[jdk17u] RFR: 8276105: C2: Conv(D|F)2(I|L)Nodes::Ideal should handle rounding correctly

[Aleksey Shipilev]

On Mon, 15 Nov 2021 10:12:02 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Clean backport to improve C2 x86_32 reliability.
> 
> Additional testing:
>  - [x] Linux x86_32 fastdebug `tier1` passes

Got the push approval.

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PR: https://git.openjdk.java.net/jdk17u/pull/261