From edc52a8f280db8d9dc9a04314741319ea8b83e67 Mon Sep 17 00:00:00 2001 From: Kenneth Graunke Date: Wed, 3 Apr 2013 23:56:57 -0700 Subject: [PATCH] glsl: Add an optimization pass to flatten simple nested if blocks. GLBenchmark 2.7's shaders contain conditional blocks like: if (x) { if (y) { ... } } where the outer conditional's then clause contains exactly one statement (the nested if) and there are no else clauses. This can easily be optimized into: if (x && y) { ... } This saves a few instructions in GLBenchmark 2.7: total instructions in shared programs: 11833 -> 11649 (-1.55%) instructions in affected programs: 8234 -> 8050 (-2.23%) It also helps CS:GO slightly (-0.05%/-0.22%). More importantly, however, it simplifies the control flow graph, which could enable other optimizations. Signed-off-by: Kenneth Graunke Reviewed-by: Matt Turner Reviewed-by: Eric Anholt --- src/glsl/Makefile.sources | 1 + src/glsl/glsl_parser_extras.cpp | 1 + src/glsl/ir_optimization.h | 1 + src/glsl/opt_flatten_nested_if_blocks.cpp | 103 ++++++++++++++++++++++++++++++ 4 files changed, 106 insertions(+) create mode 100644 src/glsl/opt_flatten_nested_if_blocks.cpp diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources index c294aa4..b5282a6 100644 --- a/src/glsl/Makefile.sources +++ b/src/glsl/Makefile.sources @@ -80,6 +80,7 @@ LIBGLSL_FILES = \ $(GLSL_SRCDIR)/opt_dead_code.cpp \ $(GLSL_SRCDIR)/opt_dead_code_local.cpp \ $(GLSL_SRCDIR)/opt_dead_functions.cpp \ + $(GLSL_SRCDIR)/opt_flatten_nested_if_blocks.cpp \ $(GLSL_SRCDIR)/opt_function_inlining.cpp \ $(GLSL_SRCDIR)/opt_if_simplification.cpp \ $(GLSL_SRCDIR)/opt_noop_swizzle.cpp \ diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp index 9740903..0992294 100644 --- a/src/glsl/glsl_parser_extras.cpp +++ b/src/glsl/glsl_parser_extras.cpp @@ -1218,6 +1218,7 @@ do_common_optimization(exec_list *ir, bool linked, progress = do_structure_splitting(ir) || progress; } progress = do_if_simplification(ir) || progress; + progress = opt_flatten_nested_if_blocks(ir) || progress; progress = do_copy_propagation(ir) || progress; progress = do_copy_propagation_elements(ir) || progress; if (linked) diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h index 2454bbe..a8885d7 100644 --- a/src/glsl/ir_optimization.h +++ b/src/glsl/ir_optimization.h @@ -82,6 +82,7 @@ bool do_function_inlining(exec_list *instructions); bool do_lower_jumps(exec_list *instructions, bool pull_out_jumps = true, bool lower_sub_return = true, bool lower_main_return = false, bool lower_continue = false, bool lower_break = false); bool do_lower_texture_projection(exec_list *instructions); bool do_if_simplification(exec_list *instructions); +bool opt_flatten_nested_if_blocks(exec_list *instructions); bool do_discard_simplification(exec_list *instructions); bool lower_if_to_cond_assign(exec_list *instructions, unsigned max_depth = 0); bool do_mat_op_to_vec(exec_list *instructions); diff --git a/src/glsl/opt_flatten_nested_if_blocks.cpp b/src/glsl/opt_flatten_nested_if_blocks.cpp new file mode 100644 index 0000000..c702102 --- /dev/null +++ b/src/glsl/opt_flatten_nested_if_blocks.cpp @@ -0,0 +1,103 @@ +/* + * Copyright © 2013 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 opt_flatten_nested_if_blocks.cpp + * + * Flattens nested if blocks such as: + * + * if (x) { + * if (y) { + * ... + * } + * } + * + * into a single if block with a combined condition: + * + * if (x && y) { + * ... + * } + */ + +#include "ir.h" +#include "ir_builder.h" + +using namespace ir_builder; + +namespace { + +class nested_if_flattener : public ir_hierarchical_visitor { +public: + nested_if_flattener() + { + progress = false; + } + + ir_visitor_status visit_leave(ir_if *); + ir_visitor_status visit_enter(ir_assignment *); + + bool progress; +}; + +} /* unnamed namespace */ + +/* We only care about the top level "if" instructions, so don't + * descend into expressions. + */ +ir_visitor_status +nested_if_flattener::visit_enter(ir_assignment *ir) +{ + (void) ir; + return visit_continue_with_parent; +} + +bool +opt_flatten_nested_if_blocks(exec_list *instructions) +{ + nested_if_flattener v; + + v.run(instructions); + return v.progress; +} + + +ir_visitor_status +nested_if_flattener::visit_leave(ir_if *ir) +{ + /* Only handle a single ir_if within the then clause of an ir_if. No extra + * instructions, no else clauses, nothing. + */ + if (ir->then_instructions.is_empty() || !ir->else_instructions.is_empty()) + return visit_continue; + + ir_if *inner = ((ir_instruction *) ir->then_instructions.head)->as_if(); + if (!inner || !inner->next->is_tail_sentinel() || + !inner->else_instructions.is_empty()) + return visit_continue; + + ir->condition = logic_and(ir->condition, inner->condition); + inner->then_instructions.move_nodes_to(&ir->then_instructions); + + progress = true; + return visit_continue; +} -- 2.7.4