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From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: "Andreas Färber" <andreas.faerber@web.de>,
	"Aurélien Jarno" <aurelien@aurel32.net>
Subject: Re: [Qemu-devel] [PATCH] ppc: Convert op_405_check_{sat,satu} to TCG
Date: Sat, 25 Oct 2008 21:09:17 +0100	[thread overview]
Message-ID: <200810252109.18477.paul@codesourcery.com> (raw)
In-Reply-To: <83999635-3F2E-4BB9-B14B-57088A1B1A8D@web.de>

On Saturday 25 October 2008, Andreas Färber wrote:
> +            tcg_gen_shri_tl(tmp, tmp, 31);
> +            tcg_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.

> +            tcg_gen_shri_tl(tmp, cpu_T[2], 31);
> +            tcg_gen_brcondi_tl(TCG_COND_EQ, tmp, 0, innerLabel);
> +
> +            tcg_gen_movi_tl(cpu_T[0], INT32_MIN);
> +            tcg_gen_br(endLabel);
> +
> +            gen_set_label(innerLabel);
> +            tcg_gen_movi_tl(cpu_T[0], INT32_MAX);

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

Paul

  reply	other threads:[~2008-10-25 20:09 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-25 19:59 [Qemu-devel] [PATCH] ppc: Convert op_405_check_{sat,satu} to TCG Andreas Färber
2008-10-25 20:09 ` Paul Brook [this message]
2008-10-25 20:25   ` Andreas Färber
2008-10-25 23:29     ` Anthony Liguori
2008-10-27 16:05       ` Hollis Blanchard
2008-10-28 20:01   ` [Qemu-devel] [PATCH v2] " Andreas Färber
2008-11-01  0:55     ` Aurélien Jarno

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