From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Ian Lance Taylor <iant@google.com>
Cc: loody <miloody@gmail.com>, Sergei Shtylyov <sshtylyov@mvista.com>,
gcc-help <gcc-help@gcc.gnu.org>,
Linux MIPS Mailing List <linux-mips@linux-mips.org>
Subject: Re: Fwd: about udelay in mips
Date: Thu, 27 Jan 2011 21:43:00 -0000 [thread overview]
Message-ID: <alpine.LFD.2.00.1101272138520.25047@eddie.linux-mips.org> (raw)
In-Reply-To: <mcrlj26owrx.fsf@google.com>
On Thu, 27 Jan 2011, Ian Lance Taylor wrote:
> I don't know the type of HZ. But assuming it is a constant, then the
> rules of C are that the expression
> us * 0x000010c7 * HZ * lpj
> gets evaluated in the type "unsigned long". The fact that you then cast
> that "unsigned long" value to "unsigned long long" does not cause the
> multiplication to be done in the type "unsigned long long".
>
> You need to write something like
> (unsigned long long) us * 0x000010c7 * HZ * (unsigned long long) lpj
> to get the multiplication to be done in the "unsigned long long" type.
Though as a matter of coding style, personally I'd rather assigned "us"
to a local variable of the "unsigned long long" type and performed all the
calculations on it instead, avoiding any explicit casts and doubts as to
what type is being used altogether.
Maciej
prev parent reply other threads:[~2011-01-27 21:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AANLkTinvdEPwQ=DmcF8nnTAa0Py_O=+p7x1pobcTNHom@mail.gmail.com>
[not found] ` <AANLkTik8hQfd8cvNj=qeq5U=6zpQHw33a9hfK-q8+x1Z@mail.gmail.com>
[not found] ` <AANLkTikpUBtg2zz8tcbcz2rcG-O+fTFwb_pTi88uZe0h@mail.gmail.com>
[not found] ` <AANLkTi=zfr5YuwBCcvH2Jas50UxnUtvzp_CDyN25sT5h@mail.gmail.com>
[not found] ` <AANLkTim_swh58fCUxZ4e6MDrM9Lqrbm+1ufnp8W767JL@mail.gmail.com>
2011-01-27 9:20 ` loody
2011-01-27 11:29 ` Sergei Shtylyov
2011-01-27 12:28 ` loody
2011-01-27 21:38 ` Ian Lance Taylor
2011-01-27 21:43 ` Maciej W. Rozycki [this message]
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