Index: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3406,6 +3406,10 @@
 def warn_division_sizeof_ptr : Warning<
   "'%0' will return the size of the pointer, not the array itself">,
   InGroup<DiagGroup<"sizeof-pointer-div">>;
+def warn_division_sizeof_array : Warning<
+  "expression does not compute the number of elements in this array; element "
+  "type is %0, not %1">,
+  InGroup<DiagGroup<"sizeof-array-div">>;
 
 def note_function_warning_silence : Note<
     "prefix with the address-of operator to silence this warning">;
Index: cfe/trunk/lib/Sema/SemaExpr.cpp
===================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp
+++ cfe/trunk/lib/Sema/SemaExpr.cpp
@@ -9158,17 +9158,28 @@
   else
     RHSTy = RUE->getArgumentExpr()->IgnoreParens()->getType();
 
-  if (!LHSTy->isPointerType() || RHSTy->isPointerType())
-    return;
-  if (LHSTy->getPointeeType().getCanonicalType().getUnqualifiedType() !=
-      RHSTy.getCanonicalType().getUnqualifiedType())
-    return;
+  if (LHSTy->isPointerType() && !RHSTy->isPointerType()) {
+    if (!S.Context.hasSameUnqualifiedType(LHSTy->getPointeeType(), RHSTy))
+      return;
 
-  S.Diag(Loc, diag::warn_division_sizeof_ptr) << LHS << LHS->getSourceRange();
-  if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
-    if (const ValueDecl *LHSArgDecl = DRE->getDecl())
-      S.Diag(LHSArgDecl->getLocation(), diag::note_pointer_declared_here)
-          << LHSArgDecl;
+    S.Diag(Loc, diag::warn_division_sizeof_ptr) << LHS << LHS->getSourceRange();
+    if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
+      if (const ValueDecl *LHSArgDecl = DRE->getDecl())
+        S.Diag(LHSArgDecl->getLocation(), diag::note_pointer_declared_here)
+            << LHSArgDecl;
+    }
+  } else if (const auto *ArrayTy = S.Context.getAsArrayType(LHSTy)) {
+    QualType ArrayElemTy = ArrayTy->getElementType();
+    if (ArrayElemTy->isDependentType() || RHSTy->isDependentType() ||
+        S.Context.getTypeSize(ArrayElemTy) == S.Context.getTypeSize(RHSTy))
+      return;
+    S.Diag(Loc, diag::warn_division_sizeof_array)
+        << LHSArg->getSourceRange() << ArrayElemTy << RHSTy;
+    if (const auto *DRE = dyn_cast<DeclRefExpr>(LHSArg)) {
+      if (const ValueDecl *LHSArgDecl = DRE->getDecl())
+        S.Diag(LHSArgDecl->getLocation(), diag::note_array_declared_here)
+            << LHSArgDecl;
+    }
   }
 }
 
Index: cfe/trunk/test/Sema/div-sizeof-array.cpp
===================================================================
--- cfe/trunk/test/Sema/div-sizeof-array.cpp
+++ cfe/trunk/test/Sema/div-sizeof-array.cpp
@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 %s -verify -Wsizeof-array-div -fsyntax-only
+
+template <typename Ty, int N>
+int f(Ty (&Array)[N]) {
+  return sizeof(Array) / sizeof(Ty); // Should not warn
+}
+
+typedef int int32;
+
+void test(void) {
+  int arr[12];                // expected-note 2 {{array 'arr' declared here}}
+  unsigned long long arr2[4];
+  int *p = &arr[0];
+  int a1 = sizeof(arr) / sizeof(*arr);
+  int a2 = sizeof arr / sizeof p; // expected-warning {{expression does not compute the number of elements in this array; element type is 'int', not 'int *'}}
+  int a4 = sizeof arr2 / sizeof p;
+  int a5 = sizeof(arr) / sizeof(short); // expected-warning {{expression does not compute the number of elements in this array; element type is 'int', not 'short'}}
+  int a6 = sizeof(arr) / sizeof(int32);
+  int a7 = sizeof(arr) / sizeof(int);
+  int a9 = sizeof(arr) / sizeof(unsigned int);
+  const char arr3[2] = "A";
+  int a10 = sizeof(arr3) / sizeof(char);
+
+  int arr4[10][12];                         // expected-note 3 {{array 'arr4' declared here}}
+  int b1 = sizeof(arr4) / sizeof(arr2[12]); // expected-warning {{expression does not compute the number of elements in this array; element type is 'int [12]', not 'unsigned long long'}}
+  int b2 = sizeof(arr4) / sizeof(int *);    // expected-warning {{expression does not compute the number of elements in this array; element type is 'int [12]', not 'int *'}}
+  int b3 = sizeof(arr4) / sizeof(short *);  // expected-warning {{expression does not compute the number of elements in this array; element type is 'int [12]', not 'short *'}}
+}