src/gallium/drivers/llvmpipe/lp_bld_blend_soa.c

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  27
  28
  29 /**
  30  * @file
  31  * Blend LLVM IR generation -- SoA layout.
  32  *
  33  * Blending in SoA is much faster than AoS, especially when separate rgb/alpha
  34  * factors/functions are used, since no channel masking/shuffling is necessary
  35  * and we can achieve the full throughput of the SIMD operations. Furthermore
  36  * the fragment shader output is also in SoA, so it fits nicely with the rest
  37  * of the fragment pipeline.
  38  *
  39  * The drawback is that to be displayed the color buffer needs to be in AoS
  40  * layout, so we need to tile/untile the color buffer before/after rendering.
  41  * A color buffer like
  42  *
  43  *  R11 G11 B11 A11 R12 G12 B12 A12  R13 G13 B13 A13 R14 G14 B14 A14  ...
  44  *  R21 G21 B21 A21 R22 G22 B22 A22  R23 G23 B23 A23 R24 G24 B24 A24  ...
  45  *
  46  *  R31 G31 B31 A31 R32 G32 B32 A32  R33 G33 B33 A33 R34 G34 B34 A34  ...
  47  *  R41 G41 B41 A41 R42 G42 B42 A42  R43 G43 B43 A43 R44 G44 B44 A44  ...
  48  *
  49  *  ... ... ... ... ... ... ... ...  ... ... ... ... ... ... ... ...  ...
  50  *
  51  * will actually be stored in memory as
  52  *
  53  *  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 ...
  54  *  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 ...
  55  *  ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
  56  *
  57  * NOTE: Run lp_blend_test after any change to this file.
  58  *
  59  * You can also run lp_blend_test to obtain AoS vs SoA benchmarks. Invoking it
  60  * as:
  61  *
  62  *  lp_blend_test -o blend.tsv
  63  *
  64  * will generate a tab-seperated-file with the test results and performance
  65  * measurements.
  66  *
  67  * @author Jose Fonseca <jfonseca@vmware.com>
  68  */
  69
  70
  71 #include "pipe/p_state.h"
  72 #include "util/u_debug.h"
  73
  74 #include "gallivm/lp_bld_type.h"
  75 #include "gallivm/lp_bld_arit.h"
  76 #include "gallivm/lp_bld_init.h"
  77 #include "lp_bld_blend.h"
  78
  79
  80 /**
  81  * We may use the same values several times, so we keep them here to avoid
  82  * recomputing them. Also reusing the values allows us to do simplifications
  83  * that LLVM optimization passes wouldn't normally be able to do.
  84  */
  85 struct lp_build_blend_soa_context
  86 {
  87    struct lp_build_context base;
  88
  89    LLVMValueRef src[4];
  90    LLVMValueRef dst[4];
  91    LLVMValueRef con[4];
  92
  93    LLVMValueRef inv_src[4];
  94    LLVMValueRef inv_dst[4];
  95    LLVMValueRef inv_con[4];
  96
  97    LLVMValueRef src_alpha_saturate;
  98
  99    /**
 100     * We store all factors in a table in order to eliminate redundant
 101     * multiplications later.
 102     * Indexes are: factor[src,dst][color,term][r,g,b,a]
 103     */
 104    LLVMValueRef factor[2][2][4];
 105
 106    /**
 107     * Table with all terms.
 108     * Indexes are: term[src,dst][r,g,b,a]
 109     */
 110    LLVMValueRef term[2][4];
 111 };
 112
 113
 114 /**
 115  * Build a single SOA blend factor for a color channel.
 116  * \param i  the color channel in [0,3]
 117  */
 118 static LLVMValueRef
 119 lp_build_blend_soa_factor(struct lp_build_blend_soa_context *bld,
 120                           unsigned factor, unsigned i)
 121 {
 122    /*
 123     * Compute src/first term RGB
 124     */
 125    switch (factor) {
 126    case PIPE_BLENDFACTOR_ONE:
 127       return bld->base.one;
 128    case PIPE_BLENDFACTOR_SRC_COLOR:
 129       return bld->src[i];
 130    case PIPE_BLENDFACTOR_SRC_ALPHA:
 131       return bld->src[3];
 132    case PIPE_BLENDFACTOR_DST_COLOR:
 133       return bld->dst[i];
 134    case PIPE_BLENDFACTOR_DST_ALPHA:
 135       return bld->dst[3];
 136    case PIPE_BLENDFACTOR_SRC_ALPHA_SATURATE:
 137       if(i == 3)
 138          return bld->base.one;
 139       else {
 140          if(!bld->inv_dst[3])
 141             bld->inv_dst[3] = lp_build_comp(&bld->base, bld->dst[3]);
 142          if(!bld->src_alpha_saturate)
 143             bld->src_alpha_saturate = lp_build_min(&bld->base, bld->src[3], bld->inv_dst[3]);
 144          return bld->src_alpha_saturate;
 145       }
 146    case PIPE_BLENDFACTOR_CONST_COLOR:
 147       return bld->con[i];
 148    case PIPE_BLENDFACTOR_CONST_ALPHA:
 149       return bld->con[3];
 150    case PIPE_BLENDFACTOR_SRC1_COLOR:
 151       /* TODO */
 152       assert(0);
 153       return bld->base.zero;
 154    case PIPE_BLENDFACTOR_SRC1_ALPHA:
 155       /* TODO */
 156       assert(0);
 157       return bld->base.zero;
 158    case PIPE_BLENDFACTOR_ZERO:
 159       return bld->base.zero;
 160    case PIPE_BLENDFACTOR_INV_SRC_COLOR:
 161       if(!bld->inv_src[i])
 162          bld->inv_src[i] = lp_build_comp(&bld->base, bld->src[i]);
 163       return bld->inv_src[i];
 164    case PIPE_BLENDFACTOR_INV_SRC_ALPHA:
 165       if(!bld->inv_src[3])
 166          bld->inv_src[3] = lp_build_comp(&bld->base, bld->src[3]);
 167       return bld->inv_src[3];
 168    case PIPE_BLENDFACTOR_INV_DST_COLOR:
 169       if(!bld->inv_dst[i])
 170          bld->inv_dst[i] = lp_build_comp(&bld->base, bld->dst[i]);
 171       return bld->inv_dst[i];
 172    case PIPE_BLENDFACTOR_INV_DST_ALPHA:
 173       if(!bld->inv_dst[3])
 174          bld->inv_dst[3] = lp_build_comp(&bld->base, bld->dst[3]);
 175       return bld->inv_dst[3];
 176    case PIPE_BLENDFACTOR_INV_CONST_COLOR:
 177       if(!bld->inv_con[i])
 178          bld->inv_con[i] = lp_build_comp(&bld->base, bld->con[i]);
 179       return bld->inv_con[i];
 180    case PIPE_BLENDFACTOR_INV_CONST_ALPHA:
 181       if(!bld->inv_con[3])
 182          bld->inv_con[3] = lp_build_comp(&bld->base, bld->con[3]);
 183       return bld->inv_con[3];
 184    case PIPE_BLENDFACTOR_INV_SRC1_COLOR:
 185       /* TODO */
 186       assert(0);
 187       return bld->base.zero;
 188    case PIPE_BLENDFACTOR_INV_SRC1_ALPHA:
 189       /* TODO */
 190       assert(0);
 191       return bld->base.zero;
 192    default:
 193       assert(0);
 194       return bld->base.zero;
 195    }
 196 }
 197
 198
 199 static boolean
 200 lp_build_blend_factor_complementary(unsigned src_factor, unsigned dst_factor)
 201 {
 202    return dst_factor == (src_factor ^ 0x10);
 203 }
 204
 205
 206 /**
 207  * Generate blend code in SOA mode.
 208  * \param rt  render target index (to index the blend / colormask state)
 209  * \param src  src/fragment color
 210  * \param dst  dst/framebuffer color
 211  * \param con  constant blend color
 212  * \param res  the result/output
 213  */
 214 void
 215 lp_build_blend_soa(struct gallivm_state *gallivm,
 216                    const struct pipe_blend_state *blend,
 217                    struct lp_type type,
 218                    unsigned rt,
 219                    LLVMValueRef src[4],
 220                    LLVMValueRef dst[4],
 221                    LLVMValueRef con[4],
 222                    LLVMValueRef res[4])
 223 {
 224    LLVMBuilderRef builder = gallivm->builder;
 225    struct lp_build_blend_soa_context bld;
 226    unsigned i, j, k;
 227
 228    assert(rt < PIPE_MAX_COLOR_BUFS);
 229
 230    /* Setup build context */
 231    memset(&bld, 0, sizeof bld);
 232    lp_build_context_init(&bld.base, gallivm, type);
 233    for (i = 0; i < 4; ++i) {
 234       bld.src[i] = src[i];
 235       bld.dst[i] = dst[i];
 236       bld.con[i] = con[i];
 237    }
 238
 239    for (i = 0; i < 4; ++i) {
 240       /* only compute blending for the color channels enabled for writing */
 241       if (blend->rt[rt].colormask & (1 << i)) {
 242          if (blend->logicop_enable) {
 243             if(!type.floating) {
 244                res[i] = lp_build_logicop(builder, blend->logicop_func, src[i], dst[i]);
 245             }
 246             else
 247                res[i] = dst[i];
 248          }
 249          else if (blend->rt[rt].blend_enable) {
 250             unsigned src_factor = i < 3 ? blend->rt[rt].rgb_src_factor : blend->rt[rt].alpha_src_factor;
 251             unsigned dst_factor = i < 3 ? blend->rt[rt].rgb_dst_factor : blend->rt[rt].alpha_dst_factor;
 252             unsigned func = i < 3 ? blend->rt[rt].rgb_func : blend->rt[rt].alpha_func;
 253             boolean func_commutative = lp_build_blend_func_commutative(func);
 254
 255             if (func == PIPE_BLEND_ADD &&
 256                 lp_build_blend_factor_complementary(src_factor, dst_factor) && 0) {
 257                /*
 258                 * Special case linear interpolation, (i.e., complementary factors).
 259                 */
 260
 261                LLVMValueRef weight;
 262                if (src_factor < dst_factor) {
 263                   weight = lp_build_blend_soa_factor(&bld, src_factor, i);
 264                   res[i] = lp_build_lerp(&bld.base, weight, dst[i], src[i]);
 265                } else {
 266                   weight = lp_build_blend_soa_factor(&bld, dst_factor, i);
 267                   res[i] = lp_build_lerp(&bld.base, weight, src[i], dst[i]);
 268                }
 269                continue;
 270             }
 271
 272             if ((func == PIPE_BLEND_ADD ||
 273                  func == PIPE_BLEND_SUBTRACT ||
 274                  func == PIPE_BLEND_REVERSE_SUBTRACT) &&
 275                 src_factor == dst_factor &&
 276                 type.floating) {
 277                /*
 278                 * Special common factor.
 279                 *
 280                 * XXX: Only for floating points for now, since saturation will
 281                 * cause different results.
 282                 */
 283
 284                LLVMValueRef factor;
 285                factor = lp_build_blend_soa_factor(&bld, src_factor, i);
 286                res[i] = lp_build_blend_func(&bld.base, func, src[i], dst[i]);
 287                res[i] = lp_build_mul(&bld.base, res[i], factor);
 288                continue;
 289             }
 290
 291             /*
 292              * Compute src/dst factors.
 293              */
 294
 295             bld.factor[0][0][i] = src[i];
 296             bld.factor[0][1][i] = lp_build_blend_soa_factor(&bld, src_factor, i);
 297             bld.factor[1][0][i] = dst[i];
 298             bld.factor[1][1][i] = lp_build_blend_soa_factor(&bld, dst_factor, i);
 299
 300             /*
 301              * Compute src/dst terms
 302              */
 303
 304             for(k = 0; k < 2; ++k) {
 305                /* See if this multiplication has been previously computed */
 306                for(j = 0; j < i; ++j) {
 307                   if((bld.factor[k][0][j] == bld.factor[k][0][i] &&
 308                       bld.factor[k][1][j] == bld.factor[k][1][i]) ||
 309                      (bld.factor[k][0][j] == bld.factor[k][1][i] &&
 310                       bld.factor[k][1][j] == bld.factor[k][0][i]))
 311                      break;
 312                }
 313
 314                if(j < i)
 315                   bld.term[k][i] = bld.term[k][j];
 316                else
 317                   bld.term[k][i] = lp_build_mul(&bld.base, bld.factor[k][0][i], bld.factor[k][1][i]);
 318
 319                if (src_factor == PIPE_BLENDFACTOR_ZERO &&
 320                    (dst_factor == PIPE_BLENDFACTOR_DST_ALPHA ||
 321                     dst_factor == PIPE_BLENDFACTOR_INV_DST_ALPHA)) {
 322                   /* XXX special case these combos to work around an apparent
 323                    * bug in LLVM.
 324                    * This hack disables the check for multiplication by zero
 325                    * in lp_bld_mul().  When we optimize away the
 326                    * multiplication, something goes wrong during code
 327                    * generation and we segfault at runtime.
 328                    */
 329                   LLVMValueRef zeroSave = bld.base.zero;
 330                   bld.base.zero = NULL;
 331                   bld.term[k][i] = lp_build_mul(&bld.base, bld.factor[k][0][i],
 332                                                 bld.factor[k][1][i]);
 333                   bld.base.zero = zeroSave;
 334                }
 335             }
 336
 337             /*
 338              * Combine terms
 339              */
 340
 341             /* See if this function has been previously applied */
 342             for(j = 0; j < i; ++j) {
 343                unsigned prev_func = j < 3 ? blend->rt[rt].rgb_func : blend->rt[rt].alpha_func;
 344                unsigned func_reverse = lp_build_blend_func_reverse(func, prev_func);
 345
 346                if((!func_reverse &&
 347                    bld.term[0][j] == bld.term[0][i] &&
 348                    bld.term[1][j] == bld.term[1][i]) ||
 349                   ((func_commutative || func_reverse) &&
 350                    bld.term[0][j] == bld.term[1][i] &&
 351                    bld.term[1][j] == bld.term[0][i]))
 352                   break;
 353             }
 354
 355             if(j < i)
 356                res[i] = res[j];
 357             else
 358                res[i] = lp_build_blend_func(&bld.base, func, bld.term[0][i], bld.term[1][i]);
 359          }
 360          else {
 361             res[i] = src[i];
 362          }
 363       }
 364       else {
 365          res[i] = dst[i];
 366       }
 367    }
 368 }