Files
clang-p2996/clang/test/CodeGenCXX/static-init.cpp
Roman Lebedev 3dd5a298bf [clang] Annotating C++'s operator new with more attributes
Summary:
Right now we annotate C++'s `operator new` with `noalias` attribute,
which very much is healthy for optimizations.

However as per [[ http://eel.is/c++draft/basic.stc.dynamic.allocation | `[basic.stc.dynamic.allocation]` ]],
there are more promises on global `operator new`, namely:
* non-`std::nothrow_t` `operator new` *never* returns `nullptr`
* If `std::align_val_t align` parameter is taken, the pointer will also be `align`-aligned
* ~~global `operator new`-returned pointer is `__STDCPP_DEFAULT_NEW_ALIGNMENT__`-aligned ~~ It's more caveated than that.

Supplying this information may not cause immediate landslide effects
on any specific benchmarks, but it for sure will be healthy for optimizer
in the sense that the IR will better reflect the guarantees provided in the source code.

The caveat is `-fno-assume-sane-operator-new`, which currently prevents emitting `noalias`
attribute, and is automatically passed by Sanitizers ([[ https://bugs.llvm.org/show_bug.cgi?id=16386 | PR16386 ]]) - should it also cover these attributes?
The problem is that the flag is back-end-specific, as seen in `test/Modules/explicit-build-flags.cpp`.
But while it is okay to add `noalias` metadata in backend, we really should be adding at least
the alignment metadata to the AST, since that allows us to perform sema checks on it.

Reviewers: erichkeane, rjmccall, jdoerfert, eugenis, rsmith

Reviewed By: rsmith

Subscribers: xbolva00, jrtc27, atanasyan, nlopes, cfe-commits

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D73380
2020-02-26 01:37:17 +03:00

176 lines
5.4 KiB
C++

// RUN: %clang_cc1 %s -triple=x86_64-pc-linuxs -emit-llvm -std=c++98 -o - | FileCheck -check-prefix=CHECK -check-prefix=CHECK98 %s
// RUN: %clang_cc1 %s -triple=x86_64-pc-linuxs -emit-llvm -std=c++11 -o - | FileCheck -check-prefix=CHECK -check-prefix=CHECK11 %s
// CHECK: @_ZZ1hvE1i = internal global i32 0, align 4
// CHECK: @base_req = global [4 x i8] c"foo\00", align 1
// CHECK: @base_req_uchar = global [4 x i8] c"bar\00", align 1
// CHECK: @_ZZN5test31BC1EvE1u = internal global { i8, [3 x i8] } { i8 97, [3 x i8] undef }, align 4
// CHECK: @_ZZ2h2vE1i = linkonce_odr global i32 0, comdat, align 4
// CHECK: @_ZGVZ2h2vE1i = linkonce_odr global i64 0, comdat, align 8{{$}}
// CHECK: @_ZZN5test1L6getvarEiE3var = internal constant [4 x i32] [i32 1, i32 0, i32 2, i32 4], align 16
// CHECK98: @_ZZN5test414useStaticLocalEvE3obj = linkonce_odr global %"struct.test4::HasVTable" zeroinitializer, comdat, align 8
// CHECK11: @_ZZN5test414useStaticLocalEvE3obj = linkonce_odr global { i8** } { i8** getelementptr inbounds ({ [3 x i8*] }, { [3 x i8*] }* @_ZTVN5test49HasVTableE, i32 0, inrange i32 0, i32 2) }, comdat, align 8
struct A {
A();
~A();
};
void f() {
// CHECK: load atomic i8, i8* bitcast (i64* @_ZGVZ1fvE1a to i8*) acquire, align 8
// CHECK: call i32 @__cxa_guard_acquire
// CHECK: call void @_ZN1AC1Ev
// CHECK: call i32 @__cxa_atexit(void (i8*)* bitcast (void (%struct.A*)* @_ZN1AD1Ev to void (i8*)*), i8* getelementptr inbounds (%struct.A, %struct.A* @_ZZ1fvE1a, i32 0, i32 0), i8* @__dso_handle)
// CHECK: call void @__cxa_guard_release
static A a;
}
void g() {
// CHECK: call noalias nonnull i8* @_Znwm(i64 1)
// CHECK: call void @_ZN1AC1Ev(
static A& a = *new A;
}
int a();
void h() {
static const int i = a();
}
// CHECK: define linkonce_odr void @_Z2h2v() {{.*}} comdat {
inline void h2() {
static int i = a();
}
void h3() {
h2();
}
// PR6980: this shouldn't crash
namespace test0 {
struct A { A(); };
__attribute__((noreturn)) int throw_exception();
void test() {
throw_exception();
static A r;
}
}
namespace test1 {
// CHECK-LABEL: define internal i32 @_ZN5test1L6getvarEi(
static inline int getvar(int index) {
static const int var[] = { 1, 0, 2, 4 };
return var[index];
}
void test() { (void) getvar(2); }
}
// Make sure we emit the initializer correctly for the following:
char base_req[] = { "foo" };
unsigned char base_req_uchar[] = { "bar" };
namespace union_static_local {
// CHECK-LABEL: define internal void @_ZZN18union_static_local4testEvEN1c4mainEv
// CHECK: call void @_ZN18union_static_local1fEPNS_1xE(%"union.union_static_local::x"* bitcast ({ [2 x i8*] }* @_ZZN18union_static_local4testEvE3foo to %"union.union_static_local::x"*))
union x { long double y; const char *x[2]; };
void f(union x*);
void test() {
static union x foo = { .x = { "a", "b" } };
struct c {
static void main() {
f(&foo);
}
};
c::main();
}
}
// rdar://problem/11091093
// Static variables should be consistent across constructor
// or destructor variants.
namespace test2 {
struct A {
A();
~A();
};
struct B : virtual A {
B();
~B();
};
// If we ever implement this as a delegate ctor call, just change
// this to take variadic arguments or something.
extern int foo();
B::B() {
static int x = foo();
}
// CHECK-LABEL: define void @_ZN5test21BC2Ev
// CHECK: load atomic i8, i8* bitcast (i64* @_ZGVZN5test21BC1EvE1x to i8*) acquire,
// CHECK: call i32 @__cxa_guard_acquire(i64* @_ZGVZN5test21BC1EvE1x)
// CHECK: [[T0:%.*]] = call i32 @_ZN5test23fooEv()
// CHECK: store i32 [[T0]], i32* @_ZZN5test21BC1EvE1x,
// CHECK: call void @__cxa_guard_release(i64* @_ZGVZN5test21BC1EvE1x)
// CHECK-LABEL: define void @_ZN5test21BC1Ev
// CHECK: load atomic i8, i8* bitcast (i64* @_ZGVZN5test21BC1EvE1x to i8*) acquire,
// CHECK: call i32 @__cxa_guard_acquire(i64* @_ZGVZN5test21BC1EvE1x)
// CHECK: [[T0:%.*]] = call i32 @_ZN5test23fooEv()
// CHECK: store i32 [[T0]], i32* @_ZZN5test21BC1EvE1x,
// CHECK: call void @__cxa_guard_release(i64* @_ZGVZN5test21BC1EvE1x)
// This is just for completeness, because we actually emit this
// using a delegate dtor call.
B::~B() {
static int y = foo();
}
// CHECK-LABEL: define void @_ZN5test21BD2Ev(
// CHECK: load atomic i8, i8* bitcast (i64* @_ZGVZN5test21BD1EvE1y to i8*) acquire,
// CHECK: call i32 @__cxa_guard_acquire(i64* @_ZGVZN5test21BD1EvE1y)
// CHECK: [[T0:%.*]] = call i32 @_ZN5test23fooEv()
// CHECK: store i32 [[T0]], i32* @_ZZN5test21BD1EvE1y,
// CHECK: call void @__cxa_guard_release(i64* @_ZGVZN5test21BD1EvE1y)
// CHECK-LABEL: define void @_ZN5test21BD1Ev(
// CHECK: call void @_ZN5test21BD2Ev(
}
// This shouldn't error out.
namespace test3 {
struct A {
A();
~A();
};
struct B : virtual A {
B();
~B();
};
B::B() {
union U { char x; int i; };
static U u = { 'a' };
}
// CHECK-LABEL: define void @_ZN5test31BC2Ev(
// CHECK-LABEL: define void @_ZN5test31BC1Ev(
}
// We forgot to set the comdat when replacing the global with a different type.
namespace test4 {
struct HasVTable {
virtual void f();
};
inline HasVTable &useStaticLocal() {
static HasVTable obj;
return obj;
}
void useit() {
useStaticLocal();
}
// CHECK: define linkonce_odr dereferenceable(8) %"struct.test4::HasVTable"* @_ZN5test414useStaticLocalEv()
// CHECK: ret %"struct.test4::HasVTable"*{{.*}} @_ZZN5test414useStaticLocalEvE3obj
}