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From: Peter Maydell <peter.maydell@linaro.org>
To: Chen Gang <xili_gchen_5257@hotmail.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>,
	qemu-devel <qemu-devel@nongnu.org>,
	Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH 1/4] target-tilegx: Add fpu header file
Date: Thu, 12 Nov 2015 16:10:04 +0000	[thread overview]
Message-ID: <CAFEAcA9OVTCupHNjHCokcm6Teo+RNq7MTCC2DREEMFHWwai5hA@mail.gmail.com> (raw)
In-Reply-To: <BLU436-SMTP8304E67322C0580627FCAB9120@phx.gbl>

On 12 November 2015 at 16:04, Chen Gang <xili_gchen_5257@hotmail.com> wrote:
> On 11/12/15 22:34, Richard Henderson wrote:
>> On 11/08/2015 06:43 AM, Chen Gang wrote:
>>
>>> +#if !defined(HOST_WORDS_BIGENDIAN)
>>> +    /* According to float(uns)sisf2 and float(uns)sidf2 in gcc tilegx.md */
>>> +    uint64_t exp : 8;             /* exp, 0x9e: 31 + TILEGX_F_EXP_FZERO */
>>> +    uint64_t uiknown0 : 2;        /* unknown */
>>
>> I would really rather you didn't use bitfields, because of exactly this sort of endianness problem.  Because, really, you can't trust this layout.  But I won't press this point, because it is complicated enough already.
>>
>
> Because of endianess issues, for me, I don't like bit fields either. But
> I can not find any other simpler ways than current.

> OK, I shall remove them.
>
>>> +#pragma pack(pop)
>>
>> Huh?  What are you attempting to do here?
>>
>
> It is for matching "#pragma pack(push, 1)" which is above all related
> struct/unions in this header file.

Please don't use 'pragma pack' or bitfields. If you need to pack
and unpack things from a target-CPU defined field use bit operations
and/or extract32/deposit32/extract64/deposit64.

thanks
-- PMM

  reply	other threads:[~2015-11-12 16:10 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-08  5:42 [Qemu-devel] [PATCH 0/4] Implment fpu floating point instructions Chen Gang
2015-11-08  5:43 ` [Qemu-devel] [PATCH 1/4] target-tilegx: Add fpu header file Chen Gang
2015-11-12 14:34   ` Richard Henderson
2015-11-12 16:04     ` Chen Gang
2015-11-12 16:10       ` Peter Maydell [this message]
2015-11-12 16:28         ` Chen Gang
2015-11-08  5:44 ` [Qemu-devel] [PATCH 2/4] target-tilegx: Implement fpu single floating point Chen Gang
2015-11-12 14:36   ` Richard Henderson
2015-11-12 16:12     ` Chen Gang
2015-11-12 16:18       ` Richard Henderson
2015-11-12 16:29         ` Chen Gang
2015-11-08  5:46 ` [Qemu-devel] [PATCH 3/4] target-tilegx: Implement fpu fdouble " Chen Gang
2015-11-08  5:47 ` [Qemu-devel] [PATCH 4/4] target-tilegx: Let fpu implementation code can be built and used Chen Gang

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