llvm-6502/include/llvm/IR/ConstantRange.h
Sanjoy Das da5f3a3ca5 [ConstantRange] Split makeICmpRegion in two.
Summary:
This change splits `makeICmpRegion` into `makeAllowedICmpRegion` and
`makeSatisfyingICmpRegion` with slightly different contracts.  The first
one is useful for determining what values some expression //may// take,
given that a certain `icmp` evaluates to true.  The second one is useful
for determining what values are guaranteed to //satisfy// a given
`icmp`.

Reviewers: nlewycky

Reviewed By: nlewycky

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8345

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232575 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-18 00:41:24 +00:00

279 lines
10 KiB
C++

//===- ConstantRange.h - Represent a range ----------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file 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: :
//
// [F, F) = {} = Empty set
// [T, F) = {T}
// [F, T) = {F}
// [T, T) = {F, T} = Full set
//
// The other integral ranges use min/max values for special range values. For
// example, for 8-bit types, it uses:
// [0, 0) = {} = Empty set
// [255, 255) = {0..255} = Full Set
//
// Note that ConstantRange can be used to represent either signed or
// unsigned ranges.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_CONSTANTRANGE_H
#define LLVM_IR_CONSTANTRANGE_H
#include "llvm/ADT/APInt.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/Support/DataTypes.h"
namespace llvm {
/// This class represents a range of values.
///
class ConstantRange {
APInt Lower, Upper;
// If we have move semantics, pass APInts by value and move them into place.
typedef APInt APIntMoveTy;
public:
/// Initialize a full (the default) or empty set for the specified bit width.
///
explicit ConstantRange(uint32_t BitWidth, bool isFullSet = true);
/// Initialize a range to hold the single specified value.
///
ConstantRange(APIntMoveTy Value);
/// @brief Initialize a range of values explicitly. This will assert out if
/// Lower==Upper and Lower != Min or Max value for its type. It will also
/// assert out if the two APInt's are not the same bit width.
ConstantRange(APIntMoveTy Lower, APIntMoveTy Upper);
/// Produce the smallest range such that all values that may satisfy the given
/// predicate with any value contained within Other is contained in the
/// returned range. Formally, this returns a superset of
/// 'union over all y in Other . { x : icmp op x y is true }'. If the exact
/// answer is not representable as a ConstantRange, the return value will be a
/// proper superset of the above.
///
/// Example: Pred = ult and Other = i8 [2, 5) returns Result = [0, 4)
static ConstantRange makeAllowedICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &Other);
/// Produce the largest range such that all values in the returned range
/// satisfy the given predicate with all values contained within Other.
/// Formally, this returns a subset of
/// 'intersection over all y in Other . { x : icmp op x y is true }'. If the
/// exact answer is not representable as a ConstantRange, the return value
/// will be a proper subset of the above.
///
/// Example: Pred = ult and Other = i8 [2, 5) returns [0, 2)
static ConstantRange makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
const ConstantRange &Other);
/// Return the lower value for this range.
///
const APInt &getLower() const { return Lower; }
/// Return the upper value for this range.
///
const APInt &getUpper() const { return Upper; }
/// Get the bit width of this ConstantRange.
///
uint32_t getBitWidth() const { return Lower.getBitWidth(); }
/// Return true if this set contains all of the elements possible
/// for this data-type.
///
bool isFullSet() const;
/// Return true if this set contains no members.
///
bool isEmptySet() const;
/// Return true if this set wraps around the top of the range.
/// For example: [100, 8).
///
bool isWrappedSet() const;
/// Return true if this set wraps around the INT_MIN of
/// its bitwidth. For example: i8 [120, 140).
///
bool isSignWrappedSet() const;
/// Return true if the specified value is in the set.
///
bool contains(const APInt &Val) const;
/// Return true if the other range is a subset of this one.
///
bool contains(const ConstantRange &CR) const;
/// If this set contains a single element, return it, otherwise return null.
///
const APInt *getSingleElement() const {
if (Upper == Lower + 1)
return &Lower;
return nullptr;
}
/// Return true if this set contains exactly one member.
///
bool isSingleElement() const { return getSingleElement() != nullptr; }
/// Return the number of elements in this set.
///
APInt getSetSize() const;
/// Return the largest unsigned value contained in the ConstantRange.
///
APInt getUnsignedMax() const;
/// Return the smallest unsigned value contained in the ConstantRange.
///
APInt getUnsignedMin() const;
/// Return the largest signed value contained in the ConstantRange.
///
APInt getSignedMax() const;
/// Return the smallest signed value contained in the ConstantRange.
///
APInt getSignedMin() const;
/// Return true if this range is equal to another range.
///
bool operator==(const ConstantRange &CR) const {
return Lower == CR.Lower && Upper == CR.Upper;
}
bool operator!=(const ConstantRange &CR) const {
return !operator==(CR);
}
/// Subtract the specified constant from the endpoints of this constant range.
ConstantRange subtract(const APInt &CI) const;
/// \brief Subtract the specified range from this range (aka relative
/// complement of the sets).
ConstantRange difference(const ConstantRange &CR) const;
/// Return the range that results from the intersection of
/// this range with another range. The resultant range is guaranteed to
/// include all elements contained in both input ranges, and to have the
/// smallest possible set size that does so. Because there may be two
/// intersections with the same set size, A.intersectWith(B) might not
/// be equal to B.intersectWith(A).
///
ConstantRange intersectWith(const ConstantRange &CR) const;
/// 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 unionWith(const ConstantRange &CR) const;
/// 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 if the source range had been
/// zero extended to BitWidth.
ConstantRange zeroExtend(uint32_t BitWidth) const;
/// 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 if the source range had been
/// sign extended to BitWidth.
ConstantRange signExtend(uint32_t BitWidth) const;
/// 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 if the source range had been
/// truncated to the specified type.
ConstantRange truncate(uint32_t BitWidth) const;
/// Make this range have the bit width given by \p BitWidth. The
/// value is zero extended, truncated, or left alone to make it that width.
ConstantRange zextOrTrunc(uint32_t BitWidth) const;
/// Make this range have the bit width given by \p BitWidth. The
/// value is sign extended, truncated, or left alone to make it that width.
ConstantRange sextOrTrunc(uint32_t BitWidth) const;
/// Return a new range representing the possible values resulting
/// from an addition of a value in this range and a value in \p Other.
ConstantRange add(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from a subtraction of a value in this range and a value in \p Other.
ConstantRange sub(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from a multiplication of a value in this range and a value in \p Other,
/// treating both this and \p Other as unsigned ranges.
ConstantRange multiply(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from a signed maximum of a value in this range and a value in \p Other.
ConstantRange smax(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from an unsigned maximum of a value in this range and a value in \p Other.
ConstantRange umax(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from an unsigned division of a value in this range and a value in
/// \p Other.
ConstantRange udiv(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from a binary-and of a value in this range by a value in \p Other.
ConstantRange binaryAnd(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from a binary-or of a value in this range by a value in \p Other.
ConstantRange binaryOr(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting
/// from a left shift of a value in this range by a value in \p Other.
/// TODO: This isn't fully implemented yet.
ConstantRange shl(const ConstantRange &Other) const;
/// Return a new range representing the possible values resulting from a
/// logical right shift of a value in this range and a value in \p Other.
ConstantRange lshr(const ConstantRange &Other) const;
/// Return a new range that is the logical not of the current set.
///
ConstantRange inverse() const;
/// Print out the bounds to a stream.
///
void print(raw_ostream &OS) const;
/// Allow printing from a debugger easily.
///
void dump() const;
};
inline raw_ostream &operator<<(raw_ostream &OS, const ConstantRange &CR) {
CR.print(OS);
return OS;
}
} // End llvm namespace
#endif