Re: [Qemu-devel] [PATCH v5 45/76] target/mips: Implement emulation of nanoMIPS LLWP/SCWP pair

[Aleksandar Markovic]

Hi, Richard,

We are going to remove obsoleted helpers, that was just an honest mistake made 
in a rush.

For unprotected access to gpr, we are going to insert if(reg1 != 0) in two 
places.

However, it looks there is a bigger problem now in SCWP. QEMU crashes with this 
message:

/qemu/tcg/tcg.c:2862: tcg fatal error

This happens in user mode only, system mode case runs fine.

the problem seems to appear as a consequence of using tcg_gen_brcond_*(().

Do you have any idea what are we doing wrong here?

> +static void gen_scwp(DisasContext *ctx, uint32_t base, int16_t offset,
> +                    uint32_t reg1, uint32_t reg2)
> +{
> +    TCGv taddr = tcg_temp_new();
> +    TCGv lladdr = tcg_temp_new();
> +    TCGv_i64 tval = tcg_temp_new_i64();
> +    TCGv_i64 llval = tcg_temp_new_i64();
> +    TCGv_i64 val = tcg_temp_new_i64();
> +    TCGv tmp1 = tcg_temp_new();
> +    TCGv tmp2 = tcg_temp_new();
> +    TCGLabel *lab_fail = gen_new_label();
> +    TCGLabel *lab_done = gen_new_label();
> +
> +    gen_base_offset_addr(ctx, taddr, base, offset);
> +
> +    tcg_gen_ld_tl(lladdr, cpu_env, offsetof(CPUMIPSState, lladdr));
> +    tcg_gen_brcond_tl(TCG_COND_NE, taddr, lladdr, lab_fail);
> +
> +    gen_load_gpr(tmp1, reg1);
> +    gen_load_gpr(tmp2, reg2);
> +
> +#ifdef TARGET_WORDS_BIGENDIAN
> +    tcg_gen_concat_tl_i64(tval, tmp2, tmp1);
> +#else
> +    tcg_gen_concat_tl_i64(tval, tmp1, tmp2);
> +#endif
> +
> +    tcg_gen_ld_i64(llval, cpu_env, offsetof(CPUMIPSState, llval_wp));
> +    tcg_gen_atomic_cmpxchg_i64(val, taddr, llval, tval,
> +                               ctx->mem_idx, MO_64);
> +    tcg_gen_movi_tl(cpu_gpr[reg1], 1);
> +    tcg_gen_brcond_i64(TCG_COND_EQ, val, llval, lab_done);
> +
> +    gen_set_label(lab_fail);
> +
> +    tcg_gen_movi_tl(cpu_gpr[reg1], 0);
> +
> +    gen_set_label(lab_done);
> +    tcg_gen_movi_tl(lladdr, -1);
> +    tcg_gen_st_tl(lladdr, cpu_env, offsetof(CPUMIPSState, lladdr));
> +}
> +

Regards,
Aleksandar