lib/Support/ConstantRange.cpp

   1 //===-- ConstantRange.cpp - ConstantRange implementation ------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // Represent a range of possible values that may occur when the program is run
  11 // for an integral value.  This keeps track of a lower and upper bound for the
  12 // constant, which MAY wrap around the end of the numeric range.  To do this, it
  13 // keeps track of a [lower, upper) bound, which specifies an interval just like
  14 // STL iterators.  When used with boolean values, the following are important
  15 // ranges (other integral ranges use min/max values for special range values):
  16 //
  17 //  [F, F) = {}     = Empty set
  18 //  [T, F) = {T}
  19 //  [F, T) = {F}
  20 //  [T, T) = {F, T} = Full set
  21 //
  22 //===----------------------------------------------------------------------===//
  23
  24 #include "llvm/Constants.h"
  25 #include "llvm/Support/ConstantRange.h"
  26 #include "llvm/Support/Debug.h"
  27 #include "llvm/Support/raw_ostream.h"
  28 #include "llvm/Instructions.h"
  29 using namespace llvm;
  30
  31 /// Initialize a full (the default) or empty set for the specified type.
  32 ///
  33 ConstantRange::ConstantRange(uint32_t BitWidth, bool Full) {
  34   if (Full)
  35     Lower = Upper = APInt::getMaxValue(BitWidth);
  36   else
  37     Lower = Upper = APInt::getMinValue(BitWidth);
  38 }
  39
  40 /// Initialize a range to hold the single specified value.
  41 ///
  42 ConstantRange::ConstantRange(const APInt &V) : Lower(V), Upper(V + 1) {}
  43
  44 ConstantRange::ConstantRange(const APInt &L, const APInt &U) :
  45   Lower(L), Upper(U) {
  46   assert(L.getBitWidth() == U.getBitWidth() &&
  47          "ConstantRange with unequal bit widths");
  48   assert((L != U || (L.isMaxValue() || L.isMinValue())) &&
  49          "Lower == Upper, but they aren't min or max value!");
  50 }
  51
  52 ConstantRange ConstantRange::makeICmpRegion(unsigned Pred,
  53                                             const ConstantRange &CR) {
  54   uint32_t W = CR.getBitWidth();
  55   switch (Pred) {
  56     default: assert(!"Invalid ICmp predicate to makeICmpRegion()");
  57     case ICmpInst::ICMP_EQ:
  58       return CR;
  59     case ICmpInst::ICMP_NE:
  60       if (CR.isSingleElement())
  61         return ConstantRange(CR.getUpper(), CR.getLower());
  62       return ConstantRange(W);
  63     case ICmpInst::ICMP_ULT:
  64       return ConstantRange(APInt::getMinValue(W), CR.getUnsignedMax());
  65     case ICmpInst::ICMP_SLT:
  66       return ConstantRange(APInt::getSignedMinValue(W), CR.getSignedMax());
  67     case ICmpInst::ICMP_ULE: {
  68       APInt UMax(CR.getUnsignedMax());
  69       if (UMax.isMaxValue())
  70         return ConstantRange(W);
  71       return ConstantRange(APInt::getMinValue(W), UMax + 1);
  72     }
  73     case ICmpInst::ICMP_SLE: {
  74       APInt SMax(CR.getSignedMax());
  75       if (SMax.isMaxSignedValue() || (SMax+1).isMaxSignedValue())
  76         return ConstantRange(W);
  77       return ConstantRange(APInt::getSignedMinValue(W), SMax + 1);
  78     }
  79     case ICmpInst::ICMP_UGT:
  80       return ConstantRange(CR.getUnsignedMin() + 1, APInt::getNullValue(W));
  81     case ICmpInst::ICMP_SGT:
  82       return ConstantRange(CR.getSignedMin() + 1,
  83                            APInt::getSignedMinValue(W));
  84     case ICmpInst::ICMP_UGE: {
  85       APInt UMin(CR.getUnsignedMin());
  86       if (UMin.isMinValue())
  87         return ConstantRange(W);
  88       return ConstantRange(UMin, APInt::getNullValue(W));
  89     }
  90     case ICmpInst::ICMP_SGE: {
  91       APInt SMin(CR.getSignedMin());
  92       if (SMin.isMinSignedValue())
  93         return ConstantRange(W);
  94       return ConstantRange(SMin, APInt::getSignedMinValue(W));
  95     }
  96   }
  97 }
  98
  99 /// isFullSet - Return true if this set contains all of the elements possible
 100 /// for this data-type
 101 bool ConstantRange::isFullSet() const {
 102   return Lower == Upper && Lower.isMaxValue();
 103 }
 104
 105 /// isEmptySet - Return true if this set contains no members.
 106 ///
 107 bool ConstantRange::isEmptySet() const {
 108   return Lower == Upper && Lower.isMinValue();
 109 }
 110
 111 /// isWrappedSet - Return true if this set wraps around the top of the range,
 112 /// for example: [100, 8)
 113 ///
 114 bool ConstantRange::isWrappedSet() const {
 115   return Lower.ugt(Upper);
 116 }
 117
 118 /// getSetSize - Return the number of elements in this set.
 119 ///
 120 APInt ConstantRange::getSetSize() const {
 121   if (isEmptySet())
 122     return APInt(getBitWidth(), 0);
 123   if (getBitWidth() == 1) {
 124     if (Lower != Upper)  // One of T or F in the set...
 125       return APInt(2, 1);
 126     return APInt(2, 2);      // Must be full set...
 127   }
 128
 129   // Simply subtract the bounds...
 130   return Upper - Lower;
 131 }
 132
 133 /// getUnsignedMax - Return the largest unsigned value contained in the
 134 /// ConstantRange.
 135 ///
 136 APInt ConstantRange::getUnsignedMax() const {
 137   if (isFullSet() || isWrappedSet())
 138     return APInt::getMaxValue(getBitWidth());
 139   else
 140     return getUpper() - 1;
 141 }
 142
 143 /// getUnsignedMin - Return the smallest unsigned value contained in the
 144 /// ConstantRange.
 145 ///
 146 APInt ConstantRange::getUnsignedMin() const {
 147   if (isFullSet() || (isWrappedSet() && getUpper() != 0))
 148     return APInt::getMinValue(getBitWidth());
 149   else
 150     return getLower();
 151 }
 152
 153 /// getSignedMax - Return the largest signed value contained in the
 154 /// ConstantRange.
 155 ///
 156 APInt ConstantRange::getSignedMax() const {
 157   APInt SignedMax(APInt::getSignedMaxValue(getBitWidth()));
 158   if (!isWrappedSet()) {
 159     if (getLower().sle(getUpper() - 1))
 160       return getUpper() - 1;
 161     else
 162       return SignedMax;
 163   } else {
 164     if (getLower().isNegative() == getUpper().isNegative())
 165       return SignedMax;
 166     else
 167       return getUpper() - 1;
 168   }
 169 }
 170
 171 /// getSignedMin - Return the smallest signed value contained in the
 172 /// ConstantRange.
 173 ///
 174 APInt ConstantRange::getSignedMin() const {
 175   APInt SignedMin(APInt::getSignedMinValue(getBitWidth()));
 176   if (!isWrappedSet()) {
 177     if (getLower().sle(getUpper() - 1))
 178       return getLower();
 179     else
 180       return SignedMin;
 181   } else {
 182     if ((getUpper() - 1).slt(getLower())) {
 183       if (getUpper() != SignedMin)
 184         return SignedMin;
 185       else
 186         return getLower();
 187     } else {
 188       return getLower();
 189     }
 190   }
 191 }
 192
 193 /// contains - Return true if the specified value is in the set.
 194 ///
 195 bool ConstantRange::contains(const APInt &V) const {
 196   if (Lower == Upper)
 197     return isFullSet();
 198
 199   if (!isWrappedSet())
 200     return Lower.ule(V) && V.ult(Upper);
 201   else
 202     return Lower.ule(V) || V.ult(Upper);
 203 }
 204
 205 /// contains - Return true if the argument is a subset of this range.
 206 /// Two equal sets contain each other. The empty set contained by all other
 207 /// sets.
 208 ///
 209 bool ConstantRange::contains(const ConstantRange &Other) const {
 210   if (isFullSet() || Other.isEmptySet()) return true;
 211   if (isEmptySet() || Other.isFullSet()) return false;
 212
 213   if (!isWrappedSet()) {
 214     if (Other.isWrappedSet())
 215       return false;
 216
 217     return Lower.ule(Other.getLower()) && Other.getUpper().ule(Upper);
 218   }
 219
 220   if (!Other.isWrappedSet())
 221     return Other.getUpper().ule(Upper) ||
 222            Lower.ule(Other.getLower());
 223
 224   return Other.getUpper().ule(Upper) && Lower.ule(Other.getLower());
 225 }
 226
 227 /// subtract - Subtract the specified constant from the endpoints of this
 228 /// constant range.
 229 ConstantRange ConstantRange::subtract(const APInt &Val) const {
 230   assert(Val.getBitWidth() == getBitWidth() && "Wrong bit width");
 231   // If the set is empty or full, don't modify the endpoints.
 232   if (Lower == Upper)
 233     return *this;
 234   return ConstantRange(Lower - Val, Upper - Val);
 235 }
 236
 237 /// intersectWith - Return the range that results from the intersection of this
 238 /// range with another range.  The resultant range is guaranteed to include all
 239 /// elements contained in both input ranges, and to have the smallest possible
 240 /// set size that does so.  Because there may be two intersections with the
 241 /// same set size, A.intersectWith(B) might not be equal to B.intersectWith(A).
 242 ConstantRange ConstantRange::intersectWith(const ConstantRange &CR) const {
 243   assert(getBitWidth() == CR.getBitWidth() &&
 244          "ConstantRange types don't agree!");
 245
 246   // Handle common cases.
 247   if (   isEmptySet() || CR.isFullSet()) return *this;
 248   if (CR.isEmptySet() ||    isFullSet()) return CR;
 249
 250   if (!isWrappedSet() && CR.isWrappedSet())
 251     return CR.intersectWith(*this);
 252
 253   if (!isWrappedSet() && !CR.isWrappedSet()) {
 254     if (Lower.ult(CR.Lower)) {
 255       if (Upper.ule(CR.Lower))
 256         return ConstantRange(getBitWidth(), false);
 257
 258       if (Upper.ult(CR.Upper))
 259         return ConstantRange(CR.Lower, Upper);
 260
 261       return CR;
 262     } else {
 263       if (Upper.ult(CR.Upper))
 264         return *this;
 265
 266       if (Lower.ult(CR.Upper))
 267         return ConstantRange(Lower, CR.Upper);
 268
 269       return ConstantRange(getBitWidth(), false);
 270     }
 271   }
 272
 273   if (isWrappedSet() && !CR.isWrappedSet()) {
 274     if (CR.Lower.ult(Upper)) {
 275       if (CR.Upper.ult(Upper))
 276         return CR;
 277
 278       if (CR.Upper.ult(Lower))
 279         return ConstantRange(CR.Lower, Upper);
 280
 281       if (getSetSize().ult(CR.getSetSize()))
 282         return *this;
 283       else
 284         return CR;
 285     } else if (CR.Lower.ult(Lower)) {
 286       if (CR.Upper.ule(Lower))
 287         return ConstantRange(getBitWidth(), false);
 288
 289       return ConstantRange(Lower, CR.Upper);
 290     }
 291     return CR;
 292   }
 293
 294   if (CR.Upper.ult(Upper)) {
 295     if (CR.Lower.ult(Upper)) {
 296       if (getSetSize().ult(CR.getSetSize()))
 297         return *this;
 298       else
 299         return CR;
 300     }
 301
 302     if (CR.Lower.ult(Lower))
 303       return ConstantRange(Lower, CR.Upper);
 304
 305     return CR;
 306   } else if (CR.Upper.ult(Lower)) {
 307     if (CR.Lower.ult(Lower))
 308       return *this;
 309
 310     return ConstantRange(CR.Lower, Upper);
 311   }
 312   if (getSetSize().ult(CR.getSetSize()))
 313     return *this;
 314   else
 315     return CR;
 316 }
 317
 318
 319 /// unionWith - Return the range that results from the union of this range with
 320 /// another range.  The resultant range is guaranteed to include the elements of
 321 /// both sets, but may contain more.  For example, [3, 9) union [12,15) is
 322 /// [3, 15), which includes 9, 10, and 11, which were not included in either
 323 /// set before.
 324 ///
 325 ConstantRange ConstantRange::unionWith(const ConstantRange &CR) const {
 326   assert(getBitWidth() == CR.getBitWidth() &&
 327          "ConstantRange types don't agree!");
 328
 329   if (   isFullSet() || CR.isEmptySet()) return *this;
 330   if (CR.isFullSet() ||    isEmptySet()) return CR;
 331
 332   if (!isWrappedSet() && CR.isWrappedSet()) return CR.unionWith(*this);
 333
 334   if (!isWrappedSet() && !CR.isWrappedSet()) {
 335     if (CR.Upper.ult(Lower) || Upper.ult(CR.Lower)) {
 336       // If the two ranges are disjoint, find the smaller gap and bridge it.
 337       APInt d1 = CR.Lower - Upper, d2 = Lower - CR.Upper;
 338       if (d1.ult(d2))
 339         return ConstantRange(Lower, CR.Upper);
 340       else
 341         return ConstantRange(CR.Lower, Upper);
 342     }
 343
 344     APInt L = Lower, U = Upper;
 345     if (CR.Lower.ult(L))
 346       L = CR.Lower;
 347     if ((CR.Upper - 1).ugt(U - 1))
 348       U = CR.Upper;
 349
 350     if (L == 0 && U == 0)
 351       return ConstantRange(getBitWidth());
 352
 353     return ConstantRange(L, U);
 354   }
 355
 356   if (!CR.isWrappedSet()) {
 357     // ------U   L-----  and  ------U   L----- : this
 358     //   L--U                            L--U  : CR
 359     if (CR.Upper.ule(Upper) || CR.Lower.uge(Lower))
 360       return *this;
 361
 362     // ------U   L----- : this
 363     //    L---------U   : CR
 364     if (CR.Lower.ule(Upper) && Lower.ule(CR.Upper))
 365       return ConstantRange(getBitWidth());
 366
 367     // ----U       L---- : this
 368     //       L---U       : CR
 369     //    <d1>  <d2>
 370     if (Upper.ule(CR.Lower) && CR.Upper.ule(Lower)) {
 371       APInt d1 = CR.Lower - Upper, d2 = Lower - CR.Upper;
 372       if (d1.ult(d2))
 373         return ConstantRange(Lower, CR.Upper);
 374       else
 375         return ConstantRange(CR.Lower, Upper);
 376     }
 377
 378     // ----U     L----- : this
 379     //        L----U    : CR
 380     if (Upper.ult(CR.Lower) && Lower.ult(CR.Upper))
 381       return ConstantRange(CR.Lower, Upper);
 382
 383     // ------U    L---- : this
 384     //    L-----U       : CR
 385     if (CR.Lower.ult(Upper) && CR.Upper.ult(Lower))
 386       return ConstantRange(Lower, CR.Upper);
 387   }
 388
 389   assert(isWrappedSet() && CR.isWrappedSet() &&
 390          "ConstantRange::unionWith missed wrapped union unwrapped case");
 391
 392   // ------U    L----  and  ------U    L---- : this
 393   // -U  L-----------  and  ------------U  L : CR
 394   if (CR.Lower.ule(Upper) || Lower.ule(CR.Upper))
 395     return ConstantRange(getBitWidth());
 396
 397   APInt L = Lower, U = Upper;
 398   if (CR.Upper.ugt(U))
 399     U = CR.Upper;
 400   if (CR.Lower.ult(L))
 401     L = CR.Lower;
 402
 403   return ConstantRange(L, U);
 404 }
 405
 406 /// zeroExtend - Return a new range in the specified integer type, which must
 407 /// be strictly larger than the current type.  The returned range will
 408 /// correspond to the possible range of values as if the source range had been
 409 /// zero extended.
 410 ConstantRange ConstantRange::zeroExtend(uint32_t DstTySize) const {
 411   unsigned SrcTySize = getBitWidth();
 412   assert(SrcTySize < DstTySize && "Not a value extension");
 413   if (isFullSet())
 414     // Change a source full set into [0, 1 << 8*numbytes)
 415     return ConstantRange(APInt(DstTySize,0), APInt(DstTySize,1).shl(SrcTySize));
 416
 417   APInt L = Lower; L.zext(DstTySize);
 418   APInt U = Upper; U.zext(DstTySize);
 419   return ConstantRange(L, U);
 420 }
 421
 422 /// signExtend - Return a new range in the specified integer type, which must
 423 /// be strictly larger than the current type.  The returned range will
 424 /// correspond to the possible range of values as if the source range had been
 425 /// sign extended.
 426 ConstantRange ConstantRange::signExtend(uint32_t DstTySize) const {
 427   unsigned SrcTySize = getBitWidth();
 428   assert(SrcTySize < DstTySize && "Not a value extension");
 429   if (isFullSet()) {
 430     return ConstantRange(APInt::getHighBitsSet(DstTySize,DstTySize-SrcTySize+1),
 431                          APInt::getLowBitsSet(DstTySize, SrcTySize-1) + 1);
 432   }
 433
 434   APInt L = Lower; L.sext(DstTySize);
 435   APInt U = Upper; U.sext(DstTySize);
 436   return ConstantRange(L, U);
 437 }
 438
 439 /// truncate - Return a new range in the specified integer type, which must be
 440 /// strictly smaller than the current type.  The returned range will
 441 /// correspond to the possible range of values as if the source range had been
 442 /// truncated to the specified type.
 443 ConstantRange ConstantRange::truncate(uint32_t DstTySize) const {
 444   unsigned SrcTySize = getBitWidth();
 445   assert(SrcTySize > DstTySize && "Not a value truncation");
 446   APInt Size(APInt::getLowBitsSet(SrcTySize, DstTySize));
 447   if (isFullSet() || getSetSize().ugt(Size))
 448     return ConstantRange(DstTySize, /*isFullSet=*/true);
 449
 450   APInt L = Lower; L.trunc(DstTySize);
 451   APInt U = Upper; U.trunc(DstTySize);
 452   return ConstantRange(L, U);
 453 }
 454
 455 /// zextOrTrunc - make this range have the bit width given by \p DstTySize. The
 456 /// value is zero extended, truncated, or left alone to make it that width.
 457 ConstantRange ConstantRange::zextOrTrunc(uint32_t DstTySize) const {
 458   unsigned SrcTySize = getBitWidth();
 459   if (SrcTySize > DstTySize)
 460     return truncate(DstTySize);
 461   else if (SrcTySize < DstTySize)
 462     return zeroExtend(DstTySize);
 463   else
 464     return *this;
 465 }
 466
 467 /// sextOrTrunc - make this range have the bit width given by \p DstTySize. The
 468 /// value is sign extended, truncated, or left alone to make it that width.
 469 ConstantRange ConstantRange::sextOrTrunc(uint32_t DstTySize) const {
 470   unsigned SrcTySize = getBitWidth();
 471   if (SrcTySize > DstTySize)
 472     return truncate(DstTySize);
 473   else if (SrcTySize < DstTySize)
 474     return signExtend(DstTySize);
 475   else
 476     return *this;
 477 }
 478
 479 ConstantRange
 480 ConstantRange::add(const ConstantRange &Other) const {
 481   if (isEmptySet() || Other.isEmptySet())
 482     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 483   if (isFullSet() || Other.isFullSet())
 484     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 485
 486   APInt Spread_X = getSetSize(), Spread_Y = Other.getSetSize();
 487   APInt NewLower = getLower() + Other.getLower();
 488   APInt NewUpper = getUpper() + Other.getUpper() - 1;
 489   if (NewLower == NewUpper)
 490     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 491
 492   ConstantRange X = ConstantRange(NewLower, NewUpper);
 493   if (X.getSetSize().ult(Spread_X) || X.getSetSize().ult(Spread_Y))
 494     // We've wrapped, therefore, full set.
 495     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 496
 497   return X;
 498 }
 499
 500 ConstantRange
 501 ConstantRange::sub(const ConstantRange &Other) const {
 502   if (isEmptySet() || Other.isEmptySet())
 503     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 504   if (isFullSet() || Other.isFullSet())
 505     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 506
 507   APInt Spread_X = getSetSize(), Spread_Y = Other.getSetSize();
 508   APInt NewLower = getLower() - Other.getLower();
 509   APInt NewUpper = getUpper() - Other.getUpper() + 1;
 510   if (NewLower == NewUpper)
 511     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 512
 513   ConstantRange X = ConstantRange(NewLower, NewUpper);
 514   if (X.getSetSize().ult(Spread_X) || X.getSetSize().ult(Spread_Y))
 515     // We've wrapped, therefore, full set.
 516     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 517
 518   return X;
 519 }
 520
 521 ConstantRange
 522 ConstantRange::multiply(const ConstantRange &Other) const {
 523   // TODO: If either operand is a single element and the multiply is known to
 524   // be non-wrapping, round the result min and max value to the appropriate
 525   // multiple of that element. If wrapping is possible, at least adjust the
 526   // range according to the greatest power-of-two factor of the single element.
 527
 528   if (isEmptySet() || Other.isEmptySet())
 529     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 530   if (isFullSet() || Other.isFullSet())
 531     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 532
 533   APInt this_min = getUnsignedMin().zext(getBitWidth() * 2);
 534   APInt this_max = getUnsignedMax().zext(getBitWidth() * 2);
 535   APInt Other_min = Other.getUnsignedMin().zext(getBitWidth() * 2);
 536   APInt Other_max = Other.getUnsignedMax().zext(getBitWidth() * 2);
 537
 538   ConstantRange Result_zext = ConstantRange(this_min * Other_min,
 539                                             this_max * Other_max + 1);
 540   return Result_zext.truncate(getBitWidth());
 541 }
 542
 543 ConstantRange
 544 ConstantRange::smax(const ConstantRange &Other) const {
 545   // X smax Y is: range(smax(X_smin, Y_smin),
 546   //                    smax(X_smax, Y_smax))
 547   if (isEmptySet() || Other.isEmptySet())
 548     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 549   APInt NewL = APIntOps::smax(getSignedMin(), Other.getSignedMin());
 550   APInt NewU = APIntOps::smax(getSignedMax(), Other.getSignedMax()) + 1;
 551   if (NewU == NewL)
 552     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 553   return ConstantRange(NewL, NewU);
 554 }
 555
 556 ConstantRange
 557 ConstantRange::umax(const ConstantRange &Other) const {
 558   // X umax Y is: range(umax(X_umin, Y_umin),
 559   //                    umax(X_umax, Y_umax))
 560   if (isEmptySet() || Other.isEmptySet())
 561     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 562   APInt NewL = APIntOps::umax(getUnsignedMin(), Other.getUnsignedMin());
 563   APInt NewU = APIntOps::umax(getUnsignedMax(), Other.getUnsignedMax()) + 1;
 564   if (NewU == NewL)
 565     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 566   return ConstantRange(NewL, NewU);
 567 }
 568
 569 ConstantRange
 570 ConstantRange::udiv(const ConstantRange &RHS) const {
 571   if (isEmptySet() || RHS.isEmptySet() || RHS.getUnsignedMax() == 0)
 572     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 573   if (RHS.isFullSet())
 574     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 575
 576   APInt Lower = getUnsignedMin().udiv(RHS.getUnsignedMax());
 577
 578   APInt RHS_umin = RHS.getUnsignedMin();
 579   if (RHS_umin == 0) {
 580     // We want the lowest value in RHS excluding zero. Usually that would be 1
 581     // except for a range in the form of [X, 1) in which case it would be X.
 582     if (RHS.getUpper() == 1)
 583       RHS_umin = RHS.getLower();
 584     else
 585       RHS_umin = APInt(getBitWidth(), 1);
 586   }
 587
 588   APInt Upper = getUnsignedMax().udiv(RHS_umin) + 1;
 589
 590   // If the LHS is Full and the RHS is a wrapped interval containing 1 then
 591   // this could occur.
 592   if (Lower == Upper)
 593     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 594
 595   return ConstantRange(Lower, Upper);
 596 }
 597
 598 ConstantRange
 599 ConstantRange::shl(const ConstantRange &Other) const {
 600   if (isEmptySet() || Other.isEmptySet())
 601     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 602
 603   APInt min = getUnsignedMin().shl(Other.getUnsignedMin());
 604   APInt max = getUnsignedMax().shl(Other.getUnsignedMax());
 605
 606   // there's no overflow!
 607   APInt Zeros(getBitWidth(), getUnsignedMax().countLeadingZeros());
 608   if (Zeros.ugt(Other.getUnsignedMax()))
 609     return ConstantRange(min, max + 1);
 610
 611   // FIXME: implement the other tricky cases
 612   return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 613 }
 614
 615 ConstantRange
 616 ConstantRange::lshr(const ConstantRange &Other) const {
 617   if (isEmptySet() || Other.isEmptySet())
 618     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 619
 620   APInt max = getUnsignedMax().lshr(Other.getUnsignedMin());
 621   APInt min = getUnsignedMin().lshr(Other.getUnsignedMax());
 622   if (min == max + 1)
 623     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 624
 625   return ConstantRange(min, max + 1);
 626 }
 627
 628 ConstantRange ConstantRange::inverse() const {
 629   if (isFullSet()) {
 630     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
 631   } else if (isEmptySet()) {
 632     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 633   }
 634   return ConstantRange(Upper, Lower);
 635 }
 636
 637 /// print - Print out the bounds to a stream...
 638 ///
 639 void ConstantRange::print(raw_ostream &OS) const {
 640   if (isFullSet())
 641     OS << "full-set";
 642   else if (isEmptySet())
 643     OS << "empty-set";
 644   else
 645     OS << "[" << Lower << "," << Upper << ")";
 646 }
 647
 648 /// dump - Allow printing from a debugger easily...
 649 ///
 650 void ConstantRange::dump() const {
 651   print(dbgs());
 652 }