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glsl/lower_ubo_reference: split struct copies into element copies

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Improves register pressure, since otherwise we end up emitting
loads for all the elements in the RHS and them emitting
stores for all elements in the LHS.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
This commit is contained in:
Iago Toral Quiroga 2015-11-23 13:53:09 +01:00
parent 867c436ca8
commit 241f15ac80
1 changed files with 54 additions and 2 deletions
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56
src/glsl/lower_ubo_reference.cpp
View file

@ -155,6 +155,7 @@ public:
ir_rvalue *offset);
bool check_for_buffer_array_copy(ir_assignment *ir);
bool check_for_buffer_struct_copy(ir_assignment *ir);
void check_for_ssbo_store(ir_assignment *ir);
void write_to_memory(ir_dereference *deref,
ir_variable *var,
@ -1190,12 +1191,60 @@ lower_ubo_reference_visitor::check_for_buffer_array_copy(ir_assignment *ir)
return true;
}
bool
lower_ubo_reference_visitor::check_for_buffer_struct_copy(ir_assignment *ir)
{
if (!ir || !ir->lhs || !ir->rhs)
return false;
/* LHS and RHS must be records */
if (!ir->lhs->type->is_record() || !ir->rhs->type->is_record())
return false;
/* RHS must be a buffer-backed variable. This is what can cause the problem
* since it would lead to a series of loads that need to live until we
* see the writes to the LHS.
*/
ir_variable *rhs_var = ir->rhs->variable_referenced();
if (!rhs_var || !is_buffer_backed_variable(rhs_var))
return false;
/* Split the struct copy into individual element copies to reduce
* register pressure
*/
ir_dereference *rhs_deref = ir->rhs->as_dereference();
if (!rhs_deref)
return false;
ir_dereference *lhs_deref = ir->lhs->as_dereference();
if (!lhs_deref)
return false;
assert(lhs_deref->type->record_compare(rhs_deref->type));
mem_ctx = ralloc_parent(shader->ir);
for (unsigned i = 0; i < lhs_deref->type->length; i++) {
const char *field_name = lhs_deref->type->fields.structure[i].name;
ir_dereference *lhs_field =
new(mem_ctx) ir_dereference_record(lhs_deref->clone(mem_ctx, NULL),
field_name);
ir_dereference *rhs_field =
new(mem_ctx) ir_dereference_record(rhs_deref->clone(mem_ctx, NULL),
field_name);
ir->insert_after(assign(lhs_field, rhs_field));
}
ir->remove();
progress = true;
return true;
}
ir_visitor_status
lower_ubo_reference_visitor::visit_enter(ir_assignment *ir)
{
/* Array copies could involve large amounts of load/store
/* Array and struct copies could involve large amounts of load/store
* operations. To improve register pressure we want to special-case
* these and split array copies into individual element copies.
* these and split them into individual element copies.
* This way we avoid emitting all the loads for the RHS first and
* all the writes for the LHS second and register usage is more
* efficient.
@ -1203,6 +1252,9 @@ lower_ubo_reference_visitor::visit_enter(ir_assignment *ir)
if (check_for_buffer_array_copy(ir))
return visit_continue_with_parent;
if (check_for_buffer_struct_copy(ir))
return visit_continue_with_parent;
check_ssbo_unsized_array_length_assignment(ir);
check_for_ssbo_store(ir);
return rvalue_visit(ir);