On Fri, Aug 18, 2017 at 10:39 PM, Christopher Li <sparse@xxxxxxxxxxx> wrote:
>
> You do need to preserve the order of the phi node, right?
> At first I was thinking always insert the phi at the first instruction.
> Then I realized that, it is possible some phi node use some other
> phi node as source in case of a loop. So the order does need
> to be preserved some how.
It's not needed because:
1) phi-nodes need to have 'parallel-assignment' semantics anyway
like in languages where you can write 'a, b = b, a' to exchange
two variables. In other words, if the order would matter it would
be a bug.
2) you can never have (the target of) a phi-node (OP_PHI)
as another phi-node' source because all such sources are
created by OP_PHISOURCEs.
-- Luc
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