/*
 * Copyright 2012 Advanced Micro Devices, Inc.
 * Author: Tom Stellard <thomas.stellard@amd.com>
 * SPDX-License-Identifier: MIT
 */

#include "radeon_compiler.h"
#include "radeon_compiler_util.h"
#include "radeon_dataflow.h"
#include "radeon_program.h"
#include "radeon_program_constants.h"

struct vert_fc_state {
   struct radeon_compiler *C;
   unsigned BranchDepth;
   unsigned LoopDepth;
   unsigned LoopsReserved;
   int PredStack[R500_PVS_MAX_LOOP_DEPTH];
   int PredicateReg;
};

static void
build_pred_src(struct rc_src_register *src, struct vert_fc_state *fc_state)
{
   src->Swizzle =
      RC_MAKE_SWIZZLE(RC_SWIZZLE_UNUSED, RC_SWIZZLE_UNUSED, RC_SWIZZLE_UNUSED, RC_SWIZZLE_W);
   src->File = RC_FILE_TEMPORARY;
   src->Index = fc_state->PredicateReg;
}

static void
build_pred_dst(struct rc_dst_register *dst, struct vert_fc_state *fc_state)
{
   dst->WriteMask = RC_MASK_W;
   dst->File = RC_FILE_TEMPORARY;
   dst->Index = fc_state->PredicateReg;
}

static void
mark_write(void *userdata, struct rc_instruction *inst, rc_register_file file, unsigned int index,
           unsigned int mask)
{
   unsigned int *writemasks = userdata;

   if (file != RC_FILE_TEMPORARY)
      return;

   if (index >= R300_VS_MAX_TEMPS)
      return;

   writemasks[index] |= mask;
}

static int
reserve_predicate_reg(struct vert_fc_state *fc_state)
{
   int i;
   unsigned int writemasks[RC_REGISTER_MAX_INDEX];
   struct rc_instruction *inst;
   memset(writemasks, 0, sizeof(writemasks));
   for (inst = fc_state->C->Program.Instructions.Next; inst != &fc_state->C->Program.Instructions;
        inst = inst->Next) {
      rc_for_all_writes_mask(inst, mark_write, writemasks);
   }

   for (i = 0; i < fc_state->C->max_temp_regs; i++) {
      /* Most of the control flow instructions only write the
       * W component of the Predicate Register, but
       * the docs say that ME_PRED_SET_CLR and
       * ME_PRED_SET_RESTORE write all components of the
       * register, so we must reserve a register that has
       * all its components free. */
      if (!writemasks[i]) {
         fc_state->PredicateReg = i;
         break;
      }
   }
   if (i == fc_state->C->max_temp_regs) {
      rc_error(fc_state->C, "No free temporary to use for predicate stack counter");
      return -1;
   }
   return 1;
}

static void
lower_bgnloop(struct rc_instruction *inst, struct vert_fc_state *fc_state)
{
   struct rc_instruction *new_inst = rc_insert_new_instruction(fc_state->C, inst->Prev);

   if ((!fc_state->C->is_r500 && fc_state->LoopsReserved >= R300_VS_MAX_LOOP_DEPTH) ||
       fc_state->LoopsReserved >= R500_PVS_MAX_LOOP_DEPTH) {
      rc_error(fc_state->C, "Loops are nested too deep.");
      return;
   }

   if (fc_state->LoopDepth == 0 && fc_state->BranchDepth == 0) {
      if (fc_state->PredicateReg == -1) {
         if (reserve_predicate_reg(fc_state) == -1) {
            return;
         }
      }

      /* Initialize the predicate bit to true. */
      new_inst->U.I.Opcode = RC_ME_PRED_SEQ;
      build_pred_dst(&new_inst->U.I.DstReg, fc_state);
      new_inst->U.I.SrcReg[0].Index = 0;
      new_inst->U.I.SrcReg[0].File = RC_FILE_NONE;
      new_inst->U.I.SrcReg[0].Swizzle = RC_SWIZZLE_0000;
   } else {
      fc_state->PredStack[fc_state->LoopDepth] = fc_state->PredicateReg;
      /* Copy the current predicate value to this loop's
       * predicate register */

      /* Use the old predicate value for src0 */
      build_pred_src(&new_inst->U.I.SrcReg[0], fc_state);

      /* Reserve this loop's predicate register */
      if (reserve_predicate_reg(fc_state) == -1) {
         return;
      }

      /* Copy the old predicate value to the new register */
      new_inst->U.I.Opcode = RC_OPCODE_ADD;
      build_pred_dst(&new_inst->U.I.DstReg, fc_state);
      new_inst->U.I.SrcReg[1].Index = 0;
      new_inst->U.I.SrcReg[1].File = RC_FILE_NONE;
      new_inst->U.I.SrcReg[1].Swizzle = RC_SWIZZLE_0000;
   }
}

static void
lower_brk(struct rc_instruction *inst, struct vert_fc_state *fc_state)
{
   if (fc_state->LoopDepth == 1) {
      inst->U.I.Opcode = RC_OPCODE_RCP;
      inst->U.I.DstReg.Pred = RC_PRED_SET;
      inst->U.I.SrcReg[0].Index = 0;
      inst->U.I.SrcReg[0].File = RC_FILE_NONE;
      inst->U.I.SrcReg[0].Swizzle = RC_SWIZZLE_0000;
   } else {
      inst->U.I.Opcode = RC_ME_PRED_SET_CLR;
      inst->U.I.DstReg.Pred = RC_PRED_SET;
   }

   build_pred_dst(&inst->U.I.DstReg, fc_state);
}

static void
lower_endloop(struct rc_instruction *inst, struct vert_fc_state *fc_state)
{
   struct rc_instruction *new_inst = rc_insert_new_instruction(fc_state->C, inst);

   new_inst->U.I.Opcode = RC_ME_PRED_SET_RESTORE;
   build_pred_dst(&new_inst->U.I.DstReg, fc_state);
   /* Restore the previous predicate register. */
   fc_state->PredicateReg = fc_state->PredStack[fc_state->LoopDepth - 1];
   build_pred_src(&new_inst->U.I.SrcReg[0], fc_state);
}

static void
lower_if(struct rc_instruction *inst, struct vert_fc_state *fc_state)
{
   /* Reserve a temporary to use as our predicate stack counter, if we
    * don't already have one. */
   if (fc_state->PredicateReg == -1) {
      /* If we are inside a loop, the Predicate Register should
       * have already been defined. */
      assert(fc_state->LoopDepth == 0);

      if (reserve_predicate_reg(fc_state) == -1) {
         return;
      }
   }

   if (fc_state->BranchDepth == 0 && fc_state->LoopDepth == 0) {
      inst->U.I.Opcode = RC_ME_PRED_SNEQ;
   } else {
      unsigned swz;
      inst->U.I.Opcode = RC_VE_PRED_SNEQ_PUSH;
      memcpy(&inst->U.I.SrcReg[1], &inst->U.I.SrcReg[0], sizeof(inst->U.I.SrcReg[1]));
      swz = rc_get_scalar_src_swz(inst->U.I.SrcReg[1].Swizzle);
      /* VE_PRED_SNEQ_PUSH needs to the branch condition to be in the
       * w component */
      inst->U.I.SrcReg[1].Swizzle =
         RC_MAKE_SWIZZLE(RC_SWIZZLE_UNUSED, RC_SWIZZLE_UNUSED, RC_SWIZZLE_UNUSED, swz);
      build_pred_src(&inst->U.I.SrcReg[0], fc_state);
   }
   build_pred_dst(&inst->U.I.DstReg, fc_state);
}

void
rc_vert_fc(struct radeon_compiler *c, void *user)
{
   struct rc_instruction *inst;
   struct vert_fc_state fc_state;

   memset(&fc_state, 0, sizeof(fc_state));
   fc_state.PredicateReg = -1;
   fc_state.C = c;

   for (inst = c->Program.Instructions.Next; inst != &c->Program.Instructions; inst = inst->Next) {

      switch (inst->U.I.Opcode) {

      case RC_OPCODE_BGNLOOP:
         lower_bgnloop(inst, &fc_state);
         fc_state.LoopDepth++;
         break;

      case RC_OPCODE_BRK:
         lower_brk(inst, &fc_state);
         break;

      case RC_OPCODE_ENDLOOP:
         if (fc_state.BranchDepth != 0 || fc_state.LoopDepth != 1) {
            lower_endloop(inst, &fc_state);
            /* Skip the new PRED_RESTORE */
            inst = inst->Next;
         }
         fc_state.LoopDepth--;
         break;
      case RC_OPCODE_IF:
         lower_if(inst, &fc_state);
         fc_state.BranchDepth++;
         break;

      case RC_OPCODE_ELSE:
         inst->U.I.Opcode = RC_ME_PRED_SET_INV;
         build_pred_dst(&inst->U.I.DstReg, &fc_state);
         build_pred_src(&inst->U.I.SrcReg[0], &fc_state);
         break;

      case RC_OPCODE_ENDIF:
         /* TODO: If LoopDepth == 1 and there is only a single break
          * we can optimize out the endif just after the break. However
          * previous attempts were buggy, so keep it simple for now.
          */
         inst->U.I.Opcode = RC_ME_PRED_SET_POP;
         build_pred_dst(&inst->U.I.DstReg, &fc_state);
         build_pred_src(&inst->U.I.SrcReg[0], &fc_state);
         fc_state.BranchDepth--;
         break;

      default:
         if (fc_state.BranchDepth || fc_state.LoopDepth) {
            inst->U.I.DstReg.Pred = RC_PRED_SET;
         }
         break;
      }

      if (c->Error) {
         return;
      }
   }
}