optimization, powerpc style

[kevin diggs]

Hi,


On Fri, Feb 11, 2011 at 11:15 AM, kevin diggs <diggskevin38@gmail.com> wrote:
>
> In both the 4.2.4 and 4.3.5 versions of mesh, the mesh_start() routine
> has a lengthy list of register assignments near the start of the
> routine:
>
> .L241:
>        lis 9,.LANCHOR0@ha       # tmp459,
>        lis 11,.LC47@ha  # tmp461,
>        la 23,.LANCHOR0@l(9)     # tmp460,, tmp459
>        lis 9,.LC48@ha   # tmp463,
>        la 19,.LC47@l(11)        # tmp462,, tmp461
>        la 18,.LC48@l(9)         # tmp464,, tmp463
>        lis 11,.LC16@ha  # tmp465,
>        lis 9,.LC50@ha   # tmp467,
>        la 17,.LC16@l(11)        # tmp466,, tmp465
>        la 22,.LC50@l(9)         # tmp468,, tmp467
>        lis 11,.LC51@ha  # tmp469,
>        lis 9,.LC57@ha   # tmp471,
>        la 21,.LC51@l(11)        # tmp470,, tmp469
>        la 20,.LC57@l(9)         # tmp472,, tmp471
>        lis 11,.LC58@ha  # tmp473,
>        lis 9,.LC59@ha   # tmp475,
>        la 16,.LC58@l(11)        # tmp474,, tmp473
>        la 15,.LC59@l(9)         # tmp476,, tmp475
>        lis 11,.LC60@ha  # tmp477,
>        lis 9,.LC53@ha   # tmp480,
>        la 14,.LC60@l(11)        # tmp478,, tmp477
>        la 24,.LC53@l(9)         # tmp482,, tmp480
>
> Later, when one of these is used you'll see:
>
>        mr 3,19  #, tmp462
>        mr 4,31  #, cmd
>        mr 6,28  #, id
>        bl printk        #
>
> for .LC47, which is "<4>mesh_start: %p ser=%lu tgt=%d cmd="
>
> These all end up in:
>
> .section        .rodata.str1.4,"aMS",@progbits,1
>
> and will have addresses close to each other, right? I don't understand
> why they can't do something like:
>
> lis 15,.LANCHOR0@ha
> la 15,.LANCHOR0@l(15)
>
> and then do something like:
>
> la 3,<some offset>(15)
>
> when each string is used. What am I missing?
>
> The above register loads also result in:
>
>        stmw 14,8(1)     #,
> and
>        lmw 14,8(1)      #,
>
> for 4.3.5. A smaller set is saved in 4.1.2
>
>        stmw 25,20(1)    #,
> and
>        lmw 25,20(1)     #,
>
> Won't this lead to unneeded memory traffic and/or cache churning?
>
> kevin
>
> P.S.:  For all those who send email from their Blackberry's and iphones:
>
> Sent from my 33 MHz 386 using Firefox 2!
>

Is this something I could have caused by screwing up the build of the
4.3.5 compiler?

Thanks!

kevin

P.S.:  NOT sent from my 33 MHz 386 (currently off - but I may play
Atarisoft Pacman later today) nor Firefox2