jit_stxi() is broken on PowerPC 64

[Paul Cercueil]

Hi,

I'm not exactly sure what's happening, but I can get Lightning to 
generate invalid code using jit_stxi() on PPC64.

Here's a simple program to reproduce the issue:

#include <lightning.h>

int main(int argc, char **argv)
{
jit_state_t *_jit;

init_jit(argv[0]);
_jit = jit_new_state();
jit_prolog();

jit_stxi(0x31a, JIT_R1, JIT_V2);

jit_ret();
jit_epilog();

jit_emit();
jit_disassemble();

jit_clear_state();
jit_destroy_state();
finish_jit();

return 0;
}


The disassembler will print the following:
   0x3fff8b230000 mflr r0
   0x3fff8b230004 std r0,16(r1)
   0x3fff8b230008 std r31,-8(r1)
   0x3fff8b23000c mr r31,r1
   0x3fff8b230010 stdu r1,-256(r1)
   0x3fff8b230014 .long 0xfb3d031a
   0x3fff8b230018 addi r1,r1,256
   0x3fff8b23001c ld r0,16(r1)
   0x3fff8b230020 mtlr r0
   0x3fff8b230024 ld r31,-8(r1)
   0x3fff8b230028 blr


Of course this program won't execute properly (since the registers 
aren't initialized), but in a real program, the ".long 0xfb3d031a" will 
result in an "illegal instruction" error.

Cheers,
-Paul