Index: llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -176,6 +176,7 @@
     Type *getType() const { return Begin->getType(); }
     const SCEV *getBegin() const { return Begin; }
     const SCEV *getEnd() const { return End; }
+    bool isEmpty() const { return Begin == End; }
   };
 
   /// This is the value the condition of the branch needs to evaluate to for the
@@ -1654,8 +1655,11 @@
 IntersectRange(ScalarEvolution &SE,
                const Optional<InductiveRangeCheck::Range> &R1,
                const InductiveRangeCheck::Range &R2) {
-  if (!R1.hasValue())
-    return R2;
+  if (!R1.hasValue()) {
+    if (!R2.isEmpty())
+      return R2;
+    return None;
+  }
   auto &R1Value = R1.getValue();
 
   // TODO: we could widen the smaller range and have this work; but for now we
@@ -1666,7 +1670,11 @@
   const SCEV *NewBegin = SE.getSMaxExpr(R1Value.getBegin(), R2.getBegin());
   const SCEV *NewEnd = SE.getSMinExpr(R1Value.getEnd(), R2.getEnd());
 
-  return InductiveRangeCheck::Range(NewBegin, NewEnd);
+  // If the resulting range is empty, just return None.
+  auto Ret = InductiveRangeCheck::Range(NewBegin, NewEnd);
+  if (Ret.isEmpty())
+    return None;
+  return Ret;
 }
 
 bool InductiveRangeCheckElimination::runOnLoop(Loop *L, LPPassManager &LPM) {
@@ -1735,6 +1743,8 @@
       auto MaybeSafeIterRange =
           IntersectRange(SE, SafeIterRange, Result.getValue());
       if (MaybeSafeIterRange.hasValue()) {
+        assert(!MaybeSafeIterRange.getValue().isEmpty() &&
+               "We should never return empty ranges!");
         RangeChecksToEliminate.push_back(IRC);
         SafeIterRange = MaybeSafeIterRange.getValue();
       }
Index: llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll
===================================================================
--- llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll
+++ llvm/trunk/test/Transforms/IRCE/correct-loop-info.ll
@@ -21,7 +21,7 @@
 ; CHECK:       innerheader.preloop.preheader:
 ; CHECK-NEXT:    br label [[INNERHEADER_PRELOOP:%.*]]
 ; CHECK:       mainloop:
-; CHECK-NEXT:    [[TMP0:%.*]] = icmp slt i32 [[INDVAR_END:%.*]], -1
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp slt i32 [[INDVAR_END:%.*]], 0
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[INNERHEADER_PREHEADER:%.*]], label [[MAIN_PSEUDO_EXIT:%.*]]
 ; CHECK:       innerheader.preheader:
 ; CHECK-NEXT:    br label [[INNERHEADER:%.*]]
@@ -31,11 +31,11 @@
 ; CHECK-NEXT:    to label [[BB5:%.*]] unwind label %outer_exiting.loopexit.split-lp.loopexit.split-lp
 ; CHECK:       bb5:
 ; CHECK-NEXT:    [[TMP6]] = add i32 [[TMP4]], 1
-; CHECK-NEXT:    [[TMP7:%.*]] = icmp ult i32 [[TMP6]], 0
+; CHECK-NEXT:    [[TMP7:%.*]] = icmp ult i32 [[TMP6]], 1
 ; CHECK-NEXT:    br i1 true, label [[BB8]], label [[EXIT3_LOOPEXIT5:%.*]]
 ; CHECK:       bb8:
 ; CHECK-NEXT:    [[TMP9:%.*]] = icmp slt i32 [[TMP6]], 84
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[TMP6]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[TMP6]], 0
 ; CHECK-NEXT:    br i1 [[TMP1]], label [[INNERHEADER]], label [[MAIN_EXIT_SELECTOR:%.*]]
 ; CHECK:       main.exit.selector:
 ; CHECK-NEXT:    [[TMP6_LCSSA:%.*]] = phi i32 [ [[TMP6]], [[BB8]] ]
@@ -90,7 +90,7 @@
 ; CHECK-NEXT:    to label [[BB5_PRELOOP:%.*]] unwind label [[OUTER_EXITING_LOOPEXIT:%.*]]
 ; CHECK:       bb5.preloop:
 ; CHECK-NEXT:    [[TMP6_PRELOOP]] = add i32 [[TMP4_PRELOOP]], 1
-; CHECK-NEXT:    [[TMP7_PRELOOP:%.*]] = icmp ult i32 [[TMP6_PRELOOP]], 0
+; CHECK-NEXT:    [[TMP7_PRELOOP:%.*]] = icmp ult i32 [[TMP6_PRELOOP]], 1
 ; CHECK-NEXT:    br i1 [[TMP7_PRELOOP]], label [[BB8_PRELOOP]], label [[EXIT3_LOOPEXIT:%.*]]
 ; CHECK:       bb8.preloop:
 ; CHECK-NEXT:    [[TMP9_PRELOOP:%.*]] = icmp slt i32 [[TMP6_PRELOOP]], 84
@@ -112,7 +112,7 @@
 ; CHECK-NEXT:    to label [[BB5_POSTLOOP:%.*]] unwind label %outer_exiting.loopexit.split-lp.loopexit
 ; CHECK:       bb5.postloop:
 ; CHECK-NEXT:    [[TMP6_POSTLOOP]] = add i32 [[TMP4_POSTLOOP]], 1
-; CHECK-NEXT:    [[TMP7_POSTLOOP:%.*]] = icmp ult i32 [[TMP6_POSTLOOP]], 0
+; CHECK-NEXT:    [[TMP7_POSTLOOP:%.*]] = icmp ult i32 [[TMP6_POSTLOOP]], 1
 ; CHECK-NEXT:    br i1 [[TMP7_POSTLOOP]], label [[BB8_POSTLOOP]], label [[EXIT3_LOOPEXIT4:%.*]]
 ; CHECK:       bb8.postloop:
 ; CHECK-NEXT:    [[TMP9_POSTLOOP:%.*]] = icmp slt i32 [[TMP6_POSTLOOP]], 84
@@ -135,7 +135,7 @@
 
 bb5:                                              ; preds = %innerheader
   %tmp6 = add i32 %tmp4, 1
-  %tmp7 = icmp ult i32 %tmp6, 0
+  %tmp7 = icmp ult i32 %tmp6, 1
   br i1 %tmp7, label %bb8, label %exit3
 
 bb8:                                              ; preds = %bb5
Index: llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll
===================================================================
--- llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll
+++ llvm/trunk/test/Transforms/IRCE/single-access-no-preloop.ll
@@ -113,5 +113,71 @@
 ; CHECK: %next.postloop = icmp slt i32 %idx.next.postloop, %n
 ; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit
 
+; Make sure that we do not do IRCE if we know that the safe iteration range of
+; the main loop is empty.
+
+define void @single_access_empty_range(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
+ entry:
+  %len = load i32, i32* %a_len_ptr, !range !0
+  %first.itr.check = icmp sgt i32 %n, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds ]
+  %idx.next = add i32 %idx, 1
+  %abc = icmp slt i32 %idx, 0
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %addr = getelementptr i32, i32* %arr, i32 %idx
+  store i32 0, i32* %addr
+  %next = icmp slt i32 %idx.next, %n
+  br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+
+; CHECK-LABEL: @single_access_empty_range(
+; CHECK-NOT:   br i1 false
+; CHECK-NOT:   preloop
+; CHECK-NOT:   postloop
+
+define void @single_access_empty_range_2(i32 *%arr, i32 *%a_len_ptr, i32 %n) {
+ entry:
+  %len = load i32, i32* %a_len_ptr, !range !0
+  %first.itr.check = icmp sgt i32 %n, 0
+  br i1 %first.itr.check, label %loop, label %exit
+
+ loop:
+  %idx = phi i32 [ 0, %entry ] , [ %idx.next, %in.bounds2 ]
+  %idx.next = add i32 %idx, 1
+  %abc = icmp slt i32 %idx, 60
+  br i1 %abc, label %in.bounds1, label %out.of.bounds, !prof !1
+
+ in.bounds1:
+  %def = icmp slt i32 %idx, 0
+  br i1 %def, label %in.bounds2, label %out.of.bounds, !prof !1
+
+in.bounds2:
+  %addr = getelementptr i32, i32* %arr, i32 %idx
+  store i32 0, i32* %addr
+  %next = icmp slt i32 %idx.next, %n
+  br i1 %next, label %loop, label %exit
+
+ out.of.bounds:
+  ret void
+
+ exit:
+  ret void
+}
+
+; CHECK-LABEL: @single_access_empty_range_2(
+; CHECK-NOT:   br i1 false
+; CHECK-NOT:   preloop
+
 !0 = !{i32 0, i32 2147483647}
 !1 = !{!"branch_weights", i32 64, i32 4}