[LLVMdev] Copy Instructions?

[Chris Lattner]

On Jan 28, 2009, at 11:00 AM, David Greene wrote:

> On Wednesday 28 January 2009 12:30, Chris Lattner wrote:
>> On Jan 28, 2009, at 9:50 AM, David Greene wrote:
>>>> Why is this a problem?  All phis execute "atomically".  What  
>>>> problem
>>>> are you seeing in practice?
>>>
>>> I'm getting incorrect answers.
>>>
>>> How can a set of phis with a dependence execute simultaenously?
>>> There is only one definition of x and it has to happen before the
>>> use of
>>> x in the phi defining y, doesn't it?
>>
>> PHIs can't depend on each other.
>
> So just to be clear, this means that all phi uses are considered to  
> execute
> before any phi derfs?

yes, the semantics are that all phis in a block read their inputs,  
after all the "reads" are done they all "store" to their results.

-Chris