r300/compiler/radeon_variable.c

/*
 * Copyright 2011 Tom Stellard <tstellar@gmail.com>
 * SPDX-License-Identifier: MIT
 */

#include "radeon_variable.h"
#include <stdio.h>
#include <stdlib.h>

#include "memory_pool.h"
#include "radeon_compiler_util.h"
#include "radeon_dataflow.h"
#include "radeon_list.h"
#include "radeon_opcodes.h"
#include "radeon_program.h"

/**
 * Rewrite the index and writemask for the destination register of var
 * and its friends to new_index and new_writemask.  This function also takes
 * care of rewriting the swizzles for the sources of var.
 */
void
rc_variable_change_dst(struct rc_variable *var, unsigned int new_index, unsigned int new_writemask)
{
   struct rc_variable *var_ptr;
   struct rc_list *readers;
   unsigned int old_mask = rc_variable_writemask_sum(var);
   unsigned int conversion_swizzle = rc_make_conversion_swizzle(old_mask, new_writemask);

   for (var_ptr = var; var_ptr; var_ptr = var_ptr->Friend) {
      if (var_ptr->Inst->Type == RC_INSTRUCTION_NORMAL) {
         rc_normal_rewrite_writemask(var_ptr->Inst, conversion_swizzle);
         var_ptr->Inst->U.I.DstReg.Index = new_index;
      } else {
         struct rc_pair_sub_instruction *sub;
         if (var_ptr->Dst.WriteMask == RC_MASK_W) {
            assert(new_writemask & RC_MASK_W);
            sub = &var_ptr->Inst->U.P.Alpha;
         } else {
            sub = &var_ptr->Inst->U.P.RGB;
            rc_pair_rewrite_writemask(sub, conversion_swizzle);
         }
         sub->DestIndex = new_index;
      }
   }

   readers = rc_variable_readers_union(var);

   for (; readers; readers = readers->Next) {
      struct rc_reader *reader = readers->Item;
      if (reader->Inst->Type == RC_INSTRUCTION_NORMAL) {
         reader->U.I.Src->Index = new_index;
         reader->U.I.Src->Swizzle =
            rc_rewrite_swizzle(reader->U.I.Src->Swizzle, conversion_swizzle);
      } else {
         struct rc_pair_instruction *pair_inst = &reader->Inst->U.P;
         unsigned int src_type = rc_source_type_swz(reader->U.P.Arg->Swizzle);

         int src_index = reader->U.P.Arg->Source;
         if (src_index == RC_PAIR_PRESUB_SRC) {
            src_index = rc_pair_get_src_index(pair_inst, reader->U.P.Src);
         }
         rc_pair_remove_src(reader->Inst, src_type, src_index);
         /* Reuse the source index of the source that
          * was just deleted and set its register
          * index.  We can't use rc_pair_alloc_source
          * for this because it might return a source
          * index that is already being used. */
         if (src_type & RC_SOURCE_RGB) {
            pair_inst->RGB.Src[src_index].Used = 1;
            pair_inst->RGB.Src[src_index].Index = new_index;
            pair_inst->RGB.Src[src_index].File = RC_FILE_TEMPORARY;
         }
         if (src_type & RC_SOURCE_ALPHA) {
            pair_inst->Alpha.Src[src_index].Used = 1;
            pair_inst->Alpha.Src[src_index].Index = new_index;
            pair_inst->Alpha.Src[src_index].File = RC_FILE_TEMPORARY;
         }
         reader->U.P.Arg->Swizzle =
            rc_rewrite_swizzle(reader->U.P.Arg->Swizzle, conversion_swizzle);
         if (reader->U.P.Arg->Source != RC_PAIR_PRESUB_SRC) {
            reader->U.P.Arg->Source = src_index;
         }
      }
   }
}

/**
 * Compute the live intervals for var and its friends.
 */
void
rc_variable_compute_live_intervals(struct rc_variable *var)
{
   while (var) {
      unsigned int i;
      unsigned int start = var->Inst->IP;

      for (i = 0; i < var->ReaderCount; i++) {
         unsigned int chan;
         unsigned int chan_start = start;
         unsigned int chan_end = var->Readers[i].Inst->IP;
         unsigned int mask = var->Readers[i].WriteMask;
         struct rc_instruction *inst;

         /* Extend the live interval of T0 to the start of the
          * loop for sequences like:
          * BGNLOOP
          * read T0
          * ...
          * write T0
          * ENDLOOP
          */
         if (var->Readers[i].Inst->IP < start) {
            struct rc_instruction *bgnloop = rc_match_endloop(var->Readers[i].Inst);
            chan_start = bgnloop->IP;
         }

         /* Extend the live interval of T0 to the start of the
          * loop in case there is a BRK instruction in the loop
          * (we don't actually check for a BRK instruction we
          * assume there is one somewhere in the loop, which
          * there usually is) for sequences like:
          * BGNLOOP
          * ...
          * conditional BRK
          * ...
          * write T0
          * ENDLOOP
          * read T0
          ***************************************************
          * Extend the live interval of T0 to the end of the
          * loop for sequences like:
          * write T0
          * BGNLOOP
          * ...
          * read T0
          * ENDLOOP
          */
         for (inst = var->Inst; inst != var->Readers[i].Inst; inst = inst->Next) {
            rc_opcode op = rc_get_flow_control_inst(inst);
            if (op == RC_OPCODE_ENDLOOP) {
               struct rc_instruction *bgnloop = rc_match_endloop(inst);
               if (bgnloop->IP < chan_start) {
                  chan_start = bgnloop->IP;
               }
            } else if (op == RC_OPCODE_BGNLOOP) {
               struct rc_instruction *endloop = rc_match_bgnloop(inst);
               if (endloop->IP > chan_end) {
                  chan_end = endloop->IP;
               }
            }
         }

         for (chan = 0; chan < 4; chan++) {
            if ((mask >> chan) & 0x1) {
               if (!var->Live[chan].Used || chan_start < var->Live[chan].Start) {
                  var->Live[chan].Start = chan_start;
               }
               if (!var->Live[chan].Used || chan_end > var->Live[chan].End) {
                  var->Live[chan].End = chan_end;
               }
               var->Live[chan].Used = 1;
            }
         }
      }
      var = var->Friend;
   }
}

/**
 * @return 1 if a and b share a reader
 * @return 0 if they do not
 */
static unsigned int
readers_intersect(struct rc_variable *a, struct rc_variable *b)
{
   unsigned int a_index, b_index;
   for (a_index = 0; a_index < a->ReaderCount; a_index++) {
      struct rc_reader reader_a = a->Readers[a_index];
      for (b_index = 0; b_index < b->ReaderCount; b_index++) {
         struct rc_reader reader_b = b->Readers[b_index];
         if (reader_a.Inst->Type == RC_INSTRUCTION_NORMAL &&
             reader_b.Inst->Type == RC_INSTRUCTION_NORMAL && reader_a.U.I.Src == reader_b.U.I.Src) {

            return 1;
         }
         if (reader_a.Inst->Type == RC_INSTRUCTION_PAIR &&
             reader_b.Inst->Type == RC_INSTRUCTION_PAIR && reader_a.U.P.Src == reader_b.U.P.Src) {

            return 1;
         }
      }
   }
   return 0;
}

void
rc_variable_add_friend(struct rc_variable *var, struct rc_variable *friend)
{
   assert(var->Dst.Index == friend->Dst.Index);
   while (var->Friend) {
      var = var->Friend;
   }
   var->Friend = friend;
}

struct rc_variable *
rc_variable(struct radeon_compiler *c, unsigned int DstFile, unsigned int DstIndex,
            unsigned int DstWriteMask, struct rc_reader_data *reader_data)
{
   struct rc_variable *new = memory_pool_malloc(&c->Pool, sizeof(struct rc_variable));
   memset(new, 0, sizeof(struct rc_variable));
   new->C = c;
   new->Dst.File = DstFile;
   new->Dst.Index = DstIndex;
   new->Dst.WriteMask = DstWriteMask;
   if (reader_data) {
      new->Inst = reader_data->Writer;
      new->ReaderCount = reader_data->ReaderCount;
      new->Readers = reader_data->Readers;
   }
   return new;
}

static void
get_variable_helper(struct rc_list **variable_list, struct rc_variable *variable)
{
   struct rc_list *list_ptr;
   for (list_ptr = *variable_list; list_ptr; list_ptr = list_ptr->Next) {
      struct rc_variable *var;
      for (var = list_ptr->Item; var; var = var->Friend) {
         if (readers_intersect(var, variable)) {
            rc_variable_add_friend(var, variable);
            return;
         }
      }
   }
   rc_list_add(variable_list, rc_list(&variable->C->Pool, variable));
}

static void
get_variable_pair_helper(struct rc_list **variable_list, struct radeon_compiler *c,
                         struct rc_instruction *inst, struct rc_pair_sub_instruction *sub_inst)
{
   struct rc_reader_data reader_data;
   struct rc_variable *new_var;
   rc_register_file file;
   unsigned int writemask;

   if (sub_inst->Opcode == RC_OPCODE_NOP) {
      return;
   }
   memset(&reader_data, 0, sizeof(struct rc_reader_data));
   rc_get_readers_sub(c, inst, sub_inst, &reader_data, NULL, NULL, NULL);

   if (reader_data.ReaderCount == 0) {
      return;
   }

   if (sub_inst->WriteMask) {
      file = RC_FILE_TEMPORARY;
      writemask = sub_inst->WriteMask;
   } else if (sub_inst->OutputWriteMask) {
      file = RC_FILE_OUTPUT;
      writemask = sub_inst->OutputWriteMask;
   } else {
      writemask = 0;
      file = RC_FILE_NONE;
   }
   new_var = rc_variable(c, file, sub_inst->DestIndex, writemask, &reader_data);
   get_variable_helper(variable_list, new_var);
}

/**
 * Compare function for sorting variable pointers by the lowest instruction
 * IP from it and its friends.
 */
static int
cmpfunc_variable_by_ip(const void *a, const void *b)
{
   struct rc_variable *var_a = *(struct rc_variable **)a;
   struct rc_variable *var_b = *(struct rc_variable **)b;
   unsigned int min_ip_a = var_a->Inst->IP;
   unsigned int min_ip_b = var_b->Inst->IP;

   /* Find the minimal IP of a variable and its friends */
   while (var_a->Friend) {
      var_a = var_a->Friend;
      if (var_a->Inst->IP < min_ip_a)
         min_ip_a = var_a->Inst->IP;
   }
   while (var_b->Friend) {
      var_b = var_b->Friend;
      if (var_b->Inst->IP < min_ip_b)
         min_ip_b = var_b->Inst->IP;
   }

   return (int)min_ip_a - (int)min_ip_b;
}

/**
 * Generate a list of variables used by the shader program.  Each instruction
 * that writes to a register is considered a variable.  The struct rc_variable
 * data structure includes a list of readers and is essentially a
 * definition-use chain.  Any two variables that share a reader are considered
 * "friends" and they are linked together via the Friend attribute.
 */
struct rc_list *
rc_get_variables(struct radeon_compiler *c)
{
   struct rc_instruction *inst;
   struct rc_list *variable_list = NULL;

   /* We search for the variables in two loops in order to get it right in
    * the following specific case
    *
    * IF aluresult.x___;
    *   ...
    *   MAD temp[0].xyz, src0.000, src0.111, src0.000
    *   MAD temp[0].w, src0.0, src0.1, src0.0
    * ELSE;
    *   ...
    *   TXB temp[0], temp[1].xy_w, 2D[0] SEM_WAIT SEM_ACQUIRE;
    * ENDIF;
    * src0.xyz = input[0], src0.w = input[0], src1.xyz = temp[0], src1.w = temp[0] SEM_WAIT
    * MAD temp[1].xyz, src0.xyz, src1.xyz, src0.000
    * MAD temp[1].w, src0.w, src1.w, src0.0
    *
    * If we go just in one loop, we will first create two variables for the
    * temp[0].xyz and temp[0].w. This happens because they don't share a reader
    * as the src1.xyz and src1.w of the instruction where the value is used are
    * in theory independent. They are not because the same register is written
    * also by the texture instruction in the other branch and TEX can't write xyz
    * and w separately.
    *
    * Therefore first search for RC_INSTRUCTION_NORMAL to create variables from
    * the texture instruction and than the pair instructions will be properly
    * marked as friends. So we will end with only one variable here as we should.
    *
    * This doesn't matter before the pair translation, because everything is
    * RC_INSTRUCTION_NORMAL.
    */
   for (inst = c->Program.Instructions.Next; inst != &c->Program.Instructions; inst = inst->Next) {
      if (inst->Type == RC_INSTRUCTION_NORMAL) {
         struct rc_reader_data reader_data;
         struct rc_variable *new_var;
         memset(&reader_data, 0, sizeof(reader_data));
         rc_get_readers(c, inst, &reader_data, NULL, NULL, NULL);
         if (reader_data.ReaderCount == 0) {
            /* Variable is only returned if there is both writer
             * and reader. This means dead writes will not get
             * register allocated as a result and can overwrite random
             * registers. Assert on dead writes instead so we can improve
             * the DCE.
             */
            const struct rc_opcode_info *opcode = rc_get_opcode_info(inst->U.I.Opcode);
            assert(c->type == RC_FRAGMENT_PROGRAM || !opcode->HasDstReg ||
                   inst->U.I.DstReg.File == RC_FILE_OUTPUT ||
                   inst->U.I.DstReg.File == RC_FILE_ADDRESS);
            continue;
         }
         new_var = rc_variable(c, inst->U.I.DstReg.File, inst->U.I.DstReg.Index,
                               inst->U.I.DstReg.WriteMask, &reader_data);
         get_variable_helper(&variable_list, new_var);
      }
   }

   bool needs_sorting = false;
   for (inst = c->Program.Instructions.Next; inst != &c->Program.Instructions; inst = inst->Next) {
      if (inst->Type != RC_INSTRUCTION_NORMAL) {
         needs_sorting = true;
         get_variable_pair_helper(&variable_list, c, inst, &inst->U.P.RGB);
         get_variable_pair_helper(&variable_list, c, inst, &inst->U.P.Alpha);
      }
   }

   if (variable_list && needs_sorting) {
      unsigned int count = rc_list_count(variable_list);
      struct rc_variable **variables =
         memory_pool_malloc(&c->Pool, sizeof(struct rc_variable *) * count);

      struct rc_list *current = variable_list;
      for (unsigned int i = 0; current; i++, current = current->Next) {
         struct rc_variable *var = current->Item;
         variables[i] = var;
      }

      qsort(variables, count, sizeof(struct rc_variable *), cmpfunc_variable_by_ip);

      current = variable_list;
      for (unsigned int i = 0; current; i++, current = current->Next) {
         current->Item = variables[i];
      }
   }

   return variable_list;
}

/**
 * @return The bitwise or of the writemasks of a variable and all of its
 * friends.
 */
unsigned int
rc_variable_writemask_sum(struct rc_variable *var)
{
   unsigned int writemask = 0;
   while (var) {
      writemask |= var->Dst.WriteMask;
      var = var->Friend;
   }
   return writemask;
}

/*
 * @return A list of readers for a variable and its friends.  Readers
 * that read from two different variable friends are only included once in
 * this list.
 */
struct rc_list *
rc_variable_readers_union(struct rc_variable *var)
{
   struct rc_list *list = NULL;
   while (var) {
      unsigned int i;
      for (i = 0; i < var->ReaderCount; i++) {
         struct rc_list *temp;
         struct rc_reader *a = &var->Readers[i];
         unsigned int match = 0;
         for (temp = list; temp; temp = temp->Next) {
            struct rc_reader *b = temp->Item;
            if (a->Inst->Type != b->Inst->Type) {
               continue;
            }
            if (a->Inst->Type == RC_INSTRUCTION_NORMAL) {
               if (a->U.I.Src == b->U.I.Src) {
                  match = 1;
                  break;
               }
            }
            if (a->Inst->Type == RC_INSTRUCTION_PAIR) {
               if (a->U.P.Arg == b->U.P.Arg && a->U.P.Src == b->U.P.Src) {
                  match = 1;
                  break;
               }
            }
         }
         if (match) {
            continue;
         }
         rc_list_add(&list, rc_list(&var->C->Pool, a));
      }
      var = var->Friend;
   }
   return list;
}

static unsigned int
reader_equals_src(struct rc_reader reader, unsigned int src_type, void *src)
{
   if (reader.Inst->Type != src_type) {
      return 0;
   }
   if (src_type == RC_INSTRUCTION_NORMAL) {
      return reader.U.I.Src == src;
   } else {
      return reader.U.P.Src == src;
   }
}

static unsigned int
variable_writes_src(struct rc_variable *var, unsigned int src_type, void *src)
{
   unsigned int i;
   for (i = 0; i < var->ReaderCount; i++) {
      if (reader_equals_src(var->Readers[i], src_type, src)) {
         return 1;
      }
   }
   return 0;
}

struct rc_list *
rc_variable_list_get_writers(struct rc_list *var_list, unsigned int src_type, void *src)
{
   struct rc_list *list_ptr;
   struct rc_list *writer_list = NULL;
   for (list_ptr = var_list; list_ptr; list_ptr = list_ptr->Next) {
      struct rc_variable *var = list_ptr->Item;
      if (variable_writes_src(var, src_type, src)) {
         struct rc_variable *friend;
         rc_list_add(&writer_list, rc_list(&var->C->Pool, var));
         for (friend = var->Friend; friend; friend = friend->Friend) {
            if (variable_writes_src(friend, src_type, src)) {
               rc_list_add(&writer_list, rc_list(&var->C->Pool, friend));
            }
         }
         /* Once we have identified the variable and its
          * friends that write this source, we can stop
          * stop searching, because we know none of the
          * other variables in the list will write this source.
          * If they did they would be friends of var.
          */
         break;
      }
   }
   return writer_list;
}

struct rc_list *
rc_variable_list_get_writers_one_reader(struct rc_list *var_list, unsigned int src_type, void *src)
{
   struct rc_list *writer_list = rc_variable_list_get_writers(var_list, src_type, src);
   struct rc_list *reader_list = rc_variable_readers_union(writer_list->Item);
   if (rc_list_count(reader_list) > 1) {
      return NULL;
   } else {
      return writer_list;
   }
}

void
rc_variable_print(struct rc_variable *var)
{
   unsigned int i;
   while (var) {
      fprintf(stderr, "%u: TEMP[%u].%u: ", var->Inst->IP, var->Dst.Index, var->Dst.WriteMask);
      for (i = 0; i < 4; i++) {
         fprintf(stderr, "chan %u: start=%u end=%u ", i, var->Live[i].Start, var->Live[i].End);
      }
      fprintf(stderr, "%u readers\n", var->ReaderCount);
      if (var->Friend) {
         fprintf(stderr, "Friend: \n\t");
      }
      var = var->Friend;
   }
}