[lworld+fp16] RFR: 8338102: x86 backend support for newly added Float16 intrinsics. [v2]

[Jatin Bhateja]

> This patch enables newly added Float16 intrinsicfication support added by [JDK-8336406](https://bugs.openjdk.org/browse/JDK-8336406) for x86 targets supporting AVX512_FP16 feature.
> 
> Kindly review and approve.
> 
> Best Regards,
> Jatin
> 
> Hi @Bhavana-Kilambi, 
> On a second thought, do you see a possibility of sharing the IR nodes by appending secondary opcode to shared IR node in applicable scenarios, so we can have one IR for each class of operations (unary / binary / ternary).  It may need defining following new matcher routines and some more interfaces:- 
> 
>    match_rule_supported_shared(int primary_opcode, int secondary_opcode)
>    match_rule_supported_vector_shared (int primary_opcode, int secondary_opcode, int vlen, BasicType bt)
>    VectorNode::opcode(int popc, int sopc, BasicType bt)
> 
> BinaryOpNode (Dst, Src1, Src2, immI_Opcode);   
> 
> 
> Secondary opcode being a immediate operand can be accessed by encoding routines. WDYT ?
> 
> Another possibility could be to encode both primary and secondary opcodes in existing opcode without disturbing the interfaces and add relevant helper routines to extract primary / secondary opcodes, I think opcodes are never -ve values, hence secondary opcode could be accommodated into higher order bits starting from (MSB-1).

Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:

  Optimizing IR checks

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1196/files
  - new: https://git.openjdk.org/valhalla/pull/1196/files/f9f76fcf..2469628c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1196&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1196&range=00-01

  Stats: 17 lines in 1 file changed: 0 ins; 12 del; 5 mod
  Patch: https://git.openjdk.org/valhalla/pull/1196.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1196/head:pull/1196

PR: https://git.openjdk.org/valhalla/pull/1196