Re: [RFC 00/65] target/riscv: support vector extension v0.9

[Alistair Francis]

On Sun, Jul 12, 2020 at 7:02 PM Frank Chang <frank.chang@sifive.com> wrote:
>
> On Sat, Jul 11, 2020 at 5:53 AM Alistair Francis <alistair23@gmail.com> wrote:
>>
>> On Fri, Jul 10, 2020 at 5:59 AM <frank.chang@sifive.com> wrote:
>> >
>> > From: Frank Chang <frank.chang@sifive.com>
>> >
>> > This patchset implements the vector extension v0.9 for RISC-V on QEMU.
>> >
>> > This patchset is sent as RFC because RVV v0.9 is still in draft state.
>> > However, as RVV v1.0 should be ratified soon and there shouldn't be
>> > critical changes between RVV v1.0 and RVV v0.9. We would like to have
>> > the community to review RVV v0.9 implementations. Once RVV v1.0 is
>> > ratified, we will then upgrade to RVV v1.0.
>> >
>> > You can change the cpu argument: vext_spec to v0.9 (i.e. vext_spec=v0.9)
>> > to run with RVV v0.9 instructions.
>>
>> Hello,
>>
>> First off thanks for the patches!
>>
>> QEMU has a policy of accepting draft specs as experimental. We
>> currently support the v0.7.1 Vector extension for example, so this
>> does not need to be an RFC and can be a full patch series that can be
>> merged into master.
>>
>> I have applied the first few patches (PR should be out next week) and
>> they should be in the QEMU 5.1 release. QEMU is currently in a freeze
>> so I won't be able to merge this series for 5.1. In saying that please
>> feel free to continue to send patches to the list, they can still be
>> reviewed.
>>
>> In general we would need to gracefully handle extension upgrades and
>> maintain backwards compatibility. This same principle doesn't apply to
>> experimental features though (such as the vector extension) so you are
>> free to remove support for the v0.7.1. For users who want v0.7.1
>> support they can always use the QEMU 5.1. release. Just make sure that
>> your series does not break bisectability.
>>
>> Thanks again for the patches!
>>
>> Alistair
>
>
> Hi Alistair,
>
> Thanks for the review.
>
> Currently I would prefer to drop 0.7.1 support because I don't know if there's
> a good way to keep both 0.7.1 and 0.9 opcodes. I'm afraid it would cause the
> encoding overlap while compiling with decodetree.

That's fine. The plan was always to only support one version of a
draft extension (and none when the final spec is frozen).

>
> Does decodetree support any feature for multi-version opcodes?

I'm not sure, but we don't want to deal with the maintenance burden of
two draft extensions anyway.

> Or if it can use something like C macros to compile with the opcodes by the 
> vspec
> user assigned? If there's any good way to keep both versions, then I can try 
> to rearrange
> my codes to support both vspecs.
>
> Otherwise, I'll keep on my current approach to drop the support of v0.7.1 as 
> the way
> Richard has mentioned:
> If you don't want to simultaneously support 0.7.1 and 0.9/1.0, then you should
> simply remove 0.7.1 in the first patch, so that there's no confusion.

That sounds good :)

Alistair

>
> Any suggestion would be appreciated.
>
> Thanks
> --
> Frank Chang
>
>>
>> >
>> > Chih-Min Chao (2):
>> >   fpu: fix float16 nan check
>> >   fpu: add api to handle alternative sNaN propagation
>> >
>> > Frank Chang (58):
>> >   target/riscv: fix rsub gvec tcg_assert_listed_vecop assertion
>> >   target/riscv: correct the gvec IR called in gen_vec_rsub16_i64()
>> >   target/riscv: fix return value of do_opivx_widen()
>> >   target/riscv: fix vill bit index in vtype register
>> >   target/riscv: remove vsll.vi, vsrl.vi, vsra.vi insns from using gvec
>> >   target/riscv: rvv-0.9: remove MLEN calculations
>> >   target/riscv: rvv-0.9: add fractional LMUL, VTA and VMA
>> >   target/riscv: rvv-0.9: update check functions
>> >   target/riscv: rvv-0.9: configure instructions
>> >   target/riscv: rvv-0.9: stride load and store instructions
>> >   target/riscv: rvv-0.9: index load and store instructions
>> >   target/riscv: rvv-0.9: fix address index overflow bug of indexed
>> >     load/store insns
>> >   target/riscv: rvv-0.9: fault-only-first unit stride load
>> >   target/riscv: rvv-0.9: amo operations
>> >   target/riscv: rvv-0.9: load/store whole register instructions
>> >   target/riscv: rvv-0.9: update vext_max_elems() for load/store insns
>> >   target/riscv: rvv-0.9: take fractional LMUL into vector max elements
>> >     calculation
>> >   target/riscv: rvv-0.9: floating-point square-root instruction
>> >   target/riscv: rvv-0.9: floating-point classify instructions
>> >   target/riscv: rvv-0.9: mask population count instruction
>> >   target/riscv: rvv-0.9: find-first-set mask bit instruction
>> >   target/riscv: rvv-0.9: set-X-first mask bit instructions
>> >   target/riscv: rvv-0.9: iota instruction
>> >   target/riscv: rvv-0.9: element index instruction
>> >   target/riscv: rvv-0.9: integer scalar move instructions
>> >   target/riscv: rvv-0.9: floating-point scalar move instructions
>> >   target/riscv: rvv-0.9: whole register move instructions
>> >   target/riscv: rvv-0.9: integer extension instructions
>> >   target/riscv: rvv-0.9: single-width averaging add and subtract
>> >     instructions
>> >   target/riscv: rvv-0.9: integer add-with-carry/subtract-with-borrow
>> >   target/riscv: rvv-0.9: narrowing integer right shift instructions
>> >   target/riscv: rvv-0.9: widening integer multiply-add instructions
>> >   target/riscv: rvv-0.9: quad-widening integer multiply-add instructions
>> >   target/riscv: rvv-0.9: integer merge and move instructions
>> >   target/riscv: rvv-0.9: single-width saturating add and subtract
>> >     instructions
>> >   target/riscv: rvv-0.9: integer comparison instructions
>> >   target/riscv: rvv-0.9: floating-point compare instructions
>> >   target/riscv: rvv-0.9: single-width integer reduction instructions
>> >   target/riscv: rvv-0.9: widening integer reduction instructions
>> >   target/riscv: rvv-0.9: mask-register logical instructions
>> >   target/riscv: rvv-0.9: register gather instructions
>> >   target/riscv: rvv-0.9: slide instructions
>> >   target/riscv: rvv-0.9: floating-point slide instructions
>> >   target/riscv: rvv-0.9: narrowing fixed-point clip instructions
>> >   target/riscv: rvv-0.9: floating-point move instructions
>> >   target/riscv: rvv-0.9: floating-point/integer type-convert
>> >     instructions
>> >   target/riscv: rvv-0.9: single-width floating-point reduction
>> >   target/riscv: rvv-0.9: widening floating-point reduction instructions
>> >   target/riscv: rvv-0.9: single-width scaling shift instructions
>> >   target/riscv: rvv-0.9: remove widening saturating scaled multiply-add
>> >   target/riscv: rvv-0.9: remove vmford.vv and vmford.vf
>> >   target/riscv: rvv-0.9: remove integer extract instruction
>> >   target/riscv: rvv-0.9: floating-point min/max instructions
>> >   target/riscv: rvv-0.9: widening floating-point/integer type-convert
>> >   target/riscv: rvv-0.9: narrowing floating-point/integer type-convert
>> >   softfloat: add fp16 and uint8/int8 interconvert functions
>> >   target/riscv: use softfloat lib float16 comparison functions
>> >   target/riscv: bump to RVV 0.9
>> >
>> > Kito Cheng (1):
>> >   fpu: implement full set compare for fp16
>> >
>> > LIU Zhiwei (4):
>> >   target/riscv: rvv-0.9: add vcsr register
>> >   target/riscv: rvv-0.9: add vector context status
>> >   target/riscv: rvv-0.9: update mstatus_vs by tb_flags
>> >   target/riscv: rvv-0.9: add vlenb register
>> >
>> >  fpu/softfloat-specialize.inc.c          |    4 +-
>> >  fpu/softfloat.c                         |  342 +++-
>> >  include/fpu/softfloat.h                 |   22 +
>> >  target/riscv/cpu.c                      |    9 +-
>> >  target/riscv/cpu.h                      |   68 +-
>> >  target/riscv/cpu_bits.h                 |    9 +
>> >  target/riscv/cpu_helper.c               |   13 +
>> >  target/riscv/csr.c                      |   53 +-
>> >  target/riscv/helper.h                   |  507 +++--
>> >  target/riscv/insn32-64.decode           |   18 +-
>> >  target/riscv/insn32.decode              |  282 +--
>> >  target/riscv/insn_trans/trans_rvv.inc.c | 2468 ++++++++++++++---------
>> >  target/riscv/internals.h                |   18 +-
>> >  target/riscv/translate.c                |   43 +-
>> >  target/riscv/vector_helper.c            | 2349 +++++++++++----------
>> >  15 files changed, 3833 insertions(+), 2372 deletions(-)
>> >
>> > --
>> > 2.17.1
>> >
>> >