[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

3 files changed, 18 insertions, 9 deletions

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);
   }
 }