RFR: 8292761: x86: Clone nodes to match complex rules [v4]

[Sandhya Viswanathan]

On Sat, 17 Sep 2022 09:42:41 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> This patch tries to clone a node if it can be matched as a part of a BMI and lea pattern. This may reduce the live range of a local or remove that local completely.
>> 
>> Please take a look and have some reviews. Thanks a lot.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   address comments

src/hotspot/cpu/x86/x86.ad line 2504:

> 2502:       Node* other = n->in((n->in(1) == m) ? 2 : 1);
> 2503:       m = other;
> 2504:     }

The caller pd_clone_node is checking if m needs to be cloned, but we are changing m here locally before doing the pattern match? The original code was not doing this. Would it now result in cloning the wrong node?

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PR: https://git.openjdk.org/jdk/pull/9977