Re: [Qemu-devel] another SPARC issue

["Laurent Desnogues" <laurent.desnogues@gmail.com>]

On Tue, Aug 5, 2008 at 10:20 PM, Vince Weaver <vince@csl.cornell.edu> wrote:
>
> The instruction is
>   ldda  [ %o1 + 0x40 ] %asi, %f16
>
> but under Qemu for some reason 0x80 is added to %o1 (instead of 0x40).
>
> Indeed if you look at the generated TCG (see below), the 0x40 is being added
> in twice.  I was digging around in translate.c but can't seem to see why
> this is happning.
>
> Any help would be appreciated...

Since I am not afraid to be ridiculous again, here is my take:

- in disas_sparc_insn, line 4199:
            } else if (IS_IMM) {     /* immediate */
                rs2 = GET_FIELDs(insn, 19, 31);
                tcg_gen_addi_tl(cpu_addr, cpu_src1, (int)rs2);

- line 4307:
                case 0x13:      /* load double word alternate */
                    save_state(dc, cpu_cond);
                    gen_ldda_asi(cpu_val, cpu_addr, insn, rd);

static inline void gen_ldda_asi(TCGv hi, TCGv addr, int insn, int rd)
{
    TCGv r_asi, r_rd;

    r_asi = gen_get_asi(insn, addr);
    r_rd = tcg_const_i32(rd);
    tcg_gen_helper_0_3(helper_ldda_asi, addr, r_asi, r_rd);
    tcg_temp_free(r_rd);
    tcg_temp_free(r_asi);
}

static inline TCGv gen_get_asi(int insn, TCGv r_addr)
{
    int asi, offset;
    TCGv r_asi;

    if (IS_IMM) {
        r_asi = tcg_temp_new(TCG_TYPE_I32);
        offset = GET_FIELD(insn, 25, 31);
        tcg_gen_addi_tl(r_addr, r_addr, offset);
        tcg_gen_ld_i32(r_asi, cpu_env, offsetof(CPUSPARCState, asi));
    } else {
        asi = GET_FIELD(insn, 19, 26);
        r_asi = tcg_const_i32(asi);
    }
    return r_asi;
}

I am not sure I followed the right path, but it seems that indeed
for asi ld/st the constant gets added twice:  once in the disas
function and once in gen_get_asi.


Laurent