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      1 /*
      2  * Copyright  2010 Intel Corporation
      3  *
      4  * Permission is hereby granted, free of charge, to any person obtaining a
      5  * copy of this software and associated documentation files (the "Software"),
      6  * to deal in the Software without restriction, including without limitation
      7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      8  * and/or sell copies of the Software, and to permit persons to whom the
      9  * Software is furnished to do so, subject to the following conditions:
     10  *
     11  * The above copyright notice and this permission notice (including the next
     12  * paragraph) shall be included in all copies or substantial portions of the
     13  * Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     21  * DEALINGS IN THE SOFTWARE.
     22  */
     23 
     24 /**
     25  * \file opt_dead_functions.cpp
     26  *
     27  * Eliminates unused functions from the linked program.
     28  */
     29 
     30 #include "ir.h"
     31 #include "ir_visitor.h"
     32 #include "ir_expression_flattening.h"
     33 #include "compiler/glsl_types.h"
     34 
     35 namespace {
     36 
     37 class signature_entry : public exec_node
     38 {
     39 public:
     40    signature_entry(ir_function_signature *sig)
     41    {
     42       this->signature = sig;
     43       this->used = false;
     44    }
     45 
     46    ir_function_signature *signature;
     47    bool used;
     48 };
     49 
     50 class ir_dead_functions_visitor : public ir_hierarchical_visitor {
     51 public:
     52    ir_dead_functions_visitor()
     53    {
     54       this->mem_ctx = ralloc_context(NULL);
     55    }
     56 
     57    ~ir_dead_functions_visitor()
     58    {
     59       ralloc_free(this->mem_ctx);
     60    }
     61 
     62    virtual ir_visitor_status visit_enter(ir_function_signature *);
     63    virtual ir_visitor_status visit_enter(ir_call *);
     64 
     65    signature_entry *get_signature_entry(ir_function_signature *var);
     66 
     67    /* List of signature_entry */
     68    exec_list signature_list;
     69    void *mem_ctx;
     70 };
     71 
     72 } /* unnamed namespace */
     73 
     74 signature_entry *
     75 ir_dead_functions_visitor::get_signature_entry(ir_function_signature *sig)
     76 {
     77    foreach_in_list(signature_entry, entry, &this->signature_list) {
     78       if (entry->signature == sig)
     79 	 return entry;
     80    }
     81 
     82    signature_entry *entry = new(mem_ctx) signature_entry(sig);
     83    this->signature_list.push_tail(entry);
     84    return entry;
     85 }
     86 
     87 
     88 ir_visitor_status
     89 ir_dead_functions_visitor::visit_enter(ir_function_signature *ir)
     90 {
     91    signature_entry *entry = this->get_signature_entry(ir);
     92 
     93    if (strcmp(ir->function_name(), "main") == 0) {
     94       entry->used = true;
     95    }
     96 
     97 
     98 
     99    return visit_continue;
    100 }
    101 
    102 
    103 ir_visitor_status
    104 ir_dead_functions_visitor::visit_enter(ir_call *ir)
    105 {
    106    signature_entry *entry = this->get_signature_entry(ir->callee);
    107 
    108    entry->used = true;
    109 
    110    return visit_continue;
    111 }
    112 
    113 bool
    114 do_dead_functions(exec_list *instructions)
    115 {
    116    ir_dead_functions_visitor v;
    117    bool progress = false;
    118 
    119    visit_list_elements(&v, instructions);
    120 
    121    /* Now that we've figured out which function signatures are used, remove
    122     * the unused ones, and remove function definitions that have no more
    123     * signatures.
    124     */
    125     foreach_in_list_safe(signature_entry, entry, &v.signature_list) {
    126       if (!entry->used) {
    127 	 entry->signature->remove();
    128 	 delete entry->signature;
    129 	 progress = true;
    130       }
    131       delete(entry);
    132    }
    133 
    134    /* We don't just do this above when we nuked a signature because of
    135     * const pointers.
    136     */
    137    foreach_in_list_safe(ir_instruction, ir, instructions) {
    138       ir_function *func = ir->as_function();
    139 
    140       if (func && func->signatures.is_empty()) {
    141 	 /* At this point (post-linking), the symbol table is no
    142 	  * longer in use, so not removing the function from the
    143 	  * symbol table should be OK.
    144 	  */
    145 	 func->remove();
    146 	 delete func;
    147 	 progress = true;
    148       }
    149    }
    150 
    151    return progress;
    152 }
    153