Re: [PATCH] ppc: Fix 'calli' when floating-point arguments are passed

[Paul Cercueil]

Le lun., sept. 5 2022 at 14:00:41 -0300, Paulo César Pereira de 
Andrade <paulo.cesar.pereira.de.andrade@gmail.com> a écrit :
> Em sáb., 3 de set. de 2022 às 12:33, Paul Cercueil
> <paul@crapouillou.net> escreveu:
> >  Hi Paulo,
> >  [...]
>
>   Hi Paul,
>
> >  >>  About the "call" check, I didn't debug it yet, but it may be
> >  >> related to
> >  >>  calling "near" code as well. I had to use the following 
> > temporary
> >  >>  workaround in my code to avoid crashes:
> >  >>  
> > https://github.com/pcercuei/lightrec/blob/master/emitter.c#L35-L47
> >  >
> >  >   This is strange. check/*.tst is full of forward and backward 
> > jumps.
> >  > Not just call.tst has them. But call.tst has a few 
> > forward/backward
> >  > tests of calls and jumps. Unless the can_sign_extend_jump_p() 
> > macro
> >  > has some bug in the displacement test, and  was never experienced
> >  > in the tests.
> >
> >  What happens is I have a pointer that I keep in the last JIT_V()
> >  register, and the jit_jmpi() call uses the same register as a 
> > temporary.
>
>   Please double check if it is JIT_V13 or jit_(13), it could be some
> mistake with jit_v_num() telling there are 14 callee save registers.
> It also happens to be "r14".

This is JIT_V(JIT_V_NUM - 1) which resolves to "r14", that's correct.

> >  Adding a jit_live() right before the jit_jmpi() fixes it, but it 
> > makes
> >  me wonder why Lightning considered it okay to use this register in 
> > the
> >  first place.
>
>   I would need at least a jit_print() of all the assembly to 
> understand the
> reason it is apparently considering the register as dead.
>
>   Please also make sure to test with assertions enabled. But this 
> should
> not make much of a difference if jit_live() is a workaround, so, it 
> should
> be some condition leading it to think the register is dead.

Here's the output of jit_print() followed by the output of 
jit_disassemble():

L0: r14 r10 /* prolog */
        #name rec_ADDIU
        movi r27 0x1
        #name rec_BNE
        #note /home/paul/dev/lightrec/emitter.c:223
        ldxi_i r26 r14 0x8
        stxi_i 0x4 r14 r27
        subi r10 r10 0x6
   beqr L2 r26 r27
L4:
        #note /home/paul/dev/lightrec/emitter.c:61
        movi r27 0xbfc06f04
   jmpi 0x20000d30
L2: r14 r10
        #name rec_JAL
        #note /home/paul/dev/lightrec/emitter.c:61
        movi r27 0xbfc06f04
        stxi_i 0x7c r14 r27
        movi r27 0xbfc0711c
        subi r10 r10 0x4
   jmpi 0x20000d30
L5:
        ret
L3: /* epilog */


       0x20002354       li      r27,1
# rec_BNE:/home/paul/dev/lightrec/emitter.c:223
       0x20002358       lwz     r26,8(r14)
       0x2000235c       stw     r27,4(r14)
       0x20002360       addi    r10,r10,-6
       0x20002364       cmpw    r26,r27
       0x20002368	beq     0x20002384 
rec_JAL:/home/paul/dev/lightrec/emitter.c:61
# rec_BNE:/home/paul/dev/lightrec/emitter.c:61
       0x2000236c       lis     r27,-16448
       0x20002370       ori     r27,r27,28420
       0x20002374       lis     r14,8192
       0x20002378       ori     r14,r14,3376
       0x2000237c       mtctr   r14
       0x20002380       bctr
# rec_JAL:/home/paul/dev/lightrec/emitter.c:61
       0x20002384       lis     r27,-16448
       0x20002388       ori     r27,r27,28420
       0x2000238c       stw     r27,124(r14)
       0x20002390       lis     r27,-16448
       0x20002394       ori     r27,r27,28956
       0x20002398       addi    r10,r10,-4
       0x2000239c       lis     r15,8192
       0x200023a0       ori     r15,r15,3376
       0x200023a4       mtctr   r15
       0x200023a8       bctr