/* * 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 "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()) { ir_rvalue *cast = new(mem_ctx) ir_expression(ir_unop_f2i, 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 < Elements(bias); i++) { iter = (increment->type->is_integer()) ? new(mem_ctx) ir_constant(iter_value + bias[i]) : new(mem_ctx) ir_constant(float(iter_value + bias[i])); 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_list(node, &ls->terminators) { loop_terminator *t = (loop_terminator *) node; 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; }