[ConstantRange] Add getFull() + getEmpty() named constructors; NFC

This adds ConstantRange::getFull(BitWidth) and
ConstantRange::getEmpty(BitWidth) named constructors as more readable
alternatives to the current ConstantRange(BitWidth, /* full */ false)
and similar. Additionally private getFull() and getEmpty() member
functions are added which return a full/empty range with the same bit
width -- these are commonly needed inside ConstantRange.cpp.

The IsFullSet argument in the ConstantRange(BitWidth, IsFullSet)
constructor is now mandatory for the few usages that still make use of it.

Differential Revision: https://reviews.llvm.org/D59716

llvm-svn: 356852

llvm/include/llvm/IR/ConstantRange.h

@@ -47,9 +47,19 @@ struct KnownBits;
 class LLVM_NODISCARD ConstantRange {
   APInt Lower, Upper;
 
+  /// Create empty constant range with same bitwidth.
+  ConstantRange getEmpty() const {
+    return ConstantRange(getBitWidth(), false);
+  }
+
+  /// Create full constant range with same bitwidth.
+  ConstantRange getFull() const {
+    return ConstantRange(getBitWidth(), true);
+  }
+
 public:
   /// Initialize a full (the default) or empty set for the specified bit width.
-  explicit ConstantRange(uint32_t BitWidth, bool isFullSet = true);
+  explicit ConstantRange(uint32_t BitWidth, bool isFullSet);
 
   /// Initialize a range to hold the single specified value.
   ConstantRange(APInt Value);
@@ -59,6 +69,16 @@ class LLVM_NODISCARD ConstantRange {
   /// assert out if the two APInt's are not the same bit width.
   ConstantRange(APInt Lower, APInt Upper);
 
+  /// Create empty constant range with the given bit width.
+  static ConstantRange getEmpty(uint32_t BitWidth) {
+    return ConstantRange(BitWidth, false);
+  }
+
+  /// Create full constant range with the given bit width.
+  static ConstantRange getFull(uint32_t BitWidth) {
+    return ConstantRange(BitWidth, true);
+  }
+
   /// Initialize a range based on a known bits constraint. The IsSigned flag
   /// indicates whether the constant range should not wrap in the signed or
   /// unsigned domain.

llvm/lib/Analysis/LazyValueInfo.cpp

@@ -963,7 +963,7 @@ Optional<ConstantRange> LazyValueInfoImpl::getRangeForOperand(unsigned Op,
 
   const unsigned OperandBitWidth =
     DL.getTypeSizeInBits(I->getOperand(Op)->getType());
-  ConstantRange Range = ConstantRange(OperandBitWidth);
+  ConstantRange Range = ConstantRange::getFull(OperandBitWidth);
   if (hasBlockValue(I->getOperand(Op), BB)) {
     ValueLatticeElement Val = getBlockValue(I->getOperand(Op), BB);
     intersectAssumeOrGuardBlockValueConstantRange(I->getOperand(Op), Val, I);
@@ -1576,14 +1576,14 @@ ConstantRange LazyValueInfo::getConstantRange(Value *V, BasicBlock *BB,
   ValueLatticeElement Result =
       getImpl(PImpl, AC, &DL, DT).getValueInBlock(V, BB, CxtI);
   if (Result.isUndefined())
-    return ConstantRange(Width, /*isFullSet=*/false);
+    return ConstantRange::getEmpty(Width);
   if (Result.isConstantRange())
     return Result.getConstantRange();
   // We represent ConstantInt constants as constant ranges but other kinds
   // of integer constants, i.e. ConstantExpr will be tagged as constants
   assert(!(Result.isConstant() && isa<ConstantInt>(Result.getConstant())) &&
          "ConstantInt value must be represented as constantrange");
-  return ConstantRange(Width, /*isFullSet=*/true);
+  return ConstantRange::getFull(Width);
 }
 
 /// Determine whether the specified value is known to be a
@@ -1615,14 +1615,14 @@ ConstantRange LazyValueInfo::getConstantRangeOnEdge(Value *V,
       getImpl(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
 
   if (Result.isUndefined())
-    return ConstantRange(Width, /*isFullSet=*/false);
+    return ConstantRange::getEmpty(Width);
   if (Result.isConstantRange())
     return Result.getConstantRange();
   // We represent ConstantInt constants as constant ranges but other kinds
   // of integer constants, i.e. ConstantExpr will be tagged as constants
   assert(!(Result.isConstant() && isa<ConstantInt>(Result.getConstant())) &&
          "ConstantInt value must be represented as constantrange");
-  return ConstantRange(Width, /*isFullSet=*/true);
+  return ConstantRange::getFull(Width);
 }
 
 static LazyValueInfo::Tristate

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -5774,7 +5774,7 @@ static ConstantRange getRangeForAffineARHelper(APInt Step,
   // FullRange), then we don't know anything about the final range either.
   // Return FullRange.
   if (StartRange.isFullSet())
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
 
   // If Step is signed and negative, then we use its absolute value, but we also
   // note that we're moving in the opposite direction.
@@ -5790,7 +5790,7 @@ static ConstantRange getRangeForAffineARHelper(APInt Step,
   // Check if Offset is more than full span of BitWidth. If it is, the
   // expression is guaranteed to overflow.
   if (APInt::getMaxValue(StartRange.getBitWidth()).udiv(Step).ult(MaxBECount))
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
 
   // Offset is by how much the expression can change. Checks above guarantee no
   // overflow here.
@@ -5809,7 +5809,7 @@ static ConstantRange getRangeForAffineARHelper(APInt Step,
   // range (due to wrap around). This means that the expression can take any
   // value in this bitwidth, and we have to return full range.
   if (StartRange.contains(MovedBoundary))
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
 
   APInt NewLower =
       Descending ? std::move(MovedBoundary) : std::move(StartLower);
@@ -5819,7 +5819,7 @@ static ConstantRange getRangeForAffineARHelper(APInt Step,
 
   // If we end up with full range, return a proper full range.
   if (NewLower == NewUpper)
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
 
   // No overflow detected, return [StartLower, StartUpper + Offset + 1) range.
   return ConstantRange(std::move(NewLower), std::move(NewUpper));
@@ -5939,17 +5939,17 @@ ConstantRange ScalarEvolution::getRangeViaFactoring(const SCEV *Start,
 
   SelectPattern StartPattern(*this, BitWidth, Start);
   if (!StartPattern.isRecognized())
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
 
   SelectPattern StepPattern(*this, BitWidth, Step);
   if (!StepPattern.isRecognized())
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
 
   if (StartPattern.Condition != StepPattern.Condition) {
     // We don't handle this case today; but we could, by considering four
     // possibilities below instead of two. I'm not sure if there are cases where
     // that will help over what getRange already does, though.
-    return ConstantRange(BitWidth, /* isFullSet = */ true);
+    return ConstantRange::getFull(BitWidth);
   }
 
   // NB! Calling ScalarEvolution::getConstant is fine, but we should not try to

llvm/lib/Analysis/ValueTracking.cpp

@@ -5711,7 +5711,7 @@ ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo) {
     setLimitsForSelectPattern(*SI, Lower, Upper);
 
   ConstantRange CR = Lower != Upper ? ConstantRange(Lower, Upper)
-                                    : ConstantRange(BitWidth, true);
+                                    : ConstantRange::getFull(BitWidth);
 
   if (auto *I = dyn_cast<Instruction>(V))
     if (auto *Range = IIQ.getMetadata(I, LLVMContext::MD_range))