On Wed, Nov 2, 2016 at 6:55 PM, Marek Olšák <mar...@gmail.com> wrote:
> On Wed, Nov 2, 2016 at 2:55 PM, Nicolai Hähnle <nhaeh...@gmail.com> wrote:
>> On 29.10.2016 01:13, Marek Olšák wrote:
>>>
>>> From: Marek Olšák <marek.ol...@amd.com>
>>>
>>> ---
>>> src/compiler/glsl/ir_optimization.h | 3 ++-
>>> src/compiler/glsl/lower_if_to_cond_assign.cpp | 23
>>> ++++++++++++++++++++---
>>> src/compiler/glsl/test_optpass.cpp | 2 +-
>>> src/mesa/drivers/dri/i965/brw_link.cpp | 2 +-
>>> src/mesa/program/ir_to_mesa.cpp | 3 ++-
>>> src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 3 ++-
>>> 6 files changed, 28 insertions(+), 8 deletions(-)
>>>
>> [snip]
>>>
>>> @@ -105,20 +109,33 @@ check_ir_node(ir_instruction *ir, void *data)
>>> case ir_type_call:
>>> case ir_type_discard:
>>> case ir_type_loop:
>>> case ir_type_loop_jump:
>>> case ir_type_return:
>>> case ir_type_emit_vertex:
>>> case ir_type_end_primitive:
>>> case ir_type_barrier:
>>> v->found_unsupported_op = true;
>>> break;
>>> +
>>> + case ir_type_dereference_variable: {
>>> + ir_variable *var =
>>> ir->as_dereference_variable()->variable_referenced();
>>> +
>>> + /* Tess control shader outputs are like shared memory with complex
>>> + * side effects, so treat it that way.
>>> + */
>>> + if (v->stage == MESA_SHADER_TESS_CTRL &&
>>> + var->data.mode == ir_var_shader_out)
>>> + v->found_unsupported_op = true;
>>> + break;
>>> + }
>>> +
>>
>>
>> I don't understand this rationale. What side effects are there, and can you
>> give an example where the transformation would be wrong?
>
> Well I can't think of a case now where it would break something.
Not sure how dereference_variable is used... what happens if you do
out[gl_InvocationId] = asdf
does that use a dereference_variable for the out? If so, this could be
problematic, e.g.
if (foo)
out[gl_InvocationId] = asdf
tmp = out[0];
You can't really "fix" that in any reasonable way... Or perhaps I'm
confused about how this pass works.
-ilia
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