Am 28.05.09 18:13 schrieb(en) Joakim Tjernlund:
hmm, these do look a bit unoptimal anyway. Any reason not to write them something like below(written by me for uClibc long time ago). You will have to add eieio()/sync
No (and I wasn't aware of the PPC pre-inc vs. post-inc stuff) - I just stumbled over this while fixing mtd accesses to the MPC5200's Local Bus in 16-bit mode which doesn't allow byte accesses. And I didn't want to go too deep into this as the real fix for me is actually somewhat different...
/* PPC can do pre increment and load/store, but not post increment and load/store.Therefore use *++ptr instead of *ptr++. */
[snip]
copy_chunks:
do {
/* make gcc to load all data, then store it */
tmp1 = *(unsigned long *)(tmp_from+4);
tmp_from += 8;
tmp2 = *(unsigned long *)tmp_from;
*(unsigned long *)(tmp_to+4) = tmp1;
tmp_to += 8;
*(unsigned long *)tmp_to = tmp2;
} while (--chunks);
Is this the same for all PPC cores, i.e. do they all benefit from loading/storing 8 instead of 4 bytes?
Best, Albrecht.
pgp51rCL2tmWP.pgp
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