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Subject: Re: [Qemu-devel] [PATCH V4 00/11] Qemu MIPS ASE DSP Support
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To: Jia Liu <proljc@gmail.com>
Cc: qemu-devel@nongnu.org, aurelien@aurel32.net

On 03/30/2012 07:42 AM, Richard Henderson wrote:
> All of your helpers, whereever they receive or return a register value, need to use
> type target_ulong and the DEF_HELPER lines need to use "tl".  All of the mips32
> helpers you've written so far that return values need to make sure to sign-extend
> their results from 32-bits.

Hmm, actually I wonder if that's the best advice.

It looks like your translated code isn't going to work well with r0.

I suspect it would be better to add a gen_load_gpr32 function for the
translator that (1) sets 0 for r0, (2a) copies the register for mips32,
and (2b) truncates the register for mips64.  That way 32-bit hosts do
not need to use 64-bit arithmetic when unnecessary.  You'd need a
gen_store_gpr32 function as well, which for mips64 sign-extends the value.


r~