Subject: Re: Bitfields and kernel
To: Brian C. Grayson <firstname.lastname@example.org>
From: David Edelsohn <email@example.com>
Date: 09/30/1999 18:28:02
Without constant propagation, there are many cases which GCC
cannot know that bitmask operations can be converted into equivalent
bitfield operations. Using bitfields on PowerPC allows GCC to generate
more efficient code using the special rotate and insert instructions.
Equivalent bitmask operations rarely are converted because GCC cannot tell
that the operations are disjoint.