On Thu, Apr 06, 2017 at 03:52:47PM +0530, Nikunj A Dadhania wrote: > Emulating LL/SC with cmpxchg is not correct, since it can suffer from > the ABA problem. However, portable parallel code is written assuming > only cmpxchg which means that in practice this is a viable alternative. > > Signed-off-by: Nikunj A Dadhania <nik...@linux.vnet.ibm.com> > --- > target/ppc/translate.c | 24 +++++++++++++++++++++--- > 1 file changed, 21 insertions(+), 3 deletions(-) > > diff --git a/target/ppc/translate.c b/target/ppc/translate.c > index b6abc60..a9c733d 100644 > --- a/target/ppc/translate.c > +++ b/target/ppc/translate.c > @@ -73,6 +73,7 @@ static TCGv cpu_cfar; > #endif > static TCGv cpu_xer, cpu_so, cpu_ov, cpu_ca, cpu_ov32, cpu_ca32; > static TCGv cpu_reserve; > +static TCGv cpu_reserve_val; > static TCGv cpu_fpscr; > static TCGv_i32 cpu_access_type; > > @@ -181,6 +182,9 @@ void ppc_translate_init(void) > cpu_reserve = tcg_global_mem_new(cpu_env, > offsetof(CPUPPCState, reserve_addr), > "reserve_addr"); > + cpu_reserve_val = tcg_global_mem_new(cpu_env, > + offsetof(CPUPPCState, reserve_val), > + "reserve_val");
I notice that lqarx is not updated. Does that matter?
> cpu_fpscr = tcg_global_mem_new(cpu_env,
> offsetof(CPUPPCState, fpscr), "fpscr");
> @@ -3023,7 +3027,7 @@ static void gen_##name(DisasContext *ctx)
> \
> } \
> tcg_gen_qemu_ld_tl(gpr, t0, ctx->mem_idx, memop); \
> tcg_gen_mov_tl(cpu_reserve, t0); \
> - tcg_gen_st_tl(gpr, cpu_env, offsetof(CPUPPCState, reserve_val)); \
> + tcg_gen_mov_tl(cpu_reserve_val, gpr); \
> tcg_temp_free(t0); \
> }
>
> @@ -3156,14 +3160,28 @@ static void gen_conditional_store(DisasContext *ctx,
> TCGv EA,
> int reg, int memop)
> {
> TCGLabel *l1;
> + TCGv_i32 tmp = tcg_temp_local_new_i32();
> + TCGv t0;
>
> + tcg_gen_movi_i32(tmp, 0);
> tcg_gen_trunc_tl_i32(cpu_crf[0], cpu_so);
> l1 = gen_new_label();
> tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, l1);
> - tcg_gen_ori_i32(cpu_crf[0], cpu_crf[0], CRF_EQ);
> - tcg_gen_qemu_st_tl(cpu_gpr[reg], EA, ctx->mem_idx, memop);
> +
> + t0 = tcg_temp_new();
> + tcg_gen_atomic_cmpxchg_tl(t0, EA, cpu_reserve_val, cpu_gpr[reg],
> + ctx->mem_idx, DEF_MEMOP(memop));
> + tcg_gen_setcond_tl(TCG_COND_EQ, t0, t0, cpu_reserve_val);
> + tcg_gen_trunc_tl_i32(tmp, t0);
> +
> gen_set_label(l1);
> + tcg_gen_shli_i32(tmp, tmp, CRF_EQ_BIT);
> + tcg_gen_or_i32(cpu_crf[0], cpu_crf[0], tmp);
> tcg_gen_movi_tl(cpu_reserve, -1);
> + tcg_gen_movi_tl(cpu_reserve_val, 0);
> +
> + tcg_temp_free(t0);
> + tcg_temp_free_i32(tmp);
> }
> #endif
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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