Re: [Qemu-ppc] MTTCG for ppc64 (removed from ppc-for-2.10)

[Richard Henderson]

On 04/21/2017 12:08 AM, Nikunj A Dadhania wrote:
> David Gibson <address@hidden> writes:
>
> > [ Unknown signature status ]
> > Hi all,
> >
> > I'm afraid I've pulled the MTTCG enablement patches for target/ppc64
> > out of my ppc-for-2.10 tree, since I discovered it was causing a
> > repeatable failure on one of the Travis builds.
> >
> > Specifically, with both the LL/SC in terms of cmpxchg and
> > enable-mttcg-by-default patches applied, and qemu build with clang,
> > then make check will fail with a tcg_abort() in the powernv
> > boot-serial test.
>
> I see that in temp_load(), ts->val_type is ending up being
> TEMP_VAL_DEAD, and the tcg_abort() is because of that.
>
> Following patch gets past this error...
>
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 4a1f24a..9a4ea5f 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -3169,6 +3169,7 @@ static void gen_conditional_store(DisasContext *ctx, TCGv 
> EA,
>      tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, l1);
>
>      t0 = tcg_temp_new();
> +    tcg_gen_movi_tl(t0, 0);
>      tcg_gen_atomic_cmpxchg_tl(t0, cpu_reserve, cpu_reserve_val,
>                                cpu_gpr[reg], ctx->mem_idx,
>                                DEF_MEMOP(memop) | MO_ALIGN);

This *shouldn't* change anything.  The arugument that you're initializing is 
pure output and is equivalent to

        t0 = 0;
        t0 = foo();

What's the test case here?


r~