llvm-project/clang/test/CodeGenObjC/objc-alloc-init.m

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// RUN: %clang_cc1 %s -fobjc-exceptions -fexceptions -fobjc-runtime=macosx-10.14.4 -emit-llvm -O0 -o - | FileCheck %s --check-prefix=OPTIMIZED --check-prefix=EITHER
// RUN: %clang_cc1 %s -fobjc-exceptions -fexceptions -fobjc-runtime=macosx-10.14.3 -emit-llvm -O0 -o - | FileCheck %s --check-prefix=NOT_OPTIMIZED --check-prefix=EITHER
// RUN: %clang_cc1 %s -fobjc-exceptions -fexceptions -fobjc-runtime=ios-12.2 -emit-llvm -O0 -o - | FileCheck %s --check-prefix=OPTIMIZED --check-prefix=EITHER
// RUN: %clang_cc1 %s -fobjc-exceptions -fexceptions -fobjc-runtime=ios-12.1 -emit-llvm -O0 -o - | FileCheck %s --check-prefix=NOT_OPTIMIZED --check-prefix=EITHER
@interface X
+(X *)alloc;
-(X *)init;
@end
void f() {
[[X alloc] init];
// OPTIMIZED: call i8* @objc_alloc_init(
// NOT_OPTIMIZED: call i8* @objc_alloc(
@try {
[[X alloc] init];
} @catch (X *x) {
}
// OPTIMIZED: invoke i8* @objc_alloc_init(
// NOT_OPTIMIZED: invoke i8* @objc_alloc(
}
@interface Y : X
Relax the rules around objc_alloc and objc_alloc_init optimizations. Today the optimization is limited to: - `[ClassName alloc]` - `[self alloc]` when within a class method However it means that when code is written this way: ``` @interface MyObject - (id)copyWithZone:(NSZone *)zone { return [[self.class alloc] _initWith...]; } @end ``` ... then the optimization doesn't kick in and `+[NSObject alloc]` ends up in IMP caches where it could have been avoided. It turns out that `+alloc` -> `+[NSObject alloc]` is the most cached SEL/IMP pair in the entire platform which is rather silly). There's two theoretical risks allowing this optimization: 1. if the receiver is nil (which it can't be today), but it turns out that `objc_alloc()`/`objc_alloc_init()` cope with a nil receiver, 2. if the `Clas` type for the receiver is a lie. However, for such a code to work today (and not fail witn an unrecognized selector anyway) you'd have to have implemented the `-alloc` **instance method**. Fortunately, `objc_alloc()` doesn't assume that the receiver is a Class, it basically starts with a test that is similar to `if (receiver->isa->bits & hasDefaultAWZ) { /* fastpath */ }`. This bit is only set on metaclasses by the runtime, so if an instance is passed to this function by accident, its isa will fail this test, and `objc_alloc()` will gracefully fallback to `objc_msgSend()`. The one thing `objc_alloc()` doesn't support is tagged pointer instances. None of the tagged pointer classes implement an instance method called `'alloc'` (actually there's a single class in the entire Apple codebase that has such a method). Differential Revision: https://reviews.llvm.org/D71682 Radar-Id: rdar://problem/58058316 Reviewed-By: Akira Hatanaka Signed-off-by: Pierre Habouzit <phabouzit@apple.com>
2020-01-15 10:56:26 +08:00
+(Class)class;
+(void)meth;
-(void)instanceMeth;
@end
@implementation Y
Relax the rules around objc_alloc and objc_alloc_init optimizations. Today the optimization is limited to: - `[ClassName alloc]` - `[self alloc]` when within a class method However it means that when code is written this way: ``` @interface MyObject - (id)copyWithZone:(NSZone *)zone { return [[self.class alloc] _initWith...]; } @end ``` ... then the optimization doesn't kick in and `+[NSObject alloc]` ends up in IMP caches where it could have been avoided. It turns out that `+alloc` -> `+[NSObject alloc]` is the most cached SEL/IMP pair in the entire platform which is rather silly). There's two theoretical risks allowing this optimization: 1. if the receiver is nil (which it can't be today), but it turns out that `objc_alloc()`/`objc_alloc_init()` cope with a nil receiver, 2. if the `Clas` type for the receiver is a lie. However, for such a code to work today (and not fail witn an unrecognized selector anyway) you'd have to have implemented the `-alloc` **instance method**. Fortunately, `objc_alloc()` doesn't assume that the receiver is a Class, it basically starts with a test that is similar to `if (receiver->isa->bits & hasDefaultAWZ) { /* fastpath */ }`. This bit is only set on metaclasses by the runtime, so if an instance is passed to this function by accident, its isa will fail this test, and `objc_alloc()` will gracefully fallback to `objc_msgSend()`. The one thing `objc_alloc()` doesn't support is tagged pointer instances. None of the tagged pointer classes implement an instance method called `'alloc'` (actually there's a single class in the entire Apple codebase that has such a method). Differential Revision: https://reviews.llvm.org/D71682 Radar-Id: rdar://problem/58058316 Reviewed-By: Akira Hatanaka Signed-off-by: Pierre Habouzit <phabouzit@apple.com>
2020-01-15 10:56:26 +08:00
+(Class)class {
return self;
}
+(void)meth {
[[self alloc] init];
// OPTIMIZED: call i8* @objc_alloc_init(
// NOT_OPTIMIZED: call i8* @objc_alloc(
}
Relax the rules around objc_alloc and objc_alloc_init optimizations. Today the optimization is limited to: - `[ClassName alloc]` - `[self alloc]` when within a class method However it means that when code is written this way: ``` @interface MyObject - (id)copyWithZone:(NSZone *)zone { return [[self.class alloc] _initWith...]; } @end ``` ... then the optimization doesn't kick in and `+[NSObject alloc]` ends up in IMP caches where it could have been avoided. It turns out that `+alloc` -> `+[NSObject alloc]` is the most cached SEL/IMP pair in the entire platform which is rather silly). There's two theoretical risks allowing this optimization: 1. if the receiver is nil (which it can't be today), but it turns out that `objc_alloc()`/`objc_alloc_init()` cope with a nil receiver, 2. if the `Clas` type for the receiver is a lie. However, for such a code to work today (and not fail witn an unrecognized selector anyway) you'd have to have implemented the `-alloc` **instance method**. Fortunately, `objc_alloc()` doesn't assume that the receiver is a Class, it basically starts with a test that is similar to `if (receiver->isa->bits & hasDefaultAWZ) { /* fastpath */ }`. This bit is only set on metaclasses by the runtime, so if an instance is passed to this function by accident, its isa will fail this test, and `objc_alloc()` will gracefully fallback to `objc_msgSend()`. The one thing `objc_alloc()` doesn't support is tagged pointer instances. None of the tagged pointer classes implement an instance method called `'alloc'` (actually there's a single class in the entire Apple codebase that has such a method). Differential Revision: https://reviews.llvm.org/D71682 Radar-Id: rdar://problem/58058316 Reviewed-By: Akira Hatanaka Signed-off-by: Pierre Habouzit <phabouzit@apple.com>
2020-01-15 10:56:26 +08:00
+ (void)meth2 {
[[[self class] alloc] init];
// OPTIMIZED: call i8* @objc_alloc_init(
// NOT_OPTIMIZED: call i8* @objc_alloc(
}
-(void)instanceMeth {
// EITHER-NOT: call i8* @objc_alloc
// EITHER: call {{.*}} @objc_msgSend
// EITHER: call {{.*}} @objc_msgSend
Relax the rules around objc_alloc and objc_alloc_init optimizations. Today the optimization is limited to: - `[ClassName alloc]` - `[self alloc]` when within a class method However it means that when code is written this way: ``` @interface MyObject - (id)copyWithZone:(NSZone *)zone { return [[self.class alloc] _initWith...]; } @end ``` ... then the optimization doesn't kick in and `+[NSObject alloc]` ends up in IMP caches where it could have been avoided. It turns out that `+alloc` -> `+[NSObject alloc]` is the most cached SEL/IMP pair in the entire platform which is rather silly). There's two theoretical risks allowing this optimization: 1. if the receiver is nil (which it can't be today), but it turns out that `objc_alloc()`/`objc_alloc_init()` cope with a nil receiver, 2. if the `Clas` type for the receiver is a lie. However, for such a code to work today (and not fail witn an unrecognized selector anyway) you'd have to have implemented the `-alloc` **instance method**. Fortunately, `objc_alloc()` doesn't assume that the receiver is a Class, it basically starts with a test that is similar to `if (receiver->isa->bits & hasDefaultAWZ) { /* fastpath */ }`. This bit is only set on metaclasses by the runtime, so if an instance is passed to this function by accident, its isa will fail this test, and `objc_alloc()` will gracefully fallback to `objc_msgSend()`. The one thing `objc_alloc()` doesn't support is tagged pointer instances. None of the tagged pointer classes implement an instance method called `'alloc'` (actually there's a single class in the entire Apple codebase that has such a method). Differential Revision: https://reviews.llvm.org/D71682 Radar-Id: rdar://problem/58058316 Reviewed-By: Akira Hatanaka Signed-off-by: Pierre Habouzit <phabouzit@apple.com>
2020-01-15 10:56:26 +08:00
[[(id)self alloc] init];
}
@end
// rdar://48247290
@interface Base
-(instancetype)init;
@end
@interface Derived : Base
@end
@implementation Derived
-(void)meth {
[super init];
}
@end