| /* |
| * Copyright © 2010 Intel Corporation |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a |
| * copy of this software and associated documentation files (the "Software"), |
| * to deal in the Software without restriction, including without limitation |
| * the rights to use, copy, modify, merge, publish, distribute, sublicense, |
| * and/or sell copies of the Software, and to permit persons to whom the |
| * Software is furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice (including the next |
| * paragraph) shall be included in all copies or substantial portions of the |
| * Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
| * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
| * DEALINGS IN THE SOFTWARE. |
| */ |
| |
| /** @file lower_discard_flow.cpp |
| * |
| * Implements the GLSL 1.30 revision 9 rule for fragment shader |
| * discard handling: |
| * |
| * "Control flow exits the shader, and subsequent implicit or |
| * explicit derivatives are undefined when this control flow is |
| * non-uniform (meaning different fragments within the primitive |
| * take different control paths)." |
| * |
| * There seem to be two conflicting things here. "Control flow exits |
| * the shader" sounds like the discarded fragments should effectively |
| * jump to the end of the shader, but that breaks derivatives in the |
| * case of uniform control flow and causes rendering failure in the |
| * bushes in Unigine Tropics. |
| * |
| * The question, then, is whether the intent was "loops stop at the |
| * point that the only active channels left are discarded pixels" or |
| * "discarded pixels become inactive at the point that control flow |
| * returns to the top of a loop". This implements the second |
| * interpretation. |
| */ |
| |
| #include "glsl_types.h" |
| #include "ir.h" |
| #include "program/hash_table.h" |
| |
| class lower_discard_flow_visitor : public ir_hierarchical_visitor { |
| public: |
| lower_discard_flow_visitor(ir_variable *discarded) |
| : discarded(discarded) |
| { |
| mem_ctx = ralloc_parent(discarded); |
| } |
| |
| ~lower_discard_flow_visitor() |
| { |
| } |
| |
| ir_visitor_status visit_enter(ir_discard *ir); |
| ir_visitor_status visit_enter(ir_loop_jump *ir); |
| ir_visitor_status visit_enter(ir_loop *ir); |
| ir_visitor_status visit_enter(ir_function_signature *ir); |
| |
| ir_if *generate_discard_break(); |
| |
| ir_variable *discarded; |
| void *mem_ctx; |
| }; |
| |
| ir_visitor_status |
| lower_discard_flow_visitor::visit_enter(ir_loop_jump *ir) |
| { |
| if (ir->mode != ir_loop_jump::jump_continue) |
| return visit_continue; |
| |
| ir->insert_before(generate_discard_break()); |
| |
| return visit_continue; |
| } |
| |
| ir_visitor_status |
| lower_discard_flow_visitor::visit_enter(ir_discard *ir) |
| { |
| ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(discarded); |
| ir_rvalue *rhs = new(mem_ctx) ir_constant(true); |
| ir_assignment *assign = new(mem_ctx) ir_assignment(lhs, rhs); |
| ir->insert_before(assign); |
| |
| return visit_continue; |
| } |
| |
| ir_visitor_status |
| lower_discard_flow_visitor::visit_enter(ir_loop *ir) |
| { |
| ir->body_instructions.push_tail(generate_discard_break()); |
| |
| return visit_continue; |
| } |
| |
| ir_visitor_status |
| lower_discard_flow_visitor::visit_enter(ir_function_signature *ir) |
| { |
| if (strcmp(ir->function_name(), "main") != 0) |
| return visit_continue; |
| |
| ir_dereference *lhs = new(mem_ctx) ir_dereference_variable(discarded); |
| ir_rvalue *rhs = new(mem_ctx) ir_constant(false); |
| ir_assignment *assign = new(mem_ctx) ir_assignment(lhs, rhs); |
| ir->body.push_head(assign); |
| |
| return visit_continue; |
| } |
| |
| ir_if * |
| lower_discard_flow_visitor::generate_discard_break() |
| { |
| ir_rvalue *if_condition = new(mem_ctx) ir_dereference_variable(discarded); |
| ir_if *if_inst = new(mem_ctx) ir_if(if_condition); |
| |
| ir_instruction *br = new(mem_ctx) ir_loop_jump(ir_loop_jump::jump_break); |
| if_inst->then_instructions.push_tail(br); |
| |
| return if_inst; |
| } |
| |
| void |
| lower_discard_flow(exec_list *ir) |
| { |
| void *mem_ctx = ir; |
| |
| ir_variable *var = new(mem_ctx) ir_variable(glsl_type::bool_type, |
| "discarded", |
| ir_var_temporary); |
| |
| ir->push_head(var); |
| |
| lower_discard_flow_visitor v(var); |
| |
| visit_list_elements(&v, ir); |
| } |