src/gallium/drivers/llvmpipe/lp_bld_depth.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2009 VMware, Inc.
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   7  * copy of this software and associated documentation files (the
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  11  * permit persons to whom the Software is furnished to do so, subject to
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  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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  26  **************************************************************************/
  27
  28 /**
  29  * @file
  30  * Depth/stencil testing to LLVM IR translation.
  31  *
  32  * To be done accurately/efficiently the depth/stencil test must be done with
  33  * the same type/format of the depth/stencil buffer, which implies massaging
  34  * the incoming depths to fit into place. Using a more straightforward
  35  * type/format for depth/stencil values internally and only convert when
  36  * flushing would avoid this, but it would most likely result in depth fighting
  37  * artifacts.
  38  *
  39  * We are free to use a different pixel layout though. Since our basic
  40  * processing unit is a quad (2x2 pixel block) we store the depth/stencil
  41  * values tiled, a quad at time. That is, a depth buffer containing
  42  *
  43  *  Z11 Z12 Z13 Z14 ...
  44  *  Z21 Z22 Z23 Z24 ...
  45  *  Z31 Z32 Z33 Z34 ...
  46  *  Z41 Z42 Z43 Z44 ...
  47  *  ... ... ... ... ...
  48  *
  49  * will actually be stored in memory as
  50  *
  51  *  Z11 Z12 Z21 Z22 Z13 Z14 Z23 Z24 ...
  52  *  Z31 Z32 Z41 Z42 Z33 Z34 Z43 Z44 ...
  53  *  ... ... ... ... ... ... ... ... ...
  54  *
  55  *
  56  * Stencil test:
  57  * Two-sided stencil test is supported but probably not as efficient as
  58  * it could be.  Currently, we use if/then/else constructs to do the
  59  * operations for front vs. back-facing polygons.  We could probably do
  60  * both the front and back arithmetic then use a Select() instruction to
  61  * choose the result depending on polyon orientation.  We'd have to
  62  * measure performance both ways and see which is better.
  63  *
  64  * @author Jose Fonseca <jfonseca@vmware.com>
  65  */
  66
  67 #include "pipe/p_state.h"
  68 #include "util/u_format.h"
  69
  70 #include "gallivm/lp_bld_type.h"
  71 #include "gallivm/lp_bld_arit.h"
  72 #include "gallivm/lp_bld_bitarit.h"
  73 #include "gallivm/lp_bld_const.h"
  74 #include "gallivm/lp_bld_logic.h"
  75 #include "gallivm/lp_bld_flow.h"
  76 #include "gallivm/lp_bld_intr.h"
  77 #include "gallivm/lp_bld_debug.h"
  78 #include "gallivm/lp_bld_swizzle.h"
  79
  80 #include "lp_bld_depth.h"
  81
  82
  83 /** Used to select fields from pipe_stencil_state */
  84 enum stencil_op {
  85    S_FAIL_OP,
  86    Z_FAIL_OP,
  87    Z_PASS_OP
  88 };
  89
  90
  91
  92 /**
  93  * Do the stencil test comparison (compare FB stencil values against ref value).
  94  * This will be used twice when generating two-sided stencil code.
  95  * \param stencil  the front/back stencil state
  96  * \param stencilRef  the stencil reference value, replicated as a vector
  97  * \param stencilVals  vector of stencil values from framebuffer
  98  * \return vector mask of pass/fail values (~0 or 0)
  99  */
 100 static LLVMValueRef
 101 lp_build_stencil_test_single(struct lp_build_context *bld,
 102                              const struct pipe_stencil_state *stencil,
 103                              LLVMValueRef stencilRef,
 104                              LLVMValueRef stencilVals)
 105 {
 106    const unsigned stencilMax = 255; /* XXX fix */
 107    struct lp_type type = bld->type;
 108    LLVMValueRef res;
 109
 110    assert(type.sign);
 111
 112    assert(stencil->enabled);
 113
 114    if (stencil->valuemask != stencilMax) {
 115       /* compute stencilRef = stencilRef & valuemask */
 116       LLVMValueRef valuemask = lp_build_const_int_vec(type, stencil->valuemask);
 117       stencilRef = LLVMBuildAnd(bld->builder, stencilRef, valuemask, "");
 118       /* compute stencilVals = stencilVals & valuemask */
 119       stencilVals = LLVMBuildAnd(bld->builder, stencilVals, valuemask, "");
 120    }
 121
 122    res = lp_build_cmp(bld, stencil->func, stencilRef, stencilVals);
 123
 124    return res;
 125 }
 126
 127
 128 /**
 129  * Do the one or two-sided stencil test comparison.
 130  * \sa lp_build_stencil_test_single
 131  * \param front_facing  an integer vector mask, indicating front (~0) or back
 132  *                      (0) facing polygon. If NULL, assume front-facing.
 133  */
 134 static LLVMValueRef
 135 lp_build_stencil_test(struct lp_build_context *bld,
 136                       const struct pipe_stencil_state stencil[2],
 137                       LLVMValueRef stencilRefs[2],
 138                       LLVMValueRef stencilVals,
 139                       LLVMValueRef front_facing)
 140 {
 141    LLVMValueRef res;
 142
 143    assert(stencil[0].enabled);
 144
 145    /* do front face test */
 146    res = lp_build_stencil_test_single(bld, &stencil[0],
 147                                       stencilRefs[0], stencilVals);
 148
 149    if (stencil[1].enabled && front_facing) {
 150       /* do back face test */
 151       LLVMValueRef back_res;
 152
 153       back_res = lp_build_stencil_test_single(bld, &stencil[1],
 154                                               stencilRefs[1], stencilVals);
 155
 156       res = lp_build_select(bld, front_facing, res, back_res);
 157    }
 158
 159    return res;
 160 }
 161
 162
 163 /**
 164  * Apply the stencil operator (add/sub/keep/etc) to the given vector
 165  * of stencil values.
 166  * \return  new stencil values vector
 167  */
 168 static LLVMValueRef
 169 lp_build_stencil_op_single(struct lp_build_context *bld,
 170                            const struct pipe_stencil_state *stencil,
 171                            enum stencil_op op,
 172                            LLVMValueRef stencilRef,
 173                            LLVMValueRef stencilVals)
 174
 175 {
 176    struct lp_type type = bld->type;
 177    LLVMValueRef res;
 178    LLVMValueRef max = lp_build_const_int_vec(type, 0xff);
 179    unsigned stencil_op;
 180
 181    assert(type.sign);
 182
 183    switch (op) {
 184    case S_FAIL_OP:
 185       stencil_op = stencil->fail_op;
 186       break;
 187    case Z_FAIL_OP:
 188       stencil_op = stencil->zfail_op;
 189       break;
 190    case Z_PASS_OP:
 191       stencil_op = stencil->zpass_op;
 192       break;
 193    default:
 194       assert(0 && "Invalid stencil_op mode");
 195       stencil_op = PIPE_STENCIL_OP_KEEP;
 196    }
 197
 198    switch (stencil_op) {
 199    case PIPE_STENCIL_OP_KEEP:
 200       res = stencilVals;
 201       /* we can return early for this case */
 202       return res;
 203    case PIPE_STENCIL_OP_ZERO:
 204       res = bld->zero;
 205       break;
 206    case PIPE_STENCIL_OP_REPLACE:
 207       res = stencilRef;
 208       break;
 209    case PIPE_STENCIL_OP_INCR:
 210       res = lp_build_add(bld, stencilVals, bld->one);
 211       res = lp_build_min(bld, res, max);
 212       break;
 213    case PIPE_STENCIL_OP_DECR:
 214       res = lp_build_sub(bld, stencilVals, bld->one);
 215       res = lp_build_max(bld, res, bld->zero);
 216       break;
 217    case PIPE_STENCIL_OP_INCR_WRAP:
 218       res = lp_build_add(bld, stencilVals, bld->one);
 219       res = LLVMBuildAnd(bld->builder, res, max, "");
 220       break;
 221    case PIPE_STENCIL_OP_DECR_WRAP:
 222       res = lp_build_sub(bld, stencilVals, bld->one);
 223       res = LLVMBuildAnd(bld->builder, res, max, "");
 224       break;
 225    case PIPE_STENCIL_OP_INVERT:
 226       res = LLVMBuildNot(bld->builder, stencilVals, "");
 227       res = LLVMBuildAnd(bld->builder, res, max, "");
 228       break;
 229    default:
 230       assert(0 && "bad stencil op mode");
 231       res = bld->undef;
 232    }
 233
 234    return res;
 235 }
 236
 237
 238 /**
 239  * Do the one or two-sided stencil test op/update.
 240  */
 241 static LLVMValueRef
 242 lp_build_stencil_op(struct lp_build_context *bld,
 243                     const struct pipe_stencil_state stencil[2],
 244                     enum stencil_op op,
 245                     LLVMValueRef stencilRefs[2],
 246                     LLVMValueRef stencilVals,
 247                     LLVMValueRef mask,
 248                     LLVMValueRef front_facing)
 249
 250 {
 251    LLVMValueRef res;
 252
 253    assert(stencil[0].enabled);
 254
 255    /* do front face op */
 256    res = lp_build_stencil_op_single(bld, &stencil[0], op,
 257                                      stencilRefs[0], stencilVals);
 258
 259    if (stencil[1].enabled && front_facing) {
 260       /* do back face op */
 261       LLVMValueRef back_res;
 262
 263       back_res = lp_build_stencil_op_single(bld, &stencil[1], op,
 264                                             stencilRefs[1], stencilVals);
 265
 266       res = lp_build_select(bld, front_facing, res, back_res);
 267    }
 268
 269    if (stencil->writemask != 0xff) {
 270       /* mask &= stencil->writemask */
 271       LLVMValueRef writemask = lp_build_const_int_vec(bld->type, stencil->writemask);
 272       mask = LLVMBuildAnd(bld->builder, mask, writemask, "");
 273       /* res = (res & mask) | (stencilVals & ~mask) */
 274       res = lp_build_select_bitwise(bld, writemask, res, stencilVals);
 275    }
 276    else {
 277       /* res = mask ? res : stencilVals */
 278       res = lp_build_select(bld, mask, res, stencilVals);
 279    }
 280
 281    return res;
 282 }
 283
 284
 285
 286 /**
 287  * Return a type appropriate for depth/stencil testing.
 288  */
 289 struct lp_type
 290 lp_depth_type(const struct util_format_description *format_desc,
 291               unsigned length)
 292 {
 293    struct lp_type type;
 294    unsigned swizzle;
 295
 296    assert(format_desc->colorspace == UTIL_FORMAT_COLORSPACE_ZS);
 297    assert(format_desc->block.width == 1);
 298    assert(format_desc->block.height == 1);
 299
 300    swizzle = format_desc->swizzle[0];
 301    assert(swizzle < 4);
 302
 303    memset(&type, 0, sizeof type);
 304    type.width = format_desc->block.bits;
 305
 306    if(format_desc->channel[swizzle].type == UTIL_FORMAT_TYPE_FLOAT) {
 307       type.floating = TRUE;
 308       assert(swizzle == 0);
 309       assert(format_desc->channel[swizzle].size == format_desc->block.bits);
 310    }
 311    else if(format_desc->channel[swizzle].type == UTIL_FORMAT_TYPE_UNSIGNED) {
 312       assert(format_desc->block.bits <= 32);
 313       if(format_desc->channel[swizzle].normalized)
 314          type.norm = TRUE;
 315    }
 316    else
 317       assert(0);
 318
 319    assert(type.width <= length);
 320    type.length = length / type.width;
 321
 322    return type;
 323 }
 324
 325
 326 /**
 327  * Compute bitmask and bit shift to apply to the incoming fragment Z values
 328  * and the Z buffer values needed before doing the Z comparison.
 329  *
 330  * Note that we leave the Z bits in the position that we find them
 331  * in the Z buffer (typically 0xffffff00 or 0x00ffffff).  That lets us
 332  * get by with fewer bit twiddling steps.
 333  */
 334 static boolean
 335 get_z_shift_and_mask(const struct util_format_description *format_desc,
 336                      unsigned *shift, unsigned *mask)
 337 {
 338    const unsigned total_bits = format_desc->block.bits;
 339    unsigned z_swizzle;
 340    unsigned chan;
 341    unsigned padding_left, padding_right;
 342
 343    assert(format_desc->colorspace == UTIL_FORMAT_COLORSPACE_ZS);
 344    assert(format_desc->block.width == 1);
 345    assert(format_desc->block.height == 1);
 346
 347    z_swizzle = format_desc->swizzle[0];
 348
 349    if (z_swizzle == UTIL_FORMAT_SWIZZLE_NONE)
 350       return FALSE;
 351
 352    padding_right = 0;
 353    for (chan = 0; chan < z_swizzle; ++chan)
 354       padding_right += format_desc->channel[chan].size;
 355
 356    padding_left =
 357       total_bits - (padding_right + format_desc->channel[z_swizzle].size);
 358
 359    if (padding_left || padding_right) {
 360       unsigned long long mask_left = (1ULL << (total_bits - padding_left)) - 1;
 361       unsigned long long mask_right = (1ULL << (padding_right)) - 1;
 362       *mask = mask_left ^ mask_right;
 363    }
 364    else {
 365       *mask = 0xffffffff;
 366    }
 367
 368    *shift = padding_left;
 369
 370    return TRUE;
 371 }
 372
 373
 374 /**
 375  * Compute bitmask and bit shift to apply to the framebuffer pixel values
 376  * to put the stencil bits in the least significant position.
 377  * (i.e. 0x000000ff)
 378  */
 379 static boolean
 380 get_s_shift_and_mask(const struct util_format_description *format_desc,
 381                      unsigned *shift, unsigned *mask)
 382 {
 383    unsigned s_swizzle;
 384    unsigned chan, sz;
 385
 386    s_swizzle = format_desc->swizzle[1];
 387
 388    if (s_swizzle == UTIL_FORMAT_SWIZZLE_NONE)
 389       return FALSE;
 390
 391    *shift = 0;
 392    for (chan = 0; chan < s_swizzle; chan++)
 393       *shift += format_desc->channel[chan].size;
 394
 395    sz = format_desc->channel[s_swizzle].size;
 396    *mask = (1U << sz) - 1U;
 397
 398    return TRUE;
 399 }
 400
 401
 402 /**
 403  * Perform the occlusion test and increase the counter.
 404  * Test the depth mask. Add the number of channel which has none zero mask
 405  * into the occlusion counter. e.g. maskvalue is {-1, -1, -1, -1}.
 406  * The counter will add 4.
 407  *
 408  * \param type holds element type of the mask vector.
 409  * \param maskvalue is the depth test mask.
 410  * \param counter is a pointer of the uint32 counter.
 411  */
 412 static void
 413 lp_build_occlusion_count(LLVMBuilderRef builder,
 414                          struct lp_type type,
 415                          LLVMValueRef maskvalue,
 416                          LLVMValueRef counter)
 417 {
 418    LLVMValueRef countmask = lp_build_const_int_vec(type, 1);
 419    LLVMValueRef countv = LLVMBuildAnd(builder, maskvalue, countmask, "countv");
 420    LLVMTypeRef i8v16 = LLVMVectorType(LLVMInt8Type(), 16);
 421    LLVMValueRef counti = LLVMBuildBitCast(builder, countv, i8v16, "counti");
 422    LLVMValueRef maskarray[4] = {
 423       LLVMConstInt(LLVMInt32Type(), 0, 0),
 424       LLVMConstInt(LLVMInt32Type(), 4, 0),
 425       LLVMConstInt(LLVMInt32Type(), 8, 0),
 426       LLVMConstInt(LLVMInt32Type(), 12, 0),
 427    };
 428    LLVMValueRef shufflemask = LLVMConstVector(maskarray, 4);
 429    LLVMValueRef shufflev =  LLVMBuildShuffleVector(builder, counti, LLVMGetUndef(i8v16), shufflemask, "shufflev");
 430    LLVMValueRef shuffle = LLVMBuildBitCast(builder, shufflev, LLVMInt32Type(), "shuffle");
 431    LLVMValueRef count = lp_build_intrinsic_unary(builder, "llvm.ctpop.i32", LLVMInt32Type(), shuffle);
 432    LLVMValueRef orig = LLVMBuildLoad(builder, counter, "orig");
 433    LLVMValueRef incr = LLVMBuildAdd(builder, orig, count, "incr");
 434    LLVMBuildStore(builder, incr, counter);
 435 }
 436
 437
 438
 439 /**
 440  * Generate code for performing depth and/or stencil tests.
 441  * We operate on a vector of values (typically a 2x2 quad).
 442  *
 443  * \param depth  the depth test state
 444  * \param stencil  the front/back stencil state
 445  * \param type  the data type of the fragment depth/stencil values
 446  * \param format_desc  description of the depth/stencil surface
 447  * \param mask  the alive/dead pixel mask for the quad (vector)
 448  * \param stencil_refs  the front/back stencil ref values (scalar)
 449  * \param z_src  the incoming depth/stencil values (a 2x2 quad)
 450  * \param zs_dst_ptr  pointer to depth/stencil values in framebuffer
 451  * \param facing  contains float value indicating front/back facing polygon
 452  */
 453 void
 454 lp_build_depth_stencil_test(LLVMBuilderRef builder,
 455                             const struct pipe_depth_state *depth,
 456                             const struct pipe_stencil_state stencil[2],
 457                             struct lp_type type,
 458                             const struct util_format_description *format_desc,
 459                             struct lp_build_mask_context *mask,
 460                             LLVMValueRef stencil_refs[2],
 461                             LLVMValueRef z_src,
 462                             LLVMValueRef zs_dst_ptr,
 463                             LLVMValueRef face,
 464                             LLVMValueRef counter)
 465 {
 466    struct lp_build_context bld;
 467    struct lp_build_context sbld;
 468    struct lp_type s_type;
 469    LLVMValueRef zs_dst, z_dst = NULL;
 470    LLVMValueRef stencil_vals = NULL;
 471    LLVMValueRef z_bitmask = NULL, stencil_shift = NULL;
 472    LLVMValueRef z_pass = NULL, s_pass_mask = NULL;
 473    LLVMValueRef orig_mask = mask->value;
 474    LLVMValueRef front_facing = NULL;
 475
 476    /* Sanity checking */
 477    {
 478       const unsigned z_swizzle = format_desc->swizzle[0];
 479       const unsigned s_swizzle = format_desc->swizzle[1];
 480
 481       assert(z_swizzle != UTIL_FORMAT_SWIZZLE_NONE ||
 482              s_swizzle != UTIL_FORMAT_SWIZZLE_NONE);
 483
 484       assert(depth->enabled || stencil[0].enabled);
 485
 486       assert(format_desc->colorspace == UTIL_FORMAT_COLORSPACE_ZS);
 487       assert(format_desc->block.width == 1);
 488       assert(format_desc->block.height == 1);
 489
 490       if (stencil[0].enabled) {
 491          assert(format_desc->format == PIPE_FORMAT_Z24_UNORM_S8_USCALED ||
 492                 format_desc->format == PIPE_FORMAT_S8_USCALED_Z24_UNORM);
 493       }
 494
 495       assert(z_swizzle < 4);
 496       assert(format_desc->block.bits == type.width);
 497       if (type.floating) {
 498          assert(z_swizzle == 0);
 499          assert(format_desc->channel[z_swizzle].type ==
 500                 UTIL_FORMAT_TYPE_FLOAT);
 501          assert(format_desc->channel[z_swizzle].size ==
 502                 format_desc->block.bits);
 503       }
 504       else {
 505          assert(format_desc->channel[z_swizzle].type ==
 506                 UTIL_FORMAT_TYPE_UNSIGNED);
 507          assert(format_desc->channel[z_swizzle].normalized);
 508          assert(!type.fixed);
 509          assert(!type.sign);
 510          assert(type.norm);
 511       }
 512    }
 513
 514
 515    /* Setup build context for Z vals */
 516    lp_build_context_init(&bld, builder, type);
 517
 518    /* Setup build context for stencil vals */
 519    s_type = lp_type_int_vec(type.width);
 520    lp_build_context_init(&sbld, builder, s_type);
 521
 522    /* Load current z/stencil value from z/stencil buffer */
 523    zs_dst = LLVMBuildLoad(builder, zs_dst_ptr, "");
 524
 525    lp_build_name(zs_dst, "zsbufval");
 526
 527
 528    /* Compute and apply the Z/stencil bitmasks and shifts.
 529     */
 530    {
 531       unsigned z_shift, z_mask;
 532       unsigned s_shift, s_mask;
 533
 534       if (get_z_shift_and_mask(format_desc, &z_shift, &z_mask)) {
 535          if (z_shift) {
 536             LLVMValueRef shift = lp_build_const_int_vec(type, z_shift);
 537             z_src = LLVMBuildLShr(builder, z_src, shift, "");
 538          }
 539
 540          if (z_mask != 0xffffffff) {
 541             LLVMValueRef mask = lp_build_const_int_vec(type, z_mask);
 542             z_src = LLVMBuildAnd(builder, z_src, mask, "");
 543             z_dst = LLVMBuildAnd(builder, zs_dst, mask, "");
 544             z_bitmask = mask;  /* used below */
 545          }
 546          else {
 547             z_dst = zs_dst;
 548          }
 549
 550          lp_build_name(z_dst, "zsbuf.z");
 551       }
 552
 553       if (get_s_shift_and_mask(format_desc, &s_shift, &s_mask)) {
 554          if (s_shift) {
 555             LLVMValueRef shift = lp_build_const_int_vec(type, s_shift);
 556             stencil_vals = LLVMBuildLShr(builder, zs_dst, shift, "");
 557             stencil_shift = shift;  /* used below */
 558          }
 559          else {
 560             stencil_vals = zs_dst;
 561          }
 562
 563          if (s_mask != 0xffffffff) {
 564             LLVMValueRef mask = lp_build_const_int_vec(type, s_mask);
 565             stencil_vals = LLVMBuildAnd(builder, stencil_vals, mask, "");
 566          }
 567
 568          lp_build_name(stencil_vals, "stencil");
 569       }
 570    }
 571
 572    if (stencil[0].enabled) {
 573
 574       if (face) {
 575          LLVMValueRef zero = LLVMConstReal(LLVMFloatType(), 0.0);
 576
 577          /* front_facing = face > 0.0 ? ~0 : 0 */
 578          front_facing = LLVMBuildFCmp(builder, LLVMRealUGT, face, zero, "");
 579          front_facing = LLVMBuildSExt(builder, front_facing,
 580                                       LLVMIntType(bld.type.length*bld.type.width),
 581                                       "");
 582          front_facing = LLVMBuildBitCast(builder, front_facing,
 583                                          bld.int_vec_type, "");
 584       }
 585
 586       /* convert scalar stencil refs into vectors */
 587       stencil_refs[0] = lp_build_broadcast_scalar(&bld, stencil_refs[0]);
 588       stencil_refs[1] = lp_build_broadcast_scalar(&bld, stencil_refs[1]);
 589
 590       s_pass_mask = lp_build_stencil_test(&sbld, stencil,
 591                                           stencil_refs, stencil_vals,
 592                                           front_facing);
 593
 594       /* apply stencil-fail operator */
 595       {
 596          LLVMValueRef s_fail_mask = lp_build_andnot(&bld, orig_mask, s_pass_mask);
 597          stencil_vals = lp_build_stencil_op(&sbld, stencil, S_FAIL_OP,
 598                                             stencil_refs, stencil_vals,
 599                                             s_fail_mask, front_facing);
 600       }
 601    }
 602
 603    if (depth->enabled) {
 604       /* compare src Z to dst Z, returning 'pass' mask */
 605       z_pass = lp_build_cmp(&bld, depth->func, z_src, z_dst);
 606
 607       if (!stencil[0].enabled) {
 608          /* We can potentially skip all remaining operations here, but only
 609           * if stencil is disabled because we still need to update the stencil
 610           * buffer values.  Don't need to update Z buffer values.
 611           */
 612          lp_build_mask_update(mask, z_pass);
 613       }
 614
 615       if (depth->writemask) {
 616          LLVMValueRef zselectmask = mask->value;
 617
 618          /* mask off bits that failed Z test */
 619          zselectmask = LLVMBuildAnd(builder, zselectmask, z_pass, "");
 620
 621          /* mask off bits that failed stencil test */
 622          if (s_pass_mask) {
 623             zselectmask = LLVMBuildAnd(builder, zselectmask, s_pass_mask, "");
 624          }
 625
 626          /* if combined Z/stencil format, mask off the stencil bits */
 627          if (z_bitmask) {
 628             zselectmask = LLVMBuildAnd(builder, zselectmask, z_bitmask, "");
 629          }
 630
 631          /* Mix the old and new Z buffer values.
 632           * z_dst[i] = (zselectmask[i] & z_src[i]) | (~zselectmask[i] & z_dst[i])
 633           */
 634          z_dst = lp_build_select_bitwise(&bld, zselectmask, z_src, z_dst);
 635       }
 636
 637       if (stencil[0].enabled) {
 638          /* update stencil buffer values according to z pass/fail result */
 639          LLVMValueRef z_fail_mask, z_pass_mask;
 640
 641          /* apply Z-fail operator */
 642          z_fail_mask = lp_build_andnot(&bld, orig_mask, z_pass);
 643          stencil_vals = lp_build_stencil_op(&sbld, stencil, Z_FAIL_OP,
 644                                             stencil_refs, stencil_vals,
 645                                             z_fail_mask, front_facing);
 646
 647          /* apply Z-pass operator */
 648          z_pass_mask = LLVMBuildAnd(bld.builder, orig_mask, z_pass, "");
 649          stencil_vals = lp_build_stencil_op(&sbld, stencil, Z_PASS_OP,
 650                                             stencil_refs, stencil_vals,
 651                                             z_pass_mask, front_facing);
 652       }
 653    }
 654    else {
 655       /* No depth test: apply Z-pass operator to stencil buffer values which
 656        * passed the stencil test.
 657        */
 658       s_pass_mask = LLVMBuildAnd(bld.builder, orig_mask, s_pass_mask, "");
 659       stencil_vals = lp_build_stencil_op(&sbld, stencil, Z_PASS_OP,
 660                                          stencil_refs, stencil_vals,
 661                                          s_pass_mask, front_facing);
 662    }
 663
 664    /* The Z bits are already in the right place but we may need to shift the
 665     * stencil bits before ORing Z with Stencil to make the final pixel value.
 666     */
 667    if (stencil_vals && stencil_shift)
 668       stencil_vals = LLVMBuildShl(bld.builder, stencil_vals,
 669                                   stencil_shift, "");
 670
 671    /* Finally, merge/store the z/stencil values */
 672    if ((depth->enabled && depth->writemask) ||
 673        (stencil[0].enabled && stencil[0].writemask)) {
 674
 675       if (z_dst && stencil_vals)
 676          zs_dst = LLVMBuildOr(bld.builder, z_dst, stencil_vals, "");
 677       else if (z_dst)
 678          zs_dst = z_dst;
 679       else
 680          zs_dst = stencil_vals;
 681
 682       LLVMBuildStore(builder, zs_dst, zs_dst_ptr);
 683    }
 684
 685    if (s_pass_mask)
 686       lp_build_mask_update(mask, s_pass_mask);
 687
 688    if (depth->enabled && stencil[0].enabled)
 689       lp_build_mask_update(mask, z_pass);
 690
 691    if (counter)
 692       lp_build_occlusion_count(builder, type, mask->value, counter);
 693 }