forked from OSchip/llvm-project
60f57369a2
There are many instruction ctors that call the setName method of the Value base class, which can throw a bad_alloc exception in OOM situations.
In such situations special User delete operators are called which are not implemented yet.
Example:
Lets look at the construction of a CallInst instruction during IR generation:
static CallInst *Create(FunctionType *Ty, Value *Func, ArrayRef<Value *> Args, .. ){
...
return new (TotalOps, DescriptorBytes) CallInst(Ty, Func, Args, Bundles, NameStr, InsertBefore);
}
CallInst::CalInst(Value* Func, ...) {
...
Op<-1>() = Func;
....
setName(name); // throws
...
}
Op<-1>() returns a reference to a Use object of the CallInst instruction and the operator= inserts this use object into the UseList of Func.
The same object is removed from that UseList by calling the User::operator delete If the CallInst object is deleted.
Since setName can throw a bad_alloc exception (if LLVM_ENABLE_EXCEPTIONS is switched on), the unwind chain runs into assertions ("Constructor throws?") in
special User::operator deletes operators:
operator delete(void* Usr, unsigned)
operator delete(void* Usr, unsigned, bool)
This situation can be fixed by simlpy calling the User::operator delete(void*) in these unimplemented methods.
To ensure that this additional call succeeds all information that is necessary to calculate the storage pointer from the Usr address
must be restored in the special case that a sublass has changed this information, e.g. GlobalVariable can change the NumberOfOperands.
Reviewd by: rnk
Differential Revision: https://reviews.llvm.org/D42731
llvm-svn: 326316
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