The spec is a draft but required by vector extension.  The reference is 
availabe at
   https://github.com/riscv/riscv-isa-manual/tree/zfh

The patch depends two unmerged patch set
  1. extend softfloat to support int8 and alternative NaN probagapation
  2. NaNBox fix

Based-on: <1596102747-20226-1-git-send-email-chihmin.chao@sifive.com>
Based-on: <20200724002807.441147-1-richard.henderson@linaro.org>

Chih-Min Chao (2):
  target/riscv: add NaN-Boxing helper for half-float
  target/riscv: support 'x-k' in cpu option

Kito Cheng (1):
  target/riscv: Implement zfh extension

 target/riscv/cpu.c                        |   4 +
 target/riscv/cpu.h                        |   2 +
 target/riscv/fpu_helper.c                 | 180 ++++++++++
 target/riscv/helper.h                     |  34 ++
 target/riscv/insn32-64.decode             |   6 +
 target/riscv/insn32.decode                |  32 ++
 target/riscv/insn_trans/trans_rvzfh.inc.c | 531 ++++++++++++++++++++++++++++++
 target/riscv/internals.h                  |  16 +
 target/riscv/translate.c                  |  16 +
 9 files changed, 821 insertions(+)
 create mode 100644 target/riscv/insn_trans/trans_rvzfh.inc.c

-- 
2.7.4