text: /*
   * Copyright © 2015 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 "nir.h"
  
  /**
   * \file nir_sweep.c
   *
   * The nir_sweep() pass performs a mark and sweep pass over a nir_shader's associated
   * memory - anything still connected to the program will be kept, and any dead memory
   * we dropped on the floor will be freed.
   *
   * The expectation is that drivers should call this when finished compiling the shader
   * (after any optimization, lowering, and so on).  However, it's also fine to call it
   * earlier, and even many times, trading CPU cycles for memory savings.
   */
  
  #define steal_list(mem_ctx, type, list) \
     foreach_list_typed(type, obj, node, list) { ralloc_steal(mem_ctx, obj); }
  
  static void sweep_cf_node(nir_shader *nir, nir_cf_node *cf_node);
  
  static bool
  sweep_src_indirect(nir_src *src, void *nir)
  {
     if (!src->is_ssa && src->reg.indirect)
        ralloc_steal(nir, src->reg.indirect);
  
     return true;
  }
  
  static bool
  sweep_dest_indirect(nir_dest *dest, void *nir)
  {
     if (!dest->is_ssa && dest->reg.indirect)
        ralloc_steal(nir, dest->reg.indirect);
  
     return true;
  }
  
  static void
  sweep_block(nir_shader *nir, nir_block *block)
  {
     ralloc_steal(nir, block);
  
     nir_foreach_instr(instr, block) {
        ralloc_steal(nir, instr);
  
        nir_foreach_src(instr, sweep_src_indirect, nir);
        nir_foreach_dest(instr, sweep_dest_indirect, nir);
     }
  }
  
  static void
  sweep_if(nir_shader *nir, nir_if *iff)
  {
     ralloc_steal(nir, iff);
  
     foreach_list_typed(nir_cf_node, cf_node, node, &iff->then_list) {
        sweep_cf_node(nir, cf_node);
     }
  
     foreach_list_typed(nir_cf_node, cf_node, node, &iff->else_list) {
        sweep_cf_node(nir, cf_node);
     }
  }
  
  static void
  sweep_loop(nir_shader *nir, nir_loop *loop)
  {
     ralloc_steal(nir, loop);
  
     foreach_list_typed(nir_cf_node, cf_node, node, &loop->body) {
        sweep_cf_node(nir, cf_node);
     }
  }
  
  static void
  sweep_cf_node(nir_shader *nir, nir_cf_node *cf_node)
  {
     switch (cf_node->type) {
     case nir_cf_node_block:
        sweep_block(nir, nir_cf_node_as_block(cf_node));
        break;
     case nir_cf_node_if:
        sweep_if(nir, nir_cf_node_as_if(cf_node));
        break;
     case nir_cf_node_loop:
        sweep_loop(nir, nir_cf_node_as_loop(cf_node));
        break;
     default:
        unreachable("Invalid CF node type");
     }
  }
  
  static void
  sweep_impl(nir_shader *nir, nir_function_impl *impl)
  {
     ralloc_steal(nir, impl);
  
     ralloc_steal(nir, impl->params);
     for (unsigned i = 0; i < impl->num_params; i++)
        ralloc_steal(nir, impl->params[i]);
     ralloc_steal(nir, impl->return_var);
     steal_list(nir, nir_variable, &impl->locals);
     steal_list(nir, nir_register, &impl->registers);
  
     foreach_list_typed(nir_cf_node, cf_node, node, &impl->body) {
        sweep_cf_node(nir, cf_node);
     }
  
     sweep_block(nir, impl->end_block);
  
     /* Wipe out all the metadata, if any. */
     nir_metadata_preserve(impl, nir_metadata_none);
  }
  
  static void
  sweep_function(nir_shader *nir, nir_function *f)
  {
     ralloc_steal(nir, f);
     ralloc_steal(nir, f->params);
  
     if (f->impl)
        sweep_impl(nir, f->impl);
  }
  
  void
  nir_sweep(nir_shader *nir)
  {
     void *rubbish = ralloc_context(NULL);
  
     /* First, move ownership of all the memory to a temporary context; assume dead. */
     ralloc_adopt(rubbish, nir);
  
     ralloc_steal(nir, (char *)nir->info.name);
     if (nir->info.label)
        ralloc_steal(nir, (char *)nir->info.label);
  
     /* Variables and registers are not dead.  Steal them back. */
     steal_list(nir, nir_variable, &nir->uniforms);
     steal_list(nir, nir_variable, &nir->inputs);
     steal_list(nir, nir_variable, &nir->outputs);
     steal_list(nir, nir_variable, &nir->shared);
     steal_list(nir, nir_variable, &nir->globals);
     steal_list(nir, nir_variable, &nir->system_values);
     steal_list(nir, nir_register, &nir->registers);
  
     /* Recurse into functions, stealing their contents back. */
     foreach_list_typed(nir_function, func, node, &nir->functions) {
        sweep_function(nir, func);
     }
  
     /* Free everything we didn't steal back. */
     ralloc_free(rubbish);
  }
  