diff --git a/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index 291ad2ed47e..25acd281893 100644
--- a/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -623,26 +623,31 @@ void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
 }
 
 // If I is an interesting memory access, return the PointerOperand
-// and set IsWrite. Otherwise return NULL.
-static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite) {
+// and set IsWrite/Alignment. Otherwise return NULL.
+static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
+                                        unsigned *Alignment) {
   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
     if (!ClInstrumentReads) return nullptr;
     *IsWrite = false;
+    *Alignment = LI->getAlignment();
     return LI->getPointerOperand();
   }
   if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
     if (!ClInstrumentWrites) return nullptr;
     *IsWrite = true;
+    *Alignment = SI->getAlignment();
     return SI->getPointerOperand();
   }
   if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
     if (!ClInstrumentAtomics) return nullptr;
     *IsWrite = true;
+    *Alignment = 0;
     return RMW->getPointerOperand();
   }
   if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
     if (!ClInstrumentAtomics) return nullptr;
     *IsWrite = true;
+    *Alignment = 0;
     return XCHG->getPointerOperand();
   }
   return nullptr;
@@ -692,7 +697,8 @@ AddressSanitizer::instrumentPointerComparisonOrSubtraction(Instruction *I) {
 
 void AddressSanitizer::instrumentMop(Instruction *I, bool UseCalls) {
   bool IsWrite = false;
-  Value *Addr = isInterestingMemoryAccess(I, &IsWrite);
+  unsigned Alignment = 0;
+  Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &Alignment);
   assert(Addr);
   if (ClOpt && ClOptGlobals) {
     if (GlobalVariable *G = dyn_cast<GlobalVariable>(Addr)) {
@@ -727,11 +733,14 @@ void AddressSanitizer::instrumentMop(Instruction *I, bool UseCalls) {
   else
     NumInstrumentedReads++;
 
-  // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check.
-  if (TypeSize == 8  || TypeSize == 16 ||
-      TypeSize == 32 || TypeSize == 64 || TypeSize == 128)
+  unsigned Granularity = 1 << Mapping.Scale;
+  // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
+  // if the data is properly aligned.
+  if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
+       TypeSize == 128) &&
+      (Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
     return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls);
-  // Instrument unusual size (but still multiple of 8).
+  // Instrument unusual size or unusual alignment.
   // We can not do it with a single check, so we do 1-byte check for the first
   // and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
   // to report the actual access size.
@@ -1328,6 +1337,7 @@ bool AddressSanitizer::runOnFunction(Function &F) {
   SmallVector<Instruction*, 16> PointerComparisonsOrSubtracts;
   int NumAllocas = 0;
   bool IsWrite;
+  unsigned Alignment;
 
   // Fill the set of memory operations to instrument.
   for (Function::iterator FI = F.begin(), FE = F.end();
@@ -1338,7 +1348,7 @@ bool AddressSanitizer::runOnFunction(Function &F) {
     for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
          BI != BE; ++BI) {
       if (LooksLikeCodeInBug11395(BI)) return false;
-      if (Value *Addr = isInterestingMemoryAccess(BI, &IsWrite)) {
+      if (Value *Addr = isInterestingMemoryAccess(BI, &IsWrite, &Alignment)) {
         if (ClOpt && ClOptSameTemp) {
           if (!TempsToInstrument.insert(Addr))
             continue;  // We've seen this temp in the current BB.
@@ -1390,7 +1400,7 @@ bool AddressSanitizer::runOnFunction(Function &F) {
     Instruction *Inst = ToInstrument[i];
     if (ClDebugMin < 0 || ClDebugMax < 0 ||
         (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
-      if (isInterestingMemoryAccess(Inst, &IsWrite))
+      if (isInterestingMemoryAccess(Inst, &IsWrite, &Alignment))
         instrumentMop(Inst, UseCalls);
       else
         instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
diff --git a/test/Instrumentation/AddressSanitizer/basic.ll b/test/Instrumentation/AddressSanitizer/basic.ll
index 7a125a39643..7d1aa0b8530 100644
--- a/test/Instrumentation/AddressSanitizer/basic.ll
+++ b/test/Instrumentation/AddressSanitizer/basic.ll
@@ -34,7 +34,7 @@ define i32 @test_load(i32* %a) sanitize_address {
 
 
 entry:
-  %tmp1 = load i32* %a
+  %tmp1 = load i32* %a, align 4
   ret i32 %tmp1
 }
 
@@ -66,7 +66,7 @@ define void @test_store(i32* %a) sanitize_address {
 ;
 
 entry:
-  store i32 42, i32* %a
+  store i32 42, i32* %a, align 4
   ret void
 }
 
@@ -115,6 +115,18 @@ define void @i40test(i40* %a, i40* %b) nounwind uwtable sanitize_address {
 ; CHECK: __asan_report_store_n{{.*}}, i64 5)
 ; CHECK: ret void
 
+define void @i64test_align1(i64* %b) nounwind uwtable sanitize_address {
+  entry:
+  store i64 0, i64* %b, align 1
+  ret void
+}
+
+; CHECK-LABEL: i64test_align1
+; CHECK: __asan_report_store_n{{.*}}, i64 8)
+; CHECK: __asan_report_store_n{{.*}}, i64 8)
+; CHECK: ret void
+
+
 define void @i80test(i80* %a, i80* %b) nounwind uwtable sanitize_address {
   entry:
   %t = load i80* %a
diff --git a/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll b/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll
index dd82444b17b..adb434112cd 100644
--- a/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll
+++ b/test/Instrumentation/AddressSanitizer/instrumentation-with-call-threshold.ll
@@ -20,10 +20,10 @@ entry:
 ; CHECK-CUSTOM-PREFIX: call void @__foo_load8
 ; CHECK-CUSTOM-PREFIX: call void @__foo_loadN
 ; CHECK-INLINE-NOT: call void @__asan_load
-  %tmp1 = load i32* %a
-  %tmp2 = load i64* %b
-  %tmp3 = load i512* %c
-  %tmp4 = load i80* %d
+  %tmp1 = load i32* %a, align 4
+  %tmp2 = load i64* %b, align 8
+  %tmp3 = load i512* %c, align 32
+  %tmp4 = load i80* %d, align 8
   ret void
 }
 
diff --git a/test/Instrumentation/AddressSanitizer/test64.ll b/test/Instrumentation/AddressSanitizer/test64.ll
index 4f3ed5b478c..fd93f4576ae 100644
--- a/test/Instrumentation/AddressSanitizer/test64.ll
+++ b/test/Instrumentation/AddressSanitizer/test64.ll
@@ -6,7 +6,7 @@ entry:
   %tmp1 = load i32* %a, align 4
   ret i32 %tmp1
 }
-; CHECK: @read_4_bytes
+; CHECK-LABEL: @read_4_bytes
 ; CHECK-NOT: ret
 ; CHECK: lshr {{.*}} 3
 ; Check for ASAN's Offset for 64-bit (7fff8000)
@@ -19,8 +19,10 @@ entry:
   ret void
 }
 
-; CHECK: @example_atomicrmw
+; CHECK-LABEL: @example_atomicrmw
 ; CHECK: lshr {{.*}} 3
+; CHECK: __asan_report_store8
+; CHECK-NOT: __asan_report
 ; CHECK: atomicrmw
 ; CHECK: ret
 
@@ -30,7 +32,9 @@ entry:
   ret void
 }
 
-; CHECK: @example_cmpxchg
+; CHECK-LABEL: @example_cmpxchg
 ; CHECK: lshr {{.*}} 3
+; CHECK: __asan_report_store8
+; CHECK-NOT: __asan_report
 ; CHECK: cmpxchg
 ; CHECK: ret