[LLVMdev] Dereference PointerType?

[Daniel Waterworth]

2009/10/20 Daniel Waterworth <da.waterworth at googlemail.com>

> Hello,
>
> I'm wondering if it's possible to dereference a PointerType. I have an
> AllocaInst and although I can find the number of elements allocated, (using
> Instruction::getOperand(0)), I can't find a way to get the size of each
> element. What I'd like to do is:
>
> AllocaInst *alloca;
>
> PointerType *ptr_type = dynamic_cast<PointerType*>(alloca);
> assert(ptr_type);
> Type *allocated_type = ptr_type->dereference(); // this is the operation
> that doesn't seem to exist.
> size_t size;
> if (isa<PointerType>(allocated_type)) {
>   size = sizeof(void*) * 8;
> } else {
>   size = allocated_type->getPrimitiveSizeInBits();
> }
> // size now equals the size (in bits) of the type allocated
>
> If it doesn't exist, how do you manage without it? Is there another way to
> write the above code?
>
> Thanks,
>
> Daniel
>

Spot the deliberate mistake [=

PointerType *ptr_type = dynamic_cast<PointerType*>(alloca);

should be,

const PointerType *ptr_type = dynamic_cast<const
PointerType*>(alloca->getType());

and,

Type *allocated_type = ptr_type->dereference();

should probably be,

const Type *allocated_type = ptr_type->dereference();

Daniel
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