Re: [Qemu-devel] [RFC 20/28] target-xtensa: implement windowed registers

[Blue Swirl]

On Wed, May 4, 2011 at 3:59 AM, Max Filippov <address@hidden> wrote:
> See ISA, 4.7.1 for details.
>
> Physical registers and currently visible window are separate fields in
> CPUEnv. Only current window is accessible to TCG. On operations that
> change window base helpers copy current window to and from physical
> registers.

I'm not sure how the register windows work, but maybe you could use
the same trick used for Sparc. There is a pool of registers
(env->regbase[]), a register window pointer (env->regwptr,
cpu_regwptr) tracks which are the currently accessible ones. The
advantage is to avoid copying (not entirely for Sparc due to the
window overlap).