llvm/lib/Support/ConstantRange.cpp

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//===-- ConstantRange.cpp - ConstantRange implementation ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Represent a range of possible values that may occur when the program is run
// for an integral value. This keeps track of a lower and upper bound for the
// constant, which MAY wrap around the end of the numeric range. To do this, it
// keeps track of a [lower, upper) bound, which specifies an interval just like
// STL iterators. When used with boolean values, the following are important
// ranges (other integral ranges use min/max values for special range values):
//
// [F, F) = {} = Empty set
// [T, F) = {T}
// [F, T) = {F}
// [T, T) = {F, T} = Full set
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Streams.h"
#include <ostream>
using namespace llvm;
/// Initialize a full (the default) or empty set for the specified type.
///
ConstantRange::ConstantRange(uint32_t BitWidth, bool Full) :
Lower(BitWidth, 0), Upper(BitWidth, 0) {
if (Full)
Lower = Upper = APInt::getMaxValue(BitWidth);
else
Lower = Upper = APInt::getMinValue(BitWidth);
}
/// Initialize a range to hold the single specified value.
///
ConstantRange::ConstantRange(const APInt & V) : Lower(V), Upper(V + 1) { }
ConstantRange::ConstantRange(const APInt &L, const APInt &U) :
Lower(L), Upper(U) {
assert(L.getBitWidth() == U.getBitWidth() &&
"ConstantRange with unequal bit widths");
uint32_t BitWidth = L.getBitWidth();
assert((L != U || (L == APInt::getMaxValue(BitWidth) ||
L == APInt::getMinValue(BitWidth))) &&
"Lower == Upper, but they aren't min or max value!");
}
/// isFullSet - Return true if this set contains all of the elements possible
/// for this data-type
bool ConstantRange::isFullSet() const {
return Lower == Upper && Lower == APInt::getMaxValue(getBitWidth());
}
/// isEmptySet - Return true if this set contains no members.
///
bool ConstantRange::isEmptySet() const {
return Lower == Upper && Lower == APInt::getMinValue(getBitWidth());
}
/// isWrappedSet - Return true if this set wraps around the top of the range,
/// for example: [100, 8)
///
bool ConstantRange::isWrappedSet() const {
return Lower.ugt(Upper);
}
/// getSetSize - Return the number of elements in this set.
///
APInt ConstantRange::getSetSize() const {
if (isEmptySet())
return APInt(getBitWidth(), 0);
if (getBitWidth() == 1) {
if (Lower != Upper) // One of T or F in the set...
return APInt(2, 1);
return APInt(2, 2); // Must be full set...
}
// Simply subtract the bounds...
return Upper - Lower;
}
/// contains - Return true if the specified value is in the set.
///
bool ConstantRange::contains(const APInt &V) const {
if (Lower == Upper)
return isFullSet();
if (!isWrappedSet())
return Lower.ule(V) && V.ult(Upper);
else
return Lower.ule(V) || V.ult(Upper);
}
/// subtract - Subtract the specified constant from the endpoints of this
/// constant range.
ConstantRange ConstantRange::subtract(const APInt &Val) const {
assert(Val.getBitWidth() == getBitWidth() && "Wrong bit width");
// If the set is empty or full, don't modify the endpoints.
if (Lower == Upper)
return *this;
return ConstantRange(Lower - Val, Upper - Val);
}
// intersect1Wrapped - This helper function is used to intersect two ranges when
// it is known that LHS is wrapped and RHS isn't.
//
ConstantRange
ConstantRange::intersect1Wrapped(const ConstantRange &LHS,
const ConstantRange &RHS) {
assert(LHS.isWrappedSet() && !RHS.isWrappedSet());
// Check to see if we overlap on the Left side of RHS...
//
if (RHS.Lower.ult(LHS.Upper)) {
// We do overlap on the left side of RHS, see if we overlap on the right of
// RHS...
if (RHS.Upper.ugt(LHS.Lower)) {
// Ok, the result overlaps on both the left and right sides. See if the
// resultant interval will be smaller if we wrap or not...
//
if (LHS.getSetSize().ult(RHS.getSetSize()))
return LHS;
else
return RHS;
} else {
// No overlap on the right, just on the left.
return ConstantRange(RHS.Lower, LHS.Upper);
}
} else {
// We don't overlap on the left side of RHS, see if we overlap on the right
// of RHS...
if (RHS.Upper.ugt(LHS.Lower)) {
// Simple overlap...
return ConstantRange(LHS.Lower, RHS.Upper);
} else {
// No overlap...
return ConstantRange(LHS.getBitWidth(), false);
}
}
}
/// intersectWith - Return the range that results from the intersection of this
/// range with another range.
///
ConstantRange ConstantRange::intersectWith(const ConstantRange &CR) const {
assert(getBitWidth() == CR.getBitWidth() &&
"ConstantRange types don't agree!");
// Handle common special cases
if (isEmptySet() || CR.isFullSet())
return *this;
if (isFullSet() || CR.isEmptySet())
return CR;
if (!isWrappedSet()) {
if (!CR.isWrappedSet()) {
using namespace APIntOps;
APInt L = umax(Lower, CR.Lower);
APInt U = umin(Upper, CR.Upper);
if (L.ult(U)) // If range isn't empty...
return ConstantRange(L, U);
else
return ConstantRange(getBitWidth(), false);// Otherwise, empty set
} else
return intersect1Wrapped(CR, *this);
} else { // We know "this" is wrapped...
if (!CR.isWrappedSet())
return intersect1Wrapped(*this, CR);
else {
// Both ranges are wrapped...
using namespace APIntOps;
APInt L = umax(Lower, CR.Lower);
APInt U = umin(Upper, CR.Upper);
return ConstantRange(L, U);
}
}
return *this;
}
/// unionWith - Return the range that results from the union of this range with
/// another range. The resultant range is guaranteed to include the elements of
/// both sets, but may contain more. For example, [3, 9) union [12,15) is [3,
/// 15), which includes 9, 10, and 11, which were not included in either set
/// before.
///
ConstantRange ConstantRange::unionWith(const ConstantRange &CR) const {
assert(getBitWidth() == CR.getBitWidth() &&
"ConstantRange types don't agree!");
if ( isFullSet() || CR.isEmptySet()) return *this;
if (CR.isFullSet() || isEmptySet()) return CR;
APInt L = Lower, U = Upper;
if (!contains(CR.Lower))
L = APIntOps::umin(L, CR.Lower);
if (!contains(CR.Upper - 1))
U = APIntOps::umax(U, CR.Upper);
return ConstantRange(L, U);
}
/// zeroExtend - Return a new range in the specified integer type, which must
/// be strictly larger than the current type. The returned range will
/// correspond to the possible range of values as if the source range had been
/// zero extended.
ConstantRange ConstantRange::zeroExtend(uint32_t DstTySize) const {
unsigned SrcTySize = getBitWidth();
assert(SrcTySize < DstTySize && "Not a value extension");
if (isFullSet())
// Change a source full set into [0, 1 << 8*numbytes)
return ConstantRange(APInt(DstTySize,0), APInt(DstTySize,1).shl(SrcTySize));
APInt L = Lower; L.zext(DstTySize);
APInt U = Upper; U.zext(DstTySize);
return ConstantRange(L, U);
}
/// truncate - Return a new range in the specified integer type, which must be
/// strictly smaller than the current type. The returned range will
/// correspond to the possible range of values as if the source range had been
/// truncated to the specified type.
ConstantRange ConstantRange::truncate(uint32_t DstTySize) const {
unsigned SrcTySize = getBitWidth();
assert(SrcTySize > DstTySize && "Not a value truncation");
APInt Size = APInt::getMaxValue(DstTySize).zext(SrcTySize);
if (isFullSet() || getSetSize().ugt(Size))
return ConstantRange(DstTySize);
APInt L = Lower; L.trunc(DstTySize);
APInt U = Upper; U.trunc(DstTySize);
return ConstantRange(L, U);
}
/// print - Print out the bounds to a stream...
///
void ConstantRange::print(std::ostream &OS) const {
OS << "[" << Lower.toStringSigned(10) << ","
<< Upper.toStringSigned(10) << " )";
}
/// dump - Allow printing from a debugger easily...
///
void ConstantRange::dump() const {
print(cerr);
}