src/gallium/auxiliary/gallivm/lp_bld_pack.c

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  27
  28
  29 /**
  30  * @file
  31  * Helper functions for packing/unpacking.
  32  *
  33  * Pack/unpacking is necessary for conversion between types of different
  34  * bit width.
  35  *
  36  * They are also commonly used when an computation needs higher
  37  * precision for the intermediate values. For example, if one needs the
  38  * function:
  39  *
  40  *   c = compute(a, b);
  41  *
  42  * to use more precision for intermediate results then one should implement it
  43  * as:
  44  *
  45  *   LLVMValueRef
  46  *   compute(LLVMBuilderRef builder struct lp_type type, LLVMValueRef a, LLVMValueRef b)
  47  *   {
  48  *      struct lp_type wide_type = lp_wider_type(type);
  49  *      LLVMValueRef al, ah, bl, bh, cl, ch, c;
  50  *
  51  *      lp_build_unpack2(builder, type, wide_type, a, &al, &ah);
  52  *      lp_build_unpack2(builder, type, wide_type, b, &bl, &bh);
  53  *
  54  *      cl = compute_half(al, bl);
  55  *      ch = compute_half(ah, bh);
  56  *
  57  *      c = lp_build_pack2(bld->builder, wide_type, type, cl, ch);
  58  *
  59  *      return c;
  60  *   }
  61  *
  62  * where compute_half() would do the computation for half the elements with
  63  * twice the precision.
  64  *
  65  * @author Jose Fonseca <jfonseca@vmware.com>
  66  */
  67
  68
  69 #include "util/u_debug.h"
  70 #include "util/u_math.h"
  71 #include "util/u_cpu_detect.h"
  72
  73 #include "lp_bld_type.h"
  74 #include "lp_bld_const.h"
  75 #include "lp_bld_init.h"
  76 #include "lp_bld_intr.h"
  77 #include "lp_bld_arit.h"
  78 #include "lp_bld_pack.h"
  79
  80
  81 /**
  82  * Build shuffle vectors that match PUNPCKLxx and PUNPCKHxx instructions.
  83  */
  84 static LLVMValueRef
  85 lp_build_const_unpack_shuffle(struct gallivm_state *gallivm,
  86                               unsigned n, unsigned lo_hi)
  87 {
  88    LLVMValueRef elems[LP_MAX_VECTOR_LENGTH];
  89    unsigned i, j;
  90
  91    assert(n <= LP_MAX_VECTOR_LENGTH);
  92    assert(lo_hi < 2);
  93
  94    /* TODO: cache results in a static table */
  95
  96    for(i = 0, j = lo_hi*n/2; i < n; i += 2, ++j) {
  97       elems[i + 0] = lp_build_const_int32(gallivm, 0 + j);
  98       elems[i + 1] = lp_build_const_int32(gallivm, n + j);
  99    }
 100
 101    return LLVMConstVector(elems, n);
 102 }
 103
 104
 105 /**
 106  * Build shuffle vectors that match PACKxx instructions.
 107  */
 108 static LLVMValueRef
 109 lp_build_const_pack_shuffle(struct gallivm_state *gallivm, unsigned n)
 110 {
 111    LLVMValueRef elems[LP_MAX_VECTOR_LENGTH];
 112    unsigned i;
 113
 114    assert(n <= LP_MAX_VECTOR_LENGTH);
 115
 116    for(i = 0; i < n; ++i)
 117       elems[i] = lp_build_const_int32(gallivm, 2*i);
 118
 119    return LLVMConstVector(elems, n);
 120 }
 121
 122
 123 /**
 124  * Interleave vector elements.
 125  *
 126  * Matches the PUNPCKLxx and PUNPCKHxx SSE instructions.
 127  */
 128 LLVMValueRef
 129 lp_build_interleave2(struct gallivm_state *gallivm,
 130                      struct lp_type type,
 131                      LLVMValueRef a,
 132                      LLVMValueRef b,
 133                      unsigned lo_hi)
 134 {
 135    LLVMValueRef shuffle;
 136
 137    shuffle = lp_build_const_unpack_shuffle(gallivm, type.length, lo_hi);
 138
 139    return LLVMBuildShuffleVector(gallivm->builder, a, b, shuffle, "");
 140 }
 141
 142
 143 /**
 144  * Double the bit width.
 145  *
 146  * This will only change the number of bits the values are represented, not the
 147  * values themselves.
 148  */
 149 void
 150 lp_build_unpack2(struct gallivm_state *gallivm,
 151                  struct lp_type src_type,
 152                  struct lp_type dst_type,
 153                  LLVMValueRef src,
 154                  LLVMValueRef *dst_lo,
 155                  LLVMValueRef *dst_hi)
 156 {
 157    LLVMBuilderRef builder = gallivm->builder;
 158    LLVMValueRef msb;
 159    LLVMTypeRef dst_vec_type;
 160
 161    assert(!src_type.floating);
 162    assert(!dst_type.floating);
 163    assert(dst_type.width == src_type.width * 2);
 164    assert(dst_type.length * 2 == src_type.length);
 165
 166    if(dst_type.sign && src_type.sign) {
 167       /* Replicate the sign bit in the most significant bits */
 168       msb = LLVMBuildAShr(builder, src, lp_build_const_int_vec(gallivm, src_type, src_type.width - 1), "");
 169    }
 170    else
 171       /* Most significant bits always zero */
 172       msb = lp_build_zero(gallivm, src_type);
 173
 174    /* Interleave bits */
 175 #ifdef PIPE_ARCH_LITTLE_ENDIAN
 176    *dst_lo = lp_build_interleave2(gallivm, src_type, src, msb, 0);
 177    *dst_hi = lp_build_interleave2(gallivm, src_type, src, msb, 1);
 178 #else
 179    *dst_lo = lp_build_interleave2(gallivm, src_type, msb, src, 0);
 180    *dst_hi = lp_build_interleave2(gallivm, src_type, msb, src, 1);
 181 #endif
 182
 183    /* Cast the result into the new type (twice as wide) */
 184
 185    dst_vec_type = lp_build_vec_type(gallivm, dst_type);
 186
 187    *dst_lo = LLVMBuildBitCast(builder, *dst_lo, dst_vec_type, "");
 188    *dst_hi = LLVMBuildBitCast(builder, *dst_hi, dst_vec_type, "");
 189 }
 190
 191
 192 /**
 193  * Expand the bit width.
 194  *
 195  * This will only change the number of bits the values are represented, not the
 196  * values themselves.
 197  */
 198 void
 199 lp_build_unpack(struct gallivm_state *gallivm,
 200                 struct lp_type src_type,
 201                 struct lp_type dst_type,
 202                 LLVMValueRef src,
 203                 LLVMValueRef *dst, unsigned num_dsts)
 204 {
 205    unsigned num_tmps;
 206    unsigned i;
 207
 208    /* Register width must remain constant */
 209    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 210
 211    /* We must not loose or gain channels. Only precision */
 212    assert(src_type.length == dst_type.length * num_dsts);
 213
 214    num_tmps = 1;
 215    dst[0] = src;
 216
 217    while(src_type.width < dst_type.width) {
 218       struct lp_type tmp_type = src_type;
 219
 220       tmp_type.width *= 2;
 221       tmp_type.length /= 2;
 222
 223       for(i = num_tmps; i--; ) {
 224          lp_build_unpack2(gallivm, src_type, tmp_type, dst[i], &dst[2*i + 0], &dst[2*i + 1]);
 225       }
 226
 227       src_type = tmp_type;
 228
 229       num_tmps *= 2;
 230    }
 231
 232    assert(num_tmps == num_dsts);
 233 }
 234
 235
 236 /**
 237  * Non-interleaved pack.
 238  *
 239  * This will move values as
 240  *
 241  *   lo =   __ l0 __ l1 __ l2 __..  __ ln
 242  *   hi =   __ h0 __ h1 __ h2 __..  __ hn
 243  *   res =  l0 l1 l2 .. ln h0 h1 h2 .. hn
 244  *
 245  * This will only change the number of bits the values are represented, not the
 246  * values themselves.
 247  *
 248  * It is assumed the values are already clamped into the destination type range.
 249  * Values outside that range will produce undefined results. Use
 250  * lp_build_packs2 instead.
 251  */
 252 LLVMValueRef
 253 lp_build_pack2(struct gallivm_state *gallivm,
 254                struct lp_type src_type,
 255                struct lp_type dst_type,
 256                LLVMValueRef lo,
 257                LLVMValueRef hi)
 258 {
 259    LLVMBuilderRef builder = gallivm->builder;
 260 #if HAVE_LLVM < 0x0207
 261    LLVMTypeRef src_vec_type = lp_build_vec_type(gallivm, src_type);
 262 #endif
 263    LLVMTypeRef dst_vec_type = lp_build_vec_type(gallivm, dst_type);
 264    LLVMValueRef shuffle;
 265    LLVMValueRef res = NULL;
 266
 267    assert(!src_type.floating);
 268    assert(!dst_type.floating);
 269    assert(src_type.width == dst_type.width * 2);
 270    assert(src_type.length * 2 == dst_type.length);
 271
 272    /* Check for special cases first */
 273    if(util_cpu_caps.has_sse2 && src_type.width * src_type.length == 128) {
 274       switch(src_type.width) {
 275       case 32:
 276          if(dst_type.sign) {
 277 #if HAVE_LLVM >= 0x0207
 278             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packssdw.128", dst_vec_type, lo, hi);
 279 #else
 280             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packssdw.128", src_vec_type, lo, hi);
 281 #endif
 282          }
 283          else {
 284             if (util_cpu_caps.has_sse4_1) {
 285                return lp_build_intrinsic_binary(builder, "llvm.x86.sse41.packusdw", dst_vec_type, lo, hi);
 286             }
 287             else {
 288                /* use generic shuffle below */
 289                res = NULL;
 290             }
 291          }
 292          break;
 293
 294       case 16:
 295          if(dst_type.sign)
 296 #if HAVE_LLVM >= 0x0207
 297             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packsswb.128", dst_vec_type, lo, hi);
 298 #else
 299             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packsswb.128", src_vec_type, lo, hi);
 300 #endif
 301          else
 302 #if HAVE_LLVM >= 0x0207
 303             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packuswb.128", dst_vec_type, lo, hi);
 304 #else
 305             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packuswb.128", src_vec_type, lo, hi);
 306 #endif
 307          break;
 308
 309       default:
 310          assert(0);
 311          return LLVMGetUndef(dst_vec_type);
 312          break;
 313       }
 314
 315       if (res) {
 316          res = LLVMBuildBitCast(builder, res, dst_vec_type, "");
 317          return res;
 318       }
 319    }
 320
 321    /* generic shuffle */
 322    lo = LLVMBuildBitCast(builder, lo, dst_vec_type, "");
 323    hi = LLVMBuildBitCast(builder, hi, dst_vec_type, "");
 324
 325    shuffle = lp_build_const_pack_shuffle(gallivm, dst_type.length);
 326
 327    res = LLVMBuildShuffleVector(builder, lo, hi, shuffle, "");
 328
 329    return res;
 330 }
 331
 332
 333
 334 /**
 335  * Non-interleaved pack and saturate.
 336  *
 337  * Same as lp_build_pack2 but will saturate values so that they fit into the
 338  * destination type.
 339  */
 340 LLVMValueRef
 341 lp_build_packs2(struct gallivm_state *gallivm,
 342                 struct lp_type src_type,
 343                 struct lp_type dst_type,
 344                 LLVMValueRef lo,
 345                 LLVMValueRef hi)
 346 {
 347    boolean clamp;
 348
 349    assert(!src_type.floating);
 350    assert(!dst_type.floating);
 351    assert(src_type.sign == dst_type.sign);
 352    assert(src_type.width == dst_type.width * 2);
 353    assert(src_type.length * 2 == dst_type.length);
 354
 355    clamp = TRUE;
 356
 357    /* All X86 SSE non-interleaved pack instructions take signed inputs and
 358     * saturate them, so no need to clamp for those cases. */
 359    if(util_cpu_caps.has_sse2 &&
 360       src_type.width * src_type.length == 128 &&
 361       src_type.sign)
 362       clamp = FALSE;
 363
 364    if(clamp) {
 365       struct lp_build_context bld;
 366       unsigned dst_bits = dst_type.sign ? dst_type.width - 1 : dst_type.width;
 367       LLVMValueRef dst_max = lp_build_const_int_vec(gallivm, src_type, ((unsigned long long)1 << dst_bits) - 1);
 368       lp_build_context_init(&bld, gallivm, src_type);
 369       lo = lp_build_min(&bld, lo, dst_max);
 370       hi = lp_build_min(&bld, hi, dst_max);
 371       /* FIXME: What about lower bound? */
 372    }
 373
 374    return lp_build_pack2(gallivm, src_type, dst_type, lo, hi);
 375 }
 376
 377
 378 /**
 379  * Truncate the bit width.
 380  *
 381  * TODO: Handle saturation consistently.
 382  */
 383 LLVMValueRef
 384 lp_build_pack(struct gallivm_state *gallivm,
 385               struct lp_type src_type,
 386               struct lp_type dst_type,
 387               boolean clamped,
 388               const LLVMValueRef *src, unsigned num_srcs)
 389 {
 390    LLVMValueRef (*pack2)(struct gallivm_state *gallivm,
 391                          struct lp_type src_type,
 392                          struct lp_type dst_type,
 393                          LLVMValueRef lo,
 394                          LLVMValueRef hi);
 395    LLVMValueRef tmp[LP_MAX_VECTOR_LENGTH];
 396    unsigned i;
 397
 398
 399    /* Register width must remain constant */
 400    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 401
 402    /* We must not loose or gain channels. Only precision */
 403    assert(src_type.length * num_srcs == dst_type.length);
 404
 405    if(clamped)
 406       pack2 = &lp_build_pack2;
 407    else
 408       pack2 = &lp_build_packs2;
 409
 410    for(i = 0; i < num_srcs; ++i)
 411       tmp[i] = src[i];
 412
 413    while(src_type.width > dst_type.width) {
 414       struct lp_type tmp_type = src_type;
 415
 416       tmp_type.width /= 2;
 417       tmp_type.length *= 2;
 418
 419       /* Take in consideration the sign changes only in the last step */
 420       if(tmp_type.width == dst_type.width)
 421          tmp_type.sign = dst_type.sign;
 422
 423       num_srcs /= 2;
 424
 425       for(i = 0; i < num_srcs; ++i)
 426          tmp[i] = pack2(gallivm, src_type, tmp_type,
 427                         tmp[2*i + 0], tmp[2*i + 1]);
 428
 429       src_type = tmp_type;
 430    }
 431
 432    assert(num_srcs == 1);
 433
 434    return tmp[0];
 435 }
 436
 437
 438 /**
 439  * Truncate or expand the bitwidth.
 440  *
 441  * NOTE: Getting the right sign flags is crucial here, as we employ some
 442  * intrinsics that do saturation.
 443  */
 444 void
 445 lp_build_resize(struct gallivm_state *gallivm,
 446                 struct lp_type src_type,
 447                 struct lp_type dst_type,
 448                 const LLVMValueRef *src, unsigned num_srcs,
 449                 LLVMValueRef *dst, unsigned num_dsts)
 450 {
 451    LLVMBuilderRef builder = gallivm->builder;
 452    LLVMValueRef tmp[LP_MAX_VECTOR_LENGTH];
 453    unsigned i;
 454
 455    /*
 456     * We don't support float <-> int conversion here. That must be done
 457     * before/after calling this function.
 458     */
 459    assert(src_type.floating == dst_type.floating);
 460
 461    /*
 462     * We don't support double <-> float conversion yet, although it could be
 463     * added with little effort.
 464     */
 465    assert((!src_type.floating && !dst_type.floating) ||
 466           src_type.width == dst_type.width);
 467
 468    /* We must not loose or gain channels. Only precision */
 469    assert(src_type.length * num_srcs == dst_type.length * num_dsts);
 470
 471    /* We don't support M:N conversion, only 1:N, M:1, or 1:1 */
 472    assert(num_srcs == 1 || num_dsts == 1);
 473
 474    assert(src_type.length <= LP_MAX_VECTOR_LENGTH);
 475    assert(dst_type.length <= LP_MAX_VECTOR_LENGTH);
 476    assert(num_srcs <= LP_MAX_VECTOR_LENGTH);
 477    assert(num_dsts <= LP_MAX_VECTOR_LENGTH);
 478
 479    if (src_type.width > dst_type.width) {
 480       /*
 481        * Truncate bit width.
 482        */
 483
 484       assert(num_dsts == 1);
 485
 486       if (src_type.width * src_type.length == dst_type.width * dst_type.length) {
 487         /*
 488          * Register width remains constant -- use vector packing intrinsics
 489          */
 490
 491          tmp[0] = lp_build_pack(gallivm, src_type, dst_type, TRUE, src, num_srcs);
 492       }
 493       else {
 494          /*
 495           * Do it element-wise.
 496           */
 497
 498          assert(src_type.length == dst_type.length);
 499          tmp[0] = lp_build_undef(gallivm, dst_type);
 500          for (i = 0; i < dst_type.length; ++i) {
 501             LLVMValueRef index = lp_build_const_int32(gallivm, i);
 502             LLVMValueRef val = LLVMBuildExtractElement(builder, src[0], index, "");
 503             val = LLVMBuildTrunc(builder, val, lp_build_elem_type(gallivm, dst_type), "");
 504             tmp[0] = LLVMBuildInsertElement(builder, tmp[0], val, index, "");
 505          }
 506       }
 507    }
 508    else if (src_type.width < dst_type.width) {
 509       /*
 510        * Expand bit width.
 511        */
 512
 513       assert(num_srcs == 1);
 514
 515       if (src_type.width * src_type.length == dst_type.width * dst_type.length) {
 516          /*
 517           * Register width remains constant -- use vector unpack intrinsics
 518           */
 519          lp_build_unpack(gallivm, src_type, dst_type, src[0], tmp, num_dsts);
 520       }
 521       else {
 522          /*
 523           * Do it element-wise.
 524           */
 525
 526          assert(src_type.length == dst_type.length);
 527          tmp[0] = lp_build_undef(gallivm, dst_type);
 528          for (i = 0; i < dst_type.length; ++i) {
 529             LLVMValueRef index = lp_build_const_int32(gallivm, i);
 530             LLVMValueRef val = LLVMBuildExtractElement(builder, src[0], index, "");
 531
 532             if (src_type.sign && dst_type.sign) {
 533                val = LLVMBuildSExt(builder, val, lp_build_elem_type(gallivm, dst_type), "");
 534             } else {
 535                val = LLVMBuildZExt(builder, val, lp_build_elem_type(gallivm, dst_type), "");
 536             }
 537             tmp[0] = LLVMBuildInsertElement(builder, tmp[0], val, index, "");
 538          }
 539       }
 540    }
 541    else {
 542       /*
 543        * No-op
 544        */
 545
 546       assert(num_srcs == 1);
 547       assert(num_dsts == 1);
 548
 549       tmp[0] = src[0];
 550    }
 551
 552    for(i = 0; i < num_dsts; ++i)
 553       dst[i] = tmp[i];
 554 }
 555
 556