path: root/src/gallium/drivers/llvmpipe/lp_bld_interp.c

/**************************************************************************
 * 
 * Copyright 2009 VMware, Inc.
 * Copyright 2007-2008 Tungsten Graphics, Inc., Cedar Park, Texas.
 * 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, sub license, 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 NON-INFRINGEMENT.
 * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS 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
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/**
 * @file
 * Position and shader input interpolation.
 *
 * @author Jose Fonseca <jfonseca@vmware.com>
 */

#include "pipe/p_shader_tokens.h"
#include "util/u_debug.h"
#include "util/u_memory.h"
#include "util/u_math.h"
#include "tgsi/tgsi_scan.h"
#include "gallivm/lp_bld_debug.h"
#include "gallivm/lp_bld_const.h"
#include "gallivm/lp_bld_arit.h"
#include "gallivm/lp_bld_swizzle.h"
#include "lp_bld_interp.h"


/*
 * The shader JIT function operates on blocks of quads.
 * Each block has 2x2 quads and each quad has 2x2 pixels.
 *
 * We iterate over the quads in order 0, 1, 2, 3:
 *
 * #################
 * #   |   #   |   #
 * #---0---#---1---#
 * #   |   #   |   #
 * #################
 * #   |   #   |   #
 * #---2---#---3---#
 * #   |   #   |   #
 * #################
 *
 * Within each quad, we have four pixels which are represented in SOA
 * order:
 *
 * #########
 * # 0 | 1 #
 * #---+---#
 * # 2 | 3 #
 * #########
 *
 * So the green channel (for example) of the four pixels is stored in
 * a single vector register: {g0, g1, g2, g3}.
 */


static void
attrib_name(LLVMValueRef val, unsigned attrib, unsigned chan, const char *suffix)
{
   if(attrib == 0)
      lp_build_name(val, "pos.%c%s", "xyzw"[chan], suffix);
   else
      lp_build_name(val, "input%u.%c%s", attrib - 1, "xyzw"[chan], suffix);
}


/**
 * Initialize the bld->a0, dadx, dady fields.  This involves fetching
 * those values from the arrays which are passed into the JIT function.
 */
static void
coeffs_init(struct lp_build_interp_soa_context *bld,
            LLVMValueRef a0_ptr,
            LLVMValueRef dadx_ptr,
            LLVMValueRef dady_ptr)
{
   LLVMBuilderRef builder = bld->base.builder;
   unsigned attrib;
   unsigned chan;

   for(attrib = 0; attrib < bld->num_attribs; ++attrib) {
      const unsigned mask = bld->mask[attrib];
      const unsigned interp = bld->interp[attrib];
      for(chan = 0; chan < NUM_CHANNELS; ++chan) {
         if(mask & (1 << chan)) {
            LLVMValueRef index = LLVMConstInt(LLVMInt32Type(), attrib*NUM_CHANNELS + chan, 0);
            LLVMValueRef a0 = bld->base.undef;
            LLVMValueRef dadx = bld->base.undef;
            LLVMValueRef dady = bld->base.undef;

            switch( interp ) {
            case LP_INTERP_PERSPECTIVE:
               /* fall-through */

            case LP_INTERP_LINEAR:
               dadx = LLVMBuildLoad(builder, LLVMBuildGEP(builder, dadx_ptr, &index, 1, ""), "");
               dady = LLVMBuildLoad(builder, LLVMBuildGEP(builder, dady_ptr, &index, 1, ""), "");
               dadx = lp_build_broadcast_scalar(&bld->base, dadx);
               dady = lp_build_broadcast_scalar(&bld->base, dady);
               attrib_name(dadx, attrib, chan, ".dadx");
               attrib_name(dady, attrib, chan, ".dady");
               /* fall-through */

            case LP_INTERP_CONSTANT:
            case LP_INTERP_FACING:
               a0 = LLVMBuildLoad(builder, LLVMBuildGEP(builder, a0_ptr, &index, 1, ""), "");
               a0 = lp_build_broadcast_scalar(&bld->base, a0);
               attrib_name(a0, attrib, chan, ".a0");
               break;

            case LP_INTERP_POSITION:
               /* Nothing to do as the position coeffs are already setup in slot 0 */
               break;

            default:
               assert(0);
               break;
            }

            bld->a0  [attrib][chan] = a0;
            bld->dadx[attrib][chan] = dadx;
            bld->dady[attrib][chan] = dady;
         }
      }
   }
}


/**
 * Emit LLVM code to compute the fragment shader input attribute values.
 * For example, for a color input, we'll compute red, green, blue and alpha
 * values for the four pixels in a quad.
 * Recall that we're operating on 4-element vectors so each arithmetic
 * operation is operating on the four pixels in a quad.
 */
static void
attribs_init(struct lp_build_interp_soa_context *bld)
{
   LLVMValueRef x = bld->pos[0];
   LLVMValueRef y = bld->pos[1];
   LLVMValueRef oow = NULL;
   unsigned attrib;
   unsigned chan;

   for(attrib = 0; attrib < bld->num_attribs; ++attrib) {
      const unsigned mask = bld->mask[attrib];
      const unsigned interp = bld->interp[attrib];
      for(chan = 0; chan < NUM_CHANNELS; ++chan) {
         if(mask & (1 << chan)) {
            if (interp == LP_INTERP_POSITION) {
               assert(attrib > 0);
               bld->attribs[attrib][chan] = bld->attribs[0][chan];
            }
            else {
               LLVMValueRef a0   = bld->a0  [attrib][chan];
               LLVMValueRef dadx = bld->dadx[attrib][chan];
               LLVMValueRef dady = bld->dady[attrib][chan];
               LLVMValueRef res;

               res = a0;

               if (interp != LP_INTERP_CONSTANT &&
                   interp != LP_INTERP_FACING) {
                  /* res = res + x * dadx */
                  res = lp_build_add(&bld->base, res, lp_build_mul(&bld->base, x, dadx));
                  /* res = res + y * dady */
                  res = lp_build_add(&bld->base, res, lp_build_mul(&bld->base, y, dady));
               }

               /* Keep the value of the attribute before perspective divide
                * for faster updates.
                */
               bld->attribs_pre[attrib][chan] = res;

               if (interp == LP_INTERP_PERSPECTIVE) {
                  LLVMValueRef w = bld->pos[3];
                  assert(attrib != 0);
                  assert(bld->mask[0] & TGSI_WRITEMASK_W);
                  if(!oow)
                     oow = lp_build_rcp(&bld->base, w);
                  res = lp_build_mul(&bld->base, res, oow);
               }

               attrib_name(res, attrib, chan, "");

               bld->attribs[attrib][chan] = res;
            }
         }
      }
   }
}


/**
 * Increment the shader input attribute values.
 * This is called when we move from one quad to the next.
 */
static void
attribs_update(struct lp_build_interp_soa_context *bld, int quad_index)
{
   LLVMValueRef oow = NULL;
   unsigned attrib;
   unsigned chan;

   assert(quad_index < 4);

   for(attrib = 0; attrib < bld->num_attribs; ++attrib) {
      const unsigned mask = bld->mask[attrib];
      const unsigned interp = bld->interp[attrib];

      if (interp != LP_INTERP_CONSTANT &&
          interp != LP_INTERP_FACING) {
         for(chan = 0; chan < NUM_CHANNELS; ++chan) {
            if(mask & (1 << chan)) {
               if (interp == LP_INTERP_POSITION) {
                  assert(attrib > 0);
                  bld->attribs[attrib][chan] = bld->attribs[0][chan];
               }
               else {
                  LLVMValueRef dadx = bld->dadx[attrib][chan];
                  LLVMValueRef dady = bld->dady[attrib][chan];
                  LLVMValueRef res;

                  res = bld->attribs_pre[attrib][chan];

                  if (quad_index == 1 || quad_index == 3) {
                     /* top-right or bottom-right quad */
                     /* build res = res + dadx + dadx */
                     res = lp_build_add(&bld->base, res, dadx);
                     res = lp_build_add(&bld->base, res, dadx);
                  }

                  if (quad_index == 2 || quad_index == 3) {
                     /* bottom-left or bottom-right quad */
                     /* build res = res + dady + dady */
                     res = lp_build_add(&bld->base, res, dady);
                     res = lp_build_add(&bld->base, res, dady);
                  }

                  if (interp == LP_INTERP_PERSPECTIVE) {
                     LLVMValueRef w = bld->pos[3];
                     assert(attrib != 0);
                     assert(bld->mask[0] & TGSI_WRITEMASK_W);
                     if(!oow)
                        oow = lp_build_rcp(&bld->base, w);
                     res = lp_build_mul(&bld->base, res, oow);
                  }

                  attrib_name(res, attrib, chan, "");

                  bld->attribs[attrib][chan] = res;
               }
            }
         }
      }
   }
}


/**
 * Generate the position vectors.
 *
 * Parameter x0, y0 are the integer values with the quad upper left coordinates.
 */
static void
pos_init(struct lp_build_interp_soa_context *bld,
         LLVMValueRef x0,
         LLVMValueRef y0)
{
   lp_build_name(x0, "pos.x");
   lp_build_name(y0, "pos.y");

   bld->attribs[0][0] = x0;
   bld->attribs[0][1] = y0;
}


/**
 * Update quad position values when moving to the next quad.
 */
static void
pos_update(struct lp_build_interp_soa_context *bld, int quad_index)
{
   LLVMValueRef x = bld->attribs[0][0];
   LLVMValueRef y = bld->attribs[0][1];
   const int xstep = 2, ystep = 2;

   if (quad_index == 1 || quad_index == 3) {
      /* top-right or bottom-right quad in block */
      /* build x += xstep */
      x = lp_build_add(&bld->base, x,
                       lp_build_const_vec(bld->base.type, xstep));
   }

   if (quad_index == 2) {
      /* bottom-left quad in block */
      /* build y += ystep */
      y = lp_build_add(&bld->base, y,
                       lp_build_const_vec(bld->base.type, ystep));
      /* build x -= xstep */
      x = lp_build_sub(&bld->base, x,
                       lp_build_const_vec(bld->base.type, xstep));
   }

   lp_build_name(x, "pos.x");
   lp_build_name(y, "pos.y");

   bld->attribs[0][0] = x;
   bld->attribs[0][1] = y;
}


/**
 * Initialize fragment shader input attribute info.
 */
void
lp_build_interp_soa_init(struct lp_build_interp_soa_context *bld,
                         unsigned num_inputs,
                         const struct lp_shader_input *inputs,
                         LLVMBuilderRef builder,
                         struct lp_type type,
                         LLVMValueRef a0_ptr,
                         LLVMValueRef dadx_ptr,
                         LLVMValueRef dady_ptr,
                         LLVMValueRef x0,
                         LLVMValueRef y0)
{
   unsigned attrib;
   unsigned chan;

   memset(bld, 0, sizeof *bld);

   lp_build_context_init(&bld->base, builder, type);

   /* For convenience */
   bld->pos = bld->attribs[0];
   bld->inputs = (const LLVMValueRef (*)[NUM_CHANNELS]) bld->attribs[1];

   /* Position */
   bld->num_attribs = 1;
   bld->mask[0] = TGSI_WRITEMASK_ZW;
   bld->interp[0] = LP_INTERP_LINEAR;

   /* Inputs */
   for (attrib = 0; attrib < num_inputs; ++attrib) {
      bld->mask[1 + attrib] = inputs[attrib].usage_mask;
      bld->interp[1 + attrib] = inputs[attrib].interp;
   }
   bld->num_attribs = 1 + num_inputs;

   /* Ensure all masked out input channels have a valid value */
   for (attrib = 0; attrib < bld->num_attribs; ++attrib) {
      for (chan = 0; chan < NUM_CHANNELS; ++chan) {
         bld->attribs[attrib][chan] = bld->base.undef;
      }
   }

   coeffs_init(bld, a0_ptr, dadx_ptr, dady_ptr);

   pos_init(bld, x0, y0);

   attribs_init(bld);
}


/**
 * Advance the position and inputs to the given quad within the block.
 */
void
lp_build_interp_soa_update(struct lp_build_interp_soa_context *bld,
                           int quad_index)
{
   assert(quad_index < 4);

   pos_update(bld, quad_index);

   attribs_update(bld, quad_index);
}