Index: lib/Transforms/Instrumentation/BoundsChecking.cpp
===================================================================
--- lib/Transforms/Instrumentation/BoundsChecking.cpp
+++ lib/Transforms/Instrumentation/BoundsChecking.cpp
@@ -47,21 +47,17 @@
 
 using BuilderTy = IRBuilder<TargetFolder>;
 
-/// Adds run-time bounds checks to memory accessing instructions.
+/// Gets the conditions under which memory accessing instructions will overflow.
 ///
 /// \p Ptr is the pointer that will be read/written, and \p InstVal is either
 /// the result from the load or the value being stored. It is used to determine
 /// the size of memory block that is touched.
 ///
-/// \p GetTrapBB is a callable that returns the trap BB to use on failure.
-///
-/// Returns true if any change was made to the IR, false otherwise.
-template <typename GetTrapBBT>
-static bool instrumentMemAccess(Value *Ptr, Value *InstVal,
-                                const DataLayout &DL, TargetLibraryInfo &TLI,
-                                ObjectSizeOffsetEvaluator &ObjSizeEval,
-                                BuilderTy &IRB, GetTrapBBT GetTrapBB,
-                                ScalarEvolution &SE) {
+/// Returns the condition under which the access will overflow.
+static Value *getBoundsCheckCond(Value *Ptr, Value *InstVal,
+                                 const DataLayout &DL, TargetLibraryInfo &TLI,
+                                 ObjectSizeOffsetEvaluator &ObjSizeEval,
+                                 BuilderTy &IRB, ScalarEvolution &SE) {
   uint64_t NeededSize = DL.getTypeStoreSize(InstVal->getType());
   LLVM_DEBUG(dbgs() << "Instrument " << *Ptr << " for " << Twine(NeededSize)
                     << " bytes\n");
@@ -70,7 +66,7 @@
 
   if (!ObjSizeEval.bothKnown(SizeOffset)) {
     ++ChecksUnable;
-    return false;
+    return nullptr;
   }
 
   Value *Size   = SizeOffset.first;
@@ -107,13 +103,23 @@
     Or = IRB.CreateOr(Cmp1, Or);
   }
 
+  return Or;
+}
+
+/// Adds run-time bounds checks to memory accessing instructions.
+///
+/// \p Or is the condition that should guard the trap.
+///
+/// \p GetTrapBB is a callable that returns the trap BB to use on failure.
+template <typename GetTrapBBT>
+static void insertBoundsCheck(Value *Or, BuilderTy IRB, GetTrapBBT GetTrapBB) {
   // check if the comparison is always false
   ConstantInt *C = dyn_cast_or_null<ConstantInt>(Or);
   if (C) {
     ++ChecksSkipped;
     // If non-zero, nothing to do.
     if (!C->getZExtValue())
-      return true;
+      return;
   }
   ++ChecksAdded;
 
@@ -127,12 +133,11 @@
     // FIXME: We should really handle this differently to bypass the splitting
     // the block.
     BranchInst::Create(GetTrapBB(IRB), OldBB);
-    return true;
+    return;
   }
 
   // Create the conditional branch.
   BranchInst::Create(GetTrapBB(IRB), Cont, Or, OldBB);
-  return true;
 }
 
 static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI,
@@ -176,29 +181,33 @@
     return TrapBB;
   };
 
-  bool MadeChange = false;
+  SmallVector<std::pair<Value *, BuilderTy>, 4> TrapInfo;
   for (Instruction *Inst : WorkList) {
+    Value *Or = nullptr;
     BuilderTy IRB(Inst->getParent(), BasicBlock::iterator(Inst), TargetFolder(DL));
     if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
-      MadeChange |= instrumentMemAccess(LI->getPointerOperand(), LI, DL, TLI,
-                                        ObjSizeEval, IRB, GetTrapBB, SE);
+      Or = getBoundsCheckCond(LI->getPointerOperand(), LI, DL, TLI,
+                              ObjSizeEval, IRB, SE);
     } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
-      MadeChange |=
-          instrumentMemAccess(SI->getPointerOperand(), SI->getValueOperand(),
-                              DL, TLI, ObjSizeEval, IRB, GetTrapBB, SE);
+      Or = getBoundsCheckCond(SI->getPointerOperand(), SI->getValueOperand(),
+                              DL, TLI, ObjSizeEval, IRB, SE);
     } else if (AtomicCmpXchgInst *AI = dyn_cast<AtomicCmpXchgInst>(Inst)) {
-      MadeChange |=
-          instrumentMemAccess(AI->getPointerOperand(), AI->getCompareOperand(),
-                              DL, TLI, ObjSizeEval, IRB, GetTrapBB, SE);
+      Or = getBoundsCheckCond(AI->getPointerOperand(), AI->getCompareOperand(),
+                              DL, TLI, ObjSizeEval, IRB, SE);
     } else if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(Inst)) {
-      MadeChange |=
-          instrumentMemAccess(AI->getPointerOperand(), AI->getValOperand(), DL,
-                              TLI, ObjSizeEval, IRB, GetTrapBB, SE);
+      Or = getBoundsCheckCond(AI->getPointerOperand(), AI->getValOperand(), DL,
+                              TLI, ObjSizeEval, IRB, SE);
     } else {
       llvm_unreachable("unknown Instruction type");
     }
+    if (Or)
+      TrapInfo.push_back(std::make_pair(Or, IRB));
   }
-  return MadeChange;
+
+  for (const auto &Entry : TrapInfo)
+    insertBoundsCheck(Entry.first, Entry.second, GetTrapBB);
+
+  return !TrapInfo.empty();
 }
 
 PreservedAnalyses BoundsCheckingPass::run(Function &F, FunctionAnalysisManager &AM) {
Index: test/Instrumentation/BoundsChecking/many-traps-2.ll
===================================================================
--- /dev/null
+++ test/Instrumentation/BoundsChecking/many-traps-2.ll
@@ -0,0 +1,39 @@
+; RUN: opt < %s -bounds-checking -S | FileCheck %s
+@array = internal global [1819 x i16] zeroinitializer, section ".bss,bss"
+@offsets = external dso_local global [10 x i16]
+
+; CHECK-LABEL: @test
+define dso_local void @test() {
+bb1:
+  br label %bb19
+
+bb20:
+  %_tmp819 = load i16, i16* null
+; CHECK: br {{.*}} %trap
+  %_tmp820 = sub nsw i16 9, %_tmp819
+  %_tmp821 = sext i16 %_tmp820 to i64
+  %_tmp822 = getelementptr [10 x i16], [10 x i16]* @offsets, i16 0, i64 %_tmp821
+  %_tmp823 = load i16, i16* %_tmp822
+  br label %bb33
+
+bb34:
+  %_tmp907 = zext i16 %i__7.107.0 to i64
+  %_tmp908 = getelementptr [1819 x i16], [1819 x i16]* @array, i16 0, i64 %_tmp907
+  store i16 0, i16* %_tmp908
+; CHECK: br {{.*}} %trap
+  %_tmp910 = add i16 %i__7.107.0, 1
+  br label %bb33
+
+bb33:
+  %i__7.107.0 = phi i16 [ undef, %bb20 ], [ %_tmp910, %bb34 ]
+  %_tmp913 = add i16 %_tmp823, 191
+  %_tmp914 = icmp ult i16 %i__7.107.0, %_tmp913
+  br i1 %_tmp914, label %bb34, label %bb19
+
+bb19:
+  %_tmp976 = icmp slt i16 0, 10
+  br i1 %_tmp976, label %bb20, label %bb39
+
+bb39:
+  ret void
+}