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Diffstat (limited to 'src/compiler/glsl/loop_controls.cpp')
| -rw-r--r-- | src/compiler/glsl/loop_controls.cpp | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/src/compiler/glsl/loop_controls.cpp b/src/compiler/glsl/loop_controls.cpp new file mode 100644 index 0000000..c717605 --- /dev/null +++ b/src/compiler/glsl/loop_controls.cpp @@ -0,0 +1,246 @@ +/* + * 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. + */ + +#include <limits.h> +#include "main/compiler.h" +#include "compiler/glsl_types.h" +#include "loop_analysis.h" +#include "ir_hierarchical_visitor.h" + +/** + * Find an initializer of a variable outside a loop + * + * Works backwards from the loop to find the pre-loop value of the variable. + * This is used, for example, to find the initial value of loop induction + * variables. + * + * \param loop Loop where \c var is an induction variable + * \param var Variable whose initializer is to be found + * + * \return + * The \c ir_rvalue assigned to the variable outside the loop. May return + * \c NULL if no initializer can be found. + */ +ir_rvalue * +find_initial_value(ir_loop *loop, ir_variable *var) +{ + for (exec_node *node = loop->prev; + !node->is_head_sentinel(); + node = node->prev) { + ir_instruction *ir = (ir_instruction *) node; + + switch (ir->ir_type) { + case ir_type_call: + case ir_type_loop: + case ir_type_loop_jump: + case ir_type_return: + case ir_type_if: + return NULL; + + case ir_type_function: + case ir_type_function_signature: + assert(!"Should not get here."); + return NULL; + + case ir_type_assignment: { + ir_assignment *assign = ir->as_assignment(); + ir_variable *assignee = assign->lhs->whole_variable_referenced(); + + if (assignee == var) + return (assign->condition != NULL) ? NULL : assign->rhs; + + break; + } + + default: + break; + } + } + + return NULL; +} + + +int +calculate_iterations(ir_rvalue *from, ir_rvalue *to, ir_rvalue *increment, + enum ir_expression_operation op) +{ + if (from == NULL || to == NULL || increment == NULL) + return -1; + + void *mem_ctx = ralloc_context(NULL); + + ir_expression *const sub = + new(mem_ctx) ir_expression(ir_binop_sub, from->type, to, from); + + ir_expression *const div = + new(mem_ctx) ir_expression(ir_binop_div, sub->type, sub, increment); + + ir_constant *iter = div->constant_expression_value(); + + if (iter == NULL) + return -1; + + if (!iter->type->is_integer()) { + const ir_expression_operation op = iter->type->is_double() + ? ir_unop_d2i : ir_unop_f2i; + ir_rvalue *cast = + new(mem_ctx) ir_expression(op, glsl_type::int_type, iter, NULL); + + iter = cast->constant_expression_value(); + } + + int iter_value = iter->get_int_component(0); + + /* Make sure that the calculated number of iterations satisfies the exit + * condition. This is needed to catch off-by-one errors and some types of + * ill-formed loops. For example, we need to detect that the following + * loop does not have a maximum iteration count. + * + * for (float x = 0.0; x != 0.9; x += 0.2) + * ; + */ + const int bias[] = { -1, 0, 1 }; + bool valid_loop = false; + + for (unsigned i = 0; i < ARRAY_SIZE(bias); i++) { + /* Increment may be of type int, uint or float. */ + switch (increment->type->base_type) { + case GLSL_TYPE_INT: + iter = new(mem_ctx) ir_constant(iter_value + bias[i]); + break; + case GLSL_TYPE_UINT: + iter = new(mem_ctx) ir_constant(unsigned(iter_value + bias[i])); + break; + case GLSL_TYPE_FLOAT: + iter = new(mem_ctx) ir_constant(float(iter_value + bias[i])); + break; + case GLSL_TYPE_DOUBLE: + iter = new(mem_ctx) ir_constant(double(iter_value + bias[i])); + break; + default: + unreachable("Unsupported type for loop iterator."); + } + + ir_expression *const mul = + new(mem_ctx) ir_expression(ir_binop_mul, increment->type, iter, + increment); + + ir_expression *const add = + new(mem_ctx) ir_expression(ir_binop_add, mul->type, mul, from); + + ir_expression *const cmp = + new(mem_ctx) ir_expression(op, glsl_type::bool_type, add, to); + + ir_constant *const cmp_result = cmp->constant_expression_value(); + + assert(cmp_result != NULL); + if (cmp_result->get_bool_component(0)) { + iter_value += bias[i]; + valid_loop = true; + break; + } + } + + ralloc_free(mem_ctx); + return (valid_loop) ? iter_value : -1; +} + +namespace { + +class loop_control_visitor : public ir_hierarchical_visitor { +public: + loop_control_visitor(loop_state *state) + { + this->state = state; + this->progress = false; + } + + virtual ir_visitor_status visit_leave(ir_loop *ir); + + loop_state *state; + + bool progress; +}; + +} /* anonymous namespace */ + +ir_visitor_status +loop_control_visitor::visit_leave(ir_loop *ir) +{ + loop_variable_state *const ls = this->state->get(ir); + + /* If we've entered a loop that hasn't been analyzed, something really, + * really bad has happened. + */ + if (ls == NULL) { + assert(ls != NULL); + return visit_continue; + } + + if (ls->limiting_terminator != NULL) { + /* If the limiting terminator has an iteration count of zero, then we've + * proven that the loop cannot run, so delete it. + */ + int iterations = ls->limiting_terminator->iterations; + if (iterations == 0) { + ir->remove(); + this->progress = true; + return visit_continue; + } + } + + /* Remove the conditional break statements associated with all terminators + * that are associated with a fixed iteration count, except for the one + * associated with the limiting terminator--that one needs to stay, since + * it terminates the loop. Exception: if the loop still has a normative + * bound, then that terminates the loop, so we don't even need the limiting + * terminator. + */ + foreach_in_list(loop_terminator, t, &ls->terminators) { + if (t->iterations < 0) + continue; + + if (t != ls->limiting_terminator) { + t->ir->remove(); + + assert(ls->num_loop_jumps > 0); + ls->num_loop_jumps--; + + this->progress = true; + } + } + + return visit_continue; +} + + +bool +set_loop_controls(exec_list *instructions, loop_state *ls) +{ + loop_control_visitor v(ls); + + v.run(instructions); + + return v.progress; +} |