[llvm-dev] PHI inst has two exact the same operands?

[Daniel Berlin via llvm-dev]

yes, this is valid assuming bb9 dominates bb10.
Not sure what you mean by "support this", unless your tool doesn't handle
certain types of CFG's


On Wed, Mar 30, 2016 at 8:12 PM, Xiaochu Liu via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Dear there,
>
> Is the following phi instruction valid?
>
> %j_8 = phi i32 [ %j_100, %"<bb 13>" ], [ %j_9133, %"<bb 10>" ], [
> %j_9133, %"<bb 9>" ]
>
> Variable %j_9133 is in bb 9.
>
> And also this one:
>
> %D.1898_8.i = phi i32 [ %D.1898_27.i, %"<bb 18>.i" ], [ -1, %"<bb 23>" ],
> [ %D.1776_193, %"<bb 4>], [ %D.1776_193, %"<bb 4>], [ %l_5.lcssa.i,
> %"<bb 17>.i" ]
>
> It has two identical operands.
> Are they valid llvm instructions? I am hacking a infrastructure which
> generates these IR. I was wondering if I should make my tool support
> this or somehow manage to resolve this situation.
>
> Thanks,
> Xiaochu
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