[PATCH] Support for MIPS R5900 (Sony Playstation 2)
Maciej W. Rozycki
macro@codesourcery.com
Thu Jan 10 23:19:00 GMT 2013
On Tue, 8 Jan 2013, "JÃŒrgen Urban" wrote:
> > As a side note -- I've noticed elsewhere in this change that the R5900
> > supports single-precision FP only. This is similar to what the
> > R4640/R4650 does (up to supporting 32 single registers in the FR mode --
> > is that any different to the R5900?), however up till now we did nothing
> > explicit for such a setup, except from respecting the -mfp32 option.
> > This change introduces extra bits however, like hardwiring -mfp32 --
> > perhaps they could be generalised in some way to cover the R4640/R4650 as
> > well? -- again, for consistency.
>
> The patch for R5900 currently sets -mfp32 with the line:
>
> if (mips_opts.arch == CPU_R5900)
> {
> mips_opts.fp32 = 1;
> }
> else
> ...
>
> This avoids updating the FPU to 64 bit when setting higher mips ISA level.
> The R4640/R4650 can be added here. Is this what you want?
I've thought of a more general approach, for example marking the missing
instructions to support the unimplemented double format for the
R4640/R4650 as well (or perhaps the other way round -- whenever -mfp32 is
active rather than for any specific processor, as otherwise these
instructions are in a sense valid, as the MIPS FPU by definition allows
deferring any operation to software emulation). There may be something
else too.
In any case, please don't feel compelled to make these changes -- unless
you really want to. I just raised it as a general point in discussion.
Maciej
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