src/gallium/auxiliary/gallivm/lp_bld_arit.c

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  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_memory.h"
  49 #include "util/u_debug.h"
  50 #include "util/u_math.h"
  51 #include "util/u_string.h"
  52 #include "util/u_cpu_detect.h"
  53
  54 #include "lp_bld_type.h"
  55 #include "lp_bld_const.h"
  56 #include "lp_bld_intr.h"
  57 #include "lp_bld_logic.h"
  58 #include "lp_bld_pack.h"
  59 #include "lp_bld_debug.h"
  60 #include "lp_bld_arit.h"
  61
  62
  63 /**
  64  * Generate min(a, b)
  65  * No checks for special case values of a or b = 1 or 0 are done.
  66  */
  67 static LLVMValueRef
  68 lp_build_min_simple(struct lp_build_context *bld,
  69                     LLVMValueRef a,
  70                     LLVMValueRef b)
  71 {
  72    const struct lp_type type = bld->type;
  73    const char *intrinsic = NULL;
  74    LLVMValueRef cond;
  75
  76    /* TODO: optimize the constant case */
  77
  78    if(type.width * type.length == 128) {
  79       if(type.floating) {
  80          if(type.width == 32 && util_cpu_caps.has_sse)
  81             intrinsic = "llvm.x86.sse.min.ps";
  82          if(type.width == 64 && util_cpu_caps.has_sse2)
  83             intrinsic = "llvm.x86.sse2.min.pd";
  84       }
  85       else {
  86          if(type.width == 8 && !type.sign && util_cpu_caps.has_sse2)
  87             intrinsic = "llvm.x86.sse2.pminu.b";
  88          if(type.width == 8 && type.sign && util_cpu_caps.has_sse4_1)
  89             intrinsic = "llvm.x86.sse41.pminsb";
  90          if(type.width == 16 && !type.sign && util_cpu_caps.has_sse4_1)
  91             intrinsic = "llvm.x86.sse41.pminuw";
  92          if(type.width == 16 && type.sign && util_cpu_caps.has_sse2)
  93             intrinsic = "llvm.x86.sse2.pmins.w";
  94          if(type.width == 32 && !type.sign && util_cpu_caps.has_sse4_1)
  95             intrinsic = "llvm.x86.sse41.pminud";
  96          if(type.width == 32 && type.sign && util_cpu_caps.has_sse4_1)
  97             intrinsic = "llvm.x86.sse41.pminsd";
  98       }
  99    }
 100
 101    if(intrinsic)
 102       return lp_build_intrinsic_binary(bld->builder, intrinsic, lp_build_vec_type(bld->type), a, b);
 103
 104    cond = lp_build_cmp(bld, PIPE_FUNC_LESS, a, b);
 105    return lp_build_select(bld, cond, a, b);
 106 }
 107
 108
 109 /**
 110  * Generate max(a, b)
 111  * No checks for special case values of a or b = 1 or 0 are done.
 112  */
 113 static LLVMValueRef
 114 lp_build_max_simple(struct lp_build_context *bld,
 115                     LLVMValueRef a,
 116                     LLVMValueRef b)
 117 {
 118    const struct lp_type type = bld->type;
 119    const char *intrinsic = NULL;
 120    LLVMValueRef cond;
 121
 122    /* TODO: optimize the constant case */
 123
 124    if(type.width * type.length == 128) {
 125       if(type.floating) {
 126          if(type.width == 32 && util_cpu_caps.has_sse)
 127             intrinsic = "llvm.x86.sse.max.ps";
 128          if(type.width == 64 && util_cpu_caps.has_sse2)
 129             intrinsic = "llvm.x86.sse2.max.pd";
 130       }
 131       else {
 132          if(type.width == 8 && !type.sign && util_cpu_caps.has_sse2)
 133             intrinsic = "llvm.x86.sse2.pmaxu.b";
 134          if(type.width == 8 && type.sign && util_cpu_caps.has_sse4_1)
 135             intrinsic = "llvm.x86.sse41.pmaxsb";
 136          if(type.width == 16 && !type.sign && util_cpu_caps.has_sse4_1)
 137             intrinsic = "llvm.x86.sse41.pmaxuw";
 138          if(type.width == 16 && type.sign && util_cpu_caps.has_sse2)
 139             intrinsic = "llvm.x86.sse2.pmaxs.w";
 140          if(type.width == 32 && !type.sign && util_cpu_caps.has_sse4_1)
 141             intrinsic = "llvm.x86.sse41.pmaxud";
 142          if(type.width == 32 && type.sign && util_cpu_caps.has_sse4_1)
 143             intrinsic = "llvm.x86.sse41.pmaxsd";
 144       }
 145    }
 146
 147    if(intrinsic)
 148       return lp_build_intrinsic_binary(bld->builder, intrinsic, lp_build_vec_type(bld->type), a, b);
 149
 150    cond = lp_build_cmp(bld, PIPE_FUNC_GREATER, a, b);
 151    return lp_build_select(bld, cond, a, b);
 152 }
 153
 154
 155 /**
 156  * Generate 1 - a, or ~a depending on bld->type.
 157  */
 158 LLVMValueRef
 159 lp_build_comp(struct lp_build_context *bld,
 160               LLVMValueRef a)
 161 {
 162    const struct lp_type type = bld->type;
 163
 164    if(a == bld->one)
 165       return bld->zero;
 166    if(a == bld->zero)
 167       return bld->one;
 168
 169    if(type.norm && !type.floating && !type.fixed && !type.sign) {
 170       if(LLVMIsConstant(a))
 171          return LLVMConstNot(a);
 172       else
 173          return LLVMBuildNot(bld->builder, a, "");
 174    }
 175
 176    if(LLVMIsConstant(a))
 177       return LLVMConstSub(bld->one, a);
 178    else
 179       return LLVMBuildSub(bld->builder, bld->one, a, "");
 180 }
 181
 182
 183 /**
 184  * Generate a + b
 185  */
 186 LLVMValueRef
 187 lp_build_add(struct lp_build_context *bld,
 188              LLVMValueRef a,
 189              LLVMValueRef b)
 190 {
 191    const struct lp_type type = bld->type;
 192    LLVMValueRef res;
 193
 194    if(a == bld->zero)
 195       return b;
 196    if(b == bld->zero)
 197       return a;
 198    if(a == bld->undef || b == bld->undef)
 199       return bld->undef;
 200
 201    if(bld->type.norm) {
 202       const char *intrinsic = NULL;
 203
 204       if(a == bld->one || b == bld->one)
 205         return bld->one;
 206
 207       if(util_cpu_caps.has_sse2 &&
 208          type.width * type.length == 128 &&
 209          !type.floating && !type.fixed) {
 210          if(type.width == 8)
 211             intrinsic = type.sign ? "llvm.x86.sse2.padds.b" : "llvm.x86.sse2.paddus.b";
 212          if(type.width == 16)
 213             intrinsic = type.sign ? "llvm.x86.sse2.padds.w" : "llvm.x86.sse2.paddus.w";
 214       }
 215
 216       if(intrinsic)
 217          return lp_build_intrinsic_binary(bld->builder, intrinsic, lp_build_vec_type(bld->type), a, b);
 218    }
 219
 220    if(LLVMIsConstant(a) && LLVMIsConstant(b))
 221       res = LLVMConstAdd(a, b);
 222    else
 223       res = LLVMBuildAdd(bld->builder, a, b, "");
 224
 225    /* clamp to ceiling of 1.0 */
 226    if(bld->type.norm && (bld->type.floating || bld->type.fixed))
 227       res = lp_build_min_simple(bld, res, bld->one);
 228
 229    /* XXX clamp to floor of -1 or 0??? */
 230
 231    return res;
 232 }
 233
 234
 235 /**
 236  * Generate a - b
 237  */
 238 LLVMValueRef
 239 lp_build_sub(struct lp_build_context *bld,
 240              LLVMValueRef a,
 241              LLVMValueRef b)
 242 {
 243    const struct lp_type type = bld->type;
 244    LLVMValueRef res;
 245
 246    if(b == bld->zero)
 247       return a;
 248    if(a == bld->undef || b == bld->undef)
 249       return bld->undef;
 250    if(a == b)
 251       return bld->zero;
 252
 253    if(bld->type.norm) {
 254       const char *intrinsic = NULL;
 255
 256       if(b == bld->one)
 257         return bld->zero;
 258
 259       if(util_cpu_caps.has_sse2 &&
 260          type.width * type.length == 128 &&
 261          !type.floating && !type.fixed) {
 262          if(type.width == 8)
 263             intrinsic = type.sign ? "llvm.x86.sse2.psubs.b" : "llvm.x86.sse2.psubus.b";
 264          if(type.width == 16)
 265             intrinsic = type.sign ? "llvm.x86.sse2.psubs.w" : "llvm.x86.sse2.psubus.w";
 266       }
 267
 268       if(intrinsic)
 269          return lp_build_intrinsic_binary(bld->builder, intrinsic, lp_build_vec_type(bld->type), a, b);
 270    }
 271
 272    if(LLVMIsConstant(a) && LLVMIsConstant(b))
 273       res = LLVMConstSub(a, b);
 274    else
 275       res = LLVMBuildSub(bld->builder, a, b, "");
 276
 277    if(bld->type.norm && (bld->type.floating || bld->type.fixed))
 278       res = lp_build_max_simple(bld, res, bld->zero);
 279
 280    return res;
 281 }
 282
 283
 284 /**
 285  * Normalized 8bit multiplication.
 286  *
 287  * - alpha plus one
 288  *
 289  *     makes the following approximation to the division (Sree)
 290  *
 291  *       a*b/255 ~= (a*(b + 1)) >> 256
 292  *
 293  *     which is the fastest method that satisfies the following OpenGL criteria
 294  *
 295  *       0*0 = 0 and 255*255 = 255
 296  *
 297  * - geometric series
 298  *
 299  *     takes the geometric series approximation to the division
 300  *
 301  *       t/255 = (t >> 8) + (t >> 16) + (t >> 24) ..
 302  *
 303  *     in this case just the first two terms to fit in 16bit arithmetic
 304  *
 305  *       t/255 ~= (t + (t >> 8)) >> 8
 306  *
 307  *     note that just by itself it doesn't satisfies the OpenGL criteria, as
 308  *     255*255 = 254, so the special case b = 255 must be accounted or roundoff
 309  *     must be used
 310  *
 311  * - geometric series plus rounding
 312  *
 313  *     when using a geometric series division instead of truncating the result
 314  *     use roundoff in the approximation (Jim Blinn)
 315  *
 316  *       t/255 ~= (t + (t >> 8) + 0x80) >> 8
 317  *
 318  *     achieving the exact results
 319  *
 320  * @sa Alvy Ray Smith, Image Compositing Fundamentals, Tech Memo 4, Aug 15, 1995,
 321  *     ftp://ftp.alvyray.com/Acrobat/4_Comp.pdf
 322  * @sa Michael Herf, The "double blend trick", May 2000,
 323  *     http://www.stereopsis.com/doubleblend.html
 324  */
 325 static LLVMValueRef
 326 lp_build_mul_u8n(LLVMBuilderRef builder,
 327                  struct lp_type i16_type,
 328                  LLVMValueRef a, LLVMValueRef b)
 329 {
 330    LLVMValueRef c8;
 331    LLVMValueRef ab;
 332
 333    c8 = lp_build_int_const_scalar(i16_type, 8);
 334
 335 #if 0
 336
 337    /* a*b/255 ~= (a*(b + 1)) >> 256 */
 338    b = LLVMBuildAdd(builder, b, lp_build_int_const_scalar(i16_type, 1), "");
 339    ab = LLVMBuildMul(builder, a, b, "");
 340
 341 #else
 342
 343    /* ab/255 ~= (ab + (ab >> 8) + 0x80) >> 8 */
 344    ab = LLVMBuildMul(builder, a, b, "");
 345    ab = LLVMBuildAdd(builder, ab, LLVMBuildLShr(builder, ab, c8, ""), "");
 346    ab = LLVMBuildAdd(builder, ab, lp_build_int_const_scalar(i16_type, 0x80), "");
 347
 348 #endif
 349
 350    ab = LLVMBuildLShr(builder, ab, c8, "");
 351
 352    return ab;
 353 }
 354
 355
 356 /**
 357  * Generate a * b
 358  */
 359 LLVMValueRef
 360 lp_build_mul(struct lp_build_context *bld,
 361              LLVMValueRef a,
 362              LLVMValueRef b)
 363 {
 364    const struct lp_type type = bld->type;
 365    LLVMValueRef shift;
 366    LLVMValueRef res;
 367
 368    if(a == bld->zero)
 369       return bld->zero;
 370    if(a == bld->one)
 371       return b;
 372    if(b == bld->zero)
 373       return bld->zero;
 374    if(b == bld->one)
 375       return a;
 376    if(a == bld->undef || b == bld->undef)
 377       return bld->undef;
 378
 379    if(!type.floating && !type.fixed && type.norm) {
 380       if(type.width == 8) {
 381          struct lp_type i16_type = lp_wider_type(type);
 382          LLVMValueRef al, ah, bl, bh, abl, abh, ab;
 383
 384          lp_build_unpack2(bld->builder, type, i16_type, a, &al, &ah);
 385          lp_build_unpack2(bld->builder, type, i16_type, b, &bl, &bh);
 386
 387          /* PMULLW, PSRLW, PADDW */
 388          abl = lp_build_mul_u8n(bld->builder, i16_type, al, bl);
 389          abh = lp_build_mul_u8n(bld->builder, i16_type, ah, bh);
 390
 391          ab = lp_build_pack2(bld->builder, i16_type, type, abl, abh);
 392
 393          return ab;
 394       }
 395
 396       /* FIXME */
 397       assert(0);
 398    }
 399
 400    if(type.fixed)
 401       shift = lp_build_int_const_scalar(type, type.width/2);
 402    else
 403       shift = NULL;
 404
 405    if(LLVMIsConstant(a) && LLVMIsConstant(b)) {
 406       res =  LLVMConstMul(a, b);
 407       if(shift) {
 408          if(type.sign)
 409             res = LLVMConstAShr(res, shift);
 410          else
 411             res = LLVMConstLShr(res, shift);
 412       }
 413    }
 414    else {
 415       res = LLVMBuildMul(bld->builder, a, b, "");
 416       if(shift) {
 417          if(type.sign)
 418             res = LLVMBuildAShr(bld->builder, res, shift, "");
 419          else
 420             res = LLVMBuildLShr(bld->builder, res, shift, "");
 421       }
 422    }
 423
 424    return res;
 425 }
 426
 427
 428 /**
 429  * Small vector x scale multiplication optimization.
 430  */
 431 LLVMValueRef
 432 lp_build_mul_imm(struct lp_build_context *bld,
 433                  LLVMValueRef a,
 434                  int b)
 435 {
 436    LLVMValueRef factor;
 437
 438    if(b == 0)
 439       return bld->zero;
 440
 441    if(b == 1)
 442       return a;
 443
 444    if(b == -1)
 445       return LLVMBuildNeg(bld->builder, a, "");
 446
 447    if(b == 2 && bld->type.floating)
 448       return lp_build_add(bld, a, a);
 449
 450    if(util_is_pot(b)) {
 451       unsigned shift = ffs(b) - 1;
 452
 453       if(bld->type.floating) {
 454 #if 0
 455          /*
 456           * Power of two multiplication by directly manipulating the mantissa.
 457           *
 458           * XXX: This might not be always faster, it will introduce a small error
 459           * for multiplication by zero, and it will produce wrong results
 460           * for Inf and NaN.
 461           */
 462          unsigned mantissa = lp_mantissa(bld->type);
 463          factor = lp_build_int_const_scalar(bld->type, (unsigned long long)shift << mantissa);
 464          a = LLVMBuildBitCast(bld->builder, a, lp_build_int_vec_type(bld->type), "");
 465          a = LLVMBuildAdd(bld->builder, a, factor, "");
 466          a = LLVMBuildBitCast(bld->builder, a, lp_build_vec_type(bld->type), "");
 467          return a;
 468 #endif
 469       }
 470       else {
 471          factor = lp_build_const_scalar(bld->type, shift);
 472          return LLVMBuildShl(bld->builder, a, factor, "");
 473       }
 474    }
 475
 476    factor = lp_build_const_scalar(bld->type, (double)b);
 477    return lp_build_mul(bld, a, factor);
 478 }
 479
 480
 481 /**
 482  * Generate a / b
 483  */
 484 LLVMValueRef
 485 lp_build_div(struct lp_build_context *bld,
 486              LLVMValueRef a,
 487              LLVMValueRef b)
 488 {
 489    const struct lp_type type = bld->type;
 490
 491    if(a == bld->zero)
 492       return bld->zero;
 493    if(a == bld->one)
 494       return lp_build_rcp(bld, b);
 495    if(b == bld->zero)
 496       return bld->undef;
 497    if(b == bld->one)
 498       return a;
 499    if(a == bld->undef || b == bld->undef)
 500       return bld->undef;
 501
 502    if(LLVMIsConstant(a) && LLVMIsConstant(b))
 503       return LLVMConstFDiv(a, b);
 504
 505    if(util_cpu_caps.has_sse && type.width == 32 && type.length == 4)
 506       return lp_build_mul(bld, a, lp_build_rcp(bld, b));
 507
 508    return LLVMBuildFDiv(bld->builder, a, b, "");
 509 }
 510
 511
 512 /**
 513  * Linear interpolation.
 514  *
 515  * This also works for integer values with a few caveats.
 516  *
 517  * @sa http://www.stereopsis.com/doubleblend.html
 518  */
 519 LLVMValueRef
 520 lp_build_lerp(struct lp_build_context *bld,
 521               LLVMValueRef x,
 522               LLVMValueRef v0,
 523               LLVMValueRef v1)
 524 {
 525    LLVMValueRef delta;
 526    LLVMValueRef res;
 527
 528    delta = lp_build_sub(bld, v1, v0);
 529
 530    res = lp_build_mul(bld, x, delta);
 531
 532    res = lp_build_add(bld, v0, res);
 533
 534    if(bld->type.fixed)
 535       /* XXX: This step is necessary for lerping 8bit colors stored on 16bits,
 536        * but it will be wrong for other uses. Basically we need a more
 537        * powerful lp_type, capable of further distinguishing the values
 538        * interpretation from the value storage. */
 539       res = LLVMBuildAnd(bld->builder, res, lp_build_int_const_scalar(bld->type, (1 << bld->type.width/2) - 1), "");
 540
 541    return res;
 542 }
 543
 544
 545 LLVMValueRef
 546 lp_build_lerp_2d(struct lp_build_context *bld,
 547                  LLVMValueRef x,
 548                  LLVMValueRef y,
 549                  LLVMValueRef v00,
 550                  LLVMValueRef v01,
 551                  LLVMValueRef v10,
 552                  LLVMValueRef v11)
 553 {
 554    LLVMValueRef v0 = lp_build_lerp(bld, x, v00, v01);
 555    LLVMValueRef v1 = lp_build_lerp(bld, x, v10, v11);
 556    return lp_build_lerp(bld, y, v0, v1);
 557 }
 558
 559
 560 /**
 561  * Generate min(a, b)
 562  * Do checks for special cases.
 563  */
 564 LLVMValueRef
 565 lp_build_min(struct lp_build_context *bld,
 566              LLVMValueRef a,
 567              LLVMValueRef b)
 568 {
 569    if(a == bld->undef || b == bld->undef)
 570       return bld->undef;
 571
 572    if(a == b)
 573       return a;
 574
 575    if(bld->type.norm) {
 576       if(a == bld->zero || b == bld->zero)
 577          return bld->zero;
 578       if(a == bld->one)
 579          return b;
 580       if(b == bld->one)
 581          return a;
 582    }
 583
 584    return lp_build_min_simple(bld, a, b);
 585 }
 586
 587
 588 /**
 589  * Generate max(a, b)
 590  * Do checks for special cases.
 591  */
 592 LLVMValueRef
 593 lp_build_max(struct lp_build_context *bld,
 594              LLVMValueRef a,
 595              LLVMValueRef b)
 596 {
 597    if(a == bld->undef || b == bld->undef)
 598       return bld->undef;
 599
 600    if(a == b)
 601       return a;
 602
 603    if(bld->type.norm) {
 604       if(a == bld->one || b == bld->one)
 605          return bld->one;
 606       if(a == bld->zero)
 607          return b;
 608       if(b == bld->zero)
 609          return a;
 610    }
 611
 612    return lp_build_max_simple(bld, a, b);
 613 }
 614
 615
 616 /**
 617  * Generate clamp(a, min, max)
 618  * Do checks for special cases.
 619  */
 620 LLVMValueRef
 621 lp_build_clamp(struct lp_build_context *bld,
 622                LLVMValueRef a,
 623                LLVMValueRef min,
 624                LLVMValueRef max)
 625 {
 626    a = lp_build_min(bld, a, max);
 627    a = lp_build_max(bld, a, min);
 628    return a;
 629 }
 630
 631
 632 /**
 633  * Generate abs(a)
 634  */
 635 LLVMValueRef
 636 lp_build_abs(struct lp_build_context *bld,
 637              LLVMValueRef a)
 638 {
 639    const struct lp_type type = bld->type;
 640    LLVMTypeRef vec_type = lp_build_vec_type(type);
 641
 642    if(!type.sign)
 643       return a;
 644
 645    if(type.floating) {
 646       /* Mask out the sign bit */
 647       LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 648       unsigned long long absMask = ~(1ULL << (type.width - 1));
 649       LLVMValueRef mask = lp_build_int_const_scalar(type, ((unsigned long long) absMask));
 650       a = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 651       a = LLVMBuildAnd(bld->builder, a, mask, "");
 652       a = LLVMBuildBitCast(bld->builder, a, vec_type, "");
 653       return a;
 654    }
 655
 656    if(type.width*type.length == 128 && util_cpu_caps.has_ssse3) {
 657       switch(type.width) {
 658       case 8:
 659          return lp_build_intrinsic_unary(bld->builder, "llvm.x86.ssse3.pabs.b.128", vec_type, a);
 660       case 16:
 661          return lp_build_intrinsic_unary(bld->builder, "llvm.x86.ssse3.pabs.w.128", vec_type, a);
 662       case 32:
 663          return lp_build_intrinsic_unary(bld->builder, "llvm.x86.ssse3.pabs.d.128", vec_type, a);
 664       }
 665    }
 666
 667    return lp_build_max(bld, a, LLVMBuildNeg(bld->builder, a, ""));
 668 }
 669
 670
 671 LLVMValueRef
 672 lp_build_negate(struct lp_build_context *bld,
 673                 LLVMValueRef a)
 674 {
 675    return LLVMBuildNeg(bld->builder, a, "");
 676 }
 677
 678
 679 LLVMValueRef
 680 lp_build_sgn(struct lp_build_context *bld,
 681              LLVMValueRef a)
 682 {
 683    const struct lp_type type = bld->type;
 684    LLVMTypeRef vec_type = lp_build_vec_type(type);
 685    LLVMValueRef cond;
 686    LLVMValueRef res;
 687
 688    /* Handle non-zero case */
 689    if(!type.sign) {
 690       /* if not zero then sign must be positive */
 691       res = bld->one;
 692    }
 693    else if(type.floating) {
 694       /* Take the sign bit and add it to 1 constant */
 695       LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 696       LLVMValueRef mask = lp_build_int_const_scalar(type, (unsigned long long)1 << (type.width - 1));
 697       LLVMValueRef sign;
 698       LLVMValueRef one;
 699       sign = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 700       sign = LLVMBuildAnd(bld->builder, sign, mask, "");
 701       one = LLVMConstBitCast(bld->one, int_vec_type);
 702       res = LLVMBuildOr(bld->builder, sign, one, "");
 703       res = LLVMBuildBitCast(bld->builder, res, vec_type, "");
 704    }
 705    else
 706    {
 707       LLVMValueRef minus_one = lp_build_const_scalar(type, -1.0);
 708       cond = lp_build_cmp(bld, PIPE_FUNC_GREATER, a, bld->zero);
 709       res = lp_build_select(bld, cond, bld->one, minus_one);
 710    }
 711
 712    /* Handle zero */
 713    cond = lp_build_cmp(bld, PIPE_FUNC_EQUAL, a, bld->zero);
 714    res = lp_build_select(bld, cond, bld->zero, bld->one);
 715
 716    return res;
 717 }
 718
 719
 720 /**
 721  * Set the sign of float vector 'a' according to 'sign'.
 722  * If sign==0, return abs(a).
 723  * If sign==1, return -abs(a);
 724  * Other values for sign produce undefined results.
 725  */
 726 LLVMValueRef
 727 lp_build_set_sign(struct lp_build_context *bld,
 728                   LLVMValueRef a, LLVMValueRef sign)
 729 {
 730    const struct lp_type type = bld->type;
 731    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 732    LLVMTypeRef vec_type = lp_build_vec_type(type);
 733    LLVMValueRef shift = lp_build_int_const_scalar(type, type.width - 1);
 734    LLVMValueRef mask = lp_build_int_const_scalar(type,
 735                              ~((unsigned long long) 1 << (type.width - 1)));
 736    LLVMValueRef val, res;
 737
 738    assert(type.floating);
 739
 740    /* val = reinterpret_cast<int>(a) */
 741    val = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 742    /* val = val & mask */
 743    val = LLVMBuildAnd(bld->builder, val, mask, "");
 744    /* sign = sign << shift */
 745    sign = LLVMBuildShl(bld->builder, sign, shift, "");
 746    /* res = val | sign */
 747    res = LLVMBuildOr(bld->builder, val, sign, "");
 748    /* res = reinterpret_cast<float>(res) */
 749    res = LLVMBuildBitCast(bld->builder, res, vec_type, "");
 750
 751    return res;
 752 }
 753
 754
 755 /**
 756  * Convert vector of int to vector of float.
 757  */
 758 LLVMValueRef
 759 lp_build_int_to_float(struct lp_build_context *bld,
 760                       LLVMValueRef a)
 761 {
 762    const struct lp_type type = bld->type;
 763
 764    assert(type.floating);
 765    /*assert(lp_check_value(type, a));*/
 766
 767    {
 768       LLVMTypeRef vec_type = lp_build_vec_type(type);
 769       /*LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);*/
 770       LLVMValueRef res;
 771       res = LLVMBuildSIToFP(bld->builder, a, vec_type, "");
 772       return res;
 773    }
 774 }
 775
 776
 777
 778 enum lp_build_round_sse41_mode
 779 {
 780    LP_BUILD_ROUND_SSE41_NEAREST = 0,
 781    LP_BUILD_ROUND_SSE41_FLOOR = 1,
 782    LP_BUILD_ROUND_SSE41_CEIL = 2,
 783    LP_BUILD_ROUND_SSE41_TRUNCATE = 3
 784 };
 785
 786
 787 static INLINE LLVMValueRef
 788 lp_build_round_sse41(struct lp_build_context *bld,
 789                      LLVMValueRef a,
 790                      enum lp_build_round_sse41_mode mode)
 791 {
 792    const struct lp_type type = bld->type;
 793    LLVMTypeRef vec_type = lp_build_vec_type(type);
 794    const char *intrinsic;
 795
 796    assert(type.floating);
 797    assert(type.width*type.length == 128);
 798    assert(lp_check_value(type, a));
 799    assert(util_cpu_caps.has_sse4_1);
 800
 801    switch(type.width) {
 802    case 32:
 803       intrinsic = "llvm.x86.sse41.round.ps";
 804       break;
 805    case 64:
 806       intrinsic = "llvm.x86.sse41.round.pd";
 807       break;
 808    default:
 809       assert(0);
 810       return bld->undef;
 811    }
 812
 813    return lp_build_intrinsic_binary(bld->builder, intrinsic, vec_type, a,
 814                                     LLVMConstInt(LLVMInt32Type(), mode, 0));
 815 }
 816
 817
 818 LLVMValueRef
 819 lp_build_trunc(struct lp_build_context *bld,
 820                LLVMValueRef a)
 821 {
 822    const struct lp_type type = bld->type;
 823
 824    assert(type.floating);
 825    assert(lp_check_value(type, a));
 826
 827    if(util_cpu_caps.has_sse4_1)
 828       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_TRUNCATE);
 829    else {
 830       LLVMTypeRef vec_type = lp_build_vec_type(type);
 831       LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 832       LLVMValueRef res;
 833       res = LLVMBuildFPToSI(bld->builder, a, int_vec_type, "");
 834       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 835       return res;
 836    }
 837 }
 838
 839
 840 LLVMValueRef
 841 lp_build_round(struct lp_build_context *bld,
 842                LLVMValueRef a)
 843 {
 844    const struct lp_type type = bld->type;
 845
 846    assert(type.floating);
 847    assert(lp_check_value(type, a));
 848
 849    if(util_cpu_caps.has_sse4_1)
 850       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_NEAREST);
 851    else {
 852       LLVMTypeRef vec_type = lp_build_vec_type(type);
 853       LLVMValueRef res;
 854       res = lp_build_iround(bld, a);
 855       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 856       return res;
 857    }
 858 }
 859
 860
 861 LLVMValueRef
 862 lp_build_floor(struct lp_build_context *bld,
 863                LLVMValueRef a)
 864 {
 865    const struct lp_type type = bld->type;
 866
 867    assert(type.floating);
 868
 869    if(util_cpu_caps.has_sse4_1)
 870       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_FLOOR);
 871    else {
 872       LLVMTypeRef vec_type = lp_build_vec_type(type);
 873       LLVMValueRef res;
 874       res = lp_build_ifloor(bld, a);
 875       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 876       return res;
 877    }
 878 }
 879
 880
 881 LLVMValueRef
 882 lp_build_ceil(struct lp_build_context *bld,
 883               LLVMValueRef a)
 884 {
 885    const struct lp_type type = bld->type;
 886
 887    assert(type.floating);
 888    assert(lp_check_value(type, a));
 889
 890    if(util_cpu_caps.has_sse4_1)
 891       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_CEIL);
 892    else {
 893       LLVMTypeRef vec_type = lp_build_vec_type(type);
 894       LLVMValueRef res;
 895       res = lp_build_iceil(bld, a);
 896       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 897       return res;
 898    }
 899 }
 900
 901
 902 /**
 903  * Return fractional part of 'a' computed as a - floor(f)
 904  * Typically used in texture coord arithmetic.
 905  */
 906 LLVMValueRef
 907 lp_build_fract(struct lp_build_context *bld,
 908                LLVMValueRef a)
 909 {
 910    assert(bld->type.floating);
 911    return lp_build_sub(bld, a, lp_build_floor(bld, a));
 912 }
 913
 914
 915 /**
 916  * Convert to integer, through whichever rounding method that's fastest,
 917  * typically truncating toward zero.
 918  */
 919 LLVMValueRef
 920 lp_build_itrunc(struct lp_build_context *bld,
 921                 LLVMValueRef a)
 922 {
 923    const struct lp_type type = bld->type;
 924    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 925
 926    assert(type.floating);
 927    assert(lp_check_value(type, a));
 928
 929    return LLVMBuildFPToSI(bld->builder, a, int_vec_type, "");
 930 }
 931
 932
 933 LLVMValueRef
 934 lp_build_iround(struct lp_build_context *bld,
 935                 LLVMValueRef a)
 936 {
 937    const struct lp_type type = bld->type;
 938    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 939    LLVMValueRef res;
 940
 941    assert(type.floating);
 942    assert(lp_check_value(type, a));
 943
 944    if(util_cpu_caps.has_sse4_1) {
 945       res = lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_NEAREST);
 946    }
 947    else {
 948       LLVMTypeRef vec_type = lp_build_vec_type(type);
 949       LLVMValueRef mask = lp_build_int_const_scalar(type, (unsigned long long)1 << (type.width - 1));
 950       LLVMValueRef sign;
 951       LLVMValueRef half;
 952
 953       /* get sign bit */
 954       sign = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 955       sign = LLVMBuildAnd(bld->builder, sign, mask, "");
 956
 957       /* sign * 0.5 */
 958       half = lp_build_const_scalar(type, 0.5);
 959       half = LLVMBuildBitCast(bld->builder, half, int_vec_type, "");
 960       half = LLVMBuildOr(bld->builder, sign, half, "");
 961       half = LLVMBuildBitCast(bld->builder, half, vec_type, "");
 962
 963       res = LLVMBuildAdd(bld->builder, a, half, "");
 964    }
 965
 966    res = LLVMBuildFPToSI(bld->builder, res, int_vec_type, "");
 967
 968    return res;
 969 }
 970
 971
 972 /**
 973  * Convert float[] to int[] with floor().
 974  */
 975 LLVMValueRef
 976 lp_build_ifloor(struct lp_build_context *bld,
 977                 LLVMValueRef a)
 978 {
 979    const struct lp_type type = bld->type;
 980    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 981    LLVMValueRef res;
 982
 983    assert(type.floating);
 984    assert(lp_check_value(type, a));
 985
 986    if(util_cpu_caps.has_sse4_1) {
 987       res = lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_FLOOR);
 988    }
 989    else {
 990       /* Take the sign bit and add it to 1 constant */
 991       LLVMTypeRef vec_type = lp_build_vec_type(type);
 992       unsigned mantissa = lp_mantissa(type);
 993       LLVMValueRef mask = lp_build_int_const_scalar(type, (unsigned long long)1 << (type.width - 1));
 994       LLVMValueRef sign;
 995       LLVMValueRef offset;
 996
 997       /* sign = a < 0 ? ~0 : 0 */
 998       sign = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 999       sign = LLVMBuildAnd(bld->builder, sign, mask, "");
1000       sign = LLVMBuildAShr(bld->builder, sign, lp_build_int_const_scalar(type, type.width - 1), "");
1001       lp_build_name(sign, "floor.sign");
1002
1003       /* offset = -0.99999(9)f */
1004       offset = lp_build_const_scalar(type, -(double)(((unsigned long long)1 << mantissa) - 1)/((unsigned long long)1 << mantissa));
1005       offset = LLVMConstBitCast(offset, int_vec_type);
1006
1007       /* offset = a < 0 ? -0.99999(9)f : 0.0f */
1008       offset = LLVMBuildAnd(bld->builder, offset, sign, "");
1009       offset = LLVMBuildBitCast(bld->builder, offset, vec_type, "");
1010       lp_build_name(offset, "floor.offset");
1011
1012       res = LLVMBuildAdd(bld->builder, a, offset, "");
1013       lp_build_name(res, "floor.res");
1014    }
1015
1016    res = LLVMBuildFPToSI(bld->builder, res, int_vec_type, "");
1017    lp_build_name(res, "floor");
1018
1019    return res;
1020 }
1021
1022
1023 LLVMValueRef
1024 lp_build_iceil(struct lp_build_context *bld,
1025                LLVMValueRef a)
1026 {
1027    const struct lp_type type = bld->type;
1028    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
1029    LLVMValueRef res;
1030
1031    assert(type.floating);
1032    assert(lp_check_value(type, a));
1033
1034    if(util_cpu_caps.has_sse4_1) {
1035       res = lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_CEIL);
1036    }
1037    else {
1038       assert(0);
1039       res = bld->undef;
1040    }
1041
1042    res = LLVMBuildFPToSI(bld->builder, res, int_vec_type, "");
1043
1044    return res;
1045 }
1046
1047
1048 LLVMValueRef
1049 lp_build_sqrt(struct lp_build_context *bld,
1050               LLVMValueRef a)
1051 {
1052    const struct lp_type type = bld->type;
1053    LLVMTypeRef vec_type = lp_build_vec_type(type);
1054    char intrinsic[32];
1055
1056    /* TODO: optimize the constant case */
1057    /* TODO: optimize the constant case */
1058
1059    assert(type.floating);
1060    util_snprintf(intrinsic, sizeof intrinsic, "llvm.sqrt.v%uf%u", type.length, type.width);
1061
1062    return lp_build_intrinsic_unary(bld->builder, intrinsic, vec_type, a);
1063 }
1064
1065
1066 LLVMValueRef
1067 lp_build_rcp(struct lp_build_context *bld,
1068              LLVMValueRef a)
1069 {
1070    const struct lp_type type = bld->type;
1071
1072    if(a == bld->zero)
1073       return bld->undef;
1074    if(a == bld->one)
1075       return bld->one;
1076    if(a == bld->undef)
1077       return bld->undef;
1078
1079    assert(type.floating);
1080
1081    if(LLVMIsConstant(a))
1082       return LLVMConstFDiv(bld->one, a);
1083
1084    if(util_cpu_caps.has_sse && type.width == 32 && type.length == 4)
1085       /* FIXME: improve precision */
1086       return lp_build_intrinsic_unary(bld->builder, "llvm.x86.sse.rcp.ps", lp_build_vec_type(type), a);
1087
1088    return LLVMBuildFDiv(bld->builder, bld->one, a, "");
1089 }
1090
1091
1092 /**
1093  * Generate 1/sqrt(a)
1094  */
1095 LLVMValueRef
1096 lp_build_rsqrt(struct lp_build_context *bld,
1097                LLVMValueRef a)
1098 {
1099    const struct lp_type type = bld->type;
1100
1101    assert(type.floating);
1102
1103    if(util_cpu_caps.has_sse && type.width == 32 && type.length == 4)
1104       return lp_build_intrinsic_unary(bld->builder, "llvm.x86.sse.rsqrt.ps", lp_build_vec_type(type), a);
1105
1106    return lp_build_rcp(bld, lp_build_sqrt(bld, a));
1107 }
1108
1109
1110 /**
1111  * Generate cos(a)
1112  */
1113 LLVMValueRef
1114 lp_build_cos(struct lp_build_context *bld,
1115               LLVMValueRef a)
1116 {
1117    const struct lp_type type = bld->type;
1118    LLVMTypeRef vec_type = lp_build_vec_type(type);
1119    char intrinsic[32];
1120
1121    /* TODO: optimize the constant case */
1122
1123    assert(type.floating);
1124    util_snprintf(intrinsic, sizeof intrinsic, "llvm.cos.v%uf%u", type.length, type.width);
1125
1126    return lp_build_intrinsic_unary(bld->builder, intrinsic, vec_type, a);
1127 }
1128
1129
1130 /**
1131  * Generate sin(a)
1132  */
1133 LLVMValueRef
1134 lp_build_sin(struct lp_build_context *bld,
1135               LLVMValueRef a)
1136 {
1137    const struct lp_type type = bld->type;
1138    LLVMTypeRef vec_type = lp_build_vec_type(type);
1139    char intrinsic[32];
1140
1141    /* TODO: optimize the constant case */
1142
1143    assert(type.floating);
1144    util_snprintf(intrinsic, sizeof intrinsic, "llvm.sin.v%uf%u", type.length, type.width);
1145
1146    return lp_build_intrinsic_unary(bld->builder, intrinsic, vec_type, a);
1147 }
1148
1149
1150 /**
1151  * Generate pow(x, y)
1152  */
1153 LLVMValueRef
1154 lp_build_pow(struct lp_build_context *bld,
1155              LLVMValueRef x,
1156              LLVMValueRef y)
1157 {
1158    /* TODO: optimize the constant case */
1159    if(LLVMIsConstant(x) && LLVMIsConstant(y))
1160       debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1161                    __FUNCTION__);
1162
1163    return lp_build_exp2(bld, lp_build_mul(bld, lp_build_log2(bld, x), y));
1164 }
1165
1166
1167 /**
1168  * Generate exp(x)
1169  */
1170 LLVMValueRef
1171 lp_build_exp(struct lp_build_context *bld,
1172              LLVMValueRef x)
1173 {
1174    /* log2(e) = 1/log(2) */
1175    LLVMValueRef log2e = lp_build_const_scalar(bld->type, 1.4426950408889634);
1176
1177    return lp_build_mul(bld, log2e, lp_build_exp2(bld, x));
1178 }
1179
1180
1181 /**
1182  * Generate log(x)
1183  */
1184 LLVMValueRef
1185 lp_build_log(struct lp_build_context *bld,
1186              LLVMValueRef x)
1187 {
1188    /* log(2) */
1189    LLVMValueRef log2 = lp_build_const_scalar(bld->type, 0.69314718055994529);
1190
1191    return lp_build_mul(bld, log2, lp_build_exp2(bld, x));
1192 }
1193
1194
1195 #define EXP_POLY_DEGREE 3
1196 #define LOG_POLY_DEGREE 5
1197
1198
1199 /**
1200  * Generate polynomial.
1201  * Ex:  coeffs[0] + x * coeffs[1] + x^2 * coeffs[2].
1202  */
1203 static LLVMValueRef
1204 lp_build_polynomial(struct lp_build_context *bld,
1205                     LLVMValueRef x,
1206                     const double *coeffs,
1207                     unsigned num_coeffs)
1208 {
1209    const struct lp_type type = bld->type;
1210    LLVMValueRef res = NULL;
1211    unsigned i;
1212
1213    /* TODO: optimize the constant case */
1214    if(LLVMIsConstant(x))
1215       debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1216                    __FUNCTION__);
1217
1218    for (i = num_coeffs; i--; ) {
1219       LLVMValueRef coeff = lp_build_const_scalar(type, coeffs[i]);
1220       if(res)
1221          res = lp_build_add(bld, coeff, lp_build_mul(bld, x, res));
1222       else
1223          res = coeff;
1224    }
1225
1226    if(res)
1227       return res;
1228    else
1229       return bld->undef;
1230 }
1231
1232
1233 /**
1234  * Minimax polynomial fit of 2**x, in range [-0.5, 0.5[
1235  */
1236 const double lp_build_exp2_polynomial[] = {
1237 #if EXP_POLY_DEGREE == 5
1238    9.9999994e-1, 6.9315308e-1, 2.4015361e-1, 5.5826318e-2, 8.9893397e-3, 1.8775767e-3
1239 #elif EXP_POLY_DEGREE == 4
1240    1.0000026, 6.9300383e-1, 2.4144275e-1, 5.2011464e-2, 1.3534167e-2
1241 #elif EXP_POLY_DEGREE == 3
1242    9.9992520e-1, 6.9583356e-1, 2.2606716e-1, 7.8024521e-2
1243 #elif EXP_POLY_DEGREE == 2
1244    1.0017247, 6.5763628e-1, 3.3718944e-1
1245 #else
1246 #error
1247 #endif
1248 };
1249
1250
1251 void
1252 lp_build_exp2_approx(struct lp_build_context *bld,
1253                      LLVMValueRef x,
1254                      LLVMValueRef *p_exp2_int_part,
1255                      LLVMValueRef *p_frac_part,
1256                      LLVMValueRef *p_exp2)
1257 {
1258    const struct lp_type type = bld->type;
1259    LLVMTypeRef vec_type = lp_build_vec_type(type);
1260    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
1261    LLVMValueRef ipart = NULL;
1262    LLVMValueRef fpart = NULL;
1263    LLVMValueRef expipart = NULL;
1264    LLVMValueRef expfpart = NULL;
1265    LLVMValueRef res = NULL;
1266
1267    if(p_exp2_int_part || p_frac_part || p_exp2) {
1268       /* TODO: optimize the constant case */
1269       if(LLVMIsConstant(x))
1270          debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1271                       __FUNCTION__);
1272
1273       assert(type.floating && type.width == 32);
1274
1275       x = lp_build_min(bld, x, lp_build_const_scalar(type,  129.0));
1276       x = lp_build_max(bld, x, lp_build_const_scalar(type, -126.99999));
1277
1278       /* ipart = int(x - 0.5) */
1279       ipart = LLVMBuildSub(bld->builder, x, lp_build_const_scalar(type, 0.5f), "");
1280       ipart = LLVMBuildFPToSI(bld->builder, ipart, int_vec_type, "");
1281
1282       /* fpart = x - ipart */
1283       fpart = LLVMBuildSIToFP(bld->builder, ipart, vec_type, "");
1284       fpart = LLVMBuildSub(bld->builder, x, fpart, "");
1285    }
1286
1287    if(p_exp2_int_part || p_exp2) {
1288       /* expipart = (float) (1 << ipart) */
1289       expipart = LLVMBuildAdd(bld->builder, ipart, lp_build_int_const_scalar(type, 127), "");
1290       expipart = LLVMBuildShl(bld->builder, expipart, lp_build_int_const_scalar(type, 23), "");
1291       expipart = LLVMBuildBitCast(bld->builder, expipart, vec_type, "");
1292    }
1293
1294    if(p_exp2) {
1295       expfpart = lp_build_polynomial(bld, fpart, lp_build_exp2_polynomial,
1296                                      Elements(lp_build_exp2_polynomial));
1297
1298       res = LLVMBuildMul(bld->builder, expipart, expfpart, "");
1299    }
1300
1301    if(p_exp2_int_part)
1302       *p_exp2_int_part = expipart;
1303
1304    if(p_frac_part)
1305       *p_frac_part = fpart;
1306
1307    if(p_exp2)
1308       *p_exp2 = res;
1309 }
1310
1311
1312 LLVMValueRef
1313 lp_build_exp2(struct lp_build_context *bld,
1314               LLVMValueRef x)
1315 {
1316    LLVMValueRef res;
1317    lp_build_exp2_approx(bld, x, NULL, NULL, &res);
1318    return res;
1319 }
1320
1321
1322 /**
1323  * Minimax polynomial fit of log2(x)/(x - 1), for x in range [1, 2[
1324  * These coefficients can be generate with
1325  * http://www.boost.org/doc/libs/1_36_0/libs/math/doc/sf_and_dist/html/math_toolkit/toolkit/internals2/minimax.html
1326  */
1327 const double lp_build_log2_polynomial[] = {
1328 #if LOG_POLY_DEGREE == 6
1329    3.11578814719469302614, -3.32419399085241980044, 2.59883907202499966007, -1.23152682416275988241, 0.318212422185251071475, -0.0344359067839062357313
1330 #elif LOG_POLY_DEGREE == 5
1331    2.8882704548164776201, -2.52074962577807006663, 1.48116647521213171641, -0.465725644288844778798, 0.0596515482674574969533
1332 #elif LOG_POLY_DEGREE == 4
1333    2.61761038894603480148, -1.75647175389045657003, 0.688243882994381274313, -0.107254423828329604454
1334 #elif LOG_POLY_DEGREE == 3
1335    2.28330284476918490682, -1.04913055217340124191, 0.204446009836232697516
1336 #else
1337 #error
1338 #endif
1339 };
1340
1341
1342 /**
1343  * See http://www.devmaster.net/forums/showthread.php?p=43580
1344  */
1345 void
1346 lp_build_log2_approx(struct lp_build_context *bld,
1347                      LLVMValueRef x,
1348                      LLVMValueRef *p_exp,
1349                      LLVMValueRef *p_floor_log2,
1350                      LLVMValueRef *p_log2)
1351 {
1352    const struct lp_type type = bld->type;
1353    LLVMTypeRef vec_type = lp_build_vec_type(type);
1354    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
1355
1356    LLVMValueRef expmask = lp_build_int_const_scalar(type, 0x7f800000);
1357    LLVMValueRef mantmask = lp_build_int_const_scalar(type, 0x007fffff);
1358    LLVMValueRef one = LLVMConstBitCast(bld->one, int_vec_type);
1359
1360    LLVMValueRef i = NULL;
1361    LLVMValueRef exp = NULL;
1362    LLVMValueRef mant = NULL;
1363    LLVMValueRef logexp = NULL;
1364    LLVMValueRef logmant = NULL;
1365    LLVMValueRef res = NULL;
1366
1367    if(p_exp || p_floor_log2 || p_log2) {
1368       /* TODO: optimize the constant case */
1369       if(LLVMIsConstant(x))
1370          debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1371                       __FUNCTION__);
1372
1373       assert(type.floating && type.width == 32);
1374
1375       i = LLVMBuildBitCast(bld->builder, x, int_vec_type, "");
1376
1377       /* exp = (float) exponent(x) */
1378       exp = LLVMBuildAnd(bld->builder, i, expmask, "");
1379    }
1380
1381    if(p_floor_log2 || p_log2) {
1382       logexp = LLVMBuildLShr(bld->builder, exp, lp_build_int_const_scalar(type, 23), "");
1383       logexp = LLVMBuildSub(bld->builder, logexp, lp_build_int_const_scalar(type, 127), "");
1384       logexp = LLVMBuildSIToFP(bld->builder, logexp, vec_type, "");
1385    }
1386
1387    if(p_log2) {
1388       /* mant = (float) mantissa(x) */
1389       mant = LLVMBuildAnd(bld->builder, i, mantmask, "");
1390       mant = LLVMBuildOr(bld->builder, mant, one, "");
1391       mant = LLVMBuildBitCast(bld->builder, mant, vec_type, "");
1392
1393       logmant = lp_build_polynomial(bld, mant, lp_build_log2_polynomial,
1394                                     Elements(lp_build_log2_polynomial));
1395
1396       /* This effectively increases the polynomial degree by one, but ensures that log2(1) == 0*/
1397       logmant = LLVMBuildMul(bld->builder, logmant, LLVMBuildSub(bld->builder, mant, bld->one, ""), "");
1398
1399       res = LLVMBuildAdd(bld->builder, logmant, logexp, "");
1400    }
1401
1402    if(p_exp)
1403       *p_exp = exp;
1404
1405    if(p_floor_log2)
1406       *p_floor_log2 = logexp;
1407
1408    if(p_log2)
1409       *p_log2 = res;
1410 }
1411
1412
1413 LLVMValueRef
1414 lp_build_log2(struct lp_build_context *bld,
1415               LLVMValueRef x)
1416 {
1417    LLVMValueRef res;
1418    lp_build_log2_approx(bld, x, NULL, NULL, &res);
1419    return res;
1420 }