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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] ppc: Convert op_405_check_{sat,satu} to TCG
Date: Sat, 25 Oct 2008 21:09:17 +0100
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To: qemu-devel@nongnu.org
Cc: Andreas =?iso-8859-1?q?F=E4rber?= <andreas.faerber@web.de>, =?iso-8859-1?q?Aur=E9lien_Jarno?= <aurelien@aurel32.net>

On Saturday 25 October 2008, Andreas F=E4rber wrote:
> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_shri_tl(tmp, tmp, 31);
> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_brcondi_tl(TCG_COND_EQ, tmp, 0, endLabel=
);

Is this really right for ppc64?
You can easily test the high bit using TCG_COND_LT.

> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_shri_tl(tmp, cpu_T[2], 31);
> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_brcondi_tl(TCG_COND_EQ, tmp, 0, innerLab=
el);
> +
> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_movi_tl(cpu_T[0], INT32_MIN);
> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_br(endLabel);
> +
> + =A0 =A0 =A0 =A0 =A0 =A0gen_set_label(innerLabel);
> + =A0 =A0 =A0 =A0 =A0 =A0tcg_gen_movi_tl(cpu_T[0], INT32_MAX);

((signed)x >> 31) ^ 0x7fffffff)
is a much more efficient way of implementing this.

Paul