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_sgn(struct lp_build_context *bld,
 673              LLVMValueRef a)
 674 {
 675    const struct lp_type type = bld->type;
 676    LLVMTypeRef vec_type = lp_build_vec_type(type);
 677    LLVMValueRef cond;
 678    LLVMValueRef res;
 679
 680    /* Handle non-zero case */
 681    if(!type.sign) {
 682       /* if not zero then sign must be positive */
 683       res = bld->one;
 684    }
 685    else if(type.floating) {
 686       /* Take the sign bit and add it to 1 constant */
 687       LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 688       LLVMValueRef mask = lp_build_int_const_scalar(type, (unsigned long long)1 << (type.width - 1));
 689       LLVMValueRef sign;
 690       LLVMValueRef one;
 691       sign = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 692       sign = LLVMBuildAnd(bld->builder, sign, mask, "");
 693       one = LLVMConstBitCast(bld->one, int_vec_type);
 694       res = LLVMBuildOr(bld->builder, sign, one, "");
 695       res = LLVMBuildBitCast(bld->builder, res, vec_type, "");
 696    }
 697    else
 698    {
 699       LLVMValueRef minus_one = lp_build_const_scalar(type, -1.0);
 700       cond = lp_build_cmp(bld, PIPE_FUNC_GREATER, a, bld->zero);
 701       res = lp_build_select(bld, cond, bld->one, minus_one);
 702    }
 703
 704    /* Handle zero */
 705    cond = lp_build_cmp(bld, PIPE_FUNC_EQUAL, a, bld->zero);
 706    res = lp_build_select(bld, cond, bld->zero, bld->one);
 707
 708    return res;
 709 }
 710
 711
 712 /**
 713  * Convert vector of int to vector of float.
 714  */
 715 LLVMValueRef
 716 lp_build_int_to_float(struct lp_build_context *bld,
 717                       LLVMValueRef a)
 718 {
 719    const struct lp_type type = bld->type;
 720
 721    assert(type.floating);
 722    /*assert(lp_check_value(type, a));*/
 723
 724    {
 725       LLVMTypeRef vec_type = lp_build_vec_type(type);
 726       /*LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);*/
 727       LLVMValueRef res;
 728       res = LLVMBuildSIToFP(bld->builder, a, vec_type, "");
 729       return res;
 730    }
 731 }
 732
 733
 734
 735 enum lp_build_round_sse41_mode
 736 {
 737    LP_BUILD_ROUND_SSE41_NEAREST = 0,
 738    LP_BUILD_ROUND_SSE41_FLOOR = 1,
 739    LP_BUILD_ROUND_SSE41_CEIL = 2,
 740    LP_BUILD_ROUND_SSE41_TRUNCATE = 3
 741 };
 742
 743
 744 static INLINE LLVMValueRef
 745 lp_build_round_sse41(struct lp_build_context *bld,
 746                      LLVMValueRef a,
 747                      enum lp_build_round_sse41_mode mode)
 748 {
 749    const struct lp_type type = bld->type;
 750    LLVMTypeRef vec_type = lp_build_vec_type(type);
 751    const char *intrinsic;
 752
 753    assert(type.floating);
 754    assert(type.width*type.length == 128);
 755    assert(lp_check_value(type, a));
 756    assert(util_cpu_caps.has_sse4_1);
 757
 758    switch(type.width) {
 759    case 32:
 760       intrinsic = "llvm.x86.sse41.round.ps";
 761       break;
 762    case 64:
 763       intrinsic = "llvm.x86.sse41.round.pd";
 764       break;
 765    default:
 766       assert(0);
 767       return bld->undef;
 768    }
 769
 770    return lp_build_intrinsic_binary(bld->builder, intrinsic, vec_type, a,
 771                                     LLVMConstInt(LLVMInt32Type(), mode, 0));
 772 }
 773
 774
 775 LLVMValueRef
 776 lp_build_trunc(struct lp_build_context *bld,
 777                LLVMValueRef a)
 778 {
 779    const struct lp_type type = bld->type;
 780
 781    assert(type.floating);
 782    assert(lp_check_value(type, a));
 783
 784    if(util_cpu_caps.has_sse4_1)
 785       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_TRUNCATE);
 786    else {
 787       LLVMTypeRef vec_type = lp_build_vec_type(type);
 788       LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 789       LLVMValueRef res;
 790       res = LLVMBuildFPToSI(bld->builder, a, int_vec_type, "");
 791       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 792       return res;
 793    }
 794 }
 795
 796
 797 LLVMValueRef
 798 lp_build_round(struct lp_build_context *bld,
 799                LLVMValueRef a)
 800 {
 801    const struct lp_type type = bld->type;
 802
 803    assert(type.floating);
 804    assert(lp_check_value(type, a));
 805
 806    if(util_cpu_caps.has_sse4_1)
 807       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_NEAREST);
 808    else {
 809       LLVMTypeRef vec_type = lp_build_vec_type(type);
 810       LLVMValueRef res;
 811       res = lp_build_iround(bld, a);
 812       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 813       return res;
 814    }
 815 }
 816
 817
 818 LLVMValueRef
 819 lp_build_floor(struct lp_build_context *bld,
 820                LLVMValueRef a)
 821 {
 822    const struct lp_type type = bld->type;
 823
 824    assert(type.floating);
 825
 826    if(util_cpu_caps.has_sse4_1)
 827       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_FLOOR);
 828    else {
 829       LLVMTypeRef vec_type = lp_build_vec_type(type);
 830       LLVMValueRef res;
 831       res = lp_build_ifloor(bld, a);
 832       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 833       return res;
 834    }
 835 }
 836
 837
 838 LLVMValueRef
 839 lp_build_ceil(struct lp_build_context *bld,
 840               LLVMValueRef a)
 841 {
 842    const struct lp_type type = bld->type;
 843
 844    assert(type.floating);
 845    assert(lp_check_value(type, a));
 846
 847    if(util_cpu_caps.has_sse4_1)
 848       return lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_CEIL);
 849    else {
 850       LLVMTypeRef vec_type = lp_build_vec_type(type);
 851       LLVMValueRef res;
 852       res = lp_build_iceil(bld, a);
 853       res = LLVMBuildSIToFP(bld->builder, res, vec_type, "");
 854       return res;
 855    }
 856 }
 857
 858
 859 /**
 860  * Convert to integer, through whichever rounding method that's fastest,
 861  * typically truncating toward zero.
 862  */
 863 LLVMValueRef
 864 lp_build_itrunc(struct lp_build_context *bld,
 865                 LLVMValueRef a)
 866 {
 867    const struct lp_type type = bld->type;
 868    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 869
 870    assert(type.floating);
 871    assert(lp_check_value(type, a));
 872
 873    return LLVMBuildFPToSI(bld->builder, a, int_vec_type, "");
 874 }
 875
 876
 877 LLVMValueRef
 878 lp_build_iround(struct lp_build_context *bld,
 879                 LLVMValueRef a)
 880 {
 881    const struct lp_type type = bld->type;
 882    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 883    LLVMValueRef res;
 884
 885    assert(type.floating);
 886    assert(lp_check_value(type, a));
 887
 888    if(util_cpu_caps.has_sse4_1) {
 889       res = lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_NEAREST);
 890    }
 891    else {
 892       LLVMTypeRef vec_type = lp_build_vec_type(type);
 893       LLVMValueRef mask = lp_build_int_const_scalar(type, (unsigned long long)1 << (type.width - 1));
 894       LLVMValueRef sign;
 895       LLVMValueRef half;
 896
 897       /* get sign bit */
 898       sign = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 899       sign = LLVMBuildAnd(bld->builder, sign, mask, "");
 900
 901       /* sign * 0.5 */
 902       half = lp_build_const_scalar(type, 0.5);
 903       half = LLVMBuildBitCast(bld->builder, half, int_vec_type, "");
 904       half = LLVMBuildOr(bld->builder, sign, half, "");
 905       half = LLVMBuildBitCast(bld->builder, half, vec_type, "");
 906
 907       res = LLVMBuildAdd(bld->builder, a, half, "");
 908    }
 909
 910    res = LLVMBuildFPToSI(bld->builder, res, int_vec_type, "");
 911
 912    return res;
 913 }
 914
 915
 916 /**
 917  * Convert float[] to int[] with floor().
 918  */
 919 LLVMValueRef
 920 lp_build_ifloor(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    LLVMValueRef res;
 926
 927    assert(type.floating);
 928    assert(lp_check_value(type, a));
 929
 930    if(util_cpu_caps.has_sse4_1) {
 931       res = lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_FLOOR);
 932    }
 933    else {
 934       /* Take the sign bit and add it to 1 constant */
 935       LLVMTypeRef vec_type = lp_build_vec_type(type);
 936       unsigned mantissa = lp_mantissa(type);
 937       LLVMValueRef mask = lp_build_int_const_scalar(type, (unsigned long long)1 << (type.width - 1));
 938       LLVMValueRef sign;
 939       LLVMValueRef offset;
 940
 941       /* sign = a < 0 ? ~0 : 0 */
 942       sign = LLVMBuildBitCast(bld->builder, a, int_vec_type, "");
 943       sign = LLVMBuildAnd(bld->builder, sign, mask, "");
 944       sign = LLVMBuildAShr(bld->builder, sign, lp_build_int_const_scalar(type, type.width - 1), "");
 945       lp_build_name(sign, "floor.sign");
 946
 947       /* offset = -0.99999(9)f */
 948       offset = lp_build_const_scalar(type, -(double)(((unsigned long long)1 << mantissa) - 1)/((unsigned long long)1 << mantissa));
 949       offset = LLVMConstBitCast(offset, int_vec_type);
 950
 951       /* offset = a < 0 ? -0.99999(9)f : 0.0f */
 952       offset = LLVMBuildAnd(bld->builder, offset, sign, "");
 953       offset = LLVMBuildBitCast(bld->builder, offset, vec_type, "");
 954       lp_build_name(offset, "floor.offset");
 955
 956       res = LLVMBuildAdd(bld->builder, a, offset, "");
 957       lp_build_name(res, "floor.res");
 958    }
 959
 960    res = LLVMBuildFPToSI(bld->builder, res, int_vec_type, "");
 961    lp_build_name(res, "floor");
 962
 963    return res;
 964 }
 965
 966
 967 LLVMValueRef
 968 lp_build_iceil(struct lp_build_context *bld,
 969                LLVMValueRef a)
 970 {
 971    const struct lp_type type = bld->type;
 972    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
 973    LLVMValueRef res;
 974
 975    assert(type.floating);
 976    assert(lp_check_value(type, a));
 977
 978    if(util_cpu_caps.has_sse4_1) {
 979       res = lp_build_round_sse41(bld, a, LP_BUILD_ROUND_SSE41_CEIL);
 980    }
 981    else {
 982       assert(0);
 983       res = bld->undef;
 984    }
 985
 986    res = LLVMBuildFPToSI(bld->builder, res, int_vec_type, "");
 987
 988    return res;
 989 }
 990
 991
 992 LLVMValueRef
 993 lp_build_sqrt(struct lp_build_context *bld,
 994               LLVMValueRef a)
 995 {
 996    const struct lp_type type = bld->type;
 997    LLVMTypeRef vec_type = lp_build_vec_type(type);
 998    char intrinsic[32];
 999
1000    /* TODO: optimize the constant case */
1001    /* TODO: optimize the constant case */
1002
1003    assert(type.floating);
1004    util_snprintf(intrinsic, sizeof intrinsic, "llvm.sqrt.v%uf%u", type.length, type.width);
1005
1006    return lp_build_intrinsic_unary(bld->builder, intrinsic, vec_type, a);
1007 }
1008
1009
1010 LLVMValueRef
1011 lp_build_rcp(struct lp_build_context *bld,
1012              LLVMValueRef a)
1013 {
1014    const struct lp_type type = bld->type;
1015
1016    if(a == bld->zero)
1017       return bld->undef;
1018    if(a == bld->one)
1019       return bld->one;
1020    if(a == bld->undef)
1021       return bld->undef;
1022
1023    assert(type.floating);
1024
1025    if(LLVMIsConstant(a))
1026       return LLVMConstFDiv(bld->one, a);
1027
1028    if(util_cpu_caps.has_sse && type.width == 32 && type.length == 4)
1029       /* FIXME: improve precision */
1030       return lp_build_intrinsic_unary(bld->builder, "llvm.x86.sse.rcp.ps", lp_build_vec_type(type), a);
1031
1032    return LLVMBuildFDiv(bld->builder, bld->one, a, "");
1033 }
1034
1035
1036 /**
1037  * Generate 1/sqrt(a)
1038  */
1039 LLVMValueRef
1040 lp_build_rsqrt(struct lp_build_context *bld,
1041                LLVMValueRef a)
1042 {
1043    const struct lp_type type = bld->type;
1044
1045    assert(type.floating);
1046
1047    if(util_cpu_caps.has_sse && type.width == 32 && type.length == 4)
1048       return lp_build_intrinsic_unary(bld->builder, "llvm.x86.sse.rsqrt.ps", lp_build_vec_type(type), a);
1049
1050    return lp_build_rcp(bld, lp_build_sqrt(bld, a));
1051 }
1052
1053
1054 /**
1055  * Generate cos(a)
1056  */
1057 LLVMValueRef
1058 lp_build_cos(struct lp_build_context *bld,
1059               LLVMValueRef a)
1060 {
1061    const struct lp_type type = bld->type;
1062    LLVMTypeRef vec_type = lp_build_vec_type(type);
1063    char intrinsic[32];
1064
1065    /* TODO: optimize the constant case */
1066
1067    assert(type.floating);
1068    util_snprintf(intrinsic, sizeof intrinsic, "llvm.cos.v%uf%u", type.length, type.width);
1069
1070    return lp_build_intrinsic_unary(bld->builder, intrinsic, vec_type, a);
1071 }
1072
1073
1074 /**
1075  * Generate sin(a)
1076  */
1077 LLVMValueRef
1078 lp_build_sin(struct lp_build_context *bld,
1079               LLVMValueRef a)
1080 {
1081    const struct lp_type type = bld->type;
1082    LLVMTypeRef vec_type = lp_build_vec_type(type);
1083    char intrinsic[32];
1084
1085    /* TODO: optimize the constant case */
1086
1087    assert(type.floating);
1088    util_snprintf(intrinsic, sizeof intrinsic, "llvm.sin.v%uf%u", type.length, type.width);
1089
1090    return lp_build_intrinsic_unary(bld->builder, intrinsic, vec_type, a);
1091 }
1092
1093
1094 /**
1095  * Generate pow(x, y)
1096  */
1097 LLVMValueRef
1098 lp_build_pow(struct lp_build_context *bld,
1099              LLVMValueRef x,
1100              LLVMValueRef y)
1101 {
1102    /* TODO: optimize the constant case */
1103    if(LLVMIsConstant(x) && LLVMIsConstant(y))
1104       debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1105                    __FUNCTION__);
1106
1107    return lp_build_exp2(bld, lp_build_mul(bld, lp_build_log2(bld, x), y));
1108 }
1109
1110
1111 /**
1112  * Generate exp(x)
1113  */
1114 LLVMValueRef
1115 lp_build_exp(struct lp_build_context *bld,
1116              LLVMValueRef x)
1117 {
1118    /* log2(e) = 1/log(2) */
1119    LLVMValueRef log2e = lp_build_const_scalar(bld->type, 1.4426950408889634);
1120
1121    return lp_build_mul(bld, log2e, lp_build_exp2(bld, x));
1122 }
1123
1124
1125 /**
1126  * Generate log(x)
1127  */
1128 LLVMValueRef
1129 lp_build_log(struct lp_build_context *bld,
1130              LLVMValueRef x)
1131 {
1132    /* log(2) */
1133    LLVMValueRef log2 = lp_build_const_scalar(bld->type, 0.69314718055994529);
1134
1135    return lp_build_mul(bld, log2, lp_build_exp2(bld, x));
1136 }
1137
1138
1139 #define EXP_POLY_DEGREE 3
1140 #define LOG_POLY_DEGREE 5
1141
1142
1143 /**
1144  * Generate polynomial.
1145  * Ex:  coeffs[0] + x * coeffs[1] + x^2 * coeffs[2].
1146  */
1147 static LLVMValueRef
1148 lp_build_polynomial(struct lp_build_context *bld,
1149                     LLVMValueRef x,
1150                     const double *coeffs,
1151                     unsigned num_coeffs)
1152 {
1153    const struct lp_type type = bld->type;
1154    LLVMValueRef res = NULL;
1155    unsigned i;
1156
1157    /* TODO: optimize the constant case */
1158    if(LLVMIsConstant(x))
1159       debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1160                    __FUNCTION__);
1161
1162    for (i = num_coeffs; i--; ) {
1163       LLVMValueRef coeff = lp_build_const_scalar(type, coeffs[i]);
1164       if(res)
1165          res = lp_build_add(bld, coeff, lp_build_mul(bld, x, res));
1166       else
1167          res = coeff;
1168    }
1169
1170    if(res)
1171       return res;
1172    else
1173       return bld->undef;
1174 }
1175
1176
1177 /**
1178  * Minimax polynomial fit of 2**x, in range [-0.5, 0.5[
1179  */
1180 const double lp_build_exp2_polynomial[] = {
1181 #if EXP_POLY_DEGREE == 5
1182    9.9999994e-1, 6.9315308e-1, 2.4015361e-1, 5.5826318e-2, 8.9893397e-3, 1.8775767e-3
1183 #elif EXP_POLY_DEGREE == 4
1184    1.0000026, 6.9300383e-1, 2.4144275e-1, 5.2011464e-2, 1.3534167e-2
1185 #elif EXP_POLY_DEGREE == 3
1186    9.9992520e-1, 6.9583356e-1, 2.2606716e-1, 7.8024521e-2
1187 #elif EXP_POLY_DEGREE == 2
1188    1.0017247, 6.5763628e-1, 3.3718944e-1
1189 #else
1190 #error
1191 #endif
1192 };
1193
1194
1195 void
1196 lp_build_exp2_approx(struct lp_build_context *bld,
1197                      LLVMValueRef x,
1198                      LLVMValueRef *p_exp2_int_part,
1199                      LLVMValueRef *p_frac_part,
1200                      LLVMValueRef *p_exp2)
1201 {
1202    const struct lp_type type = bld->type;
1203    LLVMTypeRef vec_type = lp_build_vec_type(type);
1204    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
1205    LLVMValueRef ipart = NULL;
1206    LLVMValueRef fpart = NULL;
1207    LLVMValueRef expipart = NULL;
1208    LLVMValueRef expfpart = NULL;
1209    LLVMValueRef res = NULL;
1210
1211    if(p_exp2_int_part || p_frac_part || p_exp2) {
1212       /* TODO: optimize the constant case */
1213       if(LLVMIsConstant(x))
1214          debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1215                       __FUNCTION__);
1216
1217       assert(type.floating && type.width == 32);
1218
1219       x = lp_build_min(bld, x, lp_build_const_scalar(type,  129.0));
1220       x = lp_build_max(bld, x, lp_build_const_scalar(type, -126.99999));
1221
1222       /* ipart = int(x - 0.5) */
1223       ipart = LLVMBuildSub(bld->builder, x, lp_build_const_scalar(type, 0.5f), "");
1224       ipart = LLVMBuildFPToSI(bld->builder, ipart, int_vec_type, "");
1225
1226       /* fpart = x - ipart */
1227       fpart = LLVMBuildSIToFP(bld->builder, ipart, vec_type, "");
1228       fpart = LLVMBuildSub(bld->builder, x, fpart, "");
1229    }
1230
1231    if(p_exp2_int_part || p_exp2) {
1232       /* expipart = (float) (1 << ipart) */
1233       expipart = LLVMBuildAdd(bld->builder, ipart, lp_build_int_const_scalar(type, 127), "");
1234       expipart = LLVMBuildShl(bld->builder, expipart, lp_build_int_const_scalar(type, 23), "");
1235       expipart = LLVMBuildBitCast(bld->builder, expipart, vec_type, "");
1236    }
1237
1238    if(p_exp2) {
1239       expfpart = lp_build_polynomial(bld, fpart, lp_build_exp2_polynomial,
1240                                      Elements(lp_build_exp2_polynomial));
1241
1242       res = LLVMBuildMul(bld->builder, expipart, expfpart, "");
1243    }
1244
1245    if(p_exp2_int_part)
1246       *p_exp2_int_part = expipart;
1247
1248    if(p_frac_part)
1249       *p_frac_part = fpart;
1250
1251    if(p_exp2)
1252       *p_exp2 = res;
1253 }
1254
1255
1256 LLVMValueRef
1257 lp_build_exp2(struct lp_build_context *bld,
1258               LLVMValueRef x)
1259 {
1260    LLVMValueRef res;
1261    lp_build_exp2_approx(bld, x, NULL, NULL, &res);
1262    return res;
1263 }
1264
1265
1266 /**
1267  * Minimax polynomial fit of log2(x)/(x - 1), for x in range [1, 2[
1268  * These coefficients can be generate with
1269  * http://www.boost.org/doc/libs/1_36_0/libs/math/doc/sf_and_dist/html/math_toolkit/toolkit/internals2/minimax.html
1270  */
1271 const double lp_build_log2_polynomial[] = {
1272 #if LOG_POLY_DEGREE == 6
1273    3.11578814719469302614, -3.32419399085241980044, 2.59883907202499966007, -1.23152682416275988241, 0.318212422185251071475, -0.0344359067839062357313
1274 #elif LOG_POLY_DEGREE == 5
1275    2.8882704548164776201, -2.52074962577807006663, 1.48116647521213171641, -0.465725644288844778798, 0.0596515482674574969533
1276 #elif LOG_POLY_DEGREE == 4
1277    2.61761038894603480148, -1.75647175389045657003, 0.688243882994381274313, -0.107254423828329604454
1278 #elif LOG_POLY_DEGREE == 3
1279    2.28330284476918490682, -1.04913055217340124191, 0.204446009836232697516
1280 #else
1281 #error
1282 #endif
1283 };
1284
1285
1286 /**
1287  * See http://www.devmaster.net/forums/showthread.php?p=43580
1288  */
1289 void
1290 lp_build_log2_approx(struct lp_build_context *bld,
1291                      LLVMValueRef x,
1292                      LLVMValueRef *p_exp,
1293                      LLVMValueRef *p_floor_log2,
1294                      LLVMValueRef *p_log2)
1295 {
1296    const struct lp_type type = bld->type;
1297    LLVMTypeRef vec_type = lp_build_vec_type(type);
1298    LLVMTypeRef int_vec_type = lp_build_int_vec_type(type);
1299
1300    LLVMValueRef expmask = lp_build_int_const_scalar(type, 0x7f800000);
1301    LLVMValueRef mantmask = lp_build_int_const_scalar(type, 0x007fffff);
1302    LLVMValueRef one = LLVMConstBitCast(bld->one, int_vec_type);
1303
1304    LLVMValueRef i = NULL;
1305    LLVMValueRef exp = NULL;
1306    LLVMValueRef mant = NULL;
1307    LLVMValueRef logexp = NULL;
1308    LLVMValueRef logmant = NULL;
1309    LLVMValueRef res = NULL;
1310
1311    if(p_exp || p_floor_log2 || p_log2) {
1312       /* TODO: optimize the constant case */
1313       if(LLVMIsConstant(x))
1314          debug_printf("%s: inefficient/imprecise constant arithmetic\n",
1315                       __FUNCTION__);
1316
1317       assert(type.floating && type.width == 32);
1318
1319       i = LLVMBuildBitCast(bld->builder, x, int_vec_type, "");
1320
1321       /* exp = (float) exponent(x) */
1322       exp = LLVMBuildAnd(bld->builder, i, expmask, "");
1323    }
1324
1325    if(p_floor_log2 || p_log2) {
1326       logexp = LLVMBuildLShr(bld->builder, exp, lp_build_int_const_scalar(type, 23), "");
1327       logexp = LLVMBuildSub(bld->builder, logexp, lp_build_int_const_scalar(type, 127), "");
1328       logexp = LLVMBuildSIToFP(bld->builder, logexp, vec_type, "");
1329    }
1330
1331    if(p_log2) {
1332       /* mant = (float) mantissa(x) */
1333       mant = LLVMBuildAnd(bld->builder, i, mantmask, "");
1334       mant = LLVMBuildOr(bld->builder, mant, one, "");
1335       mant = LLVMBuildBitCast(bld->builder, mant, vec_type, "");
1336
1337       logmant = lp_build_polynomial(bld, mant, lp_build_log2_polynomial,
1338                                     Elements(lp_build_log2_polynomial));
1339
1340       /* This effectively increases the polynomial degree by one, but ensures that log2(1) == 0*/
1341       logmant = LLVMBuildMul(bld->builder, logmant, LLVMBuildSub(bld->builder, mant, bld->one, ""), "");
1342
1343       res = LLVMBuildAdd(bld->builder, logmant, logexp, "");
1344    }
1345
1346    if(p_exp)
1347       *p_exp = exp;
1348
1349    if(p_floor_log2)
1350       *p_floor_log2 = logexp;
1351
1352    if(p_log2)
1353       *p_log2 = res;
1354 }
1355
1356
1357 LLVMValueRef
1358 lp_build_log2(struct lp_build_context *bld,
1359               LLVMValueRef x)
1360 {
1361    LLVMValueRef res;
1362    lp_build_log2_approx(bld, x, NULL, NULL, &res);
1363    return res;
1364 }