mirror of https://gitlab.freedesktop.org/mesa/mesa
462 lines
13 KiB
C++
462 lines
13 KiB
C++
/*
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* Copyright © 2010 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* constant of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, constant, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above constantright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR CONSTANTRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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/**
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* \file opt_constant_propagation.cpp
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*
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* Tracks assignments of constants to channels of variables, and
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* usage of those constant channels with direct usage of the constants.
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*
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* This can lead to constant folding and algebraic optimizations in
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* those later expressions, while causing no increase in instruction
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* count (due to constants being generally free to load from a
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* constant push buffer or as instruction immediate values) and
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* possibly reducing register pressure.
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*/
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#include "ir.h"
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#include "ir_visitor.h"
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#include "ir_rvalue_visitor.h"
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#include "ir_basic_block.h"
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#include "ir_optimization.h"
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#include "glsl_types.h"
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namespace {
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class acp_entry : public exec_node
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{
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public:
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acp_entry(ir_variable *var, unsigned write_mask, ir_constant *constant)
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{
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assert(var);
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assert(constant);
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this->var = var;
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this->write_mask = write_mask;
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this->constant = constant;
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this->initial_values = write_mask;
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}
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acp_entry(const acp_entry *src)
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{
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this->var = src->var;
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this->write_mask = src->write_mask;
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this->constant = src->constant;
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this->initial_values = src->initial_values;
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}
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ir_variable *var;
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ir_constant *constant;
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unsigned write_mask;
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/** Mask of values initially available in the constant. */
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unsigned initial_values;
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};
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class kill_entry : public exec_node
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{
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public:
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kill_entry(ir_variable *var, unsigned write_mask)
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{
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assert(var);
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this->var = var;
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this->write_mask = write_mask;
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}
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ir_variable *var;
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unsigned write_mask;
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};
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class ir_constant_propagation_visitor : public ir_rvalue_visitor {
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public:
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ir_constant_propagation_visitor()
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{
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progress = false;
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killed_all = false;
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mem_ctx = ralloc_context(0);
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this->acp = new(mem_ctx) exec_list;
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this->kills = new(mem_ctx) exec_list;
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}
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~ir_constant_propagation_visitor()
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{
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ralloc_free(mem_ctx);
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}
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virtual ir_visitor_status visit_enter(class ir_loop *);
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virtual ir_visitor_status visit_enter(class ir_function_signature *);
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virtual ir_visitor_status visit_enter(class ir_function *);
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virtual ir_visitor_status visit_leave(class ir_assignment *);
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virtual ir_visitor_status visit_enter(class ir_call *);
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virtual ir_visitor_status visit_enter(class ir_if *);
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void add_constant(ir_assignment *ir);
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void kill(ir_variable *ir, unsigned write_mask);
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void handle_if_block(exec_list *instructions);
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void handle_rvalue(ir_rvalue **rvalue);
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/** List of acp_entry: The available constants to propagate */
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exec_list *acp;
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/**
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* List of kill_entry: The masks of variables whose values were
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* killed in this block.
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*/
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exec_list *kills;
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bool progress;
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bool killed_all;
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void *mem_ctx;
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};
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void
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ir_constant_propagation_visitor::handle_rvalue(ir_rvalue **rvalue)
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{
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if (this->in_assignee || !*rvalue)
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return;
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const glsl_type *type = (*rvalue)->type;
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if (!type->is_scalar() && !type->is_vector())
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return;
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ir_swizzle *swiz = NULL;
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ir_dereference_variable *deref = (*rvalue)->as_dereference_variable();
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if (!deref) {
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swiz = (*rvalue)->as_swizzle();
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if (!swiz)
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return;
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deref = swiz->val->as_dereference_variable();
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if (!deref)
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return;
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}
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ir_constant_data data;
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memset(&data, 0, sizeof(data));
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for (unsigned int i = 0; i < type->components(); i++) {
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int channel;
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acp_entry *found = NULL;
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if (swiz) {
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switch (i) {
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case 0: channel = swiz->mask.x; break;
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case 1: channel = swiz->mask.y; break;
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case 2: channel = swiz->mask.z; break;
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case 3: channel = swiz->mask.w; break;
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default: assert(!"shouldn't be reached"); channel = 0; break;
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}
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} else {
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channel = i;
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}
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foreach_in_list(acp_entry, entry, this->acp) {
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if (entry->var == deref->var && entry->write_mask & (1 << channel)) {
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found = entry;
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break;
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}
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}
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if (!found)
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return;
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int rhs_channel = 0;
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for (int j = 0; j < 4; j++) {
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if (j == channel)
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break;
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if (found->initial_values & (1 << j))
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rhs_channel++;
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}
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switch (type->base_type) {
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case GLSL_TYPE_FLOAT:
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data.f[i] = found->constant->value.f[rhs_channel];
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break;
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case GLSL_TYPE_INT:
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data.i[i] = found->constant->value.i[rhs_channel];
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break;
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case GLSL_TYPE_UINT:
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data.u[i] = found->constant->value.u[rhs_channel];
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break;
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case GLSL_TYPE_BOOL:
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data.b[i] = found->constant->value.b[rhs_channel];
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break;
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default:
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assert(!"not reached");
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break;
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}
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}
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*rvalue = new(ralloc_parent(deref)) ir_constant(type, &data);
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this->progress = true;
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}
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ir_visitor_status
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ir_constant_propagation_visitor::visit_enter(ir_function_signature *ir)
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{
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/* Treat entry into a function signature as a completely separate
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* block. Any instructions at global scope will be shuffled into
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* main() at link time, so they're irrelevant to us.
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*/
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exec_list *orig_acp = this->acp;
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exec_list *orig_kills = this->kills;
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bool orig_killed_all = this->killed_all;
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this->acp = new(mem_ctx) exec_list;
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this->kills = new(mem_ctx) exec_list;
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this->killed_all = false;
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visit_list_elements(this, &ir->body);
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this->kills = orig_kills;
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this->acp = orig_acp;
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this->killed_all = orig_killed_all;
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return visit_continue_with_parent;
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}
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ir_visitor_status
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ir_constant_propagation_visitor::visit_leave(ir_assignment *ir)
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{
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if (this->in_assignee)
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return visit_continue;
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unsigned kill_mask = ir->write_mask;
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if (ir->lhs->as_dereference_array()) {
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/* The LHS of the assignment uses an array indexing operator (e.g. v[i]
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* = ...;). Since we only try to constant propagate vectors and
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* scalars, this means that either (a) array indexing is being used to
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* select a vector component, or (b) the variable in question is neither
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* a scalar or a vector, so we don't care about it. In the former case,
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* we want to kill the whole vector, since in general we can't predict
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* which vector component will be selected by array indexing. In the
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* latter case, it doesn't matter what we do, so go ahead and kill the
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* whole variable anyway.
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*
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* Note that if the array index is constant (e.g. v[2] = ...;), we could
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* in principle be smarter, but we don't need to, because a future
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* optimization pass will convert it to a simple assignment with the
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* correct mask.
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*/
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kill_mask = ~0;
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}
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kill(ir->lhs->variable_referenced(), kill_mask);
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add_constant(ir);
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return visit_continue;
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}
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ir_visitor_status
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ir_constant_propagation_visitor::visit_enter(ir_function *ir)
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{
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(void) ir;
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return visit_continue;
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}
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ir_visitor_status
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ir_constant_propagation_visitor::visit_enter(ir_call *ir)
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{
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/* Do constant propagation on call parameters, but skip any out params */
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foreach_two_lists(formal_node, &ir->callee->parameters,
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actual_node, &ir->actual_parameters) {
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ir_variable *sig_param = (ir_variable *) formal_node;
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ir_rvalue *param = (ir_rvalue *) actual_node;
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if (sig_param->data.mode != ir_var_function_out
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&& sig_param->data.mode != ir_var_function_inout) {
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ir_rvalue *new_param = param;
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handle_rvalue(&new_param);
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if (new_param != param)
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param->replace_with(new_param);
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else
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param->accept(this);
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}
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}
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/* Since we're unlinked, we don't (necssarily) know the side effects of
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* this call. So kill all copies.
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*/
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acp->make_empty();
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this->killed_all = true;
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return visit_continue_with_parent;
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}
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void
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ir_constant_propagation_visitor::handle_if_block(exec_list *instructions)
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{
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exec_list *orig_acp = this->acp;
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exec_list *orig_kills = this->kills;
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bool orig_killed_all = this->killed_all;
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this->acp = new(mem_ctx) exec_list;
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this->kills = new(mem_ctx) exec_list;
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this->killed_all = false;
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/* Populate the initial acp with a constant of the original */
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foreach_in_list(acp_entry, a, orig_acp) {
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this->acp->push_tail(new(this->mem_ctx) acp_entry(a));
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}
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visit_list_elements(this, instructions);
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if (this->killed_all) {
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orig_acp->make_empty();
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}
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exec_list *new_kills = this->kills;
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this->kills = orig_kills;
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this->acp = orig_acp;
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this->killed_all = this->killed_all || orig_killed_all;
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foreach_in_list(kill_entry, k, new_kills) {
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kill(k->var, k->write_mask);
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}
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}
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ir_visitor_status
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ir_constant_propagation_visitor::visit_enter(ir_if *ir)
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{
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ir->condition->accept(this);
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handle_rvalue(&ir->condition);
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handle_if_block(&ir->then_instructions);
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handle_if_block(&ir->else_instructions);
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/* handle_if_block() already descended into the children. */
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return visit_continue_with_parent;
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}
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ir_visitor_status
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ir_constant_propagation_visitor::visit_enter(ir_loop *ir)
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{
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exec_list *orig_acp = this->acp;
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exec_list *orig_kills = this->kills;
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bool orig_killed_all = this->killed_all;
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/* FINISHME: For now, the initial acp for loops is totally empty.
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* We could go through once, then go through again with the acp
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* cloned minus the killed entries after the first run through.
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*/
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this->acp = new(mem_ctx) exec_list;
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this->kills = new(mem_ctx) exec_list;
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this->killed_all = false;
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visit_list_elements(this, &ir->body_instructions);
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if (this->killed_all) {
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orig_acp->make_empty();
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}
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exec_list *new_kills = this->kills;
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this->kills = orig_kills;
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this->acp = orig_acp;
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this->killed_all = this->killed_all || orig_killed_all;
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foreach_in_list(kill_entry, k, new_kills) {
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kill(k->var, k->write_mask);
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}
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/* already descended into the children. */
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return visit_continue_with_parent;
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}
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void
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ir_constant_propagation_visitor::kill(ir_variable *var, unsigned write_mask)
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{
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assert(var != NULL);
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/* We don't track non-vectors. */
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if (!var->type->is_vector() && !var->type->is_scalar())
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return;
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/* Remove any entries currently in the ACP for this kill. */
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foreach_in_list_safe(acp_entry, entry, this->acp) {
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if (entry->var == var) {
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entry->write_mask &= ~write_mask;
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if (entry->write_mask == 0)
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entry->remove();
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}
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}
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/* Add this writemask of the variable to the list of killed
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* variables in this block.
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*/
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foreach_in_list(kill_entry, entry, this->kills) {
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if (entry->var == var) {
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entry->write_mask |= write_mask;
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return;
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}
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}
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/* Not already in the list. Make new entry. */
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this->kills->push_tail(new(this->mem_ctx) kill_entry(var, write_mask));
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}
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/**
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* Adds an entry to the available constant list if it's a plain assignment
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* of a variable to a variable.
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*/
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void
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ir_constant_propagation_visitor::add_constant(ir_assignment *ir)
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{
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acp_entry *entry;
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if (ir->condition)
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return;
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if (!ir->write_mask)
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return;
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ir_dereference_variable *deref = ir->lhs->as_dereference_variable();
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ir_constant *constant = ir->rhs->as_constant();
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if (!deref || !constant)
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return;
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/* Only do constant propagation on vectors. Constant matrices,
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* arrays, or structures would require more work elsewhere.
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*/
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if (!deref->var->type->is_vector() && !deref->var->type->is_scalar())
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return;
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entry = new(this->mem_ctx) acp_entry(deref->var, ir->write_mask, constant);
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this->acp->push_tail(entry);
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}
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} /* unnamed namespace */
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/**
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* Does a constant propagation pass on the code present in the instruction stream.
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*/
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bool
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do_constant_propagation(exec_list *instructions)
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{
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ir_constant_propagation_visitor v;
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visit_list_elements(&v, instructions);
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return v.progress;
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}
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