Re: [Qemu-devel] [PATCH 25/32] ppc: Handle unconditional (always/never) traps at translation time

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2016-07-27 at 12:33 +1000, David Gibson wrote:
> 
> Should you be returning true here?
> 
> Without it, IIUC, the functions below will generate the unconditional
> trap, then generate more code to actually test the condition and trap
> again.

You are right, we generate dead code, will fix.

Cheers,
Ben.

> > 
> > +    }
> > +    return false;
> > +}
> > +
> >  /* tw */
> >  static void gen_tw(DisasContext *ctx)
> >  {
> > -    TCGv_i32 t0 = tcg_const_i32(TO(ctx->opcode));
> > +    TCGv_i32 t0;
> > +
> > +    if (check_unconditional_trap(ctx)) {
> > +        return;
> > +    }
> > +    t0 = tcg_const_i32(TO(ctx->opcode));
> >      gen_helper_tw(cpu_env, cpu_gpr[rA(ctx->opcode)],
> > cpu_gpr[rB(ctx->opcode)],
> >                    t0);
> >      tcg_temp_free_i32(t0);
> > @@ -3372,8 +3391,14 @@ static void gen_tw(DisasContext *ctx)
> >  /* twi */
> >  static void gen_twi(DisasContext *ctx)
> >  {
> > -    TCGv t0 = tcg_const_tl(SIMM(ctx->opcode));
> > -    TCGv_i32 t1 = tcg_const_i32(TO(ctx->opcode));
> > +    TCGv t0;
> > +    TCGv_i32 t1;
> > +
> > +    if (check_unconditional_trap(ctx)) {
> > +        return;
> > +    }
> > +    t0 = tcg_const_tl(SIMM(ctx->opcode));
> > +    t1 = tcg_const_i32(TO(ctx->opcode));
> >      gen_helper_tw(cpu_env, cpu_gpr[rA(ctx->opcode)], t0, t1);
> >      tcg_temp_free(t0);
> >      tcg_temp_free_i32(t1);
> > @@ -3383,7 +3408,12 @@ static void gen_twi(DisasContext *ctx)
> >  /* td */
> >  static void gen_td(DisasContext *ctx)
> >  {
> > -    TCGv_i32 t0 = tcg_const_i32(TO(ctx->opcode));
> > +    TCGv_i32 t0;
> > +
> > +    if (check_unconditional_trap(ctx)) {
> > +        return;
> > +    }
> > +    t0 = tcg_const_i32(TO(ctx->opcode));
> >      gen_helper_td(cpu_env, cpu_gpr[rA(ctx->opcode)],
> > cpu_gpr[rB(ctx->opcode)],
> >                    t0);
> >      tcg_temp_free_i32(t0);
> > @@ -3392,8 +3422,14 @@ static void gen_td(DisasContext *ctx)
> >  /* tdi */
> >  static void gen_tdi(DisasContext *ctx)
> >  {
> > -    TCGv t0 = tcg_const_tl(SIMM(ctx->opcode));
> > -    TCGv_i32 t1 = tcg_const_i32(TO(ctx->opcode));
> > +    TCGv t0;
> > +    TCGv_i32 t1;
> > +
> > +    if (check_unconditional_trap(ctx)) {
> > +        return;
> > +    }
> > +    t0 = tcg_const_tl(SIMM(ctx->opcode));
> > +    t1 = tcg_const_i32(TO(ctx->opcode));
> >      gen_helper_td(cpu_env, cpu_gpr[rA(ctx->opcode)], t0, t1);
> >      tcg_temp_free(t0);
> >      tcg_temp_free_i32(t1);
>