[clang]: Add support for "-fno-delete-null-pointer-checks"

Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.

More details : https://lkml.org/lkml/2018/4/4/601

GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.

-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.

This feature is implemented in as the function attribute
"null-pointer-is-valid"="true".
This CL only adds the attribute on the function.
It also strips "nonnull" attributes from function arguments but
keeps the related warnings unchanged.

Corresponding LLVM change rL336613 already updated the
optimizations to not treat null pointer dereferencing
as undefined if the attribute is present.

Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv

Reviewed By: jyknight

Subscribers: drinkcat, xbolva00, cfe-commits

Differential Revision: https://reviews.llvm.org/D47894

llvm-svn: 337433

14 files changed, 109 insertions, 31 deletions

diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst
index 513128119e2..87c7896ba70 100644
--- a/clang/docs/ClangCommandLineReference.rst
+++ b/clang/docs/ClangCommandLineReference.rst
@@ -1543,6 +1543,14 @@ Specifies the largest alignment guaranteed by '::operator new(size\_t)'
 
 Disable implicit builtin knowledge of a specific function
 
+.. option:: -fdelete-null-pointer-checks, -fno-delete-null-pointer-checks
+
+When enabled, treat null pointer dereference, creation of a reference to null,
+or passing a null pointer to a function parameter annotated with the "nonnull"
+attribute as undefined behavior. (And, thus the optimizer may assume that any
+pointer used in such a way must not have been null and optimize away the
+branches accordingly.) On by default.
+
 .. option:: -fno-elide-type
 
 Do not elide types when printing diagnostics
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index b71d1e15ae8..60516084489 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1080,6 +1080,13 @@ def frewrite_imports : Flag<["-"], "frewrite-imports">, Group<f_Group>,
   Flags<[CC1Option]>;
 def fno_rewrite_imports : Flag<["-"], "fno-rewrite-imports">, Group<f_Group>;
 
+def fdelete_null_pointer_checks : Flag<["-"],
+  "fdelete-null-pointer-checks">, Group<f_Group>,
+  HelpText<"Treat usage of null pointers as undefined behavior.">;
+def fno_delete_null_pointer_checks : Flag<["-"],
+  "fno-delete-null-pointer-checks">, Group<f_Group>, Flags<[CC1Option]>,
+  HelpText<"Do not treat usage of null pointers as undefined behavior.">;
+
 def frewrite_map_file : Separate<["-"], "frewrite-map-file">,
                         Group<f_Group>,
                         Flags<[ DriverOption, CC1Option ]>;
@@ -2855,8 +2862,6 @@ defm reorder_blocks : BooleanFFlag<"reorder-blocks">, Group<clang_ignored_gcc_op
 defm eliminate_unused_debug_types : BooleanFFlag<"eliminate-unused-debug-types">, Group<clang_ignored_f_Group>;
 defm branch_count_reg : BooleanFFlag<"branch-count-reg">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm default_inline : BooleanFFlag<"default-inline">, Group<clang_ignored_gcc_optimization_f_Group>;
-defm delete_null_pointer_checks : BooleanFFlag<"delete-null-pointer-checks">,
-    Group<clang_ignored_gcc_optimization_f_Group>;
 defm fat_lto_objects : BooleanFFlag<"fat-lto-objects">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm float_store : BooleanFFlag<"float-store">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm friend_injection : BooleanFFlag<"friend-injection">, Group<clang_ignored_f_Group>;
diff --git a/clang/include/clang/Frontend/CodeGenOptions.def b/clang/include/clang/Frontend/CodeGenOptions.def
index c199b5428ea..2ed96d43279 100644
--- a/clang/include/clang/Frontend/CodeGenOptions.def
+++ b/clang/include/clang/Frontend/CodeGenOptions.def
@@ -130,6 +130,7 @@ CODEGENOPT(EnableSegmentedStacks , 1, 0) ///< Set when -fsplit-stack is enabled.
 CODEGENOPT(NoImplicitFloat   , 1, 0) ///< Set when -mno-implicit-float is enabled.
 CODEGENOPT(NoInfsFPMath      , 1, 0) ///< Assume FP arguments, results not +-Inf.
 CODEGENOPT(NoSignedZeros     , 1, 0) ///< Allow ignoring the signedness of FP zero
+CODEGENOPT(NullPointerIsValid , 1, 0) ///< Assume Null pointer deference is defined.
 CODEGENOPT(Reassociate       , 1, 0) ///< Allow reassociation of FP math ops
 CODEGENOPT(ReciprocalMath    , 1, 0) ///< Allow FP divisions to be reassociated.
 CODEGENOPT(NoTrappingMath    , 1, 0) ///< Set when -fno-trapping-math is enabled.
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 07fb6d56dd7..fcc8a3e5f64 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1734,6 +1734,8 @@ void CodeGenModule::ConstructDefaultFnAttrList(StringRef Name, bool HasOptnone,
     FuncAttrs.addAttribute("less-precise-fpmad",
                            llvm::toStringRef(CodeGenOpts.LessPreciseFPMAD));
 
+    if (CodeGenOpts.NullPointerIsValid)
+      FuncAttrs.addAttribute("null-pointer-is-valid", "true");
     if (!CodeGenOpts.FPDenormalMode.empty())
       FuncAttrs.addAttribute("denormal-fp-math", CodeGenOpts.FPDenormalMode);
 
@@ -1867,7 +1869,8 @@ void CodeGenModule::ConstructAttributeList(
     }
     if (TargetDecl->hasAttr<RestrictAttr>())
       RetAttrs.addAttribute(llvm::Attribute::NoAlias);
-    if (TargetDecl->hasAttr<ReturnsNonNullAttr>())
+    if (TargetDecl->hasAttr<ReturnsNonNullAttr>() &&
+        !CodeGenOpts.NullPointerIsValid)
       RetAttrs.addAttribute(llvm::Attribute::NonNull);
     if (TargetDecl->hasAttr<AnyX86NoCallerSavedRegistersAttr>())
       FuncAttrs.addAttribute("no_caller_saved_registers");
@@ -1974,7 +1977,8 @@ void CodeGenModule::ConstructAttributeList(
     if (!PTy->isIncompleteType() && PTy->isConstantSizeType())
       RetAttrs.addDereferenceableAttr(getContext().getTypeSizeInChars(PTy)
                                         .getQuantity());
-    else if (getContext().getTargetAddressSpace(PTy) == 0)
+    else if (getContext().getTargetAddressSpace(PTy) == 0 &&
+             !CodeGenOpts.NullPointerIsValid)
       RetAttrs.addAttribute(llvm::Attribute::NonNull);
   }
 
@@ -2083,7 +2087,8 @@ void CodeGenModule::ConstructAttributeList(
       if (!PTy->isIncompleteType() && PTy->isConstantSizeType())
         Attrs.addDereferenceableAttr(getContext().getTypeSizeInChars(PTy)
                                        .getQuantity());
-      else if (getContext().getTargetAddressSpace(PTy) == 0)
+      else if (getContext().getTargetAddressSpace(PTy) == 0 &&
+               !CodeGenOpts.NullPointerIsValid)
         Attrs.addAttribute(llvm::Attribute::NonNull);
     }
 
@@ -2343,7 +2348,8 @@ void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
 
         if (const ParmVarDecl *PVD = dyn_cast<ParmVarDecl>(Arg)) {
           if (getNonNullAttr(CurCodeDecl, PVD, PVD->getType(),
-                             PVD->getFunctionScopeIndex()))
+                             PVD->getFunctionScopeIndex()) &&
+              !CGM.getCodeGenOpts().NullPointerIsValid)
             AI->addAttr(llvm::Attribute::NonNull);
 
           QualType OTy = PVD->getOriginalType();
@@ -2362,7 +2368,8 @@ void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
                 Attrs.addDereferenceableAttr(
                   getContext().getTypeSizeInChars(ETy).getQuantity()*ArrSize);
                 AI->addAttrs(Attrs);
-              } else if (getContext().getTargetAddressSpace(ETy) == 0) {
+              } else if (getContext().getTargetAddressSpace(ETy) == 0 &&
+                         !CGM.getCodeGenOpts().NullPointerIsValid) {
                 AI->addAttr(llvm::Attribute::NonNull);
               }
             }
@@ -2372,7 +2379,8 @@ void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI,
             // we can't use the dereferenceable attribute, but in addrspace(0)
             // we know that it must be nonnull.
             if (ArrTy->getSizeModifier() == VariableArrayType::Static &&
-                !getContext().getTargetAddressSpace(ArrTy->getElementType()))
+                !getContext().getTargetAddressSpace(ArrTy->getElementType()) &&
+                !CGM.getCodeGenOpts().NullPointerIsValid)
               AI->addAttr(llvm::Attribute::NonNull);
           }
 
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 4db4dc19a8b..e23ff16699f 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -3348,6 +3348,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                    options::OPT_fno_merge_all_constants, false))
     CmdArgs.push_back("-fmerge-all-constants");
 
+  if (Args.hasFlag(options::OPT_fno_delete_null_pointer_checks,
+                   options::OPT_fdelete_null_pointer_checks, false))
+    CmdArgs.push_back("-fno-delete-null-pointer-checks");
+
   // LLVM Code Generator Options.
 
   if (Args.hasArg(options::OPT_frewrite_map_file) ||
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index c26d5fb79b3..9bb673d1e77 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -746,6 +746,8 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
 
   Opts.NoUseJumpTables = Args.hasArg(OPT_fno_jump_tables);
 
+  Opts.NullPointerIsValid = Args.hasArg(OPT_fno_delete_null_pointer_checks);
+
   Opts.ProfileSampleAccurate = Args.hasArg(OPT_fprofile_sample_accurate);
 
   Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
diff --git a/clang/test/CodeGen/delete-null-pointer-checks.c b/clang/test/CodeGen/delete-null-pointer-checks.c
new file mode 100644
index 00000000000..a3c1460f0a0
--- /dev/null
+++ b/clang/test/CodeGen/delete-null-pointer-checks.c
@@ -0,0 +1,20 @@
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-unknown-linux-gnu -O2 -o - %s | FileCheck -check-prefix=NULL-POINTER-INVALID  %s
+// RUN: %clang_cc1 -emit-llvm -triple x86_64-unknown-linux-gnu -O2 -o - %s -fno-delete-null-pointer-checks | FileCheck -check-prefix=NULL-POINTER-VALID  %s
+
+// Test that clang does not remove the null pointer check with
+// -fno-delete-null-pointer-checks.
+int null_check(int *P) {
+// NULL-POINTER-VALID: %[[TOBOOL:.*]] = icmp eq i32* %P, null
+// NULL-POINTER-INVALID-NOT: icmp eq
+// NULL-POINTER-VALID: %[[SEL:.*]] = select i1 %[[TOBOOL:.*]], i32* null, i32*
+// NULL-POINTER-INVALID-NOT: select i1
+// NULL-POINTER-VALID: load i32, i32* %[[SEL:.*]]
+  int *Q = P;
+  if (P) {
+    Q = P + 2;
+  }
+  return *Q;
+}
+
+// NULL-POINTER-INVALID-NOT: attributes #0 = {{.*}} "null-pointer-is-valid"="true"
+// NULL-POINTER-VALID: attributes #0 = {{.*}} "null-pointer-is-valid"="true"
diff --git a/clang/test/CodeGen/nonnull.c b/clang/test/CodeGen/nonnull.c
index 7c33e6329fd..30162441cf4 100644
--- a/clang/test/CodeGen/nonnull.c
+++ b/clang/test/CodeGen/nonnull.c
@@ -1,32 +1,39 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm < %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm < %s | FileCheck -check-prefix=NULL-INVALID %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm -fno-delete-null-pointer-checks < %s | FileCheck -check-prefix=NULL-VALID %s
 
-// CHECK: define void @foo(i32* nonnull %x)
+// NULL-INVALID: define void @foo(i32* nonnull %x)
+// NULL-VALID: define void @foo(i32* %x)
 void foo(int * __attribute__((nonnull)) x) {
   *x = 0;
 }
 
-// CHECK: define void @bar(i32* nonnull %x)
+// NULL-INVALID: define void @bar(i32* nonnull %x)
+// NULL-VALID: define void @bar(i32* %x)
 void bar(int * x) __attribute__((nonnull(1)))  {
   *x = 0;
 }
 
-// CHECK: define void @bar2(i32* %x, i32* nonnull %y)
+// NULL-INVALID: define void @bar2(i32* %x, i32* nonnull %y)
+// NULL-VALID: define void @bar2(i32* %x, i32* %y)
 void bar2(int * x, int * y) __attribute__((nonnull(2)))  {
   *x = 0;
 }
 
 static int a;
-// CHECK: define nonnull i32* @bar3()
+// NULL-INVALID: define nonnull i32* @bar3()
+// NULL-VALID: define i32* @bar3()
 int * bar3() __attribute__((returns_nonnull))  {
   return &a;
 }
 
-// CHECK: define i32 @bar4(i32 %n, i32* nonnull %p)
+// NULL-INVALID: define i32 @bar4(i32 %n, i32* nonnull %p)
+// NULL-VALID: define i32 @bar4(i32 %n, i32* %p)
 int bar4(int n, int *p) __attribute__((nonnull)) {
   return n + *p;
 }
 
-// CHECK: define i32 @bar5(i32 %n, i32* nonnull %p)
+// NULL-INVALID: define i32 @bar5(i32 %n, i32* nonnull %p)
+// NULL-VALID: define i32 @bar5(i32 %n, i32* %p)
 int bar5(int n, int *p) __attribute__((nonnull(1, 2))) {
   return n + *p;
 }
@@ -37,15 +44,18 @@ typedef union {
   double d;
 } TransparentUnion __attribute__((transparent_union));
 
-// CHECK: define i32 @bar6(i64 %
+// NULL-INVALID: define i32 @bar6(i64 %
+// NULL-VALID: define i32 @bar6(i64 %
 int bar6(TransparentUnion tu) __attribute__((nonnull(1))) {
   return *tu.p;
 }
 
-// CHECK: define void @bar7(i32* nonnull %a, i32* nonnull %b)
+// NULL-INVALID: define void @bar7(i32* nonnull %a, i32* nonnull %b)
+// NULL-VALID: define void @bar7(i32* %a, i32* %b)
 void bar7(int *a, int *b) __attribute__((nonnull(1)))
 __attribute__((nonnull(2))) {}
 
-// CHECK: define void @bar8(i32* nonnull %a, i32* nonnull %b)
+// NULL-INVALID: define void @bar8(i32* nonnull %a, i32* nonnull %b)
+// NULL-VALID: define void @bar8(i32* %a, i32* %b)
 void bar8(int *a, int *b) __attribute__((nonnull))
 __attribute__((nonnull(1))) {}
diff --git a/clang/test/CodeGen/vla.c b/clang/test/CodeGen/vla.c
index 0f2e2cdc669..37243cd1729 100644
--- a/clang/test/CodeGen/vla.c
+++ b/clang/test/CodeGen/vla.c
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -o - | FileCheck %s -check-prefixes=CHECK,NULL-INVALID
+// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -fno-delete-null-pointer-checks -o - | FileCheck %s -check-prefixes=CHECK,NULL-VALID
 
 int b(char* x);
 
@@ -202,5 +203,6 @@ void test8(int a[static 3]) { }
 // CHECK: define void @test8(i32* dereferenceable(12) %a)
 
 void test9(int n, int a[static n]) { }
-// CHECK: define void @test9(i32 %n, i32* nonnull %a)
+// NULL-INVALID: define void @test9(i32 %n, i32* nonnull %a)
+// NULL-VALID: define void @test9(i32 %n, i32* %a)
 
diff --git a/clang/test/CodeGenCXX/address-space-ref.cpp b/clang/test/CodeGenCXX/address-space-ref.cpp
index de6bddca66a..5f0a4295032 100644
--- a/clang/test/CodeGenCXX/address-space-ref.cpp
+++ b/clang/test/CodeGenCXX/address-space-ref.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 %s -std=c++11 -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s -std=c++11 -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s -check-prefixes=CHECK,NULL-INVALID
+// RUN: %clang_cc1 %s -std=c++11 -triple=x86_64-apple-darwin10 -fno-delete-null-pointer-checks -emit-llvm -o - | FileCheck %s -check-prefixes=CHECK,NULL-VALID
 
 // For a reference to a complete type, output the dereferenceable attribute (in
 // any address space).
@@ -29,6 +30,7 @@ bc & bar2(bc &x, bc & y) {
   return x;
 }
 
-// CHECK: define nonnull %class.bc* @_Z4bar2R2bcS0_(%class.bc* nonnull %x, %class.bc* nonnull %y)
+// NULL-INVALID: define nonnull %class.bc* @_Z4bar2R2bcS0_(%class.bc* nonnull %x, %class.bc* nonnull %y)
+// NULL-VALID: define %class.bc* @_Z4bar2R2bcS0_(%class.bc* %x, %class.bc* %y)
 
 
diff --git a/clang/test/CodeGenCXX/constructors.cpp b/clang/test/CodeGenCXX/constructors.cpp
index a8981403834..9322c410f27 100644
--- a/clang/test/CodeGenCXX/constructors.cpp
+++ b/clang/test/CodeGenCXX/constructors.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin10 %s -emit-llvm -o - | FileCheck %s --implicit-check-not=should_not_appear_in_output
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 %s -emit-llvm -o - | FileCheck %s --implicit-check-not=should_not_appear_in_output --check-prefixes=CHECK,NULL-INVALID
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 %s -emit-llvm -fno-delete-null-pointer-checks -o - | FileCheck %s --implicit-check-not=should_not_appear_in_output --check-prefixes=CHECK,NULL-VALID
 
 struct Member { int x; Member(); Member(int); Member(const Member &); };
 struct VBase { int x; VBase(); VBase(int); VBase(const VBase &); };
@@ -21,10 +22,12 @@ struct A {
 A::A(struct Undeclared &ref) : mem(0) {}
 
 // Check that delegation works.
-// CHECK-LABEL: define void @_ZN1AC2ER10Undeclared(%struct.A* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-INVALID-LABEL: define void @_ZN1AC2ER10Undeclared(%struct.A* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-VALID-LABEL: define void @_ZN1AC2ER10Undeclared(%struct.A* %this, %struct.Undeclared* %ref) unnamed_addr
 // CHECK: call void @_ZN6MemberC1Ei(
 
-// CHECK-LABEL: define void @_ZN1AC1ER10Undeclared(%struct.A* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-INVALID-LABEL: define void @_ZN1AC1ER10Undeclared(%struct.A* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-VALID-LABEL: define void @_ZN1AC1ER10Undeclared(%struct.A* %this, %struct.Undeclared* %ref) unnamed_addr
 // CHECK: call void @_ZN1AC2ER10Undeclared(
 
 A::A(ValueClass v) : mem(v.y - v.x) {}
@@ -43,11 +46,13 @@ struct B : A {
 
 B::B(struct Undeclared &ref) : A(ref), mem(1) {}
 
-// CHECK-LABEL: define void @_ZN1BC2ER10Undeclared(%struct.B* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-INVALID-LABEL: define void @_ZN1BC2ER10Undeclared(%struct.B* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-VALID-LABEL: define void @_ZN1BC2ER10Undeclared(%struct.B* %this, %struct.Undeclared* %ref) unnamed_addr
 // CHECK: call void @_ZN1AC2ER10Undeclared(
 // CHECK: call void @_ZN6MemberC1Ei(
 
-// CHECK-LABEL: define void @_ZN1BC1ER10Undeclared(%struct.B* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-INVALID-LABEL: define void @_ZN1BC1ER10Undeclared(%struct.B* %this, %struct.Undeclared* nonnull %ref) unnamed_addr
+// NULL-VALID-LABEL: define void @_ZN1BC1ER10Undeclared(%struct.B* %this, %struct.Undeclared* %ref) unnamed_addr
 // CHECK: call void @_ZN1BC2ER10Undeclared(
 
 
diff --git a/clang/test/CodeGenCXX/temporaries.cpp b/clang/test/CodeGenCXX/temporaries.cpp
index 21372effbcf..2eb27e71cb1 100644
--- a/clang/test/CodeGenCXX/temporaries.cpp
+++ b/clang/test/CodeGenCXX/temporaries.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin9 -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin9 -std=c++11 | FileCheck %s -check-prefixes=CHECK,NULL-INVALID
+// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin9 -std=c++11 -fno-delete-null-pointer-checks | FileCheck %s -check-prefixes=CHECK,NULL-VALID
 
 namespace PR16263 {
   const unsigned int n = 1234;
@@ -333,7 +334,8 @@ namespace PR6648 {
   struct D;
   D& zed(B);
   void foobar() {
-    // CHECK: call nonnull %"struct.PR6648::D"* @_ZN6PR66483zedENS_1BE
+    // NULL-INVALID: call nonnull %"struct.PR6648::D"* @_ZN6PR66483zedENS_1BE
+    // NULL-VALID: call %"struct.PR6648::D"* @_ZN6PR66483zedENS_1BE
     zed(foo);
   }
 }
diff --git a/clang/test/Driver/clang_f_opts.c b/clang/test/Driver/clang_f_opts.c
index be9ca2c93d6..9208d6b71bb 100644
--- a/clang/test/Driver/clang_f_opts.c
+++ b/clang/test/Driver/clang_f_opts.c
@@ -348,7 +348,6 @@
 // RUN: -fwhole-program                                                       \
 // RUN: -fcaller-saves                                                        \
 // RUN: -freorder-blocks                                                      \
-// RUN: -fdelete-null-pointer-checks                                          \
 // RUN: -ffat-lto-objects                                                     \
 // RUN: -fmerge-constants                                                     \
 // RUN: -finline-small-functions                                              \
@@ -414,7 +413,6 @@
 // CHECK-WARNING-DAG: optimization flag '-fwhole-program' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fcaller-saves' is not supported
 // CHECK-WARNING-DAG: optimization flag '-freorder-blocks' is not supported
-// CHECK-WARNING-DAG: optimization flag '-fdelete-null-pointer-checks' is not supported
 // CHECK-WARNING-DAG: optimization flag '-ffat-lto-objects' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fmerge-constants' is not supported
 // CHECK-WARNING-DAG: optimization flag '-finline-small-functions' is not supported
@@ -526,3 +524,10 @@
 // RUN: %clang -### -S -fno-merge-all-constants -fmerge-all-constants %s 2>&1 | FileCheck -check-prefix=CHECK-MERGE-ALL-CONSTANTS %s
 // CHECK-NO-MERGE-ALL-CONSTANTS-NOT: "-fmerge-all-constants"
 // CHECK-MERGE-ALL-CONSTANTS: "-fmerge-all-constants"
+
+// RUN: %clang -### -S -fdelete-null-pointer-checks %s 2>&1 | FileCheck -check-prefix=CHECK-NULL-POINTER-CHECKS %s
+// RUN: %clang -### -S -fno-delete-null-pointer-checks %s 2>&1 | FileCheck -check-prefix=CHECK-NO-NULL-POINTER-CHECKS %s
+// RUN: %clang -### -S -fdelete-null-pointer-checks -fno-delete-null-pointer-checks %s 2>&1 | FileCheck -check-prefix=CHECK-NO-NULL-POINTER-CHECKS %s
+// RUN: %clang -### -S -fno-delete-null-pointer-checks -fdelete-null-pointer-checks %s 2>&1 | FileCheck -check-prefix=CHECK-NULL-POINTER-CHECKS %s
+// CHECK-NO-NULL-POINTER-CHECKS: "-fno-delete-null-pointer-checks"
+// CHECK-NULL-POINTER-CHECKS-NOT: "-fno-delete-null-pointer-checks"
diff --git a/clang/test/Sema/nonnull.c b/clang/test/Sema/nonnull.c
index b589bb3d1ff..3410d36ddfb 100644
--- a/clang/test/Sema/nonnull.c
+++ b/clang/test/Sema/nonnull.c
@@ -1,5 +1,9 @@
 // RUN: %clang_cc1 -fsyntax-only -verify %s
 // rdar://9584012
+//
+// Verify All warnings are still issued with the option -fno-delete-null-pointer-checks
+// if nullptr is passed to function with nonnull attribute.
+// RUN: %clang_cc1 -fsyntax-only -fno-delete-null-pointer-checks -verify %s
 
 typedef struct {
 	char *str;