src/mesa/drivers/dri/i965/brw_fs_live_variables.cpp - platform/external/mesa3d - Git at Google

 /*
  * Copyright © 2012 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.
  *
  * Authors:
  *    Eric Anholt <eric@anholt.net>
  *
  */

 #include "brw_cfg.h"
 #include "brw_fs_live_variables.h"

 using namespace brw;

 #define MAX_INSTRUCTION (1 << 30)

 /** @file brw_fs_live_variables.cpp
  *
  * Support for calculating liveness information about virtual GRFs.
  *
  * This produces a live interval for each whole virtual GRF.  We could
  * choose to expose per-component live intervals for VGRFs of size > 1,
  * but we currently do not.  It is easier for the consumers of this
  * information to work with whole VGRFs.
  *
  * However, we internally track use/def information at the per-GRF level for
  * greater accuracy.  Large VGRFs may be accessed piecemeal over many
  * (possibly non-adjacent) instructions.  In this case, examining a single
  * instruction is insufficient to decide whether a whole VGRF is ultimately
  * used or defined.  Tracking individual components allows us to easily
  * assemble this information.
  *
  * See Muchnick's Advanced Compiler Design and Implementation, section
  * 14.1 (p444).
  */

 void
 fs_live_variables::setup_one_read(struct block_data *bd, fs_inst *inst,
                                   int ip, const fs_reg &reg)
 {
    int var = var_from_reg(reg);
    assert(var < num_vars);

    start[var] = MIN2(start[var], ip);
    end[var] = MAX2(end[var], ip);

    /* The use[] bitset marks when the block makes use of a variable (VGRF
     * channel) without having completely defined that variable within the
     * block.
     */
    if (!BITSET_TEST(bd->def, var))
       BITSET_SET(bd->use, var);
 }

 void
 fs_live_variables::setup_one_write(struct block_data *bd, fs_inst *inst,
                                    int ip, const fs_reg &reg)
 {
    int var = var_from_reg(reg);
    assert(var < num_vars);

    start[var] = MIN2(start[var], ip);
    end[var] = MAX2(end[var], ip);

    /* The def[] bitset marks when an initialization in a block completely
     * screens off previous updates of that variable (VGRF channel).
     */
    if (inst->dst.file == VGRF && !inst->is_partial_write()) {
       if (!BITSET_TEST(bd->use, var))
          BITSET_SET(bd->def, var);
    }
 }

 /**
  * Sets up the use[] and def[] bitsets.
  *
  * The basic-block-level live variable analysis needs to know which
  * variables get used before they're completely defined, and which
  * variables are completely defined before they're used.
  *
  * These are tracked at the per-component level, rather than whole VGRFs.
  */
 void
 fs_live_variables::setup_def_use()
 {
    int ip = 0;

    foreach_block (block, cfg) {
       assert(ip == block->start_ip);
       if (block->num > 0)
 	 assert(cfg->blocks[block->num - 1]->end_ip == ip - 1);

       struct block_data *bd = &block_data[block->num];

       foreach_inst_in_block(fs_inst, inst, block) {
 	 /* Set use[] for this instruction */
 	 for (unsigned int i = 0; i < inst->sources; i++) {
             fs_reg reg = inst->src[i];

             if (reg.file != VGRF)
                continue;

             for (unsigned j = 0; j < regs_read(inst, i); j++) {
                setup_one_read(bd, inst, ip, reg);
                reg.offset += REG_SIZE;
             }
 	 }

          bd->flag_use[0] |= inst->flags_read(v->devinfo) & ~bd->flag_def[0];

          /* Set def[] for this instruction */
          if (inst->dst.file == VGRF) {
             fs_reg reg = inst->dst;
             for (unsigned j = 0; j < regs_written(inst); j++) {
                setup_one_write(bd, inst, ip, reg);
                reg.offset += REG_SIZE;
             }
 	 }

          if (!inst->predicate && inst->exec_size >= 8)
             bd->flag_def[0] |= inst->flags_written() & ~bd->flag_use[0];

 	 ip++;
       }
    }
 }

 /**
  * The algorithm incrementally sets bits in liveout and livein,
  * propagating it through control flow.  It will eventually terminate
  * because it only ever adds bits, and stops when no bits are added in
  * a pass.
  */
 void
 fs_live_variables::compute_live_variables()
 {
    bool cont = true;

    while (cont) {
       cont = false;

       foreach_block_reverse (block, cfg) {
          struct block_data *bd = &block_data[block->num];

 	 /* Update liveout */
 	 foreach_list_typed(bblock_link, child_link, link, &block->children) {
             struct block_data *child_bd = &block_data[child_link->block->num];

 	    for (int i = 0; i < bitset_words; i++) {
                BITSET_WORD new_liveout = (child_bd->livein[i] &
                                           ~bd->liveout[i]);
                if (new_liveout) {
                   bd->liveout[i] |= new_liveout;
                   cont = true;
                }
 	    }
             BITSET_WORD new_liveout = (child_bd->flag_livein[0] &
                                        ~bd->flag_liveout[0]);
             if (new_liveout) {
                bd->flag_liveout[0] |= new_liveout;
                cont = true;
             }
 	 }

          /* Update livein */
          for (int i = 0; i < bitset_words; i++) {
             BITSET_WORD new_livein = (bd->use[i] |
                                       (bd->liveout[i] &
                                        ~bd->def[i]));
             if (new_livein & ~bd->livein[i]) {
                bd->livein[i] |= new_livein;
                cont = true;
             }
          }
          BITSET_WORD new_livein = (bd->flag_use[0] |
                                    (bd->flag_liveout[0] &
                                     ~bd->flag_def[0]));
          if (new_livein & ~bd->flag_livein[0]) {
             bd->flag_livein[0] |= new_livein;
             cont = true;
          }
       }
    }
 }

 /**
  * Extend the start/end ranges for each variable to account for the
  * new information calculated from control flow.
  */
 void
 fs_live_variables::compute_start_end()
 {
    foreach_block (block, cfg) {
       struct block_data *bd = &block_data[block->num];

       for (int i = 0; i < num_vars; i++) {
          if (BITSET_TEST(bd->livein, i)) {
             start[i] = MIN2(start[i], block->start_ip);
             end[i] = MAX2(end[i], block->start_ip);
          }

          if (BITSET_TEST(bd->liveout, i)) {
             start[i] = MIN2(start[i], block->end_ip);
             end[i] = MAX2(end[i], block->end_ip);
          }
       }
    }
 }

 fs_live_variables::fs_live_variables(fs_visitor *v, const cfg_t *cfg)
    : v(v), cfg(cfg)
 {
    mem_ctx = ralloc_context(NULL);

    num_vgrfs = v->alloc.count;
    num_vars = 0;
    var_from_vgrf = rzalloc_array(mem_ctx, int, num_vgrfs);
    for (int i = 0; i < num_vgrfs; i++) {
       var_from_vgrf[i] = num_vars;
       num_vars += v->alloc.sizes[i];
    }

    vgrf_from_var = rzalloc_array(mem_ctx, int, num_vars);
    for (int i = 0; i < num_vgrfs; i++) {
       for (unsigned j = 0; j < v->alloc.sizes[i]; j++) {
          vgrf_from_var[var_from_vgrf[i] + j] = i;
       }
    }

    start = ralloc_array(mem_ctx, int, num_vars);
    end = rzalloc_array(mem_ctx, int, num_vars);
    for (int i = 0; i < num_vars; i++) {
       start[i] = MAX_INSTRUCTION;
       end[i] = -1;
    }

    block_data= rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks);

    bitset_words = BITSET_WORDS(num_vars);
    for (int i = 0; i < cfg->num_blocks; i++) {
       block_data[i].def = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);
       block_data[i].use = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);
       block_data[i].livein = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);
       block_data[i].liveout = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);

       block_data[i].flag_def[0] = 0;
       block_data[i].flag_use[0] = 0;
       block_data[i].flag_livein[0] = 0;
       block_data[i].flag_liveout[0] = 0;
    }

    setup_def_use();
    compute_live_variables();
    compute_start_end();
 }

 fs_live_variables::~fs_live_variables()
 {
    ralloc_free(mem_ctx);
 }

 void
 fs_visitor::invalidate_live_intervals()
 {
    ralloc_free(live_intervals);
    live_intervals = NULL;
 }

 /**
  * Compute the live intervals for each virtual GRF.
  *
  * This uses the per-component use/def data, but combines it to produce
  * information about whole VGRFs.
  */
 void
 fs_visitor::calculate_live_intervals()
 {
    if (this->live_intervals)
       return;

    int num_vgrfs = this->alloc.count;
    ralloc_free(this->virtual_grf_start);
    ralloc_free(this->virtual_grf_end);
    virtual_grf_start = ralloc_array(mem_ctx, int, num_vgrfs);
    virtual_grf_end = ralloc_array(mem_ctx, int, num_vgrfs);

    for (int i = 0; i < num_vgrfs; i++) {
       virtual_grf_start[i] = MAX_INSTRUCTION;
       virtual_grf_end[i] = -1;
    }

    this->live_intervals = new(mem_ctx) fs_live_variables(this, cfg);

    /* Merge the per-component live ranges to whole VGRF live ranges. */
    for (int i = 0; i < live_intervals->num_vars; i++) {
       int vgrf = live_intervals->vgrf_from_var[i];
       virtual_grf_start[vgrf] = MIN2(virtual_grf_start[vgrf],
                                      live_intervals->start[i]);
       virtual_grf_end[vgrf] = MAX2(virtual_grf_end[vgrf],
                                    live_intervals->end[i]);
    }
 }

 bool
 fs_live_variables::vars_interfere(int a, int b)
 {
    return !(end[b] <= start[a] ||
             end[a] <= start[b]);
 }

 bool
 fs_visitor::virtual_grf_interferes(int a, int b)
 {
    return !(virtual_grf_end[a] <= virtual_grf_start[b] ||
             virtual_grf_end[b] <= virtual_grf_start[a]);
 }
	/*
	* Copyright © 2012 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.
	*
	* Authors:
	* Eric Anholt <eric@anholt.net>
	*
	*/

	#include "brw_cfg.h"
	#include "brw_fs_live_variables.h"

	using namespace brw;

	#define MAX_INSTRUCTION (1 << 30)

	/** @file brw_fs_live_variables.cpp
	*
	* Support for calculating liveness information about virtual GRFs.
	*
	* This produces a live interval for each whole virtual GRF. We could
	* choose to expose per-component live intervals for VGRFs of size > 1,
	* but we currently do not. It is easier for the consumers of this
	* information to work with whole VGRFs.
	*
	* However, we internally track use/def information at the per-GRF level for
	* greater accuracy. Large VGRFs may be accessed piecemeal over many
	* (possibly non-adjacent) instructions. In this case, examining a single
	* instruction is insufficient to decide whether a whole VGRF is ultimately
	* used or defined. Tracking individual components allows us to easily
	* assemble this information.
	*
	* See Muchnick's Advanced Compiler Design and Implementation, section
	* 14.1 (p444).
	*/

	void
	fs_live_variables::setup_one_read(struct block_data bd, fs_inst inst,
	int ip, const fs_reg &reg)
	{
	int var = var_from_reg(reg);
	assert(var < num_vars);

	start[var] = MIN2(start[var], ip);
	end[var] = MAX2(end[var], ip);

	/* The use[] bitset marks when the block makes use of a variable (VGRF
	* channel) without having completely defined that variable within the
	* block.
	*/
	if (!BITSET_TEST(bd->def, var))
	BITSET_SET(bd->use, var);
	}

	void
	fs_live_variables::setup_one_write(struct block_data bd, fs_inst inst,
	int ip, const fs_reg &reg)
	{
	int var = var_from_reg(reg);
	assert(var < num_vars);

	start[var] = MIN2(start[var], ip);
	end[var] = MAX2(end[var], ip);

	/* The def[] bitset marks when an initialization in a block completely
	* screens off previous updates of that variable (VGRF channel).
	*/
	if (inst->dst.file == VGRF && !inst->is_partial_write()) {
	if (!BITSET_TEST(bd->use, var))
	BITSET_SET(bd->def, var);
	}
	}

	/**
	* Sets up the use[] and def[] bitsets.
	*
	* The basic-block-level live variable analysis needs to know which
	* variables get used before they're completely defined, and which
	* variables are completely defined before they're used.
	*
	* These are tracked at the per-component level, rather than whole VGRFs.
	*/
	void
	fs_live_variables::setup_def_use()
	{
	int ip = 0;

	foreach_block (block, cfg) {
	assert(ip == block->start_ip);
	if (block->num > 0)
	assert(cfg->blocks[block->num - 1]->end_ip == ip - 1);

	struct block_data *bd = &block_data[block->num];

	foreach_inst_in_block(fs_inst, inst, block) {
	/* Set use[] for this instruction */
	for (unsigned int i = 0; i < inst->sources; i++) {
	fs_reg reg = inst->src[i];

	if (reg.file != VGRF)
	continue;

	for (unsigned j = 0; j < regs_read(inst, i); j++) {
	setup_one_read(bd, inst, ip, reg);
	reg.offset += REG_SIZE;
	}
	}

	bd->flag_use[0] \|= inst->flags_read(v->devinfo) & ~bd->flag_def[0];

	/* Set def[] for this instruction */
	if (inst->dst.file == VGRF) {
	fs_reg reg = inst->dst;
	for (unsigned j = 0; j < regs_written(inst); j++) {
	setup_one_write(bd, inst, ip, reg);
	reg.offset += REG_SIZE;
	}
	}

	if (!inst->predicate && inst->exec_size >= 8)
	bd->flag_def[0] \|= inst->flags_written() & ~bd->flag_use[0];

	ip++;
	}
	}
	}

	/**
	* The algorithm incrementally sets bits in liveout and livein,
	* propagating it through control flow. It will eventually terminate
	* because it only ever adds bits, and stops when no bits are added in
	* a pass.
	*/
	void
	fs_live_variables::compute_live_variables()
	{
	bool cont = true;

	while (cont) {
	cont = false;

	foreach_block_reverse (block, cfg) {
	struct block_data *bd = &block_data[block->num];

	/* Update liveout */
	foreach_list_typed(bblock_link, child_link, link, &block->children) {
	struct block_data *child_bd = &block_data[child_link->block->num];

	for (int i = 0; i < bitset_words; i++) {
	BITSET_WORD new_liveout = (child_bd->livein[i] &
	~bd->liveout[i]);
	if (new_liveout) {
	bd->liveout[i] \|= new_liveout;
	cont = true;
	}
	}
	BITSET_WORD new_liveout = (child_bd->flag_livein[0] &
	~bd->flag_liveout[0]);
	if (new_liveout) {
	bd->flag_liveout[0] \|= new_liveout;
	cont = true;
	}
	}

	/* Update livein */
	for (int i = 0; i < bitset_words; i++) {
	BITSET_WORD new_livein = (bd->use[i] \|
	(bd->liveout[i] &
	~bd->def[i]));
	if (new_livein & ~bd->livein[i]) {
	bd->livein[i] \|= new_livein;
	cont = true;
	}
	}
	BITSET_WORD new_livein = (bd->flag_use[0] \|
	(bd->flag_liveout[0] &
	~bd->flag_def[0]));
	if (new_livein & ~bd->flag_livein[0]) {
	bd->flag_livein[0] \|= new_livein;
	cont = true;
	}
	}
	}
	}

	/**
	* Extend the start/end ranges for each variable to account for the
	* new information calculated from control flow.
	*/
	void
	fs_live_variables::compute_start_end()
	{
	foreach_block (block, cfg) {
	struct block_data *bd = &block_data[block->num];

	for (int i = 0; i < num_vars; i++) {
	if (BITSET_TEST(bd->livein, i)) {
	start[i] = MIN2(start[i], block->start_ip);
	end[i] = MAX2(end[i], block->start_ip);
	}

	if (BITSET_TEST(bd->liveout, i)) {
	start[i] = MIN2(start[i], block->end_ip);
	end[i] = MAX2(end[i], block->end_ip);
	}
	}
	}
	}

	fs_live_variables::fs_live_variables(fs_visitor v, const cfg_t cfg)
	: v(v), cfg(cfg)
	{
	mem_ctx = ralloc_context(NULL);

	num_vgrfs = v->alloc.count;
	num_vars = 0;
	var_from_vgrf = rzalloc_array(mem_ctx, int, num_vgrfs);
	for (int i = 0; i < num_vgrfs; i++) {
	var_from_vgrf[i] = num_vars;
	num_vars += v->alloc.sizes[i];
	}

	vgrf_from_var = rzalloc_array(mem_ctx, int, num_vars);
	for (int i = 0; i < num_vgrfs; i++) {
	for (unsigned j = 0; j < v->alloc.sizes[i]; j++) {
	vgrf_from_var[var_from_vgrf[i] + j] = i;
	}
	}

	start = ralloc_array(mem_ctx, int, num_vars);
	end = rzalloc_array(mem_ctx, int, num_vars);
	for (int i = 0; i < num_vars; i++) {
	start[i] = MAX_INSTRUCTION;
	end[i] = -1;
	}

	block_data= rzalloc_array(mem_ctx, struct block_data, cfg->num_blocks);

	bitset_words = BITSET_WORDS(num_vars);
	for (int i = 0; i < cfg->num_blocks; i++) {
	block_data[i].def = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);
	block_data[i].use = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);
	block_data[i].livein = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);
	block_data[i].liveout = rzalloc_array(mem_ctx, BITSET_WORD, bitset_words);

	block_data[i].flag_def[0] = 0;
	block_data[i].flag_use[0] = 0;
	block_data[i].flag_livein[0] = 0;
	block_data[i].flag_liveout[0] = 0;
	}

	setup_def_use();
	compute_live_variables();
	compute_start_end();
	}

	fs_live_variables::~fs_live_variables()
	{
	ralloc_free(mem_ctx);
	}

	void
	fs_visitor::invalidate_live_intervals()
	{
	ralloc_free(live_intervals);
	live_intervals = NULL;
	}

	/**
	* Compute the live intervals for each virtual GRF.
	*
	* This uses the per-component use/def data, but combines it to produce
	* information about whole VGRFs.
	*/
	void
	fs_visitor::calculate_live_intervals()
	{
	if (this->live_intervals)
	return;

	int num_vgrfs = this->alloc.count;
	ralloc_free(this->virtual_grf_start);
	ralloc_free(this->virtual_grf_end);
	virtual_grf_start = ralloc_array(mem_ctx, int, num_vgrfs);
	virtual_grf_end = ralloc_array(mem_ctx, int, num_vgrfs);

	for (int i = 0; i < num_vgrfs; i++) {
	virtual_grf_start[i] = MAX_INSTRUCTION;
	virtual_grf_end[i] = -1;
	}

	this->live_intervals = new(mem_ctx) fs_live_variables(this, cfg);

	/* Merge the per-component live ranges to whole VGRF live ranges. */
	for (int i = 0; i < live_intervals->num_vars; i++) {
	int vgrf = live_intervals->vgrf_from_var[i];
	virtual_grf_start[vgrf] = MIN2(virtual_grf_start[vgrf],
	live_intervals->start[i]);
	virtual_grf_end[vgrf] = MAX2(virtual_grf_end[vgrf],
	live_intervals->end[i]);
	}
	}

	bool
	fs_live_variables::vars_interfere(int a, int b)
	{
	return !(end[b] <= start[a] \|\|
	end[a] <= start[b]);
	}

	bool
	fs_visitor::virtual_grf_interferes(int a, int b)
	{
	return !(virtual_grf_end[a] <= virtual_grf_start[b] \|\|
	virtual_grf_end[b] <= virtual_grf_start[a]);
	}