Hi,
I'm porting linux for a MIPS 4KEc based design;
my knowledge of MIPS CPUs generations is still rudimentary but I know
for sure this one has both features from R3000 arch but some of
R4000 as well (cache, lld/scd --- according to the software user's
manual)
but it is definitely a 32bit processor.
The implementation of down_trylock on linuxmips-2.4.25 is:
---------------------------------------------
static inline int down_trylock(struct semaphore * sem)
{
long ret, tmp, tmp2, sub;
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
__asm__ __volatile__(
" .set mips3 # down_trylock \n"
"0: lld %1, %4 \n"
" dli %3, 0x0000000100000000 # count -= 1 \n"
" dsubu %1, %3 \n"
" li %0, 0 # ret = 0 \n"
" bgez %1, 2f # if count >= 0 \n"
" sll %2, %1, 0 # extract waking \n"
" blez %2, 1f # if waking < 0 -> 1f \n"
" daddiu %1, %1, -1 # waking -= 1 \n"
" b 2f \n"
"1: daddu %1, %1, %3 # count += 1 \n"
" li %0, 1 # ret = 1 \n"
"2: scd %1, %4 \n"
" beqz %1, 0b \n"
" sync \n"
" .set mips0 \n"
: "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub)
: "m"(*sem)
: "memory");
return ret;
}
---------------------------------------------
and after synthesized assembly dli becomes:
a90: 34048000 li a0,0x8000
a94: 00042478 dsll a0,a0,0x11
which is a0=0 (wrong).
Why is this computation done on 64bit? Should I workaround a 32bit
implementation of this?
Subsidiary question: since the 4KEc core is not mentioned explicitely
in mips gas possible CPUs, I build the kernel code with:
mipsel-linux-gcc -march=r4600 -mips2 -Wa,-32 -Wa,-march=r4600 -Wa,-mips3
with gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-113.2) neon
Is this the correct option?
Thanks a lot for any clue,
Sincerely yours,
E.M.
