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Re: RFC: generic vectors and GPR/simd duality
- From: Daniel Jacobowitz <drow at false dot org>
- To: Aldy Hernandez <aldyh at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 12 May 2004 11:49:49 -0400
- Subject: Re: RFC: generic vectors and GPR/simd duality
- References: <20040512145800.GA31563@redhat.com>
On Wed, May 12, 2004 at 10:58:00AM -0400, Aldy Hernandez wrote:
> mode_multiple from V2SI to V4SI is 2, whereas nregs_multiple is 4.
> GPR #26 can hold a V2SI in just one register, but needs 4 for a V4SI.
> In other architectures, a given SIMD register can hold only one type
> of simd, whereas the e500 can hold any (albeit in subsequent registers
> for anything not V2SI). Confusion.
Why does V4SI take four GPRs, that's the question. If you treat them
as V2SI registers GCC ought to be able to synthesize the V4SI as two
V2SIs. It might be as simple as "fixing" HARD_REGNO_NREGS... probably
not, though.
--
Daniel Jacobowitz