RFR: 8252496: C2: Useless code in MergeMemNode::Ideal

[Emanuel Peter]

On Wed, 9 Feb 2022 12:31:51 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

>> This code was there since `initial load`. At that point there was other code that still depended on this code.
>> The other code was removed [here](https://github.com/eme64/jdk/commit/79ad5512cfe5c4ef7d0b61616f3763c62d3427a5). This was the change set for [JDK-8243670](https://bugs.openjdk.java.net/browse/JDK-8243670).
>> Our code was left behind.
>> 
>> I removed the useless code, and ran tests to verify that nothing broke due to side-effects.
>
> Looks good.

@iwanowww @chhagedorn @TobiHartmann thanks for the reviews!

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PR: https://git.openjdk.java.net/jdk/pull/7401