glsl/lower_vector_derefs: Don't use a temporary for TCS outputs
Tessellation control shader outputs act as if they have memory backing them and you can have multiple writes to different components of the same vector in-flight at the same time. When this happens, the load vec store pattern that gets used by ir_triop_vector_insert doesn't yield the correct results. Instead, just emit a sequence of conditional assignments. Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> Cc: mesa-stable@lists.freedesktop.org
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@ -32,8 +32,9 @@ namespace {
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class vector_deref_visitor : public ir_rvalue_enter_visitor {
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public:
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vector_deref_visitor()
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: progress(false)
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vector_deref_visitor(void *mem_ctx, gl_shader_stage shader_stage)
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: progress(false), shader_stage(shader_stage),
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factory(&factory_instructions, mem_ctx)
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{
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}
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@ -45,6 +46,9 @@ public:
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virtual ir_visitor_status visit_enter(ir_assignment *ir);
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bool progress;
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gl_shader_stage shader_stage;
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exec_list factory_instructions;
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ir_factory factory;
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};
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} /* anonymous namespace */
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@ -65,13 +69,63 @@ vector_deref_visitor::visit_enter(ir_assignment *ir)
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ir_constant *old_index_constant =
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deref->array_index->constant_expression_value(mem_ctx);
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if (!old_index_constant) {
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ir->rhs = new(mem_ctx) ir_expression(ir_triop_vector_insert,
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new_lhs->type,
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new_lhs->clone(mem_ctx, NULL),
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ir->rhs,
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deref->array_index);
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ir->write_mask = (1 << new_lhs->type->vector_elements) - 1;
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ir->set_lhs(new_lhs);
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if (shader_stage == MESA_SHADER_TESS_CTRL &&
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deref->variable_referenced()->data.mode == ir_var_shader_out) {
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/* Tessellation control shader outputs act as if they have memory
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* backing them and if we have writes from multiple threads
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* targeting the same vec4 (this can happen for patch outputs), the
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* load-vec-store pattern of ir_triop_vector_insert doesn't work.
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* Instead, we have to lower to a series of conditional write-masked
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* assignments.
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*/
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ir_variable *const src_temp =
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factory.make_temp(ir->rhs->type, "scalar_tmp");
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/* The newly created variable declaration goes before the assignment
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* because we're going to set it as the new LHS.
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*/
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ir->insert_before(factory.instructions);
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ir->set_lhs(new(mem_ctx) ir_dereference_variable(src_temp));
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ir_variable *const arr_index =
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factory.make_temp(deref->array_index->type, "index_tmp");
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factory.emit(assign(arr_index, deref->array_index));
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for (unsigned i = 0; i < new_lhs->type->vector_elements; i++) {
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ir_constant *const cmp_index =
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ir_constant::zero(factory.mem_ctx, deref->array_index->type);
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cmp_index->value.u[0] = i;
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ir_rvalue *const lhs_clone = new_lhs->clone(factory.mem_ctx, NULL);
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ir_dereference_variable *const src_temp_deref =
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new(mem_ctx) ir_dereference_variable(src_temp);
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if (new_lhs->ir_type != ir_type_swizzle) {
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assert(lhs_clone->as_dereference());
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ir_assignment *cond_assign =
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new(mem_ctx) ir_assignment(lhs_clone->as_dereference(),
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src_temp_deref,
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equal(arr_index, cmp_index),
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WRITEMASK_X << i);
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factory.emit(cond_assign);
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} else {
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ir_assignment *cond_assign =
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new(mem_ctx) ir_assignment(swizzle(lhs_clone, i, 1),
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src_temp_deref,
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equal(arr_index, cmp_index));
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factory.emit(cond_assign);
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}
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}
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ir->insert_after(factory.instructions);
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} else {
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ir->rhs = new(mem_ctx) ir_expression(ir_triop_vector_insert,
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new_lhs->type,
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new_lhs->clone(mem_ctx, NULL),
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ir->rhs,
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deref->array_index);
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ir->write_mask = (1 << new_lhs->type->vector_elements) - 1;
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ir->set_lhs(new_lhs);
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}
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} else if (new_lhs->ir_type != ir_type_swizzle) {
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ir->set_lhs(new_lhs);
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ir->write_mask = 1 << old_index_constant->get_uint_component(0);
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@ -105,7 +159,7 @@ vector_deref_visitor::handle_rvalue(ir_rvalue **rv)
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bool
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lower_vector_derefs(gl_linked_shader *shader)
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{
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vector_deref_visitor v;
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vector_deref_visitor v(shader->ir, shader->Stage);
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visit_list_elements(&v, shader->ir);
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