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/Constants.h"
#include "llvm/Instruction.h"
#include "llvm/Type.h"
#include "llvm/Support/Streams.h"
#include <ostream>
using namespace llvm;
static ConstantIntegral *getMaxValue(const Type *Ty) {
switch (Ty->getTypeID()) {
case Type::BoolTyID: return ConstantBool::getTrue();
case Type::SByteTyID:
case Type::ShortTyID:
case Type::IntTyID:
case Type::LongTyID: {
// Calculate 011111111111111...
unsigned TypeBits = Ty->getPrimitiveSize()*8;
int64_t Val = INT64_MAX; // All ones
Val >>= 64-TypeBits; // Shift out unwanted 1 bits...
return ConstantInt::get(Ty, Val);
}
case Type::UByteTyID:
case Type::UShortTyID:
case Type::UIntTyID:
case Type::ULongTyID: return ConstantInt::getAllOnesValue(Ty);
default: return 0;
}
}
// Static constructor to create the minimum constant for an integral type...
static ConstantIntegral *getMinValue(const Type *Ty) {
switch (Ty->getTypeID()) {
case Type::BoolTyID: return ConstantBool::getFalse();
case Type::SByteTyID:
case Type::ShortTyID:
case Type::IntTyID:
case Type::LongTyID: {
// Calculate 1111111111000000000000
unsigned TypeBits = Ty->getPrimitiveSize()*8;
int64_t Val = -1; // All ones
Val <<= TypeBits-1; // Shift over to the right spot
return ConstantInt::get(Ty, Val);
}
case Type::UByteTyID:
case Type::UShortTyID:
case Type::UIntTyID:
case Type::ULongTyID: return ConstantInt::get(Ty, 0);
default: return 0;
}
}
static ConstantIntegral *Next(ConstantIntegral *CI) {
if (ConstantBool *CB = dyn_cast<ConstantBool>(CI))
return ConstantBool::get(!CB->getValue());
Constant *Result = ConstantExpr::getAdd(CI,
ConstantInt::get(CI->getType(), 1));
return cast<ConstantIntegral>(Result);
}
static bool LT(ConstantIntegral *A, ConstantIntegral *B) {
Constant *C = ConstantExpr::getSetLT(A, B);
assert(isa<ConstantBool>(C) && "Constant folding of integrals not impl??");
return cast<ConstantBool>(C)->getValue();
}
static bool LTE(ConstantIntegral *A, ConstantIntegral *B) {
Constant *C = ConstantExpr::getSetLE(A, B);
assert(isa<ConstantBool>(C) && "Constant folding of integrals not impl??");
return cast<ConstantBool>(C)->getValue();
}
static bool GT(ConstantIntegral *A, ConstantIntegral *B) { return LT(B, A); }
static ConstantIntegral *Min(ConstantIntegral *A, ConstantIntegral *B) {
return LT(A, B) ? A : B;
}
static ConstantIntegral *Max(ConstantIntegral *A, ConstantIntegral *B) {
return GT(A, B) ? A : B;
}
/// 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 = getMaxValue(Ty);
else
Lower = Upper = getMinValue(Ty);
}
/// Initialize a range to hold the single specified value.
///
ConstantRange::ConstantRange(Constant *V)
: Lower(cast<ConstantIntegral>(V)), Upper(Next(cast<ConstantIntegral>(V))) {
}
/// 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(Constant *L, Constant *U)
: Lower(cast<ConstantIntegral>(L)), Upper(cast<ConstantIntegral>(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 == getMaxValue(L->getType()) ||
L == getMinValue(L->getType()))) &&
"Lower == Upper, but they aren't min or max for type!");
}
/// 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 = getMinValue(C->getType());
Upper = C;
return;
case Instruction::SetGT:
Lower = Next(C);
Upper = getMinValue(C->getType()); // Min = Next(Max)
return;
case Instruction::SetLE:
Lower = getMinValue(C->getType());
Upper = Next(C);
return;
case Instruction::SetGE:
Lower = C;
Upper = 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 == getMaxValue(getType());
}
/// isEmptySet - Return true if this set contains no members.
///
bool ConstantRange::isEmptySet() const {
return Lower == Upper && Lower == getMinValue(getType());
}
/// isWrappedSet - Return true if this set wraps around the top of the range,
/// for example: [100, 8)
///
bool ConstantRange::isWrappedSet() const {
return GT(Lower, Upper);
}
/// 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 = ConstantExpr::getSub(Upper, Lower);
return cast<ConstantInt>(Result)->getZExtValue();
}
/// contains - Return true if the specified value is in the set.
///
bool ConstantRange::contains(ConstantInt *Val) const {
if (Lower == Upper) {
if (isFullSet()) return true;
return false;
}
if (!isWrappedSet())
return LTE(Lower, Val) && LT(Val, Upper);
return LTE(Lower, Val) || LT(Val, Upper);
}
/// subtract - Subtract the specified constant from the endpoints of this
/// constant range.
ConstantRange ConstantRange::subtract(ConstantInt *CI) const {
assert(CI->getType() == getType() && getType()->isInteger() &&
"Cannot subtract from different type range or non-integer!");
// If the set is empty or full, don't modify the endpoints.
if (Lower == Upper) return *this;
return ConstantRange(ConstantExpr::getSub(Lower, CI),
ConstantExpr::getSub(Upper, CI));
}
// 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 (LT(RHS.getLower(), LHS.getUpper())) {
// We do overlap on the left side of RHS, see if we overlap on the right of
// RHS...
if (GT(RHS.getUpper(), LHS.getLower())) {
// 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 (GT(RHS.getUpper(), LHS.getLower())) {
// Simple overlap...
return ConstantRange(LHS.getLower(), RHS.getUpper());
} else {
// No overlap...
return ConstantRange(LHS.getType(), false);
}
}
}
/// 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 (LT(L, U)) // 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;
}
/// 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 if the source range had been
/// zero extended.
ConstantRange ConstantRange::zeroExtend(const Type *Ty) const {
assert(getLower()->getType()->getPrimitiveSize() < Ty->getPrimitiveSize() &&
"Not a value extension");
if (isFullSet()) {
// Change a source full set into [0, 1 << 8*numbytes)
unsigned SrcTySize = getLower()->getType()->getPrimitiveSize();
return ConstantRange(Constant::getNullValue(Ty),
ConstantInt::get(Ty, 1ULL << SrcTySize*8));
}
Constant *Lower = getLower();
Constant *Upper = getUpper();
return ConstantRange(ConstantExpr::getCast(Instruction::ZExt, Lower, Ty),
ConstantExpr::getCast(Instruction::ZExt, Upper, Ty));
}
/// 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 if the source range had been
/// truncated to the specified type.
ConstantRange ConstantRange::truncate(const Type *Ty) const {
assert(getLower()->getType()->getPrimitiveSize() > Ty->getPrimitiveSize() &&
"Not a value truncation");
uint64_t Size = 1ULL << Ty->getPrimitiveSize()*8;
if (isFullSet() || getSetSize() >= Size)
return ConstantRange(getType());
return ConstantRange(
ConstantExpr::getCast(Instruction::Trunc, getLower(), Ty),
ConstantExpr::getCast(Instruction::Trunc, getUpper(), Ty));
}
/// 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(cerr);
}