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[libcxx][atomic] Remove workaround for PR31864

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I believe the origin issue in PR31864 has been addressed by https://reviews.llvm.org/D59566.

As discussed in https://github.com/llvm/llvm-project/issues/53840, `ATOMIC_LLONG_LOCK_FREE == 2` sometimes is not consistent with `std::atomic<long long>::is_always_lock_free`, since the macro takes `long long`'s ABI alignment into account. https://reviews.llvm.org/D28213 proposed we should not rely on ABI alignment of types, thus we have consistent `ATOMIC_LLONG_LOCK_FREE` and `std::atomic<long long>::is_always_lock_free` on x86's old cpu. Currently, I plan to move on to remove the workaround which should have been addressed and don't want to break current tests.

Reviewed By: #libc, ldionne, Quuxplusone

Differential Revision: https://reviews.llvm.org/D119931
This commit is contained in:
Kai Luo 2022-03-06 00:55:22 +00:00
parent 4d2669002e
commit 86478c7ad8
1 changed files with 2 additions and 35 deletions
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37
libcxx/test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp
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@ -29,40 +29,6 @@ template <typename T> void checkAlwaysLockFree() {
assert(std::atomic<T>().is_lock_free());
}
// FIXME: This separate test is needed to work around llvm.org/PR31864
// which causes ATOMIC_LLONG_LOCK_FREE to be defined as '1' in 32-bit builds
// even though __atomic_always_lock_free returns true for the same type.
constexpr bool NeedWorkaroundForPR31864 =
#if defined(__clang__)
(sizeof(void*) == 4); // Needed on 32 bit builds
#else
false;
#endif
template <bool Disable = NeedWorkaroundForPR31864,
std::enable_if_t<!Disable>* = nullptr,
class LLong = long long,
class ULLong = unsigned long long>
void checkLongLongTypes() {
static_assert(std::atomic<LLong>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
static_assert(std::atomic<ULLong>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
}
// Used to make the calls to __atomic_always_lock_free dependent on a template
// parameter.
template <class T> constexpr size_t getSizeOf() { return sizeof(T); }
template <bool Enable = NeedWorkaroundForPR31864,
std::enable_if_t<Enable>* = nullptr,
class LLong = long long,
class ULLong = unsigned long long>
void checkLongLongTypes() {
constexpr bool ExpectLockFree = __atomic_always_lock_free(getSizeOf<LLong>(), 0);
static_assert(std::atomic<LLong>::is_always_lock_free == ExpectLockFree, "");
static_assert(std::atomic<ULLong>::is_always_lock_free == ExpectLockFree, "");
static_assert((0 != ATOMIC_LLONG_LOCK_FREE) == ExpectLockFree, "");
}
void run()
{
// structs and unions can't be defined in the template invocation.
@ -140,7 +106,8 @@ void run()
static_assert(std::atomic<unsigned int>::is_always_lock_free == (2 == ATOMIC_INT_LOCK_FREE), "");
static_assert(std::atomic<long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE), "");
static_assert(std::atomic<unsigned long>::is_always_lock_free == (2 == ATOMIC_LONG_LOCK_FREE), "");
checkLongLongTypes();
static_assert(std::atomic<long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
static_assert(std::atomic<unsigned long long>::is_always_lock_free == (2 == ATOMIC_LLONG_LOCK_FREE), "");
static_assert(std::atomic<void*>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE), "");
static_assert(std::atomic<std::nullptr_t>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE), "");