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From: Richard Henderson <rth@twiddle.net>
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Date: Tue, 30 May 2017 09:45:01 -0700
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Subject: Re: [Qemu-devel] [PATCH 25/26] target/s390x: implement TRANSLATE
 ONE/TWO TO ONE/TWO
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To: Aurelien Jarno <aurelien@aurel32.net>
Cc: qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>

On 05/29/2017 04:17 AM, Aurelien Jarno wrote:
> On 2017-05-26 10:10, Richard Henderson wrote:
>> On 05/25/2017 02:05 PM, Aurelien Jarno wrote:
>>> +uint32_t HELPER(trXX)(CPUS390XState *env, uint32_t r1, uint32_t r2,
>>> +                      uint32_t sizes)
>>> +{
>>> +    uintptr_t ra = GETPC();
>>> +    int dsize = (sizes & 1) ? 1 : 2;
>>> +    int ssize = (sizes & 2) ? 1 : 2;
>>> +    uint16_t tst = env->regs[0] & ((1 << (8 * dsize)) - 1);
>>
>> I think you should pass in tst as an argument.  That way you can pass in an
>> out-of-band value when we implement ETF2 and test field M3 bit 3.
> 
> I don't mind passing r0 as an argument. That said if we want to pass tst
> or bundle the M3 field, it means we need to use TCG instructions to do
> so. I am not sure it brings a lot compare to doing so in the helper
> side.

Not at all -- the M3 bit test would be a translation-time check.


r~