*, 16> ExitingBlocks;
   L->getExitingBlocks(ExitingBlocks);
@@ -1788,6 +1841,14 @@
   // Eliminate redundant IV cycles.
   NumElimIV += Rewriter.replaceCongruentIVs(L, DT, DeadInsts);
 
+  if (canonicalizeExitCondition(L)) {
+    Changed = true;
+    // Given we've changed exit counts, notify SCEV
+    // Some nested loops may share same folded exit basic block,
+    // thus we need to notify top most loop.
+    SE->forgetTopmostLoop(L);
+  }
+
   // Try to eliminate loop exits based on analyzeable exit counts
   if (optimizeLoopExits(L, Rewriter))  {
     Changed = true;
Index: llvm/test/Transforms/IndVarSimplify/finite-exit-comparisons.ll
===================================================================
--- llvm/test/Transforms/IndVarSimplify/finite-exit-comparisons.ll
+++ llvm/test/Transforms/IndVarSimplify/finite-exit-comparisons.ll
@@ -15,7 +15,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ [[START:%.*]], [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i16 [[ZEXT]], 254
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i16 [[ZEXT]], 254
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -42,7 +42,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i16 [[ZEXT]], [[N:%.*]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i16 [[ZEXT]], [[N:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -301,7 +301,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ [[START:%.*]], [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i16 [[ZEXT]], 254
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i16 [[ZEXT]], 254
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -328,7 +328,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i16 [[ZEXT]], [[N:%.*]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i16 [[ZEXT]], [[N:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -355,7 +355,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ [[START:%.*]], [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i16 [[ZEXT]], 254
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i16 [[ZEXT]], 254
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -382,7 +382,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i16 [[ZEXT]], [[N:%.*]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ule i16 [[ZEXT]], [[N:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -409,7 +409,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ [[START:%.*]], [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i16 [[ZEXT]], 254
+; CHECK-NEXT:    [[CMP:%.*]] = icmp uge i16 [[ZEXT]], 254
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void
@@ -436,7 +436,7 @@
 ; CHECK-NEXT:    [[IV:%.*]] = phi i8 [ [[IV_NEXT:%.*]], [[FOR_BODY]] ], [ 0, [[ENTRY:%.*]] ]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i8 [[IV]], 1
 ; CHECK-NEXT:    [[ZEXT:%.*]] = zext i8 [[IV_NEXT]] to i16
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i16 [[ZEXT]], [[N:%.*]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp uge i16 [[ZEXT]], [[N:%.*]]
 ; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
 ; CHECK:       for.end:
 ; CHECK-NEXT:    ret void