Re: [PATCH 0/1] RISC-V: Fix RV32Q conflict

[Jan Beulich <jbeulich@suse.com>]

On 07.02.2022 04:31, Tsukasa OI via Binutils wrote:
> This commit allows combination of RV32 + 'Q' extension (IEEE 754
> binary128 floating point number support).
> 
> This combination is no longer prohibited by the ISA Manual.
> 
> This restriction is introduced in binutils' RV32E support commit
> 7f99954970001cfc1b155d877ac2966d77e2c647.  At that time,
> the latest ratified version of the RISC-V ISA Manual (version 2.2)
> stated that 'Q' extension requires RV64IFD.
> 
> However, the next ratified version of the RISC-V ISA Manual
> (20190608-Base-Ratified) removed such limitation.

Ah yes, one of the anomalies I did notice a while ago and didn't get
around to writing mail about, yet. A related anomaly looks to be that
RV32E excludes F, without me being able to find respective wording in
the spec.

Jan

> I did check the version of 'Q' extension (RV32Q is allowed on 'Q'
> extension version 2.2 or later) but it may be too pedant.
> 
> This is because  change (removal of RV64IFD dependency) seemed irrevant
> to version changes but only a part of "embellishment" process as
> described by riscv-isa-manual commit
> 013ba6dc8a504ee4ad7bee42554fecaef7ba797f.
> 
> Quoting preface of 20190608-Base-Ratified (would analogously to 'Q'),
> 
>> Incremented the version numbers of the F and D extensions to 2.2,
>> reflecting that version 2.1 changed the canonical NaN, and version 2.2
>> defined the NaN-boxing scheme and changed the definition of the FMIN
>> and FMAX instructions.
> 
> Not checking the version number (just allowing RV32Q entirely) may be
> an option.
> 
> 
> References:
> 
> GNU Binutils:
>   Commit 7f99954970001cfc1b155d877ac2966d77e2c647
>     <https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=7f99954970001cfc1b155d877ac2966d77e2c647>
> 
> The RISC-V ISA Manual:
>   version 2.2
>     <https://github.com/riscv/riscv-isa-manual/releases?q=2.2>
>   version 20190608-Base-Ratified
>     <https://github.com/riscv/riscv-isa-manual/releases?q=Ratified-IMFDQC-and-Priv-v1.11>
>   commit 013ba6dc8a504ee4ad7bee42554fecaef7ba797f:
>     <https://github.com/riscv/riscv-isa-manual/commit/013ba6dc8a504ee4ad7bee42554fecaef7ba797f>
> 
> 
> 
> 
> Tsukasa OI (1):
>   RISC-V: Fix RV32Q conflict
> 
>  bfd/elfxx-riscv.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> 
> base-commit: 6a9d08661b361e497baa76dd6d8685f2cb593adb