RFR: 8288043: Optimize FP to word/sub-word integral type conversion on X86 AVX2 platforms [v5]

[Vladimir Kozlov]

On Tue, 20 Sep 2022 01:56:12 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/matcher_x86.hpp line 193:
>> 
>>> 191:       case Op_VectorCastF2X: // fall through
>>> 192:       case Op_VectorCastD2X: {
>>> 193:         return is_subword_type(ety) ? 75 : 70;
>> 
>> Add comment here and in other cases explaining numbers. Is it size of instructions or elements or something?
>
> Value now matches the one for RoundV[FD] IR nodes, currently, its a rudimentary heuristic based on emitted code size for complex IR nodes used by unroll policy. Idea is to constrain unrolling factor and prevent generating bloated loop bodies.

Please, add this information/clarification to this method's comment at line 186.

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

PR: https://git.openjdk.org/jdk/pull/9748