llvm/lib/Support/ConstantRange.cpp
Chris Lattner 20d4129fef Minor bug fix.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3577 91177308-0d34-0410-b5e6-96231b3b80d8
2002-09-03 23:12:40 +00:00

247 lines
8.3 KiB
C++

//===-- ConstantRange.cpp - ConstantRange implementation ------------------===//
//
// 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/Type.h"
#include "llvm/Instruction.h"
#include "llvm/ConstantHandling.h"
/// Initialize a full (the default) or empty set for the specified type.
///
ConstantRange::ConstantRange(const Type *Ty, bool Full) {
assert(Ty->isIntegral() &&
"Cannot make constant range of non-integral type!");
if (Full)
Lower = Upper = ConstantIntegral::getMaxValue(Ty);
else
Lower = Upper = ConstantIntegral::getMinValue(Ty);
}
/// Initialize a range of values explicitly... this will assert out if
/// Lower==Upper and Lower != Min or Max for its type (or if the two constants
/// have different types)
///
ConstantRange::ConstantRange(ConstantIntegral *L,
ConstantIntegral *U) : Lower(L), Upper(U) {
assert(Lower->getType() == Upper->getType() &&
"Incompatible types for ConstantRange!");
// Make sure that if L & U are equal that they are either Min or Max...
assert((L != U || (L == ConstantIntegral::getMaxValue(L->getType()) ||
L == ConstantIntegral::getMinValue(L->getType()))) &&
"Lower == Upper, but they aren't min or max for type!");
}
static ConstantIntegral *Next(ConstantIntegral *CI) {
if (CI->getType() == Type::BoolTy)
return CI == ConstantBool::True ? ConstantBool::False : ConstantBool::True;
// Otherwise use operator+ in the ConstantHandling Library.
Constant *Result = *ConstantInt::get(CI->getType(), 1) + *CI;
assert(Result && "ConstantHandling not implemented for integral plus!?");
return cast<ConstantIntegral>(Result);
}
/// Initialize a set of values that all satisfy the condition with C.
///
ConstantRange::ConstantRange(unsigned SetCCOpcode, ConstantIntegral *C) {
switch (SetCCOpcode) {
default: assert(0 && "Invalid SetCC opcode to ConstantRange ctor!");
case Instruction::SetEQ: Lower = C; Upper = Next(C); return;
case Instruction::SetNE: Upper = C; Lower = Next(C); return;
case Instruction::SetLT:
Lower = ConstantIntegral::getMinValue(C->getType());
Upper = C;
return;
case Instruction::SetGT:
Lower = Next(C);
Upper = ConstantIntegral::getMinValue(C->getType()); // Min = Next(Max)
return;
case Instruction::SetLE:
Lower = ConstantIntegral::getMinValue(C->getType());
Upper = Next(C);
return;
case Instruction::SetGE:
Lower = C;
Upper = ConstantIntegral::getMinValue(C->getType()); // Min = Next(Max)
return;
}
}
/// getType - Return the LLVM data type of this range.
///
const Type *ConstantRange::getType() const { return Lower->getType(); }
/// isFullSet - Return true if this set contains all of the elements possible
/// for this data-type
bool ConstantRange::isFullSet() const {
return Lower == Upper && Lower == ConstantIntegral::getMaxValue(getType());
}
/// isEmptySet - Return true if this set contains no members.
///
bool ConstantRange::isEmptySet() const {
return Lower == Upper && Lower == ConstantIntegral::getMinValue(getType());
}
/// isWrappedSet - Return true if this set wraps around the top of the range,
/// for example: [100, 8)
///
bool ConstantRange::isWrappedSet() const {
return (*(Constant*)Lower > *(Constant*)Upper)->getValue();
}
/// getSingleElement - If this set contains a single element, return it,
/// otherwise return null.
ConstantIntegral *ConstantRange::getSingleElement() const {
if (Upper == Next(Lower)) // Is it a single element range?
return Lower;
return 0;
}
/// getSetSize - Return the number of elements in this set.
///
uint64_t ConstantRange::getSetSize() const {
if (isEmptySet()) return 0;
if (getType() == Type::BoolTy) {
if (Lower != Upper) // One of T or F in the set...
return 1;
return 2; // Must be full set...
}
// Simply subtract the bounds...
Constant *Result = *(Constant*)Upper - *(Constant*)Lower;
assert(Result && "Subtraction of constant integers not implemented?");
if (getType()->isSigned())
return (uint64_t)cast<ConstantSInt>(Result)->getValue();
else
return cast<ConstantUInt>(Result)->getValue();
}
// intersect1Wrapped - This helper function is used to intersect two ranges when
// it is known that LHS is wrapped and RHS isn't.
//
static 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 ((*(Constant*)RHS.getLower() < *(Constant*)LHS.getUpper())->getValue()) {
// We do overlap on the left side of RHS, see if we overlap on the right of
// RHS...
if ((*(Constant*)RHS.getUpper() > *(Constant*)LHS.getLower())->getValue()) {
// 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() < RHS.getSetSize())
return LHS;
else
return RHS;
} else {
// No overlap on the right, just on the left.
return ConstantRange(RHS.getLower(), LHS.getUpper());
}
} else {
// We don't overlap on the left side of RHS, see if we overlap on the right
// of RHS...
if ((*(Constant*)RHS.getUpper() > *(Constant*)LHS.getLower())->getValue()) {
// Simple overlap...
return ConstantRange(LHS.getLower(), RHS.getUpper());
} else {
// No overlap...
return ConstantRange(LHS.getType(), false);
}
}
}
static ConstantIntegral *Min(ConstantIntegral *A, ConstantIntegral *B) {
if ((*(Constant*)A < *(Constant*)B)->getValue())
return A;
return B;
}
static ConstantIntegral *Max(ConstantIntegral *A, ConstantIntegral *B) {
if ((*(Constant*)A > *(Constant*)B)->getValue())
return A;
return B;
}
/// intersect - Return the range that results from the intersection of this
/// range with another range.
///
ConstantRange ConstantRange::intersectWith(const ConstantRange &CR) const {
assert(getType() == CR.getType() && "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()) {
ConstantIntegral *L = Max(Lower, CR.Lower);
ConstantIntegral *U = Min(Upper, CR.Upper);
if ((*L < *U)->getValue()) // If range isn't empty...
return ConstantRange(L, U);
else
return ConstantRange(getType(), false); // Otherwise, return 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...
ConstantIntegral *L = Max(Lower, CR.Lower);
ConstantIntegral *U = Min(Upper, CR.Upper);
return ConstantRange(L, U);
}
}
return *this;
}
/// union - 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(getType() == CR.getType() && "ConstantRange types don't agree!");
assert(0 && "Range union not implemented yet!");
return *this;
}
/// print - Print out the bounds to a stream...
///
void ConstantRange::print(std::ostream &OS) const {
OS << "[" << Lower << "," << Upper << " )";
}
/// dump - Allow printing from a debugger easily...
///
void ConstantRange::dump() const {
print(std::cerr);
}