On 09/08/2014 04:11, Miod Vallat wrote:
>> Disassembling a statically-built copy of the "sln" binary generated by
>> glibc's compile phase, there are slight differences in how gcc-4.7 and
>> gcc-4.8 are compiling the __lll_lock_wait_private function. The key
>> differences in the output asm are
>> this:
>
> [...]
>
>> gcc-4.8:
>> x+4 <START>
>> ...
>> x+24 bne v1,v0,<x+56>
>> ...
>> x+32 0x7c03e83b /* rdhwr */
>> x+36 li a2,2
>> x+40 lw a1,-29832(v1)
>> x+44 move a3,zero
>> x+48 li v0,4238
>> x+52 syscall
>> * x+56 ll v0,0(s0)
>> * x+60 li at,2
>> * x+64 sc at,0
>
> Note how the sc address is no longer 0(s0). Since the address does
> not match the address used in the ll instruction, sc will always
> fail on the R10k.
That would be a typo on my part. I typed that out by hand and just missed it. It should read:
gcc-4.8:
x+4 <START>
...
x+24 bne v1,v0,<x+56>
...
x+32 0x7c03e83b /* rdhwr */
x+36 li a2,2
x+40 lw a1,-29832(v1)
x+44 move a3,zero
x+48 li v0,4238
x+52 syscall
* x+56 ll v0,0(s0)
* x+60 li at,2
* x+64 sc at,0(s0)
x+68 beqzl at,<x+56>
x+72 nop
x+76 sync
x+80 bnez v0,<x+32>
Thanks!,
--
Joshua Kinard
Gentoo/MIPS
kumba@xxxxxxxxxx
4096R/D25D95E3 2011-03-28
"The past tempts us, the present confuses us, the future frightens us. And our lives slip away, moment by moment, lost in that vast, terrible in-between."
--Emperor Turhan, Centauri Republic
