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From: "Riley Williams" <Riley@Williams.Name>
To: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: Interrupt doesn't make it to the 8259 on a ASUS P4PE mobo
Date: Sun, 20 Jul 2003 22:04:31 +0100	[thread overview]
Message-ID: <BKEGKPICNAKILKJKMHCAMEJJEPAA.Riley@Williams.Name> (raw)
In-Reply-To: <1058294665.3845.61.camel@dhcp22.swansea.linux.org.uk>

Hi Alan.

 >>>> Use HZ/2 instead.  GCC doesn't optimize floating point constants
 >>>> to the same degree it does integers, because it doesn't know what
 >>>> mode (rounding, precision) the FPU is in.

 >>> Isn't (HZ >> 1) better?

 >> Same thing. GCC knows that division by a power of 2 is just a shift.

 > Only for unsigned

When I did the "Assembler Language Maths Logic" module for my degree,
we learned that processors used SRL (Shift Right Logical) to divide
unsigned numbers by powers of 2, and SRA (Shift Right Arithmetic) to
divide signed numbers by powers of 2. Can't GCC handle that?

Best wishes from Riley.
---
 * Nothing as pretty as a smile, nothing as ugly as a frown.

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  parent reply	other threads:[~2003-07-20 20:49 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <m3el0stw23.fsf@averell.firstfloor.org>
2003-07-15 16:14 ` Kathy Frazier
2003-07-15 15:31   ` Richard B. Johnson
2003-07-15 15:58     ` SCSI ATA driver in 2.4.22 ? Jeff Mock
2003-07-15 16:14       ` Jeff Garzik
2003-07-15 17:06   ` Interrupt doesn't make it to the 8259 on a ASUS P4PE mobo Brian Gerst
2003-07-15 17:43     ` Jamie Lokier
2003-07-15 17:59     ` Luciano Miguel Ferreira Rocha
2003-07-15 18:24       ` Brian Gerst
2003-07-15 18:44         ` Alan Cox
2003-07-15 19:44           ` Jamie Lokier
2003-07-20 21:04           ` Riley Williams [this message]
2003-07-20 22:25             ` Jeremy Fitzhardinge
     [not found] <Pine.LNX.4.53.0307141833190.4354@chaos>
2003-07-15 16:52 ` Kathy Frazier
2003-07-14 21:35 Kathy Frazier

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