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

[Stepan Dyatkovskiy]

You right here. If you know how to handle it more efficiently, wrapper will bad idea, since it will invoked 10,000 times. We must think always and select most efficient and clean way.
Though, there is also cases when we really need to transform it to 10,000 zeroes (just look at CBackend.cpp, when we print constant arrays, string #1027). There is also cases when we need to get either operand[i] or zero (SCCP.cpp, str #413). Both for CBackend and for SCCP we can reduce code size keeping performance on the same level.

-Stepan.

21.01.2012, 17:50, "Chris Lattner" <clattner at apple.com>:
> 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.