RFR: 8352585: Add special case handling for Float16.max/min x86 backend [v7]

[Emanuel Peter]

On Tue, 1 Apr 2025 16:17:22 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> This bugfix patch adds the special handling as per x86 AVX512-FP16 ISA specification[1][2] to compute max/min operations with +/-0.0 or NaN operands.
>> 
>> Special handling leverage the instruction semantic, central idea is to shuffle the operands such that smaller input gets assigned to second operand for min operation or a larger input gets assigned to second operand for max operation, in addition result equals NaN if an unordered comparison detects first input as a NaN value else we return the result of min/max operation. 
>> 
>> Kindly review and share your feedback.
>> 
>> Best Regards,
>> Jatin
>> 
>> [1] https://www.felixcloutier.com/x86/vminsh
>> [2] https://www.felixcloutier.com/x86/vmaxsh
>
> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Review comments resolution

Testing is green :)

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 7108:

> 7106:     // dst = max(xtmp1, xtmp2)
> 7107:     vmaxsh(dst, xtmp1, xtmp2);
> 7108:     // isNaN = is_unordered_quite(xtmp1)

Suggestion:

    // isNaN = is_unordered_quiet(xtmp1)

Does the Q stand for quiet or quite?

src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 7129:

> 7127:     // dst = min(xtmp1, xtmp2)
> 7128:     vminsh(dst, xtmp1, xtmp2);
> 7129:     // isNaN = is_unordered_quite(xtmp1)

Suggestion:

    // isNaN = is_unordered_quiet(xtmp1)

-------------

Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/24169#pullrequestreview-2739047288
PR Review Comment: https://git.openjdk.org/jdk/pull/24169#discussion_r2026532906
PR Review Comment: https://git.openjdk.org/jdk/pull/24169#discussion_r2026533225