RE: [PATCH] [MIPS] fix mips_prepend insn.

["Fu, Chao-Ying" <fu at mips dot com>]

Richard Sandiford [rdsandiford@googlemail.com] wrote:

> This pattern maps directly to __builtin_mips_prepend, which is defined
> to take and return an SI type, so :SI is the correct choice here.
>
> I agree it might be nice to have a function that operates on 64-bit
> values for 64-bit targets though.  For compatibility reasons,
> we'd probably have to define both a new function and a new pattern
> (or at least an iterator version of the current pattern).
> There's currently no way of generating PREPENDD or PREPENDW either.
>
> I consider this API to be owned by MTI, so we'd need to coordinate
> with them.  Chao-Ying, what do you think?  Do you already have
> something like this internally?

  As there is no MIPS64 core with dsp/dspr2 in the market, we haven't tested/ported these built-in functions to MIPS64.

  I think it's better to keep the current prototype of __builtin_mips_prepend to return an SI type.
We may need to add new built-in functions for instructions involving accumulators and for new MIPS64 dsp/dspr2 instructions to MIPS64.
For existing built-in functions involving only integer registers/immediates, we may not change them.
For Liu, is this solution suitable for you?   Thanks!

Regards,
Chao-ying