[Mesa-dev] [PATCH 4/4] nir: Add some asserts that we don't put derefs in phis

[Iago Toral]

Should we add a similar check to validate_phi_src in nir_validate.c?

On Mon, 2018-09-17 at 09:43 -0500, Jason Ekstrand wrote:
> The lcssa and phis_to_regs passes are used by various NIR
> optimizations
> that modify the CFG.  Putting a couple of asserts will help ensure
> that
> we don't accidentally put derefs in phis as part of an optimization
> pass.
> ---
>  src/compiler/nir/nir_from_ssa.c | 2 ++
>  src/compiler/nir/nir_to_lcssa.c | 3 +++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/src/compiler/nir/nir_from_ssa.c
> b/src/compiler/nir/nir_from_ssa.c
> index 1aa35509b11..19d4bc33820 100644
> --- a/src/compiler/nir/nir_from_ssa.c
> +++ b/src/compiler/nir/nir_from_ssa.c
> @@ -901,6 +901,8 @@ nir_lower_phis_to_regs_block(nir_block *block)
>  
>        nir_foreach_phi_src(src, phi) {
>           assert(src->src.is_ssa);
> +         /* We don't want derefs ending up in phi sources */
> +         assert(!nir_src_as_deref(src->src));
>           place_phi_read(shader, reg, src->src.ssa, src->pred);
>        }
>  
> diff --git a/src/compiler/nir/nir_to_lcssa.c
> b/src/compiler/nir/nir_to_lcssa.c
> index 9b3539193ea..0f62fc39400 100644
> --- a/src/compiler/nir/nir_to_lcssa.c
> +++ b/src/compiler/nir/nir_to_lcssa.c
> @@ -111,6 +111,9 @@ convert_loop_exit_for_ssa(nir_ssa_def *def, void
> *void_state)
>     if (all_uses_inside_loop)
>        return true;
>  
> +   /* We don't want derefs ending up in phi sources */
> +   assert(def->parent_instr->type != nir_instr_type_deref);
> +
>     /* Initialize a phi-instruction */
>     nir_phi_instr *phi = nir_phi_instr_create(state->shader);
>     nir_ssa_dest_init(&phi->instr, &phi->dest,