llvm dev - Jan 2011 - [LLVMdev] newbi to llvm - how to get array size

Hi,

I am new to llvm to so please be kind to me if I am asking something that is
too simple.  I want to get the bounds of an array when I have a handle to
getelementptr or insertelement or extractvalue instructions.  I am writing a
translation routine from llvm to a non-deterministic language and want to
include array bounds check in it.

The array size gets printed as part of the type of the value <pty>

<result> = getelementptr inbounds <pty>* <ptrval> (ty idx)

I am wrongly expecting I.getOperand(0)->getType()->getNumElements() to
give me the array size (after casting ptrval to array type)

I am not getting the array size, I am getting a value of zero.

Can someone point out to me how to get array size (number of elements in the
array) from the type object.  What about multi-dimension arrays too.

Thanks.

Surinder Kumar Jain
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Hi Surinder,
> I am new to llvm to so please be kind to me if I am asking something that
is too
> simple.  I want to get the bounds of an array when I have a handle to
> getelementptr or insertelement or extractvalue instructions.  I am writing
a
> translation routine from llvm to a non-deterministic language and want to
> include array bounds check in it.
> The array size gets printed as part of the type of the value <pty>
> <result> = getelementptr inbounds <pty>* <ptrval> (ty
idx)
> I am wrongly expecting I.getOperand(0)->getType()->getNumElements()
to give me
> the array size (after casting ptrval to array type)
> I am not getting the array size, I am getting a value of zero.
> Can someone point out to me how to get array size (number of elements in
the
> array) from the type object.  What about multi-dimension arrays too.
the first operand always has pointer type, you need the type of the pointee,
something like this: I.getPointerOperandType()->getElementType()
You can then cast the returned type T to an array type and grab the number
of elements:
   cast<ArrayType>(T)->getNumElements()

Ciao, Duncan.