Re: [PATCH 07/30] tcg/loongarch: Implement necessary relocation operations

[WANG Xuerui]

Hi Richard,

On 9/20/21 22:36, Richard Henderson wrote:
> On 9/20/21 1:04 AM, WANG Xuerui wrote:
> > +static bool reloc_call(tcg_insn_unit *src_rw, const tcg_insn_unit 
> > *target)
> > +{
> > +    const tcg_insn_unit *src_rx = tcg_splitwx_to_rx(src_rw);
> > +    intptr_t offset = (intptr_t)target - (intptr_t)src_rx;
> > +    int32_t lo = sextreg(offset, 0, 12);
> > +    int32_t hi = offset - lo;
> > +
> > +    tcg_debug_assert((offset & 2) == 0);
> > +    if (offset == hi + lo) {
> > +        hi >>= 12;
> > +        src_rw[0] |= (hi << 5) & 0x1ffffe0; /* pcaddu12i's Sj20 imm */
> > +        lo >>= 2;
> > +        src_rw[1] |= (lo << 10) & 0x3fffc00; /* jirl's Sk16 imm */
> > +        return true;
> > +    }
> > +
> > +    return false;
> > +}
>
> This doesn't seem to belong as a "reloc".
> Certainly it doesn't seem like something that can simply be allowed to 
> fail.
Yes, you're right on this; on closer look at the riscv port they 
actually reused this logic once (the riscv port drops large constants to 
pool, hence need some PC-relative hackery). For LoongArch the only usage 
of this code is for generating calls, so I'll just merge this into the 
commit doing tcg_out_call, and inline if the resulting code is still 
readable.

And it's 1 a.m. here in China, so I'll be processing the other review 
comments after getting some sleep. (Today's in the middle of the 3-day 
Mid-Autumn Festival holiday here, and that's why I can work on this 
hobby project like it's $DAY_JOB!) I'll send the v2 hopefully at 
afternoon local time (tomorrow in your timezone).

> r~