[LLVMdev] How to force the creation of arrays with zeroes?

[Chris Lattner]

How many times will a typical client call getOperand on your helper when it wraps a 10,000 element ConstantAggregateZero?

With CAZ the client is force to think about this case, and often handles it much much more efficiently.  CAZ is a time optimization as well as a space optimization.

-Chris

On Jan 21, 2012, at 12:03 AM, Stepan Dyatkovskiy <STPWORLD at narod.ru> wrote:

> Hi Chris. There is no zero arrays created. Probably this patch is not optimal and I'll reworked it today. But the main idea is keep a single zero-item when ConstantAggregateZero was wrapped and return this zero item as result of getOperand call.
> Note that wrapper has no parent classes, it has very local and short lifetime (method body), it exists outside the LLVMContext and needed for replacement of isa<ConstantAggregateZero>(C) checks only.
> 
> -Stepan
> 
> 21.01.2012, 08:12, "Chris Lattner" <clattner at apple.com>:
>> I'd really rather not do this.  Faking that large zero filled array is represented with ConstantArray means that the compiler will inevitably end up calling getOperand on each of those elements, burning a ton of compile time.