src/gallium/drivers/llvmpipe/lp_bld_conv.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2009 VMware, Inc.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
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  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  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
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
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  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28
  29 /**
  30  * @file
  31  * Helper
  32  *
  33  * LLVM IR doesn't support all basic arithmetic operations we care about (most
  34  * notably min/max and saturated operations), and it is often necessary to
  35  * resort machine-specific intrinsics directly. The functions here hide all
  36  * these implementation details from the other modules.
  37  *
  38  * We also do simple expressions simplification here. Reasons are:
  39  * - it is very easy given we have all necessary information readily available
  40  * - LLVM optimization passes fail to simplify several vector expressions
  41  * - We often know value constraints which the optimization passes have no way
  42  *   of knowing, such as when source arguments are known to be in [0, 1] range.
  43  *
  44  * @author Jose Fonseca <jfonseca@vmware.com>
  45  */
  46
  47
  48 #include "util/u_debug.h"
  49 #include "util/u_math.h"
  50
  51 #include "lp_bld_type.h"
  52 #include "lp_bld_const.h"
  53 #include "lp_bld_intr.h"
  54 #include "lp_bld_arit.h"
  55 #include "lp_bld_conv.h"
  56
  57
  58 LLVMValueRef
  59 lp_build_clamped_float_to_unsigned_norm(LLVMBuilderRef builder,
  60                                         union lp_type src_type,
  61                                         unsigned dst_width,
  62                                         LLVMValueRef src)
  63 {
  64    LLVMTypeRef int_vec_type = lp_build_int_vec_type(src_type);
  65    LLVMValueRef res;
  66    unsigned mantissa;
  67    unsigned n;
  68    unsigned long long ubound;
  69    unsigned long long mask;
  70    double scale;
  71    double bias;
  72
  73    assert(src_type.floating);
  74
  75    mantissa = lp_mantissa(src_type);
  76
  77    /* We cannot carry more bits than the mantissa */
  78    n = MIN2(mantissa, dst_width);
  79
  80    /* This magic coefficients will make the desired result to appear in the
  81     * lowest significant bits of the mantissa.
  82     */
  83    ubound = ((unsigned long long)1 << n);
  84    mask = ubound - 1;
  85    scale = (double)mask/ubound;
  86    bias = (double)((unsigned long long)1 << (mantissa - n));
  87
  88    res = LLVMBuildMul(builder, src, lp_build_const_uni(src_type, scale), "");
  89    res = LLVMBuildAdd(builder, res, lp_build_const_uni(src_type, bias), "");
  90    res = LLVMBuildBitCast(builder, res, int_vec_type, "");
  91
  92    if(dst_width > n) {
  93       int shift = dst_width - n;
  94       res = LLVMBuildShl(builder, res, lp_build_int_const_uni(src_type, shift), "");
  95
  96       /* Fill in the empty lower bits for added precision? */
  97 #if 0
  98       {
  99          LLVMValueRef msb;
 100          msb = LLVMBuildLShr(builder, res, lp_build_int_const_uni(src_type, dst_width - 1), "");
 101          msb = LLVMBuildShl(builder, msb, lp_build_int_const_uni(src_type, shift), "");
 102          msb = LLVMBuildSub(builder, msb, lp_build_int_const_uni(src_type, 1), "");
 103          res = LLVMBuildOr(builder, res, msb, "");
 104       }
 105 #elif 0
 106       while(shift > 0) {
 107          res = LLVMBuildOr(builder, res, LLVMBuildLShr(builder, res, lp_build_int_const_uni(src_type, n), ""), "");
 108          shift -= n;
 109          n *= 2;
 110       }
 111 #endif
 112    }
 113    else
 114       res = LLVMBuildAnd(builder, res, lp_build_int_const_uni(src_type, mask), "");
 115
 116    return res;
 117 }
 118
 119
 120 /**
 121  * Inverse of lp_build_clamped_float_to_unsigned_norm.
 122  */
 123 LLVMValueRef
 124 lp_build_unsigned_norm_to_float(LLVMBuilderRef builder,
 125                                 unsigned src_width,
 126                                 union lp_type dst_type,
 127                                 LLVMValueRef src)
 128 {
 129    LLVMTypeRef vec_type = lp_build_vec_type(dst_type);
 130    LLVMTypeRef int_vec_type = lp_build_int_vec_type(dst_type);
 131    LLVMValueRef bias_;
 132    LLVMValueRef res;
 133    unsigned mantissa;
 134    unsigned n;
 135    unsigned long long ubound;
 136    unsigned long long mask;
 137    double scale;
 138    double bias;
 139
 140    mantissa = lp_mantissa(dst_type);
 141
 142    /* We cannot carry more bits than the mantissa */
 143    n = MIN2(mantissa, src_width);
 144
 145    ubound = ((unsigned long long)1 << n);
 146    mask = ubound - 1;
 147    scale = (double)ubound/mask;
 148    bias = (double)((unsigned long long)1 << (mantissa - n));
 149
 150    res = src;
 151
 152    if(src_width > mantissa) {
 153       int shift = src_width - mantissa;
 154       res = LLVMBuildLShr(builder, res, lp_build_int_const_uni(dst_type, shift), "");
 155    }
 156
 157    bias_ = lp_build_const_uni(dst_type, bias);
 158
 159    res = LLVMBuildOr(builder,
 160                      res,
 161                      LLVMBuildBitCast(builder, bias_, int_vec_type, ""), "");
 162
 163    res = LLVMBuildBitCast(builder, res, vec_type, "");
 164
 165    res = LLVMBuildSub(builder, res, bias_, "");
 166    res = LLVMBuildMul(builder, res, lp_build_const_uni(dst_type, scale), "");
 167
 168    return res;
 169 }
 170
 171
 172 /**
 173  * Build shuffle vectors that match PUNPCKLxx and PUNPCKHxx instructions.
 174  */
 175 static LLVMValueRef
 176 lp_build_const_unpack_shuffle(unsigned n, unsigned lo_hi)
 177 {
 178    LLVMValueRef elems[LP_MAX_VECTOR_LENGTH];
 179    unsigned i, j;
 180
 181    assert(n <= LP_MAX_VECTOR_LENGTH);
 182    assert(lo_hi < 2);
 183
 184    /* TODO: cache results in a static table */
 185
 186    for(i = 0, j = lo_hi*n/2; i < n; i += 2, ++j) {
 187       elems[i + 0] = LLVMConstInt(LLVMInt32Type(), 0 + j, 0);
 188       elems[i + 1] = LLVMConstInt(LLVMInt32Type(), n + j, 0);
 189    }
 190
 191    return LLVMConstVector(elems, n);
 192 }
 193
 194
 195 /**
 196  * Build shuffle vectors that match PACKxx instructions.
 197  */
 198 static LLVMValueRef
 199 lp_build_const_pack_shuffle(unsigned n)
 200 {
 201    LLVMValueRef elems[LP_MAX_VECTOR_LENGTH];
 202    unsigned i;
 203
 204    assert(n <= LP_MAX_VECTOR_LENGTH);
 205
 206    /* TODO: cache results in a static table */
 207
 208    for(i = 0; i < n; ++i)
 209       elems[i] = LLVMConstInt(LLVMInt32Type(), 2*i, 0);
 210
 211    return LLVMConstVector(elems, n);
 212 }
 213
 214
 215 static void
 216 lp_build_expand(LLVMBuilderRef builder,
 217                union lp_type src_type,
 218                union lp_type dst_type,
 219                LLVMValueRef src,
 220                LLVMValueRef *dst, unsigned num_dsts)
 221 {
 222    unsigned num_tmps;
 223    unsigned i;
 224
 225    /* Register width must remain constant */
 226    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 227
 228    /* We must not loose or gain channels. Only precision */
 229    assert(src_type.length == dst_type.length * num_dsts);
 230
 231    num_tmps = 1;
 232    dst[0] = src;
 233
 234    while(src_type.width < dst_type.width) {
 235       union lp_type new_type = src_type;
 236       LLVMTypeRef new_vec_type;
 237
 238       new_type.width *= 2;
 239       new_type.length /= 2;
 240       new_vec_type = lp_build_vec_type(new_type);
 241
 242       for(i = num_tmps; i--; ) {
 243          LLVMValueRef zero;
 244          LLVMValueRef shuffle_lo;
 245          LLVMValueRef shuffle_hi;
 246          LLVMValueRef lo;
 247          LLVMValueRef hi;
 248
 249          zero = lp_build_zero(src_type);
 250          shuffle_lo = lp_build_const_unpack_shuffle(src_type.length, 0);
 251          shuffle_hi = lp_build_const_unpack_shuffle(src_type.length, 1);
 252
 253          /*  PUNPCKLBW, PUNPCKHBW */
 254          lo = LLVMBuildShuffleVector(builder, dst[i], zero, shuffle_lo, "");
 255          hi = LLVMBuildShuffleVector(builder, dst[i], zero, shuffle_hi, "");
 256
 257          dst[2*i + 0] = LLVMBuildBitCast(builder, lo, new_vec_type, "");
 258          dst[2*i + 1] = LLVMBuildBitCast(builder, hi, new_vec_type, "");
 259       }
 260
 261       src_type = new_type;
 262
 263       num_tmps *= 2;
 264    }
 265
 266    assert(num_tmps == num_dsts);
 267 }
 268
 269
 270 /**
 271  * Non-interleaved pack.
 272  *
 273  * lo =   __ l0 __ l1 __ l2 __..  __ ln
 274  * hi  =  __ h0 __ h1 __ h2 __..  __ hn
 275  * res =  l0 l1 l2 .. ln h0 h1 h2 .. hn
 276  */
 277 static LLVMValueRef
 278 lp_build_pack2(LLVMBuilderRef builder,
 279                union lp_type src_type,
 280                union lp_type dst_type,
 281                LLVMValueRef lo,
 282                LLVMValueRef hi)
 283 {
 284    LLVMTypeRef src_vec_type = lp_build_vec_type(src_type);
 285    LLVMTypeRef dst_vec_type = lp_build_vec_type(dst_type);
 286    LLVMValueRef shuffle;
 287    LLVMValueRef res;
 288
 289    /* Register width must remain constant */
 290    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 291
 292    /* We must not loose or gain channels. Only precision */
 293    assert(src_type.length * 2 == dst_type.length);
 294
 295    assert(!src_type.floating);
 296    assert(!dst_type.floating);
 297
 298 #if defined(PIPE_ARCH_X86) || defined(PIPE_ARCH_X86_64)
 299    if(src_type.width * src_type.length == 128) {
 300       /* All X86 non-interleaved pack instructions all take signed inputs and
 301        * saturate them, so saturate beforehand. */
 302       if(!src_type.sign) {
 303          struct lp_build_context bld;
 304          unsigned dst_bits = dst_type.sign ? dst_type.width - 1 : dst_type.width;
 305          LLVMValueRef dst_max = lp_build_int_const_uni(src_type, ((unsigned long long)1 << dst_bits) - 1);
 306          lp_build_context_init(&bld, builder, src_type);
 307          lo = lp_build_min(&bld, lo, dst_max);
 308          hi = lp_build_min(&bld, hi, dst_max);
 309       }
 310
 311       switch(src_type.width) {
 312       case 32:
 313          if(dst_type.sign)
 314             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packssdw.128", src_vec_type, lo, hi);
 315          else
 316             /* PACKUSDW is the only instrinsic with a consistent signature */
 317             return lp_build_intrinsic_binary(builder, "llvm.x86.sse41.packusdw", dst_vec_type, lo, hi);
 318          break;
 319
 320       case 16:
 321          if(dst_type.sign)
 322             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packsswb.128", src_vec_type, lo, hi);
 323          else
 324             res = lp_build_intrinsic_binary(builder, "llvm.x86.sse2.packuswb.128", src_vec_type, lo, hi);
 325          break;
 326
 327       default:
 328          assert(0);
 329          return LLVMGetUndef(dst_vec_type);
 330          break;
 331       }
 332
 333       res = LLVMBuildBitCast(builder, res, dst_vec_type, "");
 334       return res;
 335    }
 336 #endif
 337
 338    lo = LLVMBuildBitCast(builder, lo, dst_vec_type, "");
 339    hi = LLVMBuildBitCast(builder, hi, dst_vec_type, "");
 340
 341    shuffle = lp_build_const_pack_shuffle(dst_type.length);
 342
 343    res = LLVMBuildShuffleVector(builder, lo, hi, shuffle, "");
 344
 345    return res;
 346 }
 347
 348
 349 static LLVMValueRef
 350 lp_build_trunc(LLVMBuilderRef builder,
 351                union lp_type src_type,
 352                union lp_type dst_type,
 353                const LLVMValueRef *src, unsigned num_srcs)
 354 {
 355    LLVMValueRef tmp[LP_MAX_VECTOR_LENGTH];
 356    unsigned i;
 357
 358    /* Register width must remain constant */
 359    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 360
 361    /* We must not loose or gain channels. Only precision */
 362    assert(src_type.length * num_srcs == dst_type.length);
 363
 364    for(i = 0; i < num_srcs; ++i)
 365       tmp[i] = src[i];
 366
 367    while(src_type.width > dst_type.width) {
 368       union lp_type new_type = src_type;
 369
 370       new_type.width /= 2;
 371       new_type.length *= 2;
 372
 373       /* Take in consideration the sign changes only in the last step */
 374       if(new_type.width == dst_type.width)
 375          new_type.sign = dst_type.sign;
 376
 377       num_srcs /= 2;
 378
 379       for(i = 0; i < num_srcs; ++i)
 380          tmp[i] = lp_build_pack2(builder, src_type, new_type, tmp[2*i + 0], tmp[2*i + 1]);
 381
 382       src_type = new_type;
 383    }
 384
 385    assert(num_srcs == 1);
 386
 387    return tmp[0];
 388 }
 389
 390
 391 /**
 392  * Convert between two SIMD types.
 393  *
 394  * Converting between SIMD types of different element width poses a problem:
 395  * SIMD registers have a fixed number of bits, so different element widths
 396  * imply different vector lengths. Therefore we must multiplex the multiple
 397  * incoming sources into a single destination vector, or demux a single incoming
 398  * vector into multiple vectors.
 399  */
 400 void
 401 lp_build_conv(LLVMBuilderRef builder,
 402               union lp_type src_type,
 403               union lp_type dst_type,
 404               const LLVMValueRef *src, unsigned num_srcs,
 405               LLVMValueRef *dst, unsigned num_dsts)
 406 {
 407    union lp_type tmp_type;
 408    LLVMValueRef tmp[LP_MAX_VECTOR_LENGTH];
 409    unsigned num_tmps;
 410    unsigned i;
 411
 412    /* Register width must remain constant */
 413    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 414
 415    /* We must not loose or gain channels. Only precision */
 416    assert(src_type.length * num_srcs == dst_type.length * num_dsts);
 417
 418    assert(src_type.length <= LP_MAX_VECTOR_LENGTH);
 419    assert(dst_type.length <= LP_MAX_VECTOR_LENGTH);
 420
 421    tmp_type = src_type;
 422    for(i = 0; i < num_srcs; ++i)
 423       tmp[i] = src[i];
 424    num_tmps = num_srcs;
 425
 426    /*
 427     * Clamp if necessary
 428     */
 429
 430    if(src_type.value != dst_type.value) {
 431       struct lp_build_context bld;
 432       double src_min = lp_const_min(src_type);
 433       double dst_min = lp_const_min(dst_type);
 434       double src_max = lp_const_max(src_type);
 435       double dst_max = lp_const_max(dst_type);
 436       LLVMValueRef thres;
 437
 438       lp_build_context_init(&bld, builder, tmp_type);
 439
 440       if(src_min < dst_min) {
 441          if(dst_min == 0.0)
 442             thres = bld.zero;
 443          else
 444             thres = lp_build_const_uni(src_type, dst_min);
 445          for(i = 0; i < num_tmps; ++i)
 446             tmp[i] = lp_build_max(&bld, tmp[i], thres);
 447       }
 448
 449       if(src_max > dst_max) {
 450          if(dst_max == 1.0)
 451             thres = bld.one;
 452          else
 453             thres = lp_build_const_uni(src_type, dst_max);
 454          for(i = 0; i < num_tmps; ++i)
 455             tmp[i] = lp_build_min(&bld, tmp[i], thres);
 456       }
 457    }
 458
 459    /*
 460     * Scale to the narrowest range
 461     */
 462
 463    if(dst_type.floating) {
 464       /* Nothing to do */
 465    }
 466    else if(tmp_type.floating) {
 467       if(!dst_type.fixed && !dst_type.sign && dst_type.norm) {
 468          for(i = 0; i < num_tmps; ++i) {
 469             tmp[i] = lp_build_clamped_float_to_unsigned_norm(builder,
 470                                                              tmp_type,
 471                                                              dst_type.width,
 472                                                              tmp[i]);
 473          }
 474          tmp_type.floating = FALSE;
 475       }
 476       else {
 477          double dst_scale = lp_const_scale(dst_type);
 478          LLVMTypeRef tmp_vec_type;
 479
 480          if (dst_scale != 1.0) {
 481             LLVMValueRef scale = lp_build_const_uni(tmp_type, dst_scale);
 482             for(i = 0; i < num_tmps; ++i)
 483                tmp[i] = LLVMBuildMul(builder, tmp[i], scale, "");
 484          }
 485
 486          /* Use an equally sized integer for intermediate computations */
 487          tmp_type.floating = FALSE;
 488          tmp_vec_type = lp_build_vec_type(tmp_type);
 489          for(i = 0; i < num_tmps; ++i) {
 490 #if 0
 491             if(dst_type.sign)
 492                tmp[i] = LLVMBuildFPToSI(builder, tmp[i], tmp_vec_type, "");
 493             else
 494                tmp[i] = LLVMBuildFPToUI(builder, tmp[i], tmp_vec_type, "");
 495 #else
 496            /* FIXME: there is no SSE counterpart for LLVMBuildFPToUI */
 497             tmp[i] = LLVMBuildFPToSI(builder, tmp[i], tmp_vec_type, "");
 498 #endif
 499          }
 500       }
 501    }
 502    else {
 503       unsigned src_shift = lp_const_shift(src_type);
 504       unsigned dst_shift = lp_const_shift(dst_type);
 505
 506       /* FIXME: compensate different offsets too */
 507       if(src_shift > dst_shift) {
 508          LLVMValueRef shift = lp_build_int_const_uni(tmp_type, src_shift - dst_shift);
 509          for(i = 0; i < num_tmps; ++i)
 510             if(src_type.sign)
 511                tmp[i] = LLVMBuildAShr(builder, tmp[i], shift, "");
 512             else
 513                tmp[i] = LLVMBuildLShr(builder, tmp[i], shift, "");
 514       }
 515    }
 516
 517    /*
 518     * Truncate or expand bit width
 519     */
 520
 521    assert(!tmp_type.floating || tmp_type.width == dst_type.width);
 522
 523    if(tmp_type.width > dst_type.width) {
 524       assert(num_dsts == 1);
 525       tmp[0] = lp_build_trunc(builder, tmp_type, dst_type, tmp, num_tmps);
 526       tmp_type.width = dst_type.width;
 527       tmp_type.length = dst_type.length;
 528       num_tmps = 1;
 529    }
 530
 531    if(tmp_type.width < dst_type.width) {
 532       assert(num_tmps == 1);
 533       lp_build_expand(builder, tmp_type, dst_type, tmp[0], tmp, num_dsts);
 534       tmp_type.width = dst_type.width;
 535       tmp_type.length = dst_type.length;
 536       num_tmps = num_dsts;
 537    }
 538
 539    assert(tmp_type.width == dst_type.width);
 540    assert(tmp_type.length == dst_type.length);
 541    assert(num_tmps == num_dsts);
 542
 543    /*
 544     * Scale to the widest range
 545     */
 546
 547    if(src_type.floating) {
 548       /* Nothing to do */
 549    }
 550    else if(!src_type.floating && dst_type.floating) {
 551       if(!src_type.fixed && !src_type.sign && src_type.norm) {
 552          for(i = 0; i < num_tmps; ++i) {
 553             tmp[i] = lp_build_unsigned_norm_to_float(builder,
 554                                                      src_type.width,
 555                                                      dst_type,
 556                                                      tmp[i]);
 557          }
 558          tmp_type.floating = TRUE;
 559       }
 560       else {
 561          double src_scale = lp_const_scale(src_type);
 562          LLVMTypeRef tmp_vec_type;
 563
 564          /* Use an equally sized integer for intermediate computations */
 565          tmp_type.floating = TRUE;
 566          tmp_type.sign = TRUE;
 567          tmp_vec_type = lp_build_vec_type(tmp_type);
 568          for(i = 0; i < num_tmps; ++i) {
 569 #if 0
 570             if(dst_type.sign)
 571                tmp[i] = LLVMBuildSIToFP(builder, tmp[i], tmp_vec_type, "");
 572             else
 573                tmp[i] = LLVMBuildUIToFP(builder, tmp[i], tmp_vec_type, "");
 574 #else
 575             /* FIXME: there is no SSE counterpart for LLVMBuildUIToFP */
 576             tmp[i] = LLVMBuildSIToFP(builder, tmp[i], tmp_vec_type, "");
 577 #endif
 578           }
 579
 580           if (src_scale != 1.0) {
 581              LLVMValueRef scale = lp_build_const_uni(tmp_type, 1.0/src_scale);
 582              for(i = 0; i < num_tmps; ++i)
 583                 tmp[i] = LLVMBuildMul(builder, tmp[i], scale, "");
 584           }
 585       }
 586     }
 587     else {
 588        unsigned src_shift = lp_const_shift(src_type);
 589        unsigned dst_shift = lp_const_shift(dst_type);
 590
 591        /* FIXME: compensate different offsets too */
 592        if(src_shift < dst_shift) {
 593           LLVMValueRef shift = lp_build_int_const_uni(tmp_type, dst_shift - src_shift);
 594           for(i = 0; i < num_tmps; ++i)
 595              tmp[i] = LLVMBuildShl(builder, tmp[i], shift, "");
 596        }
 597     }
 598
 599    for(i = 0; i < num_dsts; ++i)
 600       dst[i] = tmp[i];
 601 }
 602
 603
 604 /**
 605  * Convenience wrapper around lp_build_conv for bit masks.
 606  */
 607 void
 608 lp_build_conv_mask(LLVMBuilderRef builder,
 609                    union lp_type src_type,
 610                    union lp_type dst_type,
 611                    const LLVMValueRef *src, unsigned num_srcs,
 612                    LLVMValueRef *dst, unsigned num_dsts)
 613 {
 614    /* Register width must remain constant */
 615    assert(src_type.width * src_type.length == dst_type.width * dst_type.length);
 616
 617    /* We must not loose or gain channels. Only precision */
 618    assert(src_type.length * num_srcs == dst_type.length * num_dsts);
 619
 620    src_type.floating = FALSE;
 621    src_type.fixed = FALSE;
 622    src_type.sign = FALSE;
 623    src_type.norm = TRUE;
 624
 625    dst_type.floating = FALSE;
 626    dst_type.fixed = FALSE;
 627    dst_type.sign = FALSE;
 628    dst_type.norm = TRUE;
 629
 630    /*
 631     * Truncate or expand bit width
 632     */
 633
 634    if(src_type.width > dst_type.width) {
 635       assert(num_dsts == 1);
 636       dst[0] = lp_build_trunc(builder, src_type, dst_type, src, num_srcs);
 637    }
 638    else if(src_type.width < dst_type.width) {
 639       assert(num_srcs == 1);
 640       lp_build_expand(builder, src_type, dst_type, src[0], dst, num_dsts);
 641    }
 642    else {
 643       assert(num_srcs == num_dsts);
 644       memcpy(dst, src, num_dsts * sizeof *dst);
 645    }
 646 }