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259 lines
8.7 KiB
C++
259 lines
8.7 KiB
C++
//===-- ConstantRange.cpp - ConstantRange implementation ------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Represent a range of possible values that may occur when the program is run
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// for an integral value. This keeps track of a lower and upper bound for the
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// constant, which MAY wrap around the end of the numeric range. To do this, it
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// keeps track of a [lower, upper) bound, which specifies an interval just like
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// STL iterators. When used with boolean values, the following are important
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// ranges (other integral ranges use min/max values for special range values):
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//
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// [F, F) = {} = Empty set
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// [T, F) = {T}
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// [F, T) = {F}
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// [T, T) = {F, T} = Full set
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/ConstantRange.h"
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#include "llvm/Constants.h"
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#include "llvm/Instruction.h"
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#include "llvm/Type.h"
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using namespace llvm;
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static bool LT(ConstantIntegral *A, ConstantIntegral *B) {
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Constant *C = ConstantExpr::get(Instruction::SetLT, A, B);
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assert(isa<ConstantBool>(C) && "Constant folding of integrals not impl??");
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return cast<ConstantBool>(C)->getValue();
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}
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static bool GT(ConstantIntegral *A, ConstantIntegral *B) {
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Constant *C = ConstantExpr::get(Instruction::SetGT, A, B);
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assert(isa<ConstantBool>(C) && "Constant folding of integrals not impl??");
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return cast<ConstantBool>(C)->getValue();
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}
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static ConstantIntegral *Min(ConstantIntegral *A, ConstantIntegral *B) {
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return LT(A, B) ? A : B;
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}
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static ConstantIntegral *Max(ConstantIntegral *A, ConstantIntegral *B) {
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return GT(A, B) ? A : B;
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}
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/// Initialize a full (the default) or empty set for the specified type.
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///
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ConstantRange::ConstantRange(const Type *Ty, bool Full) {
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assert(Ty->isIntegral() &&
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"Cannot make constant range of non-integral type!");
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if (Full)
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Lower = Upper = ConstantIntegral::getMaxValue(Ty);
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else
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Lower = Upper = ConstantIntegral::getMinValue(Ty);
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}
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/// Initialize a range of values explicitly... this will assert out if
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/// Lower==Upper and Lower != Min or Max for its type (or if the two constants
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/// have different types)
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///
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ConstantRange::ConstantRange(ConstantIntegral *L,
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ConstantIntegral *U) : Lower(L), Upper(U) {
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assert(Lower->getType() == Upper->getType() &&
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"Incompatible types for ConstantRange!");
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// Make sure that if L & U are equal that they are either Min or Max...
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assert((L != U || (L == ConstantIntegral::getMaxValue(L->getType()) ||
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L == ConstantIntegral::getMinValue(L->getType()))) &&
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"Lower == Upper, but they aren't min or max for type!");
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}
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static ConstantIntegral *Next(ConstantIntegral *CI) {
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if (CI->getType() == Type::BoolTy)
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return CI == ConstantBool::True ? ConstantBool::False : ConstantBool::True;
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Constant *Result = ConstantExpr::get(Instruction::Add, CI,
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ConstantInt::get(CI->getType(), 1));
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return cast<ConstantIntegral>(Result);
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}
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/// Initialize a set of values that all satisfy the condition with C.
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///
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ConstantRange::ConstantRange(unsigned SetCCOpcode, ConstantIntegral *C) {
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switch (SetCCOpcode) {
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default: assert(0 && "Invalid SetCC opcode to ConstantRange ctor!");
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case Instruction::SetEQ: Lower = C; Upper = Next(C); return;
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case Instruction::SetNE: Upper = C; Lower = Next(C); return;
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case Instruction::SetLT:
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Lower = ConstantIntegral::getMinValue(C->getType());
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Upper = C;
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return;
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case Instruction::SetGT:
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Lower = Next(C);
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Upper = ConstantIntegral::getMinValue(C->getType()); // Min = Next(Max)
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return;
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case Instruction::SetLE:
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Lower = ConstantIntegral::getMinValue(C->getType());
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Upper = Next(C);
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return;
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case Instruction::SetGE:
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Lower = C;
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Upper = ConstantIntegral::getMinValue(C->getType()); // Min = Next(Max)
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return;
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}
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}
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/// getType - Return the LLVM data type of this range.
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///
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const Type *ConstantRange::getType() const { return Lower->getType(); }
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/// isFullSet - Return true if this set contains all of the elements possible
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/// for this data-type
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bool ConstantRange::isFullSet() const {
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return Lower == Upper && Lower == ConstantIntegral::getMaxValue(getType());
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}
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/// isEmptySet - Return true if this set contains no members.
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///
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bool ConstantRange::isEmptySet() const {
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return Lower == Upper && Lower == ConstantIntegral::getMinValue(getType());
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}
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/// isWrappedSet - Return true if this set wraps around the top of the range,
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/// for example: [100, 8)
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///
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bool ConstantRange::isWrappedSet() const {
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return GT(Lower, Upper);
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}
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/// getSingleElement - If this set contains a single element, return it,
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/// otherwise return null.
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ConstantIntegral *ConstantRange::getSingleElement() const {
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if (Upper == Next(Lower)) // Is it a single element range?
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return Lower;
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return 0;
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}
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/// getSetSize - Return the number of elements in this set.
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///
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uint64_t ConstantRange::getSetSize() const {
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if (isEmptySet()) return 0;
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if (getType() == Type::BoolTy) {
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if (Lower != Upper) // One of T or F in the set...
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return 1;
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return 2; // Must be full set...
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}
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// Simply subtract the bounds...
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Constant *Result =
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ConstantExpr::get(Instruction::Sub, (Constant*)Upper, (Constant*)Lower);
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return cast<ConstantInt>(Result)->getRawValue();
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}
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// intersect1Wrapped - This helper function is used to intersect two ranges when
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// it is known that LHS is wrapped and RHS isn't.
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//
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static ConstantRange intersect1Wrapped(const ConstantRange &LHS,
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const ConstantRange &RHS) {
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assert(LHS.isWrappedSet() && !RHS.isWrappedSet());
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// Check to see if we overlap on the Left side of RHS...
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//
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if (LT(RHS.getLower(), LHS.getUpper())) {
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// We do overlap on the left side of RHS, see if we overlap on the right of
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// RHS...
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if (GT(RHS.getUpper(), LHS.getLower())) {
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// Ok, the result overlaps on both the left and right sides. See if the
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// resultant interval will be smaller if we wrap or not...
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//
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if (LHS.getSetSize() < RHS.getSetSize())
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return LHS;
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else
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return RHS;
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} else {
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// No overlap on the right, just on the left.
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return ConstantRange(RHS.getLower(), LHS.getUpper());
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}
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} else {
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// We don't overlap on the left side of RHS, see if we overlap on the right
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// of RHS...
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if (GT(RHS.getUpper(), LHS.getLower())) {
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// Simple overlap...
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return ConstantRange(LHS.getLower(), RHS.getUpper());
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} else {
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// No overlap...
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return ConstantRange(LHS.getType(), false);
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}
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}
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}
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/// intersect - Return the range that results from the intersection of this
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/// range with another range.
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///
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ConstantRange ConstantRange::intersectWith(const ConstantRange &CR) const {
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assert(getType() == CR.getType() && "ConstantRange types don't agree!");
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// Handle common special cases
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if (isEmptySet() || CR.isFullSet()) return *this;
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if (isFullSet() || CR.isEmptySet()) return CR;
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if (!isWrappedSet()) {
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if (!CR.isWrappedSet()) {
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ConstantIntegral *L = Max(Lower, CR.Lower);
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ConstantIntegral *U = Min(Upper, CR.Upper);
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if (LT(L, U)) // If range isn't empty...
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return ConstantRange(L, U);
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else
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return ConstantRange(getType(), false); // Otherwise, return empty set
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} else
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return intersect1Wrapped(CR, *this);
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} else { // We know "this" is wrapped...
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if (!CR.isWrappedSet())
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return intersect1Wrapped(*this, CR);
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else {
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// Both ranges are wrapped...
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ConstantIntegral *L = Max(Lower, CR.Lower);
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ConstantIntegral *U = Min(Upper, CR.Upper);
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return ConstantRange(L, U);
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}
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}
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return *this;
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}
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/// union - Return the range that results from the union of this range with
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/// another range. The resultant range is guaranteed to include the elements of
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/// both sets, but may contain more. For example, [3, 9) union [12,15) is [3,
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/// 15), which includes 9, 10, and 11, which were not included in either set
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/// before.
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///
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ConstantRange ConstantRange::unionWith(const ConstantRange &CR) const {
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assert(getType() == CR.getType() && "ConstantRange types don't agree!");
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assert(0 && "Range union not implemented yet!");
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return *this;
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}
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/// print - Print out the bounds to a stream...
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///
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void ConstantRange::print(std::ostream &OS) const {
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OS << "[" << Lower << "," << Upper << " )";
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}
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/// dump - Allow printing from a debugger easily...
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///
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void ConstantRange::dump() const {
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print(std::cerr);
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}
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