dnrops
/
clang
mirror of https://github.com/microsoft/clang.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

[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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@337433 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Manoj Gupta 2018-07-19 00:44:52 +00:00
parent fed5a86cd1
commit cdd3c71916
14 changed files with 109 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
docs/ClangCommandLineReference.rst
View File

@ -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

9
include/clang/Driver/Options.td
View File

@ -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>;

1
include/clang/Frontend/CodeGenOptions.def
View File

@ -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.

20
lib/CodeGen/CGCall.cpp
View File

@ -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);
}

4
lib/Driver/ToolChains/Clang.cpp
View File

@ -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) ||

2
lib/Frontend/CompilerInvocation.cpp
View File

@ -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);

20
test/CodeGen/delete-null-pointer-checks.c Normal file
View File

@ -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"

30
test/CodeGen/nonnull.c
View File

@ -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))) {}

6
test/CodeGen/vla.c
View File

@ -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)

6
test/CodeGenCXX/address-space-ref.cpp
View File

@ -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)

15
test/CodeGenCXX/constructors.cpp
View File

@ -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(

6
test/CodeGenCXX/temporaries.cpp
View File

@ -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);
}
}

9
test/Driver/clang_f_opts.c
View File

@ -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"

4
test/Sema/nonnull.c
View File

@ -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;