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/*

 * Mesa 3-D graphics library

 *

 * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.

 *

 * 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 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.

 */

/**

 * \file  programopt.c

 * Vertex/Fragment program optimizations and transformations for program

 * options, etc.

 *

 * \author Brian Paul

 */

#include "main/glheader.h"

#include "main/context.h"

#include "prog_parameter.h"

#include "prog_statevars.h"

#include "program.h"

#include "programopt.h"

#include "prog_instruction.h"

/**

 * This function inserts instructions for coordinate modelview * projection

 * into a vertex program.

 * May be used to implement the position_invariant option.

 */

static void

_mesa_insert_mvp_dp4_code(struct gl_context *ctx, struct gl_vertex_program *vprog)

{

   struct prog_instruction *newInst;

   const GLuint origLen = vprog->Base.NumInstructions;

   const GLuint newLen = origLen + 4;

   GLuint i;

   /*

    * Setup state references for the modelview/projection matrix.

    * XXX we should check if these state vars are already declared.

    */

   static const gl_state_index mvpState[4][STATE_LENGTH] = {

      { STATE_MVP_MATRIX, 0, 0, 0, 0 },  /* state.matrix.mvp.row[0] */

      { STATE_MVP_MATRIX, 0, 1, 1, 0 },  /* state.matrix.mvp.row[1] */

      { STATE_MVP_MATRIX, 0, 2, 2, 0 },  /* state.matrix.mvp.row[2] */

      { STATE_MVP_MATRIX, 0, 3, 3, 0 },  /* state.matrix.mvp.row[3] */

   };

   GLint mvpRef[4];

   for (i = 0; i < 4; i++) {

      mvpRef[i] = _mesa_add_state_reference(vprog->Base.Parameters,

                                            mvpState[i]);

   }

   /* Alloc storage for new instructions */

   newInst = _mesa_alloc_instructions(newLen);

   if (!newInst) {

      _mesa_error(ctx, GL_OUT_OF_MEMORY,

                  "glProgramString(inserting position_invariant code)");

      return;

   }

   /*

    * Generated instructions:

    * newInst[0] = DP4 result.position.x, mvp.row[0], vertex.position;

    * newInst[1] = DP4 result.position.y, mvp.row[1], vertex.position;

    * newInst[2] = DP4 result.position.z, mvp.row[2], vertex.position;

    * newInst[3] = DP4 result.position.w, mvp.row[3], vertex.position;

    */

   _mesa_init_instructions(newInst, 4);

   for (i = 0; i < 4; i++) {

      newInst[i].Opcode = OPCODE_DP4;

      newInst[i].DstReg.File = PROGRAM_OUTPUT;

      newInst[i].DstReg.Index = VARYING_SLOT_POS;

      newInst[i].DstReg.WriteMask = (WRITEMASK_X << i);

      newInst[i].SrcReg[0].File = PROGRAM_STATE_VAR;

      newInst[i].SrcReg[0].Index = mvpRef[i];

      newInst[i].SrcReg[0].Swizzle = SWIZZLE_NOOP;

      newInst[i].SrcReg[1].File = PROGRAM_INPUT;

      newInst[i].SrcReg[1].Index = VERT_ATTRIB_POS;

      newInst[i].SrcReg[1].Swizzle = SWIZZLE_NOOP;

   }

   /* Append original instructions after new instructions */

   _mesa_copy_instructions (newInst + 4, vprog->Base.Instructions, origLen);

   /* free old instructions */

   _mesa_free_instructions(vprog->Base.Instructions, origLen);

   /* install new instructions */

   vprog->Base.Instructions = newInst;

   vprog->Base.NumInstructions = newLen;

   vprog->Base.InputsRead |= VERT_BIT_POS;

   vprog->Base.OutputsWritten |= BITFIELD64_BIT(VARYING_SLOT_POS);

}

static void

_mesa_insert_mvp_mad_code(struct gl_context *ctx, struct gl_vertex_program *vprog)

{

   struct prog_instruction *newInst;

   const GLuint origLen = vprog->Base.NumInstructions;

   const GLuint newLen = origLen + 4;

   GLuint hposTemp;

   GLuint i;

   /*

    * Setup state references for the modelview/projection matrix.

    * XXX we should check if these state vars are already declared.

    */

   static const gl_state_index mvpState[4][STATE_LENGTH] = {

      { STATE_MVP_MATRIX, 0, 0, 0, STATE_MATRIX_TRANSPOSE },

      { STATE_MVP_MATRIX, 0, 1, 1, STATE_MATRIX_TRANSPOSE },

      { STATE_MVP_MATRIX, 0, 2, 2, STATE_MATRIX_TRANSPOSE },

      { STATE_MVP_MATRIX, 0, 3, 3, STATE_MATRIX_TRANSPOSE },

   };

   GLint mvpRef[4];

   for (i = 0; i < 4; i++) {

      mvpRef[i] = _mesa_add_state_reference(vprog->Base.Parameters,

                                            mvpState[i]);

   }

   /* Alloc storage for new instructions */

   newInst = _mesa_alloc_instructions(newLen);

   if (!newInst) {

      _mesa_error(ctx, GL_OUT_OF_MEMORY,

                  "glProgramString(inserting position_invariant code)");

      return;

   }

   /* TEMP hposTemp; */

   hposTemp = vprog->Base.NumTemporaries++;

   /*

    * Generated instructions:

    *    emit_op2(p, OPCODE_MUL, tmp, 0, swizzle1(src,X), mat[0]);

    *    emit_op3(p, OPCODE_MAD, tmp, 0, swizzle1(src,Y), mat[1], tmp);

    *    emit_op3(p, OPCODE_MAD, tmp, 0, swizzle1(src,Z), mat[2], tmp);

    *    emit_op3(p, OPCODE_MAD, dest, 0, swizzle1(src,W), mat[3], tmp);

    */

   _mesa_init_instructions(newInst, 4);

   newInst[0].Opcode = OPCODE_MUL;

   newInst[0].DstReg.File = PROGRAM_TEMPORARY;

   newInst[0].DstReg.Index = hposTemp;

   newInst[0].DstReg.WriteMask = WRITEMASK_XYZW;

   newInst[0].SrcReg[0].File = PROGRAM_INPUT;

   newInst[0].SrcReg[0].Index = VERT_ATTRIB_POS;

   newInst[0].SrcReg[0].Swizzle = SWIZZLE_XXXX;

   newInst[0].SrcReg[1].File = PROGRAM_STATE_VAR;

   newInst[0].SrcReg[1].Index = mvpRef[0];

   newInst[0].SrcReg[1].Swizzle = SWIZZLE_NOOP;

   for (i = 1; i <= 2; i++) {

      newInst[i].Opcode = OPCODE_MAD;

      newInst[i].DstReg.File = PROGRAM_TEMPORARY;

      newInst[i].DstReg.Index = hposTemp;

      newInst[i].DstReg.WriteMask = WRITEMASK_XYZW;

      newInst[i].SrcReg[0].File = PROGRAM_INPUT;

      newInst[i].SrcReg[0].Index = VERT_ATTRIB_POS;

      newInst[i].SrcReg[0].Swizzle = MAKE_SWIZZLE4(i,i,i,i);

      newInst[i].SrcReg[1].File = PROGRAM_STATE_VAR;

      newInst[i].SrcReg[1].Index = mvpRef[i];

      newInst[i].SrcReg[1].Swizzle = SWIZZLE_NOOP;

      newInst[i].SrcReg[2].File = PROGRAM_TEMPORARY;

      newInst[i].SrcReg[2].Index = hposTemp;

      newInst[1].SrcReg[2].Swizzle = SWIZZLE_NOOP;

   }

   newInst[3].Opcode = OPCODE_MAD;

   newInst[3].DstReg.File = PROGRAM_OUTPUT;

   newInst[3].DstReg.Index = VARYING_SLOT_POS;

   newInst[3].DstReg.WriteMask = WRITEMASK_XYZW;

   newInst[3].SrcReg[0].File = PROGRAM_INPUT;

   newInst[3].SrcReg[0].Index = VERT_ATTRIB_POS;

   newInst[3].SrcReg[0].Swizzle = SWIZZLE_WWWW;

   newInst[3].SrcReg[1].File = PROGRAM_STATE_VAR;

   newInst[3].SrcReg[1].Index = mvpRef[3];

   newInst[3].SrcReg[1].Swizzle = SWIZZLE_NOOP;

   newInst[3].SrcReg[2].File = PROGRAM_TEMPORARY;

   newInst[3].SrcReg[2].Index = hposTemp;

   newInst[3].SrcReg[2].Swizzle = SWIZZLE_NOOP;

   /* Append original instructions after new instructions */

   _mesa_copy_instructions (newInst + 4, vprog->Base.Instructions, origLen);

   /* free old instructions */

   _mesa_free_instructions(vprog->Base.Instructions, origLen);

   /* install new instructions */

   vprog->Base.Instructions = newInst;

   vprog->Base.NumInstructions = newLen;

   vprog->Base.InputsRead |= VERT_BIT_POS;

   vprog->Base.OutputsWritten |= BITFIELD64_BIT(VARYING_SLOT_POS);

}

void

_mesa_insert_mvp_code(struct gl_context *ctx, struct gl_vertex_program *vprog)

{

   if (ctx->Const.ShaderCompilerOptions[MESA_SHADER_VERTEX].OptimizeForAOS)

      _mesa_insert_mvp_dp4_code( ctx, vprog );

   else

      _mesa_insert_mvp_mad_code( ctx, vprog );

}

/**

 * Append instructions to implement fog

 *

 * The \c fragment.fogcoord input is used to compute the fog blend factor.

 *

 * \param ctx      The GL context

 * \param fprog    Fragment program that fog instructions will be appended to.

 * \param fog_mode Fog mode.  One of \c GL_EXP, \c GL_EXP2, or \c GL_LINEAR.

 * \param saturate True if writes to color outputs should be clamped to [0, 1]

 *

 * \note

 * This function sets \c VARYING_BIT_FOGC in \c fprog->Base.InputsRead.

 *

 * \todo With a little work, this function could be adapted to add fog code

 * to vertex programs too.

 */

void

_mesa_append_fog_code(struct gl_context *ctx,

		      struct gl_fragment_program *fprog, GLenum fog_mode,

		      GLboolean saturate)

{

   static const gl_state_index fogPStateOpt[STATE_LENGTH]

      = { STATE_INTERNAL, STATE_FOG_PARAMS_OPTIMIZED, 0, 0, 0 };

   static const gl_state_index fogColorState[STATE_LENGTH]

      = { STATE_FOG_COLOR, 0, 0, 0, 0};

   struct prog_instruction *newInst, *inst;

   const GLuint origLen = fprog->Base.NumInstructions;

   const GLuint newLen = origLen + 5;

   GLuint i;

   GLint fogPRefOpt, fogColorRef; /* state references */

   GLuint colorTemp, fogFactorTemp; /* temporary registerss */

   if (fog_mode == GL_NONE) {

      _mesa_problem(ctx, "_mesa_append_fog_code() called for fragment program"

                    " with fog_mode == GL_NONE");

      return;

   }

   if (!(fprog->Base.OutputsWritten & (1 << FRAG_RESULT_COLOR))) {

      /* program doesn't output color, so nothing to do */

      return;

   }

   /* Alloc storage for new instructions */

   newInst = _mesa_alloc_instructions(newLen);

   if (!newInst) {

      _mesa_error(ctx, GL_OUT_OF_MEMORY,

                  "glProgramString(inserting fog_option code)");

      return;

   }

   /* Copy orig instructions into new instruction buffer */

   _mesa_copy_instructions(newInst, fprog->Base.Instructions, origLen);

   /* PARAM fogParamsRefOpt = internal optimized fog params; */

   fogPRefOpt

      = _mesa_add_state_reference(fprog->Base.Parameters, fogPStateOpt);

   /* PARAM fogColorRef = state.fog.color; */

   fogColorRef

      = _mesa_add_state_reference(fprog->Base.Parameters, fogColorState);

   /* TEMP colorTemp; */

   colorTemp = fprog->Base.NumTemporaries++;

   /* TEMP fogFactorTemp; */

   fogFactorTemp = fprog->Base.NumTemporaries++;

   /* Scan program to find where result.color is written */

   inst = newInst;

   for (i = 0; i < fprog->Base.NumInstructions; i++) {

      if (inst->Opcode == OPCODE_END)

         break;

      if (inst->DstReg.File == PROGRAM_OUTPUT &&

          inst->DstReg.Index == FRAG_RESULT_COLOR) {

         /* change the instruction to write to colorTemp w/ clamping */

         inst->DstReg.File = PROGRAM_TEMPORARY;

         inst->DstReg.Index = colorTemp;

         inst->SaturateMode = saturate;

         /* don't break (may be several writes to result.color) */

      }

      inst++;

   }

   assert(inst->Opcode == OPCODE_END); /* we'll overwrite this inst */

   _mesa_init_instructions(inst, 5);

   /* emit instructions to compute fog blending factor */

   /* this is always clamped to [0, 1] regardless of fragment clamping */

   if (fog_mode == GL_LINEAR) {

      /* MAD fogFactorTemp.x, fragment.fogcoord.x, fogPRefOpt.x, fogPRefOpt.y; */

      inst->Opcode = OPCODE_MAD;

      inst->DstReg.File = PROGRAM_TEMPORARY;

      inst->DstReg.Index = fogFactorTemp;

      inst->DstReg.WriteMask = WRITEMASK_X;

      inst->SrcReg[0].File = PROGRAM_INPUT;

      inst->SrcReg[0].Index = VARYING_SLOT_FOGC;

      inst->SrcReg[0].Swizzle = SWIZZLE_XXXX;

      inst->SrcReg[1].File = PROGRAM_STATE_VAR;

      inst->SrcReg[1].Index = fogPRefOpt;

      inst->SrcReg[1].Swizzle = SWIZZLE_XXXX;

      inst->SrcReg[2].File = PROGRAM_STATE_VAR;

      inst->SrcReg[2].Index = fogPRefOpt;

      inst->SrcReg[2].Swizzle = SWIZZLE_YYYY;

      inst->SaturateMode = SATURATE_ZERO_ONE;

      inst++;

   }

   else {

      assert(fog_mode == GL_EXP || fog_mode == GL_EXP2);

      /* fogPRefOpt.z = d/ln(2), fogPRefOpt.w = d/sqrt(ln(2) */

      /* EXP: MUL fogFactorTemp.x, fogPRefOpt.z, fragment.fogcoord.x; */

      /* EXP2: MUL fogFactorTemp.x, fogPRefOpt.w, fragment.fogcoord.x; */

      inst->Opcode = OPCODE_MUL;

      inst->DstReg.File = PROGRAM_TEMPORARY;

      inst->DstReg.Index = fogFactorTemp;

      inst->DstReg.WriteMask = WRITEMASK_X;

      inst->SrcReg[0].File = PROGRAM_STATE_VAR;

      inst->SrcReg[0].Index = fogPRefOpt;

      inst->SrcReg[0].Swizzle

         = (fog_mode == GL_EXP) ? SWIZZLE_ZZZZ : SWIZZLE_WWWW;

      inst->SrcReg[1].File = PROGRAM_INPUT;

      inst->SrcReg[1].Index = VARYING_SLOT_FOGC;

      inst->SrcReg[1].Swizzle = SWIZZLE_XXXX;

      inst++;

      if (fog_mode == GL_EXP2) {

         /* MUL fogFactorTemp.x, fogFactorTemp.x, fogFactorTemp.x; */

         inst->Opcode = OPCODE_MUL;

         inst->DstReg.File = PROGRAM_TEMPORARY;

         inst->DstReg.Index = fogFactorTemp;

         inst->DstReg.WriteMask = WRITEMASK_X;

         inst->SrcReg[0].File = PROGRAM_TEMPORARY;

         inst->SrcReg[0].Index = fogFactorTemp;

         inst->SrcReg[0].Swizzle = SWIZZLE_XXXX;

         inst->SrcReg[1].File = PROGRAM_TEMPORARY;

         inst->SrcReg[1].Index = fogFactorTemp;

         inst->SrcReg[1].Swizzle = SWIZZLE_XXXX;

         inst++;

      }

      /* EX2_SAT fogFactorTemp.x, -fogFactorTemp.x; */

      inst->Opcode = OPCODE_EX2;

      inst->DstReg.File = PROGRAM_TEMPORARY;

      inst->DstReg.Index = fogFactorTemp;

      inst->DstReg.WriteMask = WRITEMASK_X;

      inst->SrcReg[0].File = PROGRAM_TEMPORARY;

      inst->SrcReg[0].Index = fogFactorTemp;

      inst->SrcReg[0].Negate = NEGATE_XYZW;

      inst->SrcReg[0].Swizzle = SWIZZLE_XXXX;

      inst->SaturateMode = SATURATE_ZERO_ONE;

      inst++;

   }

   /* LRP result.color.xyz, fogFactorTemp.xxxx, colorTemp, fogColorRef; */

   inst->Opcode = OPCODE_LRP;

   inst->DstReg.File = PROGRAM_OUTPUT;

   inst->DstReg.Index = FRAG_RESULT_COLOR;

   inst->DstReg.WriteMask = WRITEMASK_XYZ;

   inst->SrcReg[0].File = PROGRAM_TEMPORARY;

   inst->SrcReg[0].Index = fogFactorTemp;

   inst->SrcReg[0].Swizzle = SWIZZLE_XXXX;

   inst->SrcReg[1].File = PROGRAM_TEMPORARY;

   inst->SrcReg[1].Index = colorTemp;

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

   inst->SrcReg[2].File = PROGRAM_STATE_VAR;

   inst->SrcReg[2].Index = fogColorRef;

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

   inst++;

   /* MOV result.color.w, colorTemp.x;  # copy alpha */

   inst->Opcode = OPCODE_MOV;

   inst->DstReg.File = PROGRAM_OUTPUT;

   inst->DstReg.Index = FRAG_RESULT_COLOR;

   inst->DstReg.WriteMask = WRITEMASK_W;

   inst->SrcReg[0].File = PROGRAM_TEMPORARY;

   inst->SrcReg[0].Index = colorTemp;

   inst->SrcReg[0].Swizzle = SWIZZLE_NOOP;

   inst++;

   /* END; */

   inst->Opcode = OPCODE_END;

   inst++;

   /* free old instructions */

   _mesa_free_instructions(fprog->Base.Instructions, origLen);

   /* install new instructions */

   fprog->Base.Instructions = newInst;

   fprog->Base.NumInstructions = inst - newInst;

   fprog->Base.InputsRead |= VARYING_BIT_FOGC;

   assert(fprog->Base.OutputsWritten & (1 << FRAG_RESULT_COLOR));

}

static GLboolean

is_texture_instruction(const struct prog_instruction *inst)

{

   switch (inst->Opcode) {

   case OPCODE_TEX:

   case OPCODE_TXB:

   case OPCODE_TXD:

   case OPCODE_TXL:

   case OPCODE_TXP:

   case OPCODE_TXP_NV:

      return GL_TRUE;

   default:

      return GL_FALSE;

   }

}

/**

 * Count the number of texure indirections in the given program.

 * The program's NumTexIndirections field will be updated.

 * See the GL_ARB_fragment_program spec (issue 24) for details.

 * XXX we count texture indirections in texenvprogram.c (maybe use this code

 * instead and elsewhere).

 */

void

_mesa_count_texture_indirections(struct gl_program *prog)

{

   GLuint indirections = 1;

   GLbitfield tempsOutput = 0x0;

   GLbitfield aluTemps = 0x0;

   GLuint i;

   for (i = 0; i < prog->NumInstructions; i++) {

      const struct prog_instruction *inst = prog->Instructions + i;

      if (is_texture_instruction(inst)) {

         if (((inst->SrcReg[0].File == PROGRAM_TEMPORARY) &&

              (tempsOutput & (1 << inst->SrcReg[0].Index))) ||

             ((inst->Opcode != OPCODE_KIL) &&

              (inst->DstReg.File == PROGRAM_TEMPORARY) &&

              (aluTemps & (1 << inst->DstReg.Index))))

            {

               indirections++;

               tempsOutput = 0x0;

               aluTemps = 0x0;

            }

      }

      else {

         GLuint j;

         for (j = 0; j < 3; j++) {

            if (inst->SrcReg[j].File == PROGRAM_TEMPORARY)

               aluTemps |= (1 << inst->SrcReg[j].Index);

         }

         if (inst->DstReg.File == PROGRAM_TEMPORARY)

            aluTemps |= (1 << inst->DstReg.Index);

      }

      if ((inst->Opcode != OPCODE_KIL) && (inst->DstReg.File == PROGRAM_TEMPORARY))

         tempsOutput |= (1 << inst->DstReg.Index);

   }

   prog->NumTexIndirections = indirections;

}

/**

 * Count number of texture instructions in given program and update the

 * program's NumTexInstructions field.

 */

void

_mesa_count_texture_instructions(struct gl_program *prog)

{

   GLuint i;

   prog->NumTexInstructions = 0;

   for (i = 0; i < prog->NumInstructions; i++) {

      prog->NumTexInstructions += is_texture_instruction(prog->Instructions + i);

   }

}

/**

 * Scan/rewrite program to remove reads of custom (output) registers.

 * The passed type has to be PROGRAM_OUTPUT.

 * On some hardware, trying to read an output register causes trouble.

 * So, rewrite the program to use a temporary register in this case.

 */

void

_mesa_remove_output_reads(struct gl_program *prog, gl_register_file type)

{

   GLuint i;

   GLint outputMap[VARYING_SLOT_MAX];

   GLuint numVaryingReads = 0;

   GLboolean usedTemps[MAX_PROGRAM_TEMPS];

   GLuint firstTemp = 0;

   _mesa_find_used_registers(prog, PROGRAM_TEMPORARY,

                             usedTemps, MAX_PROGRAM_TEMPS);

   assert(type == PROGRAM_OUTPUT);

   for (i = 0; i < VARYING_SLOT_MAX; i++)

      outputMap[i] = -1;

   /* look for instructions which read from varying vars */

   for (i = 0; i < prog->NumInstructions; i++) {

      struct prog_instruction *inst = prog->Instructions + i;

      const GLuint numSrc = _mesa_num_inst_src_regs(inst->Opcode);

      GLuint j;

      for (j = 0; j < numSrc; j++) {

         if (inst->SrcReg[j].File == type) {

            /* replace the read with a temp reg */

            const GLuint var = inst->SrcReg[j].Index;

            if (outputMap[var] == -1) {

               numVaryingReads++;

               outputMap[var] = _mesa_find_free_register(usedTemps,

                                                         MAX_PROGRAM_TEMPS,

                                                         firstTemp);

               firstTemp = outputMap[var] + 1;

            }

            inst->SrcReg[j].File = PROGRAM_TEMPORARY;

            inst->SrcReg[j].Index = outputMap[var];

         }

      }

   }

   if (numVaryingReads == 0)

      return; /* nothing to be done */

   /* look for instructions which write to the varying vars identified above */

   for (i = 0; i < prog->NumInstructions; i++) {

      struct prog_instruction *inst = prog->Instructions + i;

      if (inst->DstReg.File == type &&

          outputMap[inst->DstReg.Index] >= 0) {

         /* change inst to write to the temp reg, instead of the varying */

         inst->DstReg.File = PROGRAM_TEMPORARY;

         inst->DstReg.Index = outputMap[inst->DstReg.Index];

      }

   }

   /* insert new instructions to copy the temp vars to the varying vars */

   {

      struct prog_instruction *inst;

      GLint endPos, var;

      /* Look for END instruction and insert the new varying writes */

      endPos = -1;

      for (i = 0; i < prog->NumInstructions; i++) {

         struct prog_instruction *inst = prog->Instructions + i;

         if (inst->Opcode == OPCODE_END) {

            endPos = i;

            _mesa_insert_instructions(prog, i, numVaryingReads);

            break;

         }

      }

      assert(endPos >= 0);

      /* insert new MOV instructions here */

      inst = prog->Instructions + endPos;

      for (var = 0; var < VARYING_SLOT_MAX; var++) {

         if (outputMap[var] >= 0) {

            /* MOV VAR[var], TEMP[tmp]; */

            inst->Opcode = OPCODE_MOV;

            inst->DstReg.File = type;

            inst->DstReg.Index = var;

            inst->SrcReg[0].File = PROGRAM_TEMPORARY;

            inst->SrcReg[0].Index = outputMap[var];

            inst++;

         }

      }

   }

}