Are you sure you've specified your CPU type as "MIPS32"?
----- Original Message -----
From: "Emmanuel Michon" <em@xxxxxxxxxxxx>
To: <linux-mips@xxxxxxxxxxxxxx>
Sent: Wednesday, May 26, 2004 18:35
Subject: down_trylock() implementation for MIPS 4KEc CPU implies 64bitarithmetics?
> 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.
>
>
>
