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/*

 * 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"

static bool debug = false;

namespace {

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;

};

} /* unnamed namespace */

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 *ir)

{

   /* 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];

   int chans;

   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_iter(exec_list_iterator, iter, *this->acp) {

      acp_entry *entry = (acp_entry *)iter.get();

      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]];

	    }

	 }

      }

   }

   /* 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);

   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);

   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 */

   exec_list_iterator sig_param_iter = ir->callee->parameters.iterator();

   foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {

      ir_variable *sig_param = (ir_variable *)sig_param_iter.get();

      ir_instruction *ir = (ir_instruction *)iter.get();

      if (sig_param->mode != ir_var_function_out

          && sig_param->mode != ir_var_function_inout) {

         ir->accept(this);

      }

      sig_param_iter.next();

   }

   /* Since we're unlinked, we don't (necessarily) know the side effects of

    * this call.  So kill all copies.

    */

   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_iter(exec_list_iterator, iter, *orig_acp) {

      acp_entry *a = (acp_entry *)iter.get();

      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_list_safe(node, new_kills) {

      kill_entry *k = (kill_entry *)node;

      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_list_safe(node, new_kills) {

      kill_entry *k = (kill_entry *)node;

      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_list_safe(node, acp) {

      acp_entry *entry = (acp_entry *)node;

      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++];

   }

   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);

}

bool

do_copy_propagation_elements(exec_list *instructions)

{

   ir_copy_propagation_elements_visitor v;

   visit_list_elements(&v, instructions);

   return v.progress;

}