text: /*
   * 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.
   */
  
  /**
   * \file opt_copy_propagation_elements.cpp
   *
   * Replaces usage of recently-copied components of variables with the
   * previous copy of the variable.
   *
   * This pass can be compared with opt_copy_propagation, which operands
   * on arbitrary whole-variable copies.  However, in order to handle
   * the copy propagation of swizzled variables or writemasked writes,
   * we want to track things on a channel-wise basis.  I found that
   * trying to mix the swizzled/writemasked support here with the
   * whole-variable stuff in opt_copy_propagation.cpp just made a mess,
   * so this is separate despite the ACP handling being somewhat
   * similar.
   *
   * This should reduce the number of MOV instructions in the generated
   * programs unless copy propagation is also done on the LIR, and may
   * help anyway by triggering other optimizations that live in the HIR.
   */
  
  #include "ir.h"
  #include "ir_rvalue_visitor.h"
  #include "ir_basic_block.h"
  #include "ir_optimization.h"
  #include "glsl_types.h"
  
  
  namespace OPT_COPY_PROPAGATION_ELEMENTS {
  
  static bool debug = false;
  
  class acp_entry : public exec_node
  {
  public:
     acp_entry(ir_variable *lhs, ir_variable *rhs, int write_mask, int swizzle[4])
     {
        this->lhs = lhs;
        this->rhs = rhs;
        this->write_mask = write_mask;
        memcpy(this->swizzle, swizzle, sizeof(this->swizzle));
     }
  
     acp_entry(acp_entry *a)
     {
        this->lhs = a->lhs;
        this->rhs = a->rhs;
        this->write_mask = a->write_mask;
        memcpy(this->swizzle, a->swizzle, sizeof(this->swizzle));
     }
  
     ir_variable *lhs;
     ir_variable *rhs;
     unsigned int write_mask;
     int swizzle[4];
  };
  
  
  class kill_entry : public exec_node
  {
  public:
     kill_entry(ir_variable *var, int write_mask)
     {
        this->var = var;
        this->write_mask = write_mask;
     }
  
     ir_variable *var;
     unsigned int write_mask;
  };
  
  class ir_copy_propagation_elements_visitor : public ir_rvalue_visitor {
  public:
     ir_copy_propagation_elements_visitor()
     {
        this->progress = false;
        this->killed_all = false;
        this->mem_ctx = ralloc_context(NULL);
        this->shader_mem_ctx = NULL;
        this->acp = new(mem_ctx) exec_list;
        this->kills = new(mem_ctx) exec_list;
     }
     ~ir_copy_propagation_elements_visitor()
     {
        ralloc_free(mem_ctx);
     }
  
     virtual ir_visitor_status visit_enter(class ir_loop *);
     virtual ir_visitor_status visit_enter(class ir_function_signature *);
     virtual ir_visitor_status visit_leave(class ir_assignment *);
     virtual ir_visitor_status visit_enter(class ir_call *);
     virtual ir_visitor_status visit_enter(class ir_if *);
     virtual ir_visitor_status visit_leave(class ir_swizzle *);
  
     void handle_rvalue(ir_rvalue **rvalue);
  
     void add_copy(ir_assignment *ir);
     void kill(kill_entry *k);
     void handle_if_block(exec_list *instructions);
  
     /** List of acp_entry: The available copies to propagate */
     exec_list *acp;
     /**
      * List of kill_entry: The variables whose values were killed in this
      * block.
      */
     exec_list *kills;
  
     bool progress;
  
     bool killed_all;
  
     /* Context for our local data structures. */
     void *mem_ctx;
     /* Context for allocating new shader nodes. */
     void *shader_mem_ctx;
  };
  
  ir_visitor_status
  ir_copy_propagation_elements_visitor::visit_enter(ir_function_signature *ir)
  {
     /* Treat entry into a function signature as a completely separate
      * block.  Any instructions at global scope will be shuffled into
      * main() at link time, so they're irrelevant to us.
      */
     exec_list *orig_acp = this->acp;
     exec_list *orig_kills = this->kills;
     bool orig_killed_all = this->killed_all;
  
     this->acp = new(mem_ctx) exec_list;
     this->kills = new(mem_ctx) exec_list;
     this->killed_all = false;
  
     visit_list_elements(this, &ir->body);
  
     this->kills = orig_kills;
     this->acp = orig_acp;
     this->killed_all = orig_killed_all;
  
     return visit_continue_with_parent;
  }
  
  ir_visitor_status
  ir_copy_propagation_elements_visitor::visit_leave(ir_assignment *ir)
  {
     ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
     ir_variable *var = ir->lhs->variable_referenced();
  
     if (var->type->is_scalar() || var->type->is_vector()) {
        kill_entry *k;
  
        if (lhs)
  	 k = new(mem_ctx) kill_entry(var, ir->write_mask);
        else
  	 k = new(mem_ctx) kill_entry(var, ~0);
  
        kill(k);
     }
  
     add_copy(ir);
  
     return visit_continue;
  }
  
  ir_visitor_status
  ir_copy_propagation_elements_visitor::visit_leave(ir_swizzle *)
  {
     /* Don't visit the values of swizzles since they are handled while
      * visiting the swizzle itself.
      */
     return visit_continue;
  }
  
  /**
   * Replaces dereferences of ACP RHS variables with ACP LHS variables.
   *
   * This is where the actual copy propagation occurs.  Note that the
   * rewriting of ir_dereference means that the ir_dereference instance
   * must not be shared by multiple IR operations!
   */
  void
  ir_copy_propagation_elements_visitor::handle_rvalue(ir_rvalue **ir)
  {
     int swizzle_chan[4];
     ir_dereference_variable *deref_var;
     ir_variable *source[4] = {NULL, NULL, NULL, NULL};
     int source_chan[4] = {0, 0, 0, 0};
     int chans;
     bool noop_swizzle = true;
  
     if (!*ir)
        return;
  
     ir_swizzle *swizzle = (*ir)->as_swizzle();
     if (swizzle) {
        deref_var = swizzle->val->as_dereference_variable();
        if (!deref_var)
  	 return;
  
        swizzle_chan[0] = swizzle->mask.x;
        swizzle_chan[1] = swizzle->mask.y;
        swizzle_chan[2] = swizzle->mask.z;
        swizzle_chan[3] = swizzle->mask.w;
        chans = swizzle->type->vector_elements;
     } else {
        deref_var = (*ir)->as_dereference_variable();
        if (!deref_var)
  	 return;
  
        swizzle_chan[0] = 0;
        swizzle_chan[1] = 1;
        swizzle_chan[2] = 2;
        swizzle_chan[3] = 3;
        chans = deref_var->type->vector_elements;
     }
  
     if (this->in_assignee)
        return;
  
     ir_variable *var = deref_var->var;
  
     /* Try to find ACP entries covering swizzle_chan[], hoping they're
      * the same source variable.
      */
     foreach_in_list(acp_entry, entry, this->acp) {
        if (var == entry->lhs) {
  	 for (int c = 0; c < chans; c++) {
  	    if (entry->write_mask & (1 << swizzle_chan[c])) {
  	       source[c] = entry->rhs;
  	       source_chan[c] = entry->swizzle[swizzle_chan[c]];
  
                 if (source_chan[c] != swizzle_chan[c])
                    noop_swizzle = false;
  	    }
  	 }
        }
     }
  
     /* Make sure all channels are copying from the same source variable. */
     if (!source[0])
        return;
     for (int c = 1; c < chans; c++) {
        if (source[c] != source[0])
  	 return;
     }
  
     if (!shader_mem_ctx)
        shader_mem_ctx = ralloc_parent(deref_var);
  
     /* Don't pointlessly replace the rvalue with itself (or a noop swizzle
      * of itself, which would just be deleted by opt_noop_swizzle).
      */
     if (source[0] == var && noop_swizzle)
        return;
  
     if (debug) {
        printf("Copy propagation from:\n");
        (*ir)->print();
     }
  
     deref_var = new(shader_mem_ctx) ir_dereference_variable(source[0]);
     *ir = new(shader_mem_ctx) ir_swizzle(deref_var,
  					source_chan[0],
  					source_chan[1],
  					source_chan[2],
  					source_chan[3],
  					chans);
     progress = true;
  
     if (debug) {
        printf("to:\n");
        (*ir)->print();
        printf("\n");
     }
  }
  
  
  ir_visitor_status
  ir_copy_propagation_elements_visitor::visit_enter(ir_call *ir)
  {
     /* Do copy propagation on call parameters, but skip any out params */
     foreach_two_lists(formal_node, &ir->callee->parameters,
                       actual_node, &ir->actual_parameters) {
        ir_variable *sig_param = (ir_variable *) formal_node;
        ir_rvalue *ir = (ir_rvalue *) actual_node;
        if (sig_param->data.mode != ir_var_function_out
            && sig_param->data.mode != ir_var_function_inout) {
           ir->accept(this);
        }
     }
  
     /* Since we're unlinked, we don't (necessarily) know the side effects of
      * this call.  So kill all copies. Except if it's a built-in; we know
  	* they are side effect free.
      */
     if (!ir->callee->is_builtin()) {
        acp->make_empty();
        this->killed_all = true;
     }
  
     return visit_continue_with_parent;
  }
  
  void
  ir_copy_propagation_elements_visitor::handle_if_block(exec_list *instructions)
  {
     exec_list *orig_acp = this->acp;
     exec_list *orig_kills = this->kills;
     bool orig_killed_all = this->killed_all;
  
     this->acp = new(mem_ctx) exec_list;
     this->kills = new(mem_ctx) exec_list;
     this->killed_all = false;
  
     /* Populate the initial acp with a copy of the original */
     foreach_in_list(acp_entry, a, orig_acp) {
        this->acp->push_tail(new(this->mem_ctx) acp_entry(a));
     }
  
     visit_list_elements(this, instructions);
  
     if (this->killed_all) {
        orig_acp->make_empty();
     }
  
     exec_list *new_kills = this->kills;
     this->kills = orig_kills;
     this->acp = orig_acp;
     this->killed_all = this->killed_all || orig_killed_all;
  
     /* Move the new kills into the parent block's list, removing them
      * from the parent's ACP list in the process.
      */
     foreach_in_list_safe(kill_entry, k, new_kills) {
        kill(k);
     }
  }
  
  ir_visitor_status
  ir_copy_propagation_elements_visitor::visit_enter(ir_if *ir)
  {
     ir->condition->accept(this);
  
     handle_if_block(&ir->then_instructions);
     handle_if_block(&ir->else_instructions);
  
     /* handle_if_block() already descended into the children. */
     return visit_continue_with_parent;
  }
  
  ir_visitor_status
  ir_copy_propagation_elements_visitor::visit_enter(ir_loop *ir)
  {
     exec_list *orig_acp = this->acp;
     exec_list *orig_kills = this->kills;
     bool orig_killed_all = this->killed_all;
  
     /* FINISHME: For now, the initial acp for loops is totally empty.
      * We could go through once, then go through again with the acp
      * cloned minus the killed entries after the first run through.
      */
     this->acp = new(mem_ctx) exec_list;
     this->kills = new(mem_ctx) exec_list;
     this->killed_all = false;
  
     visit_list_elements(this, &ir->body_instructions);
  
     if (this->killed_all) {
        orig_acp->make_empty();
     }
  
     exec_list *new_kills = this->kills;
     this->kills = orig_kills;
     this->acp = orig_acp;
     this->killed_all = this->killed_all || orig_killed_all;
  
     foreach_in_list_safe(kill_entry, k, new_kills) {
        kill(k);
     }
  
     /* already descended into the children. */
     return visit_continue_with_parent;
  }
  
  /* Remove any entries currently in the ACP for this kill. */
  void
  ir_copy_propagation_elements_visitor::kill(kill_entry *k)
  {
     foreach_in_list_safe(acp_entry, entry, acp) {
        if (entry->lhs == k->var) {
  	 entry->write_mask = entry->write_mask & ~k->write_mask;
  	 if (entry->write_mask == 0) {
  	    entry->remove();
  	    continue;
  	 }
        }
        if (entry->rhs == k->var) {
  	 entry->remove();
        }
     }
  
     /* If we were on a list, remove ourselves before inserting */
     if (k->next)
        k->remove();
  
     this->kills->push_tail(k);
  }
  
  /**
   * Adds directly-copied channels between vector variables to the available
   * copy propagation list.
   */
  void
  ir_copy_propagation_elements_visitor::add_copy(ir_assignment *ir)
  {
     acp_entry *entry;
     int orig_swizzle[4] = {0, 1, 2, 3};
     int swizzle[4];
  
     if (ir->condition)
        return;
  
     ir_dereference_variable *lhs = ir->lhs->as_dereference_variable();
     if (!lhs || !(lhs->type->is_scalar() || lhs->type->is_vector()))
        return;
  
     ir_dereference_variable *rhs = ir->rhs->as_dereference_variable();
     if (!rhs) {
        ir_swizzle *swiz = ir->rhs->as_swizzle();
        if (!swiz)
  	 return;
  
        rhs = swiz->val->as_dereference_variable();
        if (!rhs)
  	 return;
  
        orig_swizzle[0] = swiz->mask.x;
        orig_swizzle[1] = swiz->mask.y;
        orig_swizzle[2] = swiz->mask.z;
        orig_swizzle[3] = swiz->mask.w;
     }
  
     /* Move the swizzle channels out to the positions they match in the
      * destination.  We don't want to have to rewrite the swizzle[]
      * array every time we clear a bit of the write_mask.
      */
     int j = 0;
     for (int i = 0; i < 4; i++) {
        if (ir->write_mask & (1 << i))
  	 swizzle[i] = orig_swizzle[j++];
     }
  	
     if (lhs->var->data.precision != rhs->var->data.precision && lhs->var->data.precision!=glsl_precision_undefined && rhs->var->data.precision!=glsl_precision_undefined)
        return;
  
     int write_mask = ir->write_mask;
     if (lhs->var == rhs->var) {
        /* If this is a copy from the variable to itself, then we need
         * to be sure not to include the updated channels from this
         * instruction in the set of new source channels to be
         * copy-propagated from.
         */
        for (int i = 0; i < 4; i++) {
  	 if (ir->write_mask & (1 << orig_swizzle[i]))
  	    write_mask &= ~(1 << i);
        }
     }
  
     entry = new(this->mem_ctx) acp_entry(lhs->var, rhs->var, write_mask,
  					swizzle);
     this->acp->push_tail(entry);
  }
  
  } /* unnamed namespace */
  
  bool
  do_copy_propagation_elements(exec_list *instructions)
  {
     OPT_COPY_PROPAGATION_ELEMENTS::ir_copy_propagation_elements_visitor v;
  
     visit_list_elements(&v, instructions);
  
     return v.progress;
  }
  