This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
#define SLOW_BYTE_ACCESS in i386.h
- From: Hui-May Chang <hm dot chang at apple dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 24 Aug 2006 09:12:38 -0700
- Subject: #define SLOW_BYTE_ACCESS in i386.h
I have a question regarding "#define SLOW_BYTE_ACCESS" in i386.h. It
is used in "get_best_mode" routine which finds the best mode to use
when referencing a bit field. It is currently set to 0. If it is set
it to 1, it means "accessing less than a word of memory is no faster
than accessing a word of memory". I experimented with it and
observed great performance improvement. It is set to 1 for some other
configurations (e.g., rs6000, pa, ia64). Is it always a win to set
it? Is it better to set it for certain i386 architectures?
Hui-May Chang
Apple Computer