Index: llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
+++ llvm/trunk/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
@@ -399,6 +399,34 @@
                                                   Checks, Visited);
 }
 
+// Add metadata to the loop L to disable loop optimizations. Callers need to
+// confirm that optimizing loop L is not beneficial.
+static void DisableAllLoopOptsOnLoop(Loop &L) {
+  // We do not care about any existing loopID related metadata for L, since we
+  // are setting all loop metadata to false.
+  LLVMContext &Context = L.getHeader()->getContext();
+  // Reserve first location for self reference to the LoopID metadata node.
+  MDNode *Dummy = MDNode::get(Context, {});
+  MDNode *DisableUnroll = MDNode::get(
+      Context, {MDString::get(Context, "llvm.loop.unroll.disable")});
+  Metadata *FalseVal =
+      ConstantAsMetadata::get(ConstantInt::get(Type::getInt1Ty(Context), 0));
+  MDNode *DisableVectorize = MDNode::get(
+      Context,
+      {MDString::get(Context, "llvm.loop.vectorize.enable"), FalseVal});
+  MDNode *DisableLICMVersioning = MDNode::get(
+      Context, {MDString::get(Context, "llvm.loop.licm_versioning.disable")});
+  MDNode *DisableDistribution= MDNode::get(
+      Context,
+      {MDString::get(Context, "llvm.loop.distribute.enable"), FalseVal});
+  MDNode *NewLoopID =
+      MDNode::get(Context, {Dummy, DisableUnroll, DisableVectorize,
+                            DisableLICMVersioning, DisableDistribution});
+  // Set operand 0 to refer to the loop id itself.
+  NewLoopID->replaceOperandWith(0, NewLoopID);
+  L.setLoopID(NewLoopID);
+}
+
 namespace {
 
 // Keeps track of the structure of a loop.  This is similar to llvm::Loop,
@@ -1309,6 +1337,9 @@
         &OriginalLoop, OriginalLoop.getParentLoop(), PreLoop.Map);
     formLCSSARecursively(*L, DT, &LI, &SE);
     simplifyLoop(L, &DT, &LI, &SE, nullptr, true);
+    // Pre loops are slow paths, we do not need to perform any loop
+    // optimizations on them.
+    DisableAllLoopOptsOnLoop(*L);
   }
 
   if (!PostLoop.Blocks.empty()) {
@@ -1316,6 +1347,9 @@
         &OriginalLoop, OriginalLoop.getParentLoop(), PostLoop.Map);
     formLCSSARecursively(*L, DT, &LI, &SE);
     simplifyLoop(L, &DT, &LI, &SE, nullptr, true);
+    // Post loops are slow paths, we do not need to perform any loop
+    // optimizations on them.
+    DisableAllLoopOptsOnLoop(*L);
   }
 
   formLCSSARecursively(OriginalLoop, DT, &LI, &SE);
Index: llvm/trunk/test/Transforms/IRCE/add-metadata-pre-post-loops.ll
===================================================================
--- llvm/trunk/test/Transforms/IRCE/add-metadata-pre-post-loops.ll
+++ llvm/trunk/test/Transforms/IRCE/add-metadata-pre-post-loops.ll
@@ -0,0 +1,81 @@
+; RUN: opt -irce -S < %s 2>&1 | FileCheck %s
+
+; test that the pre and post loops have loop metadata which disables any further
+; loop optimizations.
+
+; generates a post loop, which should have metadata !llvm.loop !2
+; Function Attrs: alwaysinline
+define void @inner_loop(i32* %arr, i32* %a_len_ptr, i32 %n) #0 {
+; CHECK-LABEL: inner_loop(
+; CHECK-LABEL: in.bounds.postloop
+; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit.loopexit, !llvm.loop !2, !irce.loop.clone !7
+
+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:                                             ; preds = %in.bounds, %entry
+  %idx = phi i32 [ 0, %entry ], [ %idx.next, %in.bounds ]
+  %idx.next = add i32 %idx, 1
+  %abc = icmp slt i32 %idx, %len
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+in.bounds:                                        ; preds = %loop
+  %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:                                    ; preds = %loop
+  ret void
+
+exit:                                             ; preds = %in.bounds, %entry
+  ret void
+}
+
+; add loop metadata for pre and post loops
+define void @single_access_with_preloop(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32 %offset) {
+; CHECK-LABEL: @single_access_with_preloop(
+; CHECK-LABEL: in.bounds.preloop
+; CHECK: br i1 %14, label %loop.preloop, label %preloop.exit.selector, !llvm.loop !8, !irce.loop.clone !7
+; CHECK-LABEL: in.bounds.postloop
+; CHECK: br i1 %next.postloop, label %loop.postloop, label %exit.loopexit.loopexit, !llvm.loop !9, !irce.loop.clone !7
+ 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
+  %array.idx = add i32 %idx, %offset
+  %abc.high = icmp slt i32 %array.idx, %len
+  %abc.low = icmp sge i32 %array.idx, 0
+  %abc = and i1 %abc.low, %abc.high
+  br i1 %abc, label %in.bounds, label %out.of.bounds, !prof !1
+
+ in.bounds:
+  %addr = getelementptr i32, i32* %arr, i32 %array.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
+}
+attributes #0 = { alwaysinline }
+
+!0 = !{i32 0, i32 2147483647}
+!1 = !{!"branch_weights", i32 64, i32 4}
+!2 = distinct !{!2, !3, !4, !5, !6}
+!3 = !{!"llvm.loop.unroll.disable"}
+!4 = !{!"llvm.loop.vectorize.enable", i1 false}
+!5 = !{!"llvm.loop.licm_versioning.disable"}
+!6 = !{!"llvm.loop.distribute.enable", i1 false}
+!7 = !{}
+!8 = distinct !{!8, !3, !4, !5}
+!9 = distinct !{!9, !3, !4, !5}