RFR: 8352585: Add special case handling for Float16.max/min x86 backend [v2]

[Sandhya Viswanathan]

On Wed, 26 Mar 2025 11:17:42 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> emit_fp_min_max in x86_64.ad doesn't have any blend emulation.
>
> Hi @sviswa7 ,
> Instruction sequence similar to emit_fp_min_max for half floats prevent issuance of micro-ops from Decoded ICache, this makes its performance worse than the proposed sequence, it seems existence of several branches within 32 byte window is the problem. Section 3.4.2.5 "Optimization for Decoded ICache" has more details on this. The proposed sequence is also vector-friendly.  
> 
> ![image](https://github.com/user-attachments/assets/0efcb12b-dcb4-4346-b3fa-9fefeb46636f)
> 
> [max_micro_sequences.txt](https://github.com/user-attachments/files/19465321/max_micro_sequences.txt)
> 
> Do you suggest going with the proposed performant sequence to fix this bug and addressing any shortcoming after more experimintation later?

Thanks for investigating this, let us take it up in a separate PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24169#discussion_r2014797608