src/compiler/glsl/opt_copy_propagation.cpp - third_party/mesa - Git at Google

 /*
  * 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.cpp
  *
  * Moves usage of recently-copied variables to the previous copy of
  * the variable.
  *
  * 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_visitor.h"
 #include "ir_basic_block.h"
 #include "ir_optimization.h"
 #include "compiler/glsl_types.h"
 #include "util/hash_table.h"
 #include "util/set.h"

 namespace {

 class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
 public:
    ir_copy_propagation_visitor()
    {
       progress = false;
       mem_ctx = ralloc_context(0);
       lin_ctx = linear_alloc_parent(mem_ctx, 0);
       acp = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
                                     _mesa_key_pointer_equal);
       kills = _mesa_set_create(mem_ctx, _mesa_hash_pointer,
                                _mesa_key_pointer_equal);
       killed_all = false;
    }
    ~ir_copy_propagation_visitor()
    {
       ralloc_free(mem_ctx);
    }

    virtual ir_visitor_status visit(class ir_dereference_variable *);
    void handle_loop(class ir_loop *, bool keep_acp);
    virtual ir_visitor_status visit_enter(class ir_loop *);
    virtual ir_visitor_status visit_enter(class ir_function_signature *);
    virtual ir_visitor_status visit_enter(class ir_function *);
    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 *);

    void add_copy(ir_assignment *ir);
    void kill(ir_variable *ir);
    void handle_if_block(exec_list *instructions);

    /** Hash of lhs->rhs: The available copies to propagate */
    hash_table *acp;

    /**
     * Set of ir_variables: Whose values were killed in this block.
     */
    set *kills;

    bool progress;

    bool killed_all;

    void *mem_ctx;
    void *lin_ctx;
 };

 } /* unnamed namespace */

 ir_visitor_status
 ir_copy_propagation_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.
     */
    hash_table *orig_acp = this->acp;
    set *orig_kills = this->kills;
    bool orig_killed_all = this->killed_all;

    acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                                  _mesa_key_pointer_equal);
    kills = _mesa_set_create(NULL, _mesa_hash_pointer,
                             _mesa_key_pointer_equal);
    this->killed_all = false;

    visit_list_elements(this, &ir->body);

    _mesa_hash_table_destroy(acp, NULL);
    _mesa_set_destroy(kills, NULL);

    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_visitor::visit_leave(ir_assignment *ir)
 {
    kill(ir->lhs->variable_referenced());

    add_copy(ir);

    return visit_continue;
 }

 ir_visitor_status
 ir_copy_propagation_visitor::visit_enter(ir_function *ir)
 {
    (void) ir;
    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!
  */
 ir_visitor_status
 ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
 {
    if (this->in_assignee)
       return visit_continue;

    struct hash_entry *entry = _mesa_hash_table_search(acp, ir->var);
    if (entry) {
       ir->var = (ir_variable *) entry->data;
       progress = true;
    }

    return visit_continue;
 }


 ir_visitor_status
 ir_copy_propagation_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 this pass can run when unlinked, we don't (necessarily) know
     * the side effects of calls.  (When linked, most calls are inlined
     * anyway, so it doesn't matter much.)
     *
     * One place where this does matter is IR intrinsics.  They're never
     * inlined.  We also know what they do - while some have side effects
     * (such as image writes), none edit random global variables.  So we
     * can assume they're side-effect free (other than the return value
     * and out parameters).
     */
    if (!ir->callee->is_intrinsic()) {
       _mesa_hash_table_clear(acp, NULL);
       this->killed_all = true;
    } else {
       if (ir->return_deref)
          kill(ir->return_deref->var);

       foreach_two_lists(formal_node, &ir->callee->parameters,
                         actual_node, &ir->actual_parameters) {
          ir_variable *sig_param = (ir_variable *) formal_node;
          if (sig_param->data.mode == ir_var_function_out ||
              sig_param->data.mode == ir_var_function_inout) {
             ir_rvalue *ir = (ir_rvalue *) actual_node;
             ir_variable *var = ir->variable_referenced();
             kill(var);
          }
       }
    }

    return visit_continue_with_parent;
 }

 void
 ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
 {
    hash_table *orig_acp = this->acp;
    set *orig_kills = this->kills;
    bool orig_killed_all = this->killed_all;

    kills = _mesa_set_create(NULL, _mesa_hash_pointer,
                             _mesa_key_pointer_equal);
    this->killed_all = false;

    /* Populate the initial acp with a copy of the original */
    acp = _mesa_hash_table_clone(orig_acp, NULL);

    visit_list_elements(this, instructions);

    if (this->killed_all) {
       _mesa_hash_table_clear(orig_acp, NULL);
    }

    set *new_kills = this->kills;
    this->kills = orig_kills;
    _mesa_hash_table_destroy(acp, NULL);
    this->acp = orig_acp;
    this->killed_all = this->killed_all || orig_killed_all;

    struct set_entry *s_entry;
    set_foreach(new_kills, s_entry) {
       kill((ir_variable *) s_entry->key);
    }

    _mesa_set_destroy(new_kills, NULL);
 }

 ir_visitor_status
 ir_copy_propagation_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;
 }

 void
 ir_copy_propagation_visitor::handle_loop(ir_loop *ir, bool keep_acp)
 {
    hash_table *orig_acp = this->acp;
    set *orig_kills = this->kills;
    bool orig_killed_all = this->killed_all;

    kills = _mesa_set_create(NULL, _mesa_hash_pointer,
                             _mesa_key_pointer_equal);
    this->killed_all = false;

    if (keep_acp) {
       acp = _mesa_hash_table_clone(orig_acp, NULL);
    } else {
       acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
                                     _mesa_key_pointer_equal);
    }

    visit_list_elements(this, &ir->body_instructions);

    if (this->killed_all) {
       _mesa_hash_table_clear(orig_acp, NULL);
    }

    set *new_kills = this->kills;
    this->kills = orig_kills;
    _mesa_hash_table_destroy(acp, NULL);
    this->acp = orig_acp;
    this->killed_all = this->killed_all || orig_killed_all;

    struct set_entry *entry;
    set_foreach(new_kills, entry) {
       kill((ir_variable *) entry->key);
    }

    _mesa_set_destroy(new_kills, NULL);
 }

 ir_visitor_status
 ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
 {
    /* Make a conservative first pass over the loop with an empty ACP set.
     * This also removes any killed entries from the original ACP set.
     */
    handle_loop(ir, false);

    /* Then, run it again with the real ACP set, minus any killed entries.
     * This takes care of propagating values from before the loop into it.
     */
    handle_loop(ir, true);

    /* already descended into the children. */
    return visit_continue_with_parent;
 }

 void
 ir_copy_propagation_visitor::kill(ir_variable *var)
 {
    assert(var != NULL);

    /* Remove any entries currently in the ACP for this kill. */
    struct hash_entry *entry = _mesa_hash_table_search(acp, var);
    if (entry) {
       _mesa_hash_table_remove(acp, entry);
    }

    hash_table_foreach(acp, entry) {
       if (var == (ir_variable *) entry->data) {
          _mesa_hash_table_remove(acp, entry);
       }
    }

    /* Add the LHS variable to the set of killed variables in this block. */
    _mesa_set_add(kills, var);
 }

 /**
  * Adds an entry to the available copy list if it's a plain assignment
  * of a variable to a variable.
  */
 void
 ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
 {
    if (ir->condition)
       return;

    ir_variable *lhs_var = ir->whole_variable_written();
    ir_variable *rhs_var = ir->rhs->whole_variable_referenced();

    /* Don't try to remove a dumb assignment of a variable to itself.  Removing
     * it now would mess up the loop iteration calling us.
     */
    if (lhs_var != NULL && rhs_var != NULL && lhs_var != rhs_var) {
       if (lhs_var->data.mode != ir_var_shader_storage &&
           lhs_var->data.mode != ir_var_shader_shared &&
           rhs_var->data.mode != ir_var_shader_storage &&
           rhs_var->data.mode != ir_var_shader_shared &&
           lhs_var->data.precise == rhs_var->data.precise) {
          _mesa_hash_table_insert(acp, lhs_var, rhs_var);
       }
    }
 }

 /**
  * Does a copy propagation pass on the code present in the instruction stream.
  */
 bool
 do_copy_propagation(exec_list *instructions)
 {
    ir_copy_propagation_visitor v;

    visit_list_elements(&v, instructions);

    return v.progress;
 }
	/*
	* 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.cpp
	*
	* Moves usage of recently-copied variables to the previous copy of
	* the variable.
	*
	* 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_visitor.h"
	#include "ir_basic_block.h"
	#include "ir_optimization.h"
	#include "compiler/glsl_types.h"
	#include "util/hash_table.h"
	#include "util/set.h"

	namespace {

	class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
	public:
	ir_copy_propagation_visitor()
	{
	progress = false;
	mem_ctx = ralloc_context(0);
	lin_ctx = linear_alloc_parent(mem_ctx, 0);
	acp = _mesa_hash_table_create(mem_ctx, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	kills = _mesa_set_create(mem_ctx, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	killed_all = false;
	}
	~ir_copy_propagation_visitor()
	{
	ralloc_free(mem_ctx);
	}

	virtual ir_visitor_status visit(class ir_dereference_variable *);
	void handle_loop(class ir_loop *, bool keep_acp);
	virtual ir_visitor_status visit_enter(class ir_loop *);
	virtual ir_visitor_status visit_enter(class ir_function_signature *);
	virtual ir_visitor_status visit_enter(class ir_function *);
	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 *);

	void add_copy(ir_assignment *ir);
	void kill(ir_variable *ir);
	void handle_if_block(exec_list *instructions);

	/** Hash of lhs->rhs: The available copies to propagate */
	hash_table *acp;

	/**
	* Set of ir_variables: Whose values were killed in this block.
	*/
	set *kills;

	bool progress;

	bool killed_all;

	void *mem_ctx;
	void *lin_ctx;
	};

	} /* unnamed namespace */

	ir_visitor_status
	ir_copy_propagation_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.
	*/
	hash_table *orig_acp = this->acp;
	set *orig_kills = this->kills;
	bool orig_killed_all = this->killed_all;

	acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	kills = _mesa_set_create(NULL, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	this->killed_all = false;

	visit_list_elements(this, &ir->body);

	_mesa_hash_table_destroy(acp, NULL);
	_mesa_set_destroy(kills, NULL);

	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_visitor::visit_leave(ir_assignment *ir)
	{
	kill(ir->lhs->variable_referenced());

	add_copy(ir);

	return visit_continue;
	}

	ir_visitor_status
	ir_copy_propagation_visitor::visit_enter(ir_function *ir)
	{
	(void) ir;
	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!
	*/
	ir_visitor_status
	ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
	{
	if (this->in_assignee)
	return visit_continue;

	struct hash_entry *entry = _mesa_hash_table_search(acp, ir->var);
	if (entry) {
	ir->var = (ir_variable *) entry->data;
	progress = true;
	}

	return visit_continue;
	}


	ir_visitor_status
	ir_copy_propagation_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 this pass can run when unlinked, we don't (necessarily) know
	* the side effects of calls. (When linked, most calls are inlined
	* anyway, so it doesn't matter much.)
	*
	* One place where this does matter is IR intrinsics. They're never
	* inlined. We also know what they do - while some have side effects
	* (such as image writes), none edit random global variables. So we
	* can assume they're side-effect free (other than the return value
	* and out parameters).
	*/
	if (!ir->callee->is_intrinsic()) {
	_mesa_hash_table_clear(acp, NULL);
	this->killed_all = true;
	} else {
	if (ir->return_deref)
	kill(ir->return_deref->var);

	foreach_two_lists(formal_node, &ir->callee->parameters,
	actual_node, &ir->actual_parameters) {
	ir_variable sig_param = (ir_variable ) formal_node;
	if (sig_param->data.mode == ir_var_function_out \|\|
	sig_param->data.mode == ir_var_function_inout) {
	ir_rvalue ir = (ir_rvalue ) actual_node;
	ir_variable *var = ir->variable_referenced();
	kill(var);
	}
	}
	}

	return visit_continue_with_parent;
	}

	void
	ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
	{
	hash_table *orig_acp = this->acp;
	set *orig_kills = this->kills;
	bool orig_killed_all = this->killed_all;

	kills = _mesa_set_create(NULL, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	this->killed_all = false;

	/* Populate the initial acp with a copy of the original */
	acp = _mesa_hash_table_clone(orig_acp, NULL);

	visit_list_elements(this, instructions);

	if (this->killed_all) {
	_mesa_hash_table_clear(orig_acp, NULL);
	}

	set *new_kills = this->kills;
	this->kills = orig_kills;
	_mesa_hash_table_destroy(acp, NULL);
	this->acp = orig_acp;
	this->killed_all = this->killed_all \|\| orig_killed_all;

	struct set_entry *s_entry;
	set_foreach(new_kills, s_entry) {
	kill((ir_variable *) s_entry->key);
	}

	_mesa_set_destroy(new_kills, NULL);
	}

	ir_visitor_status
	ir_copy_propagation_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;
	}

	void
	ir_copy_propagation_visitor::handle_loop(ir_loop *ir, bool keep_acp)
	{
	hash_table *orig_acp = this->acp;
	set *orig_kills = this->kills;
	bool orig_killed_all = this->killed_all;

	kills = _mesa_set_create(NULL, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	this->killed_all = false;

	if (keep_acp) {
	acp = _mesa_hash_table_clone(orig_acp, NULL);
	} else {
	acp = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
	_mesa_key_pointer_equal);
	}

	visit_list_elements(this, &ir->body_instructions);

	if (this->killed_all) {
	_mesa_hash_table_clear(orig_acp, NULL);
	}

	set *new_kills = this->kills;
	this->kills = orig_kills;
	_mesa_hash_table_destroy(acp, NULL);
	this->acp = orig_acp;
	this->killed_all = this->killed_all \|\| orig_killed_all;

	struct set_entry *entry;
	set_foreach(new_kills, entry) {
	kill((ir_variable *) entry->key);
	}

	_mesa_set_destroy(new_kills, NULL);
	}

	ir_visitor_status
	ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
	{
	/* Make a conservative first pass over the loop with an empty ACP set.
	* This also removes any killed entries from the original ACP set.
	*/
	handle_loop(ir, false);

	/* Then, run it again with the real ACP set, minus any killed entries.
	* This takes care of propagating values from before the loop into it.
	*/
	handle_loop(ir, true);

	/* already descended into the children. */
	return visit_continue_with_parent;
	}

	void
	ir_copy_propagation_visitor::kill(ir_variable *var)
	{
	assert(var != NULL);

	/* Remove any entries currently in the ACP for this kill. */
	struct hash_entry *entry = _mesa_hash_table_search(acp, var);
	if (entry) {
	_mesa_hash_table_remove(acp, entry);
	}

	hash_table_foreach(acp, entry) {
	if (var == (ir_variable *) entry->data) {
	_mesa_hash_table_remove(acp, entry);
	}
	}

	/* Add the LHS variable to the set of killed variables in this block. */
	_mesa_set_add(kills, var);
	}

	/**
	* Adds an entry to the available copy list if it's a plain assignment
	* of a variable to a variable.
	*/
	void
	ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
	{
	if (ir->condition)
	return;

	ir_variable *lhs_var = ir->whole_variable_written();
	ir_variable *rhs_var = ir->rhs->whole_variable_referenced();

	/* Don't try to remove a dumb assignment of a variable to itself. Removing
	* it now would mess up the loop iteration calling us.
	*/
	if (lhs_var != NULL && rhs_var != NULL && lhs_var != rhs_var) {
	if (lhs_var->data.mode != ir_var_shader_storage &&
	lhs_var->data.mode != ir_var_shader_shared &&
	rhs_var->data.mode != ir_var_shader_storage &&
	rhs_var->data.mode != ir_var_shader_shared &&
	lhs_var->data.precise == rhs_var->data.precise) {
	_mesa_hash_table_insert(acp, lhs_var, rhs_var);
	}
	}
	}

	/**
	* Does a copy propagation pass on the code present in the instruction stream.
	*/
	bool
	do_copy_propagation(exec_list *instructions)
	{
	ir_copy_propagation_visitor v;

	visit_list_elements(&v, instructions);

	return v.progress;
	}