RFR: 8301814: RISCV: Delete unused CountLoopEnd instruct with CmpX

[SUN Guoyun]

On Mon, 20 Feb 2023 07:34:08 GMT, SUN Guoyun <duke at openjdk.org> wrote:

> CountLoopEnd only for T_int, therefore the following instructs in riscv.ad are useless and should be deleted.
> 
> CountedLoopEnd cmp (CmpL op1 op2)
> CountedLoopEnd cmp (CmpU op1 op2)
> CountedLoopEnd cmp (CmpP op1 op2)
> CountedLoopEnd cmp (CmpN op1 op2)
> CountedLoopEnd cmp (CmpF op1 op2)
> CountedLoopEnd cmp (CmpD op1 op2)
> 
> Please help review it.
> 
> Thanks.

1. I only did tier1-3 and openjvm2008 tests on the LoongArch64 architecture(Linux platform) and confirmed that none of these types were used, including CmpU.
2. Do you sure the U version of CountedLoopEnd be used on AArch64? I guess it is unused also but I will also confirm further.
3. Yes, I will update the Patch for keep the Long version. I'm also evaluating the performance benefits of `LongCountedLoopEndNode` to decide whether to implement it.

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PR: https://git.openjdk.org/jdk/pull/12648