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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [RFC][PATCH] tcg: allocate memory to spill registers
	on startup
Date: Fri, 10 Apr 2009 16:52:31 +0100
References: <20090410085406.GA15094@volta.aurel32.net>
	<200904101620.10589.paul@codesourcery.com>
	<49DF664E.2080607@aurel32.net>
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To: qemu-devel@nongnu.org
Cc: Aurelien Jarno <aurelien@aurel32.net>

> I am trying to fix the following comment from Fabrice (tcg.c)
>
> /* XXX: for load/store we could do that only for the slow path
>    (i.e. when a memory callback is called) */
>
> The idea is not to do register allocation/spilling in tcg-target.c, but
> to save registers containing TCG globals to memory in the slow path only
> and without touching the TCGTemp structure. That's why it has to be done
> in tcg-target.c

Hmm, you don't actually have to allocate a slot, just you need to stash the 
values somewhere while you're making the slow call, then restore them 
afterwards. The bits that do need writing back to home locations (i.e. 
visible guest cpu state) already have memory locations.

Paul