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Use double-checked locking for this lazy initialization.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73653 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2009-06-17 22:53:57 +00:00
parent b983d67465
commit a23d2c1262
1 changed files with 21 additions and 2 deletions
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23
lib/VMCore/Type.cpp
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@ -453,8 +453,27 @@ void DerivedType::dropAllTypeUses() {
if (NumContainedTys != 0) {
// The type must stay abstract. To do this, we insert a pointer to a type
// that will never get resolved, thus will always be abstract.
static Type *AlwaysOpaqueTy = OpaqueType::get();
static PATypeHolder Holder(AlwaysOpaqueTy);
static Type *AlwaysOpaqueTy = 0;
static PATypeHolder* Holder = 0;
if (!AlwaysOpaqueTy) {
if (llvm_is_multithreaded()) {
llvm_acquire_global_lock();
if (!AlwaysOpaqueTy) {
Type *tmp = OpaqueType::get();
PATypeHolder* tmp2 = new PATypeHolder(AlwaysOpaqueTy);
sys::MemoryFence();
AlwaysOpaqueTy = tmp;
Holder = tmp2;
}
llvm_release_global_lock();
} else {
AlwaysOpaqueTy = OpaqueType::get();
Holder = new PATypeHolder(AlwaysOpaqueTy);
}
}
ContainedTys[0] = AlwaysOpaqueTy;
// Change the rest of the types to be Int32Ty's. It doesn't matter what we