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[scudo][standalone] Remove unused atomic_compare_exchange_weak

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`atomic_compare_exchange_weak` is unused in Scudo, and its associated
test is actually wrong since the weak variant is allowed to fail
spuriously (thanks Roland).

This lead to flakes such as:
```
[ RUN      ] ScudoAtomicTest.AtomicCompareExchangeTest
../../zircon/third_party/scudo/src/tests/atomic_test.cpp:98: Failure: Expected atomic_compare_exchange_weak(reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed) is true.
    Expected: true
    Which is: 01
    Actual  : atomic_compare_exchange_weak(reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed)
    Which is: 00
../../zircon/third_party/scudo/src/tests/atomic_test.cpp💯 Failure: Expected atomic_compare_exchange_weak( reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed) is false.
    Expected: false
    Which is: 00
    Actual  : atomic_compare_exchange_weak( reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed)
    Which is: 01
../../zircon/third_party/scudo/src/tests/atomic_test.cpp:101: Failure: Expected OldVal == NewVal.
    Expected: NewVal
    Which is: 24
    Actual  : OldVal
    Which is: 42
[  FAILED  ] ScudoAtomicTest.AtomicCompareExchangeTest (0 ms)
[----------] 2 tests from ScudoAtomicTest (1 ms total)
```

So I am removing this, if someone ever needs the weak variant, feel
free to add it back with a test that is not as terrible. This test was
initially ported from sanitizer_common, but their weak version calls
the strong version, so it works for them.

Differential Revision: https://reviews.llvm.org/D88443
This commit is contained in:
Kostya Kortchinsky
2020-09-28 13:07:33 -07:00
parent 1e86d637eb
commit f668a84b58
2 changed files with 7 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
compiler-rt/lib/scudo/standalone/atomic_helpers.h
View File

@@ -106,14 +106,6 @@ inline bool atomic_compare_exchange_strong(volatile T *A, typename T::Type *Cmp,
__ATOMIC_RELAXED);
}
template <typename T>
inline bool atomic_compare_exchange_weak(volatile T *A, typename T::Type *Cmp,
typename T::Type Xchg,
memory_order MO) {
return __atomic_compare_exchange(&A->ValDoNotUse, Cmp, &Xchg, true, MO,
__ATOMIC_RELAXED);
}
// Clutter-reducing helpers.
template <typename T>

26
compiler-rt/lib/scudo/standalone/tests/atomic_test.cpp
View File

@@ -80,26 +80,14 @@ TEST(ScudoAtomicTest, AtomicStoreLoad) {
template <typename T> void checkAtomicCompareExchange() {
typedef typename T::Type Type;
{
Type OldVal = 42;
Type NewVal = 24;
Type V = OldVal;
EXPECT_TRUE(atomic_compare_exchange_strong(
reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed));
EXPECT_FALSE(atomic_compare_exchange_strong(
reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed));
EXPECT_EQ(NewVal, OldVal);
}
{
Type OldVal = 42;
Type NewVal = 24;
Type V = OldVal;
EXPECT_TRUE(atomic_compare_exchange_weak(reinterpret_cast<T *>(&V), &OldVal,
Type OldVal = 42;
Type NewVal = 24;
Type V = OldVal;
EXPECT_TRUE(atomic_compare_exchange_strong(reinterpret_cast<T *>(&V), &OldVal,
NewVal, memory_order_relaxed));
EXPECT_FALSE(atomic_compare_exchange_weak(
reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed));
EXPECT_EQ(NewVal, OldVal);
}
EXPECT_FALSE(atomic_compare_exchange_strong(
reinterpret_cast<T *>(&V), &OldVal, NewVal, memory_order_relaxed));
EXPECT_EQ(NewVal, OldVal);
}
TEST(ScudoAtomicTest, AtomicCompareExchangeTest) {