path: root/src/mesa/drivers/dri/i965/brw_vec4.cpp

/*
 * Copyright © 2011 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 "brw_vec4.h"
extern "C" {
#include "main/macros.h"
#include "program/prog_parameter.h"
}

#define MAX_INSTRUCTION (1 << 30)

namespace brw {

void
vec4_visitor::calculate_live_intervals()
{
   int *def = ralloc_array(mem_ctx, int, virtual_grf_count);
   int *use = ralloc_array(mem_ctx, int, virtual_grf_count);
   int loop_depth = 0;
   int loop_start = 0;

   if (this->live_intervals_valid)
      return;

   for (int i = 0; i < virtual_grf_count; i++) {
      def[i] = MAX_INSTRUCTION;
      use[i] = -1;
   }

   int ip = 0;
   foreach_list(node, &this->instructions) {
      vec4_instruction *inst = (vec4_instruction *)node;

      if (inst->opcode == BRW_OPCODE_DO) {
	 if (loop_depth++ == 0)
	    loop_start = ip;
      } else if (inst->opcode == BRW_OPCODE_WHILE) {
	 loop_depth--;

	 if (loop_depth == 0) {
	    /* Patches up the use of vars marked for being live across
	     * the whole loop.
	     */
	    for (int i = 0; i < virtual_grf_count; i++) {
	       if (use[i] == loop_start) {
		  use[i] = ip;
	       }
	    }
	 }
      } else {
	 for (unsigned int i = 0; i < 3; i++) {
	    if (inst->src[i].file == GRF) {
	       int reg = inst->src[i].reg;

	       if (!loop_depth) {
		  use[reg] = ip;
	       } else {
		  def[reg] = MIN2(loop_start, def[reg]);
		  use[reg] = loop_start;

		  /* Nobody else is going to go smash our start to
		   * later in the loop now, because def[reg] now
		   * points before the bb header.
		   */
	       }
	    }
	 }
	 if (inst->dst.file == GRF) {
	    int reg = inst->dst.reg;

	    if (!loop_depth) {
	       def[reg] = MIN2(def[reg], ip);
	    } else {
	       def[reg] = MIN2(def[reg], loop_start);
	    }
	 }
      }

      ip++;
   }

   ralloc_free(this->virtual_grf_def);
   ralloc_free(this->virtual_grf_use);
   this->virtual_grf_def = def;
   this->virtual_grf_use = use;

   this->live_intervals_valid = true;
}

bool
vec4_visitor::virtual_grf_interferes(int a, int b)
{
   int start = MAX2(this->virtual_grf_def[a], this->virtual_grf_def[b]);
   int end = MIN2(this->virtual_grf_use[a], this->virtual_grf_use[b]);

   /* We can't handle dead register writes here, without iterating
    * over the whole instruction stream to find every single dead
    * write to that register to compare to the live interval of the
    * other register.  Just assert that dead_code_eliminate() has been
    * called.
    */
   assert((this->virtual_grf_use[a] != -1 ||
	   this->virtual_grf_def[a] == MAX_INSTRUCTION) &&
	  (this->virtual_grf_use[b] != -1 ||
	   this->virtual_grf_def[b] == MAX_INSTRUCTION));

   return start < end;
}

/**
 * Must be called after calculate_live_intervales() to remove unused
 * writes to registers -- register allocation will fail otherwise
 * because something deffed but not used won't be considered to
 * interfere with other regs.
 */
bool
vec4_visitor::dead_code_eliminate()
{
   bool progress = false;
   int pc = 0;

   calculate_live_intervals();

   foreach_list_safe(node, &this->instructions) {
      vec4_instruction *inst = (vec4_instruction *)node;

      if (inst->dst.file == GRF && this->virtual_grf_use[inst->dst.reg] <= pc) {
	 inst->remove();
	 progress = true;
      }

      pc++;
   }

   if (progress)
      live_intervals_valid = false;

   return progress;
}

void
vec4_visitor::split_uniform_registers()
{
   /* Prior to this, uniforms have been in an array sized according to
    * the number of vector uniforms present, sparsely filled (so an
    * aggregate results in reg indices being skipped over).  Now we're
    * going to cut those aggregates up so each .reg index is one
    * vector.  The goal is to make elimination of unused uniform
    * components easier later.
    */
   foreach_list(node, &this->instructions) {
      vec4_instruction *inst = (vec4_instruction *)node;

      for (int i = 0 ; i < 3; i++) {
	 if (inst->src[i].file != UNIFORM)
	    continue;

	 assert(!inst->src[i].reladdr);

	 inst->src[i].reg += inst->src[i].reg_offset;
	 inst->src[i].reg_offset = 0;
      }
   }

   /* Update that everything is now vector-sized. */
   for (int i = 0; i < this->uniforms; i++) {
      this->uniform_size[i] = 1;
   }
}

void
vec4_visitor::pack_uniform_registers()
{
   bool uniform_used[this->uniforms];
   int new_loc[this->uniforms];
   int new_chan[this->uniforms];

   memset(uniform_used, 0, sizeof(uniform_used));
   memset(new_loc, 0, sizeof(new_loc));
   memset(new_chan, 0, sizeof(new_chan));

   /* Find which uniform vectors are actually used by the program.  We
    * expect unused vector elements when we've moved array access out
    * to pull constants, and from some GLSL code generators like wine.
    */
   foreach_list(node, &this->instructions) {
      vec4_instruction *inst = (vec4_instruction *)node;

      for (int i = 0 ; i < 3; i++) {
	 if (inst->src[i].file != UNIFORM)
	    continue;

	 uniform_used[inst->src[i].reg] = true;
      }
   }

   int new_uniform_count = 0;

   /* Now, figure out a packing of the live uniform vectors into our
    * push constants.
    */
   for (int src = 0; src < uniforms; src++) {
      int size = this->uniform_vector_size[src];

      if (!uniform_used[src]) {
	 this->uniform_vector_size[src] = 0;
	 continue;
      }

      int dst;
      /* Find the lowest place we can slot this uniform in. */
      for (dst = 0; dst < src; dst++) {
	 if (this->uniform_vector_size[dst] + size <= 4)
	    break;
      }

      if (src == dst) {
	 new_loc[src] = dst;
	 new_chan[src] = 0;
      } else {
	 new_loc[src] = dst;
	 new_chan[src] = this->uniform_vector_size[dst];

	 /* Move the references to the data */
	 for (int j = 0; j < size; j++) {
	    c->prog_data.param[dst * 4 + new_chan[src] + j] =
	       c->prog_data.param[src * 4 + j];
	 }

	 this->uniform_vector_size[dst] += size;
	 this->uniform_vector_size[src] = 0;
      }

      new_uniform_count = MAX2(new_uniform_count, dst + 1);
   }

   this->uniforms = new_uniform_count;

   /* Now, update the instructions for our repacked uniforms. */
   foreach_list(node, &this->instructions) {
      vec4_instruction *inst = (vec4_instruction *)node;

      for (int i = 0 ; i < 3; i++) {
	 int src = inst->src[i].reg;

	 if (inst->src[i].file != UNIFORM)
	    continue;

	 inst->src[i].reg = new_loc[src];

	 int sx = BRW_GET_SWZ(inst->src[i].swizzle, 0) + new_chan[src];
	 int sy = BRW_GET_SWZ(inst->src[i].swizzle, 1) + new_chan[src];
	 int sz = BRW_GET_SWZ(inst->src[i].swizzle, 2) + new_chan[src];
	 int sw = BRW_GET_SWZ(inst->src[i].swizzle, 3) + new_chan[src];
	 inst->src[i].swizzle = BRW_SWIZZLE4(sx, sy, sz, sw);
      }
   }
}

} /* namespace brw */