/*
 * 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.
 */

#include "main/glheader.h"
#include "main/context.h"
#include "main/macros.h"
#include "program.h"
#include "prog_instruction.h"
#include "prog_optimize.h"
#include "prog_parameter.h"
#include <stdbool.h>

static bool
src_regs_are_constant(const struct prog_instruction *inst, unsigned num_srcs)
{
   unsigned i;

   for (i = 0; i < num_srcs; i++) {
      if (inst->SrcReg[i].File != PROGRAM_CONSTANT)
	 return false;
      if (inst->SrcReg[i].RelAddr)
         return false;
   }

   return true;
}

static struct prog_src_register
src_reg_for_float(struct gl_program *prog, float val)
{
   struct prog_src_register src;
   unsigned swiz;

   memset(&src, 0, sizeof(src));

   src.File = PROGRAM_CONSTANT;
   src.Index = _mesa_add_unnamed_constant(prog->Parameters,
					  (gl_constant_value *) &val, 1, &swiz);
   src.Swizzle = swiz;
   return src;
}

static struct prog_src_register
src_reg_for_vec4(struct gl_program *prog, const float *val)
{
   struct prog_src_register src;
   unsigned swiz;

   memset(&src, 0, sizeof(src));

   src.File = PROGRAM_CONSTANT;
   src.Index = _mesa_add_unnamed_constant(prog->Parameters,
					  (gl_constant_value *) val, 4, &swiz);
   src.Swizzle = swiz;
   return src;
}

static bool
src_regs_are_same(const struct prog_src_register *a,
		  const struct prog_src_register *b)
{
   return (a->File == b->File)
      && (a->Index == b->Index)
      && (a->Swizzle == b->Swizzle)
      && (a->Negate == b->Negate)
      && (a->RelAddr == 0)
      && (b->RelAddr == 0);
}

static void
get_value(struct gl_program *prog, struct prog_src_register *r, float *data)
{
   const gl_constant_value *const value =
      prog->Parameters->ParameterValues[r->Index];

   data[0] = value[GET_SWZ(r->Swizzle, 0)].f;
   data[1] = value[GET_SWZ(r->Swizzle, 1)].f;
   data[2] = value[GET_SWZ(r->Swizzle, 2)].f;
   data[3] = value[GET_SWZ(r->Swizzle, 3)].f;

   if (r->Negate & 0x01) {
      data[0] = -data[0];
   }

   if (r->Negate & 0x02) {
      data[1] = -data[1];
   }

   if (r->Negate & 0x04) {
      data[2] = -data[2];
   }

   if (r->Negate & 0x08) {
      data[3] = -data[3];
   }
}

/**
 * Try to replace instructions that produce a constant result with simple moves
 *
 * The hope is that a following copy propagation pass will eliminate the
 * unnecessary move instructions.
 */
GLboolean
_mesa_constant_fold(struct gl_program *prog)
{
   bool progress = false;
   unsigned i;

   for (i = 0; i < prog->NumInstructions; i++) {
      struct prog_instruction *const inst = &prog->Instructions[i];

      switch (inst->Opcode) {
      case OPCODE_ADD:
	 if (src_regs_are_constant(inst, 2)) {
	    float a[4];
	    float b[4];
	    float result[4];

	    get_value(prog, &inst->SrcReg[0], a);
	    get_value(prog, &inst->SrcReg[1], b);

	    result[0] = a[0] + b[0];
	    result[1] = a[1] + b[1];
	    result[2] = a[2] + b[2];
	    result[3] = a[3] + b[3];

	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_vec4(prog, result);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 }
	 break;

      case OPCODE_CMP:
	 /* FINISHME: We could also optimize CMP instructions where the first
	  * FINISHME: source is a constant that is either all < 0.0 or all
	  * FINISHME: >= 0.0.
	  */
	 if (src_regs_are_constant(inst, 3)) {
	    float a[4];
	    float b[4];
	    float c[4];
	    float result[4];

	    get_value(prog, &inst->SrcReg[0], a);
	    get_value(prog, &inst->SrcReg[1], b);
	    get_value(prog, &inst->SrcReg[2], c);

            result[0] = a[0] < 0.0f ? b[0] : c[0];
            result[1] = a[1] < 0.0f ? b[1] : c[1];
            result[2] = a[2] < 0.0f ? b[2] : c[2];
            result[3] = a[3] < 0.0f ? b[3] : c[3];

	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_vec4(prog, result);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;
	    inst->SrcReg[2].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[2].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 }
	 break;

      case OPCODE_DP2:
      case OPCODE_DP3:
      case OPCODE_DP4:
	 if (src_regs_are_constant(inst, 2)) {
	    float a[4];
	    float b[4];
	    float result;

	    get_value(prog, &inst->SrcReg[0], a);
	    get_value(prog, &inst->SrcReg[1], b);

	    result = (a[0] * b[0]) + (a[1] * b[1]);

	    if (inst->Opcode >= OPCODE_DP3)
	       result += a[2] * b[2];

	    if (inst->Opcode == OPCODE_DP4)
	       result += a[3] * b[3];

	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_float(prog, result);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 }
	 break;

      case OPCODE_MUL:
	 if (src_regs_are_constant(inst, 2)) {
	    float a[4];
	    float b[4];
	    float result[4];

	    get_value(prog, &inst->SrcReg[0], a);
	    get_value(prog, &inst->SrcReg[1], b);

	    result[0] = a[0] * b[0];
	    result[1] = a[1] * b[1];
	    result[2] = a[2] * b[2];
	    result[3] = a[3] * b[3];

	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_vec4(prog, result);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 }
	 break;

      case OPCODE_SGE:
	 if (src_regs_are_constant(inst, 2)) {
	    float a[4];
	    float b[4];
	    float result[4];

	    get_value(prog, &inst->SrcReg[0], a);
	    get_value(prog, &inst->SrcReg[1], b);

	    result[0] = (a[0] >= b[0]) ? 1.0f : 0.0f;
	    result[1] = (a[1] >= b[1]) ? 1.0f : 0.0f;
	    result[2] = (a[2] >= b[2]) ? 1.0f : 0.0f;
	    result[3] = (a[3] >= b[3]) ? 1.0f : 0.0f;

	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_vec4(prog, result);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 } else if (src_regs_are_same(&inst->SrcReg[0], &inst->SrcReg[1])) {
	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_float(prog, 1.0f);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 }
	 break;

      case OPCODE_SLT:
	 if (src_regs_are_constant(inst, 2)) {
	    float a[4];
	    float b[4];
	    float result[4];

	    get_value(prog, &inst->SrcReg[0], a);
	    get_value(prog, &inst->SrcReg[1], b);

	    result[0] = (a[0] < b[0]) ? 1.0f : 0.0f;
	    result[1] = (a[1] < b[1]) ? 1.0f : 0.0f;
	    result[2] = (a[2] < b[2]) ? 1.0f : 0.0f;
	    result[3] = (a[3] < b[3]) ? 1.0f : 0.0f;

	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_vec4(prog, result);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 } else if (src_regs_are_same(&inst->SrcReg[0], &inst->SrcReg[1])) {
	    inst->Opcode = OPCODE_MOV;
	    inst->SrcReg[0] = src_reg_for_float(prog, 0.0f);

	    inst->SrcReg[1].File = PROGRAM_UNDEFINED;
	    inst->SrcReg[1].Swizzle = SWIZZLE_NOOP;

	    progress = true;
	 }
	 break;

      default:
	 break;
      }
   }

   return progress;
}
