Re: MIPS32R2 simulator fixes

[Thiemo Seufer <ths at networkno dot de>]

Richard Sandiford wrote:
> When extending GCC's -mpaired-single support to MIPS32R2, I noticed
> that many of the instructions weren't simulated correctly for
> mipsisa32r2-elfoabi:
> 
>   - Most of the instructions that are implemented by MIPS32R2 targets
>     with a 64-bit FPU have the requisite "*mips32r2" marker, but their
>     filter is "64,f" rather than "32,f".  ("32" and "64" are the word
>     size, not the FPU size.)
> 
>   - 64-bit loads and stores need to use do_load_double and
>     do_store_double for 32-bit targets.
> 
>   - SDXC1 and SUXC1 weren't implemented for MIPS32R2.
> 
>   - The MIPS32R2 version of check_fmt_p checks UX and PX, but those
>     flags are always read as 0 on MIPS32R2 targets.  There isn't
>     AFAIK any way of turning off paired-single instructions when
>     using a MIPS32R2 target that has a 64-bit FPU.

It is correct that there's no separate switch to disable paired single
when the MIPS-3D ASE is implemented. There is, however, the 3D bit in
FCR0 which announces the availablity of paired single instructions,
it should be set for the MIPS32R2/MIPS64* emulations.

>     (check_fmt_p
>     doesn't need to check that the 64-bit FPU is in 64-bit mode;
>     that's done elsewhere.)
> 
>   - LUXC1 and SUXC1 are unpredictable when the FPU is not in 64-bit mode.
>     (True for MIPS64 as well as MIPS32, and unpredictability is ignored
>     for MIPS V.)
> 
> Note that mips*-sde-elf* uses mips64r2, so users of that configuration
> wouldn't have come across the first four problems.
> 
> Tested with GCC on mipsisa32r2-elfoabi and mipsisa64r2-elfoabi.
> OK to install?
> 
> Richard
> 
> 
> sim/mips/
> 	* mips.igen (check_fmt_p): Provide a separate mips32r2 definition
> 	that unconditionally allows fmt_ps.
> 	(ALNV.PS, CEIL.L.fmt, CVT.L.fmt, CVT.PS.S, CVT.S.PL, CVT.S.PU)
> 	(FLOOR.L.fmt, LWXC1, MADD.fmt, MSUB.fmt, NMADD.fmt, NMSUB.fmt)
> 	(PLL.PS, PLU.PS, PUL.PS, PUU.PS, ROUND.L.fmt, TRUNC.L.fmt): Change
> 	filter from 64,f to 32,f.
> 	(PREFX): Change filter from 64 to 32.
> 	(LDXC1, LUXC1): Provide separate mips32r2 implementations
> 	that use do_load_double instead of do_load.  Make both LUXC1
> 	versions unpredictable if SizeFGR () != 64.
> 	(SDXC1, SUXC1): Extend to mips32r2, using do_store_double
> 	instead of do_store.  Remove unused variable.  Make both SUXC1
> 	versions unpredictable if SizeFGR () != 64.

Looks good.


Thiemo