Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5395,9 +5395,6 @@
   "zero size arrays are an extension">, InGroup<ZeroLengthArray>;
 def err_typecheck_zero_array_size : Error<
   "zero-length arrays are not permitted in C++">;
-def warn_typecheck_zero_static_array_size : Warning<
-  "'static' has no effect on zero-length arrays">,
-  InGroup<ArrayBounds>;
 def err_array_size_non_int : Error<"size of array has non-integer type %0">;
 def err_init_element_not_constant : Error<
   "initializer element is not a compile-time constant">;
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -2500,12 +2500,20 @@
             if (ArrTy->getSizeModifier() == ArrayType::Static) {
               QualType ETy = ArrTy->getElementType();
               uint64_t ArrSize = ArrTy->getSize().getZExtValue();
-              if (!ETy->isIncompleteType() && ETy->isConstantSizeType() &&
-                  ArrSize) {
-                llvm::AttrBuilder Attrs;
-                Attrs.addDereferenceableAttr(
-                  getContext().getTypeSizeInChars(ETy).getQuantity()*ArrSize);
-                AI->addAttrs(Attrs);
+              if (!ETy->isIncompleteType() && ETy->isConstantSizeType()) {
+                // If the type is complete and we know the array size is non-
+                // zero, then we know the dereferencable range of memory.
+                // Otherwise, if the array size is zero, we only know that the
+                // memory must be nonnull.
+                if (ArrSize) {
+                  llvm::AttrBuilder Attrs;
+                  Attrs.addDereferenceableAttr(
+                      getContext().getTypeSizeInChars(ETy).getQuantity() *
+                      ArrSize);
+                  AI->addAttrs(Attrs);
+                } else {
+                  AI->addAttr(llvm::Attribute::NonNull);
+                }
               } else if (getContext().getTargetAddressSpace(ETy) == 0 &&
                          !CGM.getCodeGenOpts().NullPointerIsValid) {
                 AI->addAttr(llvm::Attribute::NonNull);
Index: clang/lib/Sema/SemaType.cpp
===================================================================
--- clang/lib/Sema/SemaType.cpp
+++ clang/lib/Sema/SemaType.cpp
@@ -2393,13 +2393,6 @@
                                          ? diag::err_typecheck_zero_array_size
                                          : diag::ext_typecheck_zero_array_size)
           << ArraySize->getSourceRange();
-
-      if (ASM == ArrayType::Static) {
-        Diag(ArraySize->getBeginLoc(),
-             diag::warn_typecheck_zero_static_array_size)
-            << ArraySize->getSourceRange();
-        ASM = ArrayType::Normal;
-      }
     } else if (!T->isDependentType() && !T->isVariablyModifiedType() &&
                !T->isIncompleteType() && !T->isUndeducedType()) {
       // Is the array too large?
Index: clang/test/CodeGen/vla.c
===================================================================
--- clang/test/CodeGen/vla.c
+++ clang/test/CodeGen/vla.c
@@ -206,3 +206,6 @@
 // NULL-INVALID: define void @test9(i32 %n, i32* nonnull %a)
 // NULL-VALID: define void @test9(i32 %n, i32* %a)
 
+// Make sure a zero-sized static array extent is still required to be nonnull.
+void test10(int a[static 0]) {}
+// CHECK: define void @test10(i32* nonnull %a)
Index: clang/test/Sema/static-array.c
===================================================================
--- clang/test/Sema/static-array.c
+++ clang/test/Sema/static-array.c
@@ -1,6 +1,7 @@
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -fsyntax-only -fblocks -verify %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -fsyntax-only -fblocks -pedantic -verify %s
 
-void cat0(int a[static 0]) {} // expected-warning {{'static' has no effect on zero-length arrays}}
+void cat0(int a[static 0]) {} // expected-warning {{zero size arrays are an extension}} \
+                              // expected-note {{callee declares array parameter as static here}}
 
 void cat(int a[static 3]) {} // expected-note 4 {{callee declares array parameter as static here}} expected-note 2 {{passing argument to parameter 'a' here}}
 
@@ -9,7 +10,7 @@
 void f(int *p) {
   int a[2], b[3], c[4];
 
-  cat0(0);
+  cat0(0); // expected-warning {{null passed to a callee that requires a non-null argument}}
 
   cat(0); // expected-warning {{null passed to a callee that requires a non-null argument}}
   cat(a); // expected-warning {{array argument is too small; contains 2 elements, callee requires at least 3}}