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From: Richard Henderson <rth@twiddle.net>
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Date: Thu, 12 Nov 2015 15:34:27 +0100
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Subject: Re: [Qemu-devel] [PATCH 1/4] target-tilegx: Add fpu header file
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To: Chen Gang <xili_gchen_5257@hotmail.com>, Peter Maydell <peter.maydell@linaro.org>, Chris Metcalf <cmetcalf@ezchip.com>
Cc: qemu-devel <qemu-devel@nongnu.org>

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.

> +#endif
> +} TileGXFPSFmt;
> +/*

Watch your spacing.

> + * Double exp analyzing: (0x21b00 << 1) - 0x36(54) = 0x400
> + *
> + *   17  16  15  14  13  12  11  10   9   8   7    6   5   4   3   2   1   0
> + *
> + *    1   0   0   0   0   1   1   0   1   1   0    0   0   0   0   0   0   0
> + *
> + *    0   0   0   0   0   1   1   0   1   1   1    => 0x37(55)
> + *
> + *    0   1   1   1   1   1   1   1   1   1   1    => 0x3ff

What is this table supposed to mean?

> +#if 0
> +        uint64_t exp : 11;        /* exp, 0x21b << 1: 55 + TILEGX_F_EXP_DZERO */
> +        uint64_t ov : 1;          /* overflow for mul, low priority */
> +        uint64_t uv : 1;          /* underflow for mul, high priority */
> +#endif


No if 0.

> +#pragma pack(pop)

Huh?  What are you attempting to do here?


r~