On Thu, 2006-07-20 at 14:56 -0700, Brian D. Carlstrom wrote:

At Thu, 20 Jul 2006 14:05:23 -0500, Olof Johansson wrote:

quoted

http://penguinppc.org/dev/glibc/glibc-powerpc-cpu-addon.html

Very interesting. According to that page, the memcpy optimizations seem
to be using 64-bit operations and that 128-bit AltiVec operations are
still being solicited. 

I was encouraged to see the following: 

    If you need to build generic distributions (supporting several
    <cpu_types>) you can leverage the dl_procinfo support built into
    glibc. This mechanism allows for multiple versions of the core
    libraries (libc, libm, librt, libpthread, libpthread_db) to be
    stored in hardware/platform specific subdirectories under /lib[64].

Actually, this support is not limited to the core glibc routines or
the system lib directors /lib/ and /usr/lib/.  This works just as well
for third party shipped libraries in their own library trees as the
following example (on a power5 box) shows:

bergner@vervainp1:~/cpu-tuned-libs> pwd
/home/bergner/cpu-tuned-libs

bergner@vervainp1:~/cpu-tuned-libs> ls lib/ lib/power5/
lib/:
libfoo.so  power5/

lib/power5/:
libfoo.so

bergner@vervainp1:~/cpu-tuned-libs> gcc
-L/home/bergner/cpu-tuned-libs/lib -R/home/bergner/cpu-tuned-libs/lib
main.c -lfoo

bergner@vervainp1:~/cpu-tuned-libs> ldd a.out
        linux-vdso32.so.1 =>  (0x00100000)
        libfoo.so => /home/bergner/cpu-tuned-libs/lib/power5/libfoo.so
(0x0ffde000)
        libc.so.6 => /lib/power5/libc.so.6 (0x0fe69000)
        /lib/ld.so.1 (0xf7fe1000)

bergner@vervainp1:~/cpu-tuned-libs> ./a.out
Loaded the optimzed lib

bergner@vervainp1:~/cpu-tuned-libs> rm lib/power5/libfoo.so

bergner@vervainp1:~/cpu-tuned-libs> ldd a.out
        linux-vdso32.so.1 =>  (0x00100000)
        libfoo.so => /home/bergner/cpu-tuned-libs/lib/libfoo.so
(0x0ffde000)
        libc.so.6 => /lib/power5/libc.so.6 (0x0fe69000)
        /lib/ld.so.1 (0xf7fe1000)

bergner@vervainp1:~/cpu-tuned-libs> ./a.out
Loaded the unoptimzed lib


The runtime loader magic uses the AT_PLATFORM string value as
the subdirectory to search in under the .../lib/ or .../lib64/
library directory.  To find out what your AT_PLATFORM value is
on your current box, you can do:

bergner@vervainp1:~/cpu-tuned-libs> LD_SHOW_AUXV=1 /bin/true
AT_DCACHEBSIZE:  0x80
AT_ICACHEBSIZE:  0x80
AT_UCACHEBSIZE:  0x0
AT_SYSINFO_EHDR: 0x100000
AT_HWCAP:        power5 mmu fpu ppc64 ppc32
AT_PAGESZ:       4096
AT_CLKTCK:       100
AT_PHDR:         0x10000034
AT_PHENT:        32
AT_PHNUM:        9
AT_BASE:         0xf7fe1000
AT_FLAGS:        0x0
AT_ENTRY:        0x10000980
AT_UID:          1001
AT_EUID:         1001
AT_GID:          100
AT_EGID:         100
AT_SECURE:       0
AT_PLATFORM:     power5

However, I'm guessing this addon is not something found in common
distributions for PowerPC like Debian, Fedora, Gentoo, Ubuntu, ...

At last years GCC Developers Summit, one of the Ubuntu guys mentioned
he was interested in adding it to Ubuntu.  I haven't heard whether that
has shown up yet though.  It will be available in upcoming SUSE and
Red Hat enterprise distros.  I don't know about the others.  As Olof
mentioned, it can take some lead time for this to get picked up.
There's also the question of how many and which processors a distro
will ship cpu optimized libraries for.  Given all of the PowerPC
variants, they obviously can ship optimized libs for everything.

Peter