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From: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <a3803e94-e04e-e72d-1266-cd6d910b6d73@linaro.org>
Date: Mon, 22 Jan 2018 11:56:07 -0800
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Subject: Re: [Qemu-devel] [PATCH v10.5 01/20] tcg: Allow multiple word
 entries into the constant pool
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To: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>, Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>

On 01/22/2018 11:15 AM, Alex Bennée wrote:
>>>  typedef struct TCGLabelPoolData {
>>>      struct TCGLabelPoolData *next;
>>> -    tcg_target_ulong data;
>>>      tcg_insn_unit *label;
>>> -    intptr_t addend;
>>> -    int type;
>>> +    int addend  : 32;
>>> +    int rtype   : 16;
>>> +    int nlong   : 16;
>>> +    tcg_target_ulong data[];
>>>  } TCGLabelPoolData;
>>>
>>
>> Seems a bit odd to use bitfields for 32 and 16 bit values, but whatever.
>> (My default reaction to bitfields is "be suspicious" :-))
> 
> I'm guessing this is the same reason as the softfloat re-factor. By
> manually forcing stuff into a bitfield the compiler does a better job of
> passing multiple structure elements in a single register?
> 
> It would be nice if the compiler could spot this itself though.

You're probably right that I could just use int16_t etc.


r~