| /* |
| * Copyright © 2014 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_rebalance_tree.cpp |
| * |
| * Rebalances a reduction expression tree. |
| * |
| * For reduction operations (e.g., x + y + z + w) we generate an expression |
| * tree like |
| * |
| * + |
| * / \ |
| * + w |
| * / \ |
| * + z |
| * / \ |
| * x y |
| * |
| * which we can rebalance into |
| * |
| * + |
| * / \ |
| * / \ |
| * + + |
| * / \ / \ |
| * x y z w |
| * |
| * to get a better instruction scheduling. |
| * |
| * See "Tree Rebalancing in Optimal Editor Time and Space" by Quentin F. Stout |
| * and Bette L. Warren. |
| * |
| * Also see http://penguin.ewu.edu/~trolfe/DSWpaper/ for a very readable |
| * explanation of the of the tree_to_vine() (rightward rotation) and |
| * vine_to_tree() (leftward rotation) algorithms. |
| */ |
| |
| #include "ir.h" |
| #include "ir_visitor.h" |
| #include "ir_rvalue_visitor.h" |
| #include "ir_optimization.h" |
| #include "main/macros.h" /* for MAX2 */ |
| |
| /* The DSW algorithm generates a degenerate tree (really, a linked list) in |
| * tree_to_vine(). We'd rather not leave a binary expression with only one |
| * operand, so trivial modifications (the ternary operators below) are needed |
| * to ensure that we only rotate around the ir_expression nodes of the tree. |
| */ |
| static unsigned |
| tree_to_vine(ir_expression *root) |
| { |
| unsigned size = 0; |
| ir_rvalue *vine_tail = root; |
| ir_rvalue *remainder = root->operands[1]; |
| |
| while (remainder != NULL) { |
| ir_expression *remainder_temp = remainder->as_expression(); |
| ir_expression *remainder_left = remainder_temp ? |
| remainder_temp->operands[0]->as_expression() : NULL; |
| |
| if (remainder_left == NULL) { |
| /* move vine_tail down one */ |
| vine_tail = remainder; |
| remainder = remainder->as_expression() ? |
| ((ir_expression *)remainder)->operands[1] : NULL; |
| size++; |
| } else { |
| /* rotate */ |
| ir_expression *tempptr = remainder_left; |
| ((ir_expression *)remainder)->operands[0] = tempptr->operands[1]; |
| tempptr->operands[1] = remainder; |
| remainder = tempptr; |
| ((ir_expression *)vine_tail)->operands[1] = tempptr; |
| } |
| } |
| |
| return size; |
| } |
| |
| static void |
| compression(ir_expression *root, unsigned count) |
| { |
| ir_expression *scanner = root; |
| |
| for (unsigned i = 0; i < count; i++) { |
| ir_expression *child = (ir_expression *)scanner->operands[1]; |
| scanner->operands[1] = child->operands[1]; |
| scanner = (ir_expression *)scanner->operands[1]; |
| child->operands[1] = scanner->operands[0]; |
| scanner->operands[0] = child; |
| } |
| } |
| |
| static void |
| vine_to_tree(ir_expression *root, unsigned size) |
| { |
| int n = size - 1; |
| for (int m = n / 2; m > 0; m = n / 2) { |
| compression(root, m); |
| n -= m + 1; |
| } |
| } |
| |
| namespace { |
| |
| class ir_rebalance_visitor : public ir_rvalue_enter_visitor { |
| public: |
| ir_rebalance_visitor() |
| { |
| progress = false; |
| } |
| |
| void handle_rvalue(ir_rvalue **rvalue); |
| |
| bool progress; |
| }; |
| |
| struct is_reduction_data { |
| ir_expression_operation operation; |
| const glsl_type *type; |
| unsigned num_expr; |
| bool is_reduction; |
| bool contains_constant; |
| }; |
| |
| } /* anonymous namespace */ |
| |
| static bool |
| is_reduction_operation(ir_expression_operation operation) |
| { |
| switch (operation) { |
| case ir_binop_add: |
| case ir_binop_mul: |
| case ir_binop_bit_and: |
| case ir_binop_bit_xor: |
| case ir_binop_bit_or: |
| case ir_binop_logic_and: |
| case ir_binop_logic_xor: |
| case ir_binop_logic_or: |
| case ir_binop_min: |
| case ir_binop_max: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| /* Note that this function does not attempt to recognize that reduction trees |
| * are already balanced. |
| * |
| * We return false from this function for a number of reasons other than an |
| * expression tree not being a mathematical reduction. Namely, |
| * |
| * - if the tree contains multiple constants that we may be able to combine. |
| * - if the tree contains matrices: |
| * - they might contain vec4's with many constant components that we can |
| * simplify after splitting. |
| * - applying the matrix chain ordering optimization is more than just |
| * balancing an expression tree. |
| * - if the tree contains operations on multiple types. |
| * - if the tree contains ir_dereference_{array,record}, since foo[a+b] + c |
| * would trick the visiting pass. |
| */ |
| static void |
| is_reduction(ir_instruction *ir, void *data) |
| { |
| struct is_reduction_data *ird = (struct is_reduction_data *)data; |
| if (!ird->is_reduction) |
| return; |
| |
| /* We don't want to balance a tree that contains multiple constants, since |
| * we'll be able to constant fold them if they're not in separate subtrees. |
| */ |
| if (ir->as_constant()) { |
| if (ird->contains_constant) { |
| ird->is_reduction = false; |
| } |
| ird->contains_constant = true; |
| return; |
| } |
| |
| /* Array/record dereferences have subtrees that are not part of the expr |
| * tree we're balancing. Skip trees containing them. |
| */ |
| if (ir->ir_type == ir_type_dereference_array || |
| ir->ir_type == ir_type_dereference_record) { |
| ird->is_reduction = false; |
| return; |
| } |
| |
| ir_expression *expr = ir->as_expression(); |
| if (!expr) |
| return; |
| |
| /* Non-constant matrices might still contain constant vec4 that we can |
| * constant fold once split up. Handling matrices will need some more |
| * work. |
| */ |
| if (expr->type->is_matrix() || |
| expr->operands[0]->type->is_matrix() || |
| (expr->operands[1] && expr->operands[1]->type->is_matrix())) { |
| ird->is_reduction = false; |
| return; |
| } |
| |
| if (ird->type != NULL && ird->type != expr->type) { |
| ird->is_reduction = false; |
| return; |
| } |
| ird->type = expr->type; |
| |
| ird->num_expr++; |
| if (is_reduction_operation(expr->operation)) { |
| if (ird->operation != 0 && ird->operation != expr->operation) |
| ird->is_reduction = false; |
| ird->operation = expr->operation; |
| } else { |
| ird->is_reduction = false; |
| } |
| } |
| |
| static ir_rvalue * |
| handle_expression(ir_expression *expr) |
| { |
| struct is_reduction_data ird; |
| ird.operation = (ir_expression_operation)0; |
| ird.type = NULL; |
| ird.num_expr = 0; |
| ird.is_reduction = true; |
| ird.contains_constant = false; |
| |
| visit_tree(expr, is_reduction, (void *)&ird); |
| |
| if (ird.is_reduction && ird.num_expr > 2) { |
| ir_constant z = ir_constant(0.0f); |
| ir_expression pseudo_root = ir_expression(ir_binop_add, &z, expr); |
| |
| unsigned size = tree_to_vine(&pseudo_root); |
| vine_to_tree(&pseudo_root, size); |
| |
| expr = (ir_expression *)pseudo_root.operands[1]; |
| } |
| return expr; |
| } |
| |
| static void |
| update_types(ir_instruction *ir, void *) |
| { |
| ir_expression *expr = ir->as_expression(); |
| if (!expr) |
| return; |
| |
| const glsl_type *const new_type = |
| glsl_type::get_instance(expr->type->base_type, |
| MAX2(expr->operands[0]->type->vector_elements, |
| expr->operands[1]->type->vector_elements), |
| 1); |
| assert(new_type != glsl_type::error_type); |
| expr->type = new_type; |
| } |
| |
| void |
| ir_rebalance_visitor::handle_rvalue(ir_rvalue **rvalue) |
| { |
| if (!*rvalue) |
| return; |
| |
| ir_expression *expr = (*rvalue)->as_expression(); |
| if (!expr || !is_reduction_operation(expr->operation)) |
| return; |
| |
| ir_rvalue *new_rvalue = handle_expression(expr); |
| |
| /* If we failed to rebalance the tree (e.g., because it wasn't a reduction, |
| * or some other set of cases) new_rvalue will point to the same root as |
| * before. |
| * |
| * Similarly, if the tree rooted at *rvalue was a reduction and was already |
| * balanced, the algorithm will rearrange the tree but will ultimately |
| * return an identical tree, so this check will handle that as well and |
| * will not set progress = true. |
| */ |
| if (new_rvalue == *rvalue) |
| return; |
| |
| visit_tree(new_rvalue, NULL, NULL, update_types); |
| |
| *rvalue = new_rvalue; |
| this->progress = true; |
| } |
| |
| bool |
| do_rebalance_tree(exec_list *instructions) |
| { |
| ir_rebalance_visitor v; |
| |
| v.run(instructions); |
| |
| return v.progress; |
| } |