Index: lib/IR/Verifier.cpp
===================================================================
--- lib/IR/Verifier.cpp
+++ lib/IR/Verifier.cpp
@@ -114,6 +114,9 @@
 
 using namespace llvm;
 
+static cl::opt<bool> VerifyAtomicAlignment("verify-atomic-alignment",
+                                           cl::init(false));
+
 namespace llvm {
 
 struct VerifierSupport {
@@ -3299,6 +3302,9 @@
            "atomic load operand must have integer, pointer, or floating point "
            "type!",
            ElTy, &LI);
+    Assert(!VerifyAtomicAlignment ||
+               LI.getAlignment() >= DL.getTypeSizeInBits(ElTy) / 8,
+           "atomic load alignment leads to undefined behavior!", &LI);
     checkAtomicMemAccessSize(ElTy, &LI);
   } else {
     Assert(LI.getSyncScopeID() == SyncScope::System,
@@ -3327,6 +3333,9 @@
            "atomic store operand must have integer, pointer, or floating point "
            "type!",
            ElTy, &SI);
+    Assert(!VerifyAtomicAlignment ||
+               SI.getAlignment() >= DL.getTypeSizeInBits(ElTy) / 8,
+           "atomic store alignment leads to undefined behavior!", &SI);
     checkAtomicMemAccessSize(ElTy, &SI);
   } else {
     Assert(SI.getSyncScopeID() == SyncScope::System,
Index: test/Verifier/atomics.ll
===================================================================
--- test/Verifier/atomics.ll
+++ test/Verifier/atomics.ll
@@ -1,7 +1,9 @@
-; RUN: not opt -verify < %s 2>&1 | FileCheck %s
+; RUN: not opt -verify -verify-atomic-alignment=true < %s 2>&1 | FileCheck %s
 
 ; CHECK: atomic store operand must have integer, pointer, or floating point type!
 ; CHECK: atomic load operand must have integer, pointer, or floating point type!
+; CHECK: atomic load alignment leads to undefined behavior!
+; CHECK: atomic store alignment leads to undefined behavior!
 
 define void @foo(x86_mmx* %P, x86_mmx %v) {
   store atomic x86_mmx %v, x86_mmx* %P unordered, align 8
@@ -12,3 +14,13 @@
   %v = load atomic x86_mmx, x86_mmx* %P unordered, align 8
   ret x86_mmx %v
 }
+
+define i32 @load_alignment(i32* %p) {
+  %v = load atomic i32, i32* %p unordered, align 2
+  ret i32 %v
+}
+
+define void @store_alignment(i32* %p, i32 %v) {
+  store atomic i32 %v, i32* %p unordered, align 2
+  ret void
+}