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Re: [Qemu-devel] [PATCH] bitops.h: Add field32() and field64() functions
Re: [Qemu-devel] [PATCH] bitops.h: Add field32() and field64() functions to extract bitfields
Sun, 08 Jul 2012 14:37:56 +0300
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0
On 06/28/2012 08:58 AM, Markus Armbruster wrote:
>>> Better code is an argument only if the effect can be demonstrated.
>> I don't know even for which compilers or CPUs this is true so it's
>> unlikely I could demonstrate it. However, googling finds a few
>> articles in defense of this.
> Hearsay. Your honor, I rest my case :)
On x86_64, conversion from unsigned to unsigned long takes zero
instructions, but conversion from int to long takes one instruction. So
expressions like a[i] are one instruction shorter if the index is unsigned.
unsigned is also slightly safer from a security perspective, since you
only need to consider overflow, not underflow.
I used to be an int fan but I have been converted. My fingers still
prefer int though.
error compiling committee.c: too many arguments to function
- Re: [Qemu-devel] [PATCH] bitops.h: Add field32() and field64() functions to extract bitfields,
Avi Kivity <=