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Re: [Qemu-devel] [PATCH][ppc] reorganize register set for SPE + TCG

From: Aurelien Jarno
Subject: Re: [Qemu-devel] [PATCH][ppc] reorganize register set for SPE + TCG
Date: Wed, 15 Oct 2008 18:11:30 +0200
User-agent: Mozilla-Thunderbird (X11/20080724)

Nathan Froyd a écrit :
> The (large, invasive) patch below is a preparation patch for converting
> (most) SPE instructions to use TCG.  The rationale is that your ordinary
> SPE instruction deals with three 64-bit quantaties (and a potential
> 64-bit accumulator).  In the current implementation, it's extremely
> laborious/difficult to pass those 64-bit quantaties to helpers, since
> the high/low words for SPE registers are not contiguous in the
> environment.  (TCG helpers for SPE instructions are not yet implemented,
> but they will be necessary as part of the total conversion to TCG.)

You can pass 64-bit TCG registers to helpers. And you can create one TCG
64-bit value from two 32-bits value if needed, and split it back later.
This is exactly what is already done with load_gpr64() and store_gpr64().

Then the limit on the number of arguments of TCG helpers is not a
problem anymore.

  .''`.  Aurelien Jarno             | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
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