The main follow-up item to https://github.com/llvm/llvm-project/pull/160790 was changing -O0 codegen to convert in-memory i8 bool values to i1 with the `nonzero` rule (`icmp ne i8 %val, 0`) rather than the `truncate` rule (`trunc i8 %val to i1`). Bool values can only be `true` or `false`. While they are notionally a single bit, the smallest addressable unit is CHAR_BIT bits large, and CHAR_BIT is typically 8. Programming errors (such as memcpying a random byte to a `bool`) can cause the 8-bit storage for a `bool` value to have a bit pattern that is different from `true` or `false`, which then leads to undefined behavior. Clang has historically taken advantage of this in optimized builds (everything other than -O0) by attaching range metadata to `bool` loads to assume that the value loaded can only be 0 or 1. This leads to exploitable security issues, and the correct behavior is not always easy to explain to C developers. To remedy this situation, Clang accepted a [-fstrict-bool](https://discourse.llvm.org/t/defining-what-happens-when-a-bool-isn-t-0-or-1/86778) switch to control whether it can assume that loaded bool values are always necessarily 0 or 1. By default, it does (maintaining the status quo), and users must specify `-fno-strict-bool` to opt out of that behavior. When opting out, users can optionally request that bool i8 values are converted to i1 either by truncation or by comparing to 0. The default is comparing to 0. However, since `-O0` alone _technically_ uses -fstrict-bool, unoptimized builds convert i8 bool values to i1 with a `trunc` operation, whereas `-O1 -fno-strict-bool` converts i8 bool values to i1 with `icmp ne 0`. This is a surprising inconsistency. This PR changes -O0 codegen to align with -fno-strict-bool. This is achieved with a single-line change: ``` bool isConvertingBoolWithCmp0() const { switch (getLoadBoolFromMem()) { case BoolFromMem::Strict: + return !isOptimizedBuild(); case BoolFromMem::Truncate: ``` However, it impacts a _very large_ number of tests, so we agreed to move it out of the -fstrict-bool PR to reduce the chances we would have to back out the whole thing for this secondary item. This PR does the change and modifies the tests accordingly. I expect that it will go stale rather quickly. If this needs more discussion, I'll only update it once we reach consensus.
303 lines
8.2 KiB
C++
303 lines
8.2 KiB
C++
// RUN: %clang_cc1 %s -fblocks -triple x86_64-apple-darwin -emit-llvm -o - | FileCheck %s
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// CHECK: @[[BLOCK_DESCRIPTOR22:.*]] = internal constant { i64, i64, ptr, ptr, ptr, ptr } { i64 0, i64 36, ptr @__copy_helper_block_8_32c22_ZTSN12_GLOBAL__N_11BE, ptr @__destroy_helper_block_8_32c22_ZTSN12_GLOBAL__N_11BE, ptr @{{.*}}, ptr null }, align 8
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namespace test0 {
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// CHECK-LABEL: define{{.*}} void @_ZN5test04testEi(
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// CHECK: define internal void @___ZN5test04testEi_block_invoke{{.*}}(
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// CHECK: define internal void @___ZN5test04testEi_block_invoke_2{{.*}}(
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void test(int x) {
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^{ ^{ (void) x; }; };
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}
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}
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extern void (^out)();
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namespace test1 {
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// Capturing const objects doesn't require a local block.
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// CHECK-LABEL: define{{.*}} void @_ZN5test15test1Ev()
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// CHECK: store ptr @__block_literal_global{{.*}}, ptr @out
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void test1() {
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const int NumHorsemen = 4;
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out = ^{ (void) NumHorsemen; };
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}
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// That applies to structs too...
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// CHECK-LABEL: define{{.*}} void @_ZN5test15test2Ev()
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// CHECK: store ptr @__block_literal_global{{.*}}, ptr @out
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struct loc { double x, y; };
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void test2() {
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const loc target = { 5, 6 };
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out = ^{ (void) target; };
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}
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// ...unless they have mutable fields...
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// CHECK-LABEL: define{{.*}} void @_ZN5test15test3Ev()
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// CHECK: [[BLOCK:%.*]] = alloca [[BLOCK_T:<{.*}>]],
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// CHECK: store ptr [[BLOCK]], ptr @out
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struct mut { mutable int x; };
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void test3() {
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const mut obj = { 5 };
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out = ^{ (void) obj; };
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}
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// ...or non-trivial destructors...
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// CHECK-LABEL: define{{.*}} void @_ZN5test15test4Ev()
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// CHECK: [[OBJ:%.*]] = alloca
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// CHECK: [[BLOCK:%.*]] = alloca [[BLOCK_T:<{.*}>]],
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// CHECK: store ptr [[BLOCK]], ptr @out
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struct scope { int x; ~scope(); };
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void test4() {
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const scope obj = { 5 };
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out = ^{ (void) obj; };
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}
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// ...or non-trivial copy constructors, but it's not clear how to do
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// that and still have a constant initializer in '03.
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}
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namespace test2 {
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struct A {
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A();
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A(const A &);
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~A();
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};
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struct B {
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B();
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B(const B &);
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~B();
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};
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// CHECK-LABEL: define{{.*}} void @_ZN5test24testEv()
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void test() {
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__block A a;
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__block B b;
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^{ (void)a; (void)b; };
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}
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// CHECK-LABEL: define internal void @__Block_byref_object_copy
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// CHECK: call void @_ZN5test21AC1ERKS0_(
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// CHECK-LABEL: define internal void @__Block_byref_object_dispose
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// CHECK: call void @_ZN5test21AD1Ev(
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// CHECK-LABEL: define internal void @__Block_byref_object_copy
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// CHECK: call void @_ZN5test21BC1ERKS0_(
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// CHECK-LABEL: define internal void @__Block_byref_object_dispose
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// CHECK: call void @_ZN5test21BD1Ev(
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}
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// Make sure we mark destructors for parameters captured in blocks.
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namespace test3 {
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struct A {
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A(const A&);
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~A();
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};
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struct B : A {
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};
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void test(B b) {
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extern void consume(void(^)());
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consume(^{ (void) b; });
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}
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}
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namespace test4 {
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struct A {
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A();
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~A();
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};
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void foo(A a);
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void test() {
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extern void consume(void(^)());
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consume(^{ return foo(A()); });
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}
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// CHECK-LABEL: define{{.*}} void @_ZN5test44testEv()
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// CHECK-LABEL: define internal void @___ZN5test44testEv_block_invoke
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// CHECK: [[TMP:%.*]] = alloca [[A:%.*]], align 1
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// CHECK-NEXT: store ptr [[BLOCKDESC:%.*]], ptr {{.*}}, align 8
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// CHECK: call void @_ZN5test41AC1Ev(ptr {{[^,]*}} [[TMP]])
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// CHECK-NEXT: call void @_ZN5test43fooENS_1AE(ptr noundef [[TMP]])
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// CHECK-NEXT: call void @_ZN5test41AD1Ev(ptr {{[^,]*}} [[TMP]])
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// CHECK-NEXT: ret void
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}
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namespace test5 {
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struct A {
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unsigned afield;
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A();
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A(const A&);
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~A();
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void foo() const;
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};
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void doWithBlock(void(^)());
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void test(bool cond) {
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A x;
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void (^b)() = (cond ? ^{ x.foo(); } : (void(^)()) 0);
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doWithBlock(b);
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}
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// CHECK-LABEL: define{{.*}} void @_ZN5test54testEb(
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// CHECK: [[COND:%.*]] = alloca i8
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// CHECK-NEXT: [[X:%.*]] = alloca [[A:%.*]], align 4
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// CHECK-NEXT: [[B:%.*]] = alloca ptr, align 8
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// CHECK-NEXT: [[BLOCK:%.*]] = alloca [[BLOCK_T:.*]], align 8
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// CHECK-NEXT: [[COND_CLEANUP_SAVE:%.*]] = alloca ptr, align 8
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// CHECK-NEXT: [[CLEANUP_ACTIVE:%.*]] = alloca i1
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// CHECK-NEXT: [[T0:%.*]] = zext i1
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// CHECK-NEXT: store i8 [[T0]], ptr [[COND]], align 1
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// CHECK-NEXT: call void @_ZN5test51AC1Ev(ptr {{[^,]*}} [[X]])
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// CHECK-NEXT: [[T0:%.*]] = load i8, ptr [[COND]], align 1
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// CHECK-NEXT: [[T1:%.*]] = icmp ne i8 [[T0]], 0
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// CHECK-NEXT: store i1 false, ptr [[CLEANUP_ACTIVE]]
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// CHECK-NEXT: br i1 [[T1]],
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// CHECK-NOT: br
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// CHECK: [[CAPTURE:%.*]] = getelementptr inbounds nuw [[BLOCK_T]], ptr [[BLOCK]], i32 0, i32 5
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// CHECK-NEXT: call void @_ZN5test51AC1ERKS0_(ptr {{[^,]*}} [[CAPTURE]], ptr noundef nonnull align {{[0-9]+}} dereferenceable({{[0-9]+}}) [[X]])
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// CHECK-NEXT: store ptr [[CAPTURE]], ptr [[COND_CLEANUP_SAVE]], align 8
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// CHECK-NEXT: store i1 true, ptr [[CLEANUP_ACTIVE]]
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// CHECK-NEXT: br label
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// CHECK: br label
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// CHECK: phi
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// CHECK-NEXT: store
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// CHECK-NEXT: load
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// CHECK-NEXT: call void @_ZN5test511doWithBlockEU13block_pointerFvvE(
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// CHECK-NEXT: [[T0:%.*]] = load i1, ptr [[CLEANUP_ACTIVE]]
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// CHECK-NEXT: br i1 [[T0]]
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// CHECK: [[T3:%.*]] = load ptr, ptr [[COND_CLEANUP_SAVE]], align 8
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// CHECK-NEXT: call void @_ZN5test51AD1Ev(ptr {{[^,]*}} [[T3]])
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// CHECK-NEXT: br label
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// CHECK: call void @_ZN5test51AD1Ev(ptr {{[^,]*}} [[X]])
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// CHECK-NEXT: ret void
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}
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namespace test6 {
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struct A {
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A();
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~A();
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};
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void foo(const A &, void (^)());
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void bar();
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void test() {
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// Make sure that the temporary cleanup isn't somehow captured
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// within the block.
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foo(A(), ^{ bar(); });
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bar();
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}
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// CHECK-LABEL: define{{.*}} void @_ZN5test64testEv()
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// CHECK: [[TEMP:%.*]] = alloca [[A:%.*]], align 1
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// CHECK-NEXT: call void @_ZN5test61AC1Ev(ptr {{[^,]*}} [[TEMP]])
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// CHECK-NEXT: call void @_ZN5test63fooERKNS_1AEU13block_pointerFvvE(
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// CHECK-NEXT: call void @_ZN5test61AD1Ev(ptr {{[^,]*}} [[TEMP]])
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// CHECK-NEXT: call void @_ZN5test63barEv()
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// CHECK-NEXT: ret void
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}
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namespace test7 {
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int f() {
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static int n;
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int *const p = &n;
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return ^{ return *p; }();
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}
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}
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namespace test8 {
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// failure to capture this after skipping rebuild of the 'this' pointer.
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struct X {
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int x;
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template<typename T>
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int foo() {
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return ^ { return x; }();
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}
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};
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template int X::foo<int>();
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}
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namespace test9 {
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struct B {
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void *p;
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B();
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B(const B&);
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~B();
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};
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void use_block(void (^)());
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void use_block_2(void (^)(), const B &a);
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// Ensuring that creating a non-trivial capture copy expression
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// doesn't end up stealing the block registration for the block we
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// just parsed. That block must have captures or else it won't
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// force registration. Must occur within a block for some reason.
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void test() {
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B x;
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use_block(^{
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int y;
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use_block_2(^{ (void)y; }, x);
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});
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}
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}
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namespace test10 {
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// Check that 'v' is included in the copy helper function name to indicate
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// the constructor taking a volatile parameter is called to copy the captured
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// object.
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// CHECK-LABEL: define linkonce_odr hidden void @__copy_helper_block_8_32c16_ZTSVN6test101BE(
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// CHECK: call void @_ZN6test101BC1ERVKS0_(
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// CHECK-LABEL: define linkonce_odr hidden void @__destroy_helper_block_8_32c16_ZTSVN6test101BE(
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// CHECK: call void @_ZN6test101BD1Ev(
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struct B {
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int a;
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B();
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B(const B &);
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B(const volatile B &);
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~B();
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};
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void test() {
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volatile B x;
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^{ (void)x; };
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}
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}
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// Copy/dispose helper functions and block descriptors of blocks that capture
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// objects that are non-external and non-trivial have internal linkage.
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// CHECK-LABEL: define internal void @_ZN12_GLOBAL__N_14testEv(
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// CHECK: store ptr @[[BLOCK_DESCRIPTOR22]], ptr %{{.*}}, align 8
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// CHECK-LABEL: define internal void @__copy_helper_block_8_32c22_ZTSN12_GLOBAL__N_11BE(
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// CHECK-LABEL: define internal void @__destroy_helper_block_8_32c22_ZTSN12_GLOBAL__N_11BE(
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namespace {
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struct B {
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int a;
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B();
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B(const B &);
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~B();
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};
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void test() {
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B x;
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^{ (void)x; };
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}
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}
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void callTest() {
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test();
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}
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