drivers/llvmpipe/lp_bld_blend_soa.c

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/**
 * @file
 * Blend LLVM IR generation -- SoA layout.
 *
 * Blending in SoA is much faster than AoS, especially when separate rgb/alpha
 * factors/functions are used, since no channel masking/shuffling is necessary
 * and we can achieve the full throughput of the SIMD operations. Furthermore
 * the fragment shader output is also in SoA, so it fits nicely with the rest
 * of the fragment pipeline.
 *
 * The drawback is that to be displayed the color buffer needs to be in AoS
 * layout, so we need to tile/untile the color buffer before/after rendering.
 * A color buffer like
 *
 *  R11 G11 B11 A11 R12 G12 B12 A12  R13 G13 B13 A13 R14 G14 B14 A14  ...
 *  R21 G21 B21 A21 R22 G22 B22 A22  R23 G23 B23 A23 R24 G24 B24 A24  ...
 *
 *  R31 G31 B31 A31 R32 G32 B32 A32  R33 G33 B33 A33 R34 G34 B34 A34  ...
 *  R41 G41 B41 A41 R42 G42 B42 A42  R43 G43 B43 A43 R44 G44 B44 A44  ...
 *
 *  ... ... ... ... ... ... ... ...  ... ... ... ... ... ... ... ...  ...
 *
 * will actually be stored in memory as
 *
 *  R11 R12 R21 R22 R13 R14 R23 R24 ... G11 G12 G21 G22 G13 G14 G23 G24 ... B11 B12 B21 B22 B13 B14 B23 B24 ... A11 A12 A21 A22 A13 A14 A23 A24 ...
 *  R31 R32 R41 R42 R33 R34 R43 R44 ... G31 G32 G41 G42 G33 G34 G43 G44 ... B31 B32 B41 B42 B33 B34 B43 B44 ... A31 A32 A41 A42 A33 A34 A43 A44 ...
 *  ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
 *
 * NOTE: Run lp_blend_test after any change to this file.
 *
 * You can also run lp_blend_test to obtain AoS vs SoA benchmarks. Invoking it
 * as:
 *
 *  lp_blend_test -o blend.tsv
 *
 * will generate a tab-seperated-file with the test results and performance
 * measurements.
 *
 * @author Jose Fonseca <jfonseca@vmware.com>
 */


#include "pipe/p_state.h"
#include "util/u_debug.h"

#include "gallivm/lp_bld_type.h"
#include "gallivm/lp_bld_arit.h"
#include "gallivm/lp_bld_init.h"
#include "lp_bld_blend.h"


/**
 * We may use the same values several times, so we keep them here to avoid
 * recomputing them. Also reusing the values allows us to do simplifications
 * that LLVM optimization passes wouldn't normally be able to do.
 */
struct lp_build_blend_soa_context
{
   struct lp_build_context base;

   LLVMValueRef src[4];
   LLVMValueRef dst[4];
   LLVMValueRef con[4];

   LLVMValueRef inv_src[4];
   LLVMValueRef inv_dst[4];
   LLVMValueRef inv_con[4];

   LLVMValueRef src_alpha_saturate;

   /**
    * We store all factors in a table in order to eliminate redundant
    * multiplications later.
    * Indexes are: factor[src,dst][color,term][r,g,b,a]
    */
   LLVMValueRef factor[2][2][4];

   /**
    * Table with all terms.
    * Indexes are: term[src,dst][r,g,b,a]
    */
   LLVMValueRef term[2][4];
};


/**
 * Build a single SOA blend factor for a color channel.
 * \param i  the color channel in [0,3]
 */
static LLVMValueRef
lp_build_blend_soa_factor(struct lp_build_blend_soa_context *bld,
                          unsigned factor, unsigned i)
{
   /*
    * Compute src/first term RGB
    */
   switch (factor) {
   case PIPE_BLENDFACTOR_ONE:
      return bld->base.one;
   case PIPE_BLENDFACTOR_SRC_COLOR:
      return bld->src[i];
   case PIPE_BLENDFACTOR_SRC_ALPHA:
      return bld->src[3];
   case PIPE_BLENDFACTOR_DST_COLOR:
      return bld->dst[i];
   case PIPE_BLENDFACTOR_DST_ALPHA:
      return bld->dst[3];
   case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
      if(i == 3)
         return bld->base.one;
      else {
         if(!bld->inv_dst[3])
            bld->inv_dst[3] = lp_build_comp(&bld->base, bld->dst[3]);
         if(!bld->src_alpha_saturate)
            bld->src_alpha_saturate = lp_build_min(&bld->base, bld->src[3], bld->inv_dst[3]);
         return bld->src_alpha_saturate;
      }
   case PIPE_BLENDFACTOR_CONST_COLOR:
      return bld->con[i];
   case PIPE_BLENDFACTOR_CONST_ALPHA:
      return bld->con[3];
   case PIPE_BLENDFACTOR_SRC1_COLOR:
      /* TODO */
      assert(0);
      return bld->base.zero;
   case PIPE_BLENDFACTOR_SRC1_ALPHA:
      /* TODO */
      assert(0);
      return bld->base.zero;
   case PIPE_BLENDFACTOR_ZERO:
      return bld->base.zero;
   case PIPE_BLENDFACTOR_INV_SRC_COLOR:
      if(!bld->inv_src[i])
         bld->inv_src[i] = lp_build_comp(&bld->base, bld->src[i]);
      return bld->inv_src[i];
   case PIPE_BLENDFACTOR_INV_SRC_ALPHA:
      if(!bld->inv_src[3])
         bld->inv_src[3] = lp_build_comp(&bld->base, bld->src[3]);
      return bld->inv_src[3];
   case PIPE_BLENDFACTOR_INV_DST_COLOR:
      if(!bld->inv_dst[i])
         bld->inv_dst[i] = lp_build_comp(&bld->base, bld->dst[i]);
      return bld->inv_dst[i];
   case PIPE_BLENDFACTOR_INV_DST_ALPHA:
      if(!bld->inv_dst[3])
         bld->inv_dst[3] = lp_build_comp(&bld->base, bld->dst[3]);
      return bld->inv_dst[3];
   case PIPE_BLENDFACTOR_INV_CONST_COLOR:
      if(!bld->inv_con[i])
         bld->inv_con[i] = lp_build_comp(&bld->base, bld->con[i]);
      return bld->inv_con[i];
   case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
      if(!bld->inv_con[3])
         bld->inv_con[3] = lp_build_comp(&bld->base, bld->con[3]);
      return bld->inv_con[3];
   case PIPE_BLENDFACTOR_INV_SRC1_COLOR:
      /* TODO */
      assert(0);
      return bld->base.zero;
   case PIPE_BLENDFACTOR_INV_SRC1_ALPHA:
      /* TODO */
      assert(0);
      return bld->base.zero;
   default:
      assert(0);
      return bld->base.zero;
   }
}


static boolean
lp_build_blend_factor_complementary(unsigned src_factor, unsigned dst_factor)
{
   return dst_factor == (src_factor ^ 0x10);
}


/**
 * Generate blend code in SOA mode.
 * \param rt  render target index (to index the blend / colormask state)
 * \param src  src/fragment color
 * \param dst  dst/framebuffer color
 * \param con  constant blend color
 * \param res  the result/output
 */
void
lp_build_blend_soa(struct gallivm_state *gallivm,
                   const struct pipe_blend_state *blend,
                   struct lp_type type,
                   unsigned rt,
                   LLVMValueRef src[4],
                   LLVMValueRef dst[4],
                   LLVMValueRef con[4],
                   LLVMValueRef res[4])
{
   LLVMBuilderRef builder = gallivm->builder;
   struct lp_build_blend_soa_context bld;
   unsigned i, j, k;

   assert(rt < PIPE_MAX_COLOR_BUFS);

   /* Setup build context */
   memset(&bld, 0, sizeof bld);
   lp_build_context_init(&bld.base, gallivm, type);
   for (i = 0; i < 4; ++i) {
      bld.src[i] = src[i];
      bld.dst[i] = dst[i];
      bld.con[i] = con[i];
   }

   for (i = 0; i < 4; ++i) {
      /* only compute blending for the color channels enabled for writing */
      if (blend->rt[rt].colormask & (1 << i)) {
         if (blend->logicop_enable) {
            if(!type.floating) {
               res[i] = lp_build_logicop(builder, blend->logicop_func, src[i], dst[i]);
            }
            else
               res[i] = dst[i];
         }
         else if (blend->rt[rt].blend_enable) {
            unsigned src_factor = i < 3 ? blend->rt[rt].rgb_src_factor : blend->rt[rt].alpha_src_factor;
            unsigned dst_factor = i < 3 ? blend->rt[rt].rgb_dst_factor : blend->rt[rt].alpha_dst_factor;
            unsigned func = i < 3 ? blend->rt[rt].rgb_func : blend->rt[rt].alpha_func;
            boolean func_commutative = lp_build_blend_func_commutative(func);

	    if (func == PIPE_BLEND_ADD &&
		lp_build_blend_factor_complementary(src_factor, dst_factor) && 0) {
               /*
                * Special case linear interpolation, (i.e., complementary factors).
                */

	       LLVMValueRef weight;
	       if (src_factor < dst_factor) {
		  weight = lp_build_blend_soa_factor(&bld, src_factor, i);
		  res[i] = lp_build_lerp(&bld.base, weight, dst[i], src[i]);
	       } else {
		  weight = lp_build_blend_soa_factor(&bld, dst_factor, i);
		  res[i] = lp_build_lerp(&bld.base, weight, src[i], dst[i]);
	       }
	       continue;
	    }

	    if ((func == PIPE_BLEND_ADD ||
                 func == PIPE_BLEND_SUBTRACT ||
                 func == PIPE_BLEND_REVERSE_SUBTRACT) &&
		src_factor == dst_factor &&
                type.floating) {
               /*
                * Special common factor.
                *
                * XXX: Only for floating points for now, since saturation will
                * cause different results.
                */

	       LLVMValueRef factor;
               factor = lp_build_blend_soa_factor(&bld, src_factor, i);
               res[i] = lp_build_blend_func(&bld.base, func, src[i], dst[i]);
               res[i] = lp_build_mul(&bld.base, res[i], factor);
	       continue;
	    }

            /*
             * Compute src/dst factors.
             */

            bld.factor[0][0][i] = src[i];
            bld.factor[0][1][i] = lp_build_blend_soa_factor(&bld, src_factor, i);
            bld.factor[1][0][i] = dst[i];
            bld.factor[1][1][i] = lp_build_blend_soa_factor(&bld, dst_factor, i);

            /*
             * Compute src/dst terms
             */

            for(k = 0; k < 2; ++k) {
               /* See if this multiplication has been previously computed */
               for(j = 0; j < i; ++j) {
                  if((bld.factor[k][0][j] == bld.factor[k][0][i] &&
                      bld.factor[k][1][j] == bld.factor[k][1][i]) ||
                     (bld.factor[k][0][j] == bld.factor[k][1][i] &&
                      bld.factor[k][1][j] == bld.factor[k][0][i]))
                     break;
               }

               if(j < i)
                  bld.term[k][i] = bld.term[k][j];
               else
                  bld.term[k][i] = lp_build_mul(&bld.base, bld.factor[k][0][i], bld.factor[k][1][i]);

               if (src_factor == PIPE_BLENDFACTOR_ZERO &&
                   (dst_factor == PIPE_BLENDFACTOR_DST_ALPHA ||
                    dst_factor == PIPE_BLENDFACTOR_INV_DST_ALPHA)) {
                  /* XXX special case these combos to work around an apparent
                   * bug in LLVM.
                   * This hack disables the check for multiplication by zero
                   * in lp_bld_mul().  When we optimize away the
                   * multiplication, something goes wrong during code
                   * generation and we segfault at runtime.
                   */
                  LLVMValueRef zeroSave = bld.base.zero;
                  bld.base.zero = NULL;
                  bld.term[k][i] = lp_build_mul(&bld.base, bld.factor[k][0][i],
                                                bld.factor[k][1][i]);
                  bld.base.zero = zeroSave;
               }
            }

            /*
             * Combine terms
             */

            /* See if this function has been previously applied */
            for(j = 0; j < i; ++j) {
               unsigned prev_func = j < 3 ? blend->rt[rt].rgb_func : blend->rt[rt].alpha_func;
               unsigned func_reverse = lp_build_blend_func_reverse(func, prev_func);

               if((!func_reverse &&
                   bld.term[0][j] == bld.term[0][i] &&
                   bld.term[1][j] == bld.term[1][i]) ||
                  ((func_commutative || func_reverse) &&
                   bld.term[0][j] == bld.term[1][i] &&
                   bld.term[1][j] == bld.term[0][i]))
                  break;
            }

            if(j < i)
               res[i] = res[j];
            else
               res[i] = lp_build_blend_func(&bld.base, func, bld.term[0][i], bld.term[1][i]);
         }
         else {
            res[i] = src[i];
         }
      }
      else {
         res[i] = dst[i];
      }
   }
}