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//===-- LiveInterval.cpp - Live Interval Representation -------------------===//
//
// 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.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveRange and LiveInterval classes. Given some
// numbering of each the machine instructions an interval [i, j) is said to be a
// live interval for register v if there is no instruction with number j' > j
// such that v is live at j' abd there is no instruction with number i' < i such
// that v is live at i'. In this implementation intervals can have holes,
// i.e. an interval might look like [1,20), [50,65), [1000,1001). Each
// individual range is represented as an instance of LiveRange, and the whole
// interval is represented as an instance of LiveInterval.
//
//===----------------------------------------------------------------------===//
#include "LiveInterval.h"
#include "Support/STLExtras.h"
#include <ostream>
using namespace llvm;
// An example for liveAt():
//
// this = [1,4), liveAt(0) will return false. The instruction defining this
// spans slots [0,3]. The interval belongs to an spilled definition of the
// variable it represents. This is because slot 1 is used (def slot) and spans
// up to slot 3 (store slot).
//
bool LiveInterval::liveAt(unsigned I) const {
Ranges::const_iterator r = std::upper_bound(ranges.begin(), ranges.end(), I);
if (r == ranges.begin())
return false;
--r;
return r->contains(I);
}
// An example for overlaps():
//
// 0: A = ...
// 4: B = ...
// 8: C = A + B ;; last use of A
//
// The live intervals should look like:
//
// A = [3, 11)
// B = [7, x)
// C = [11, y)
//
// A->overlaps(C) should return false since we want to be able to join
// A and C.
bool LiveInterval::overlaps(const LiveInterval& other) const {
Ranges::const_iterator i = ranges.begin();
Ranges::const_iterator ie = ranges.end();
Ranges::const_iterator j = other.ranges.begin();
Ranges::const_iterator je = other.ranges.end();
if (i->start < j->start) {
i = std::upper_bound(i, ie, j->start);
if (i != ranges.begin()) --i;
} else if (j->start < i->start) {
j = std::upper_bound(j, je, i->start);
if (j != other.ranges.begin()) --j;
} else {
return true;
}
while (i != ie && j != je) {
if (i->start == j->start)
return true;
if (i->start > j->start) {
swap(i, j);
swap(ie, je);
}
assert(i->start < j->start);
if (i->end > j->start)
return true;
++i;
}
return false;
}
/// extendIntervalEndTo - This method is used when we want to extend the range
/// specified by I to end at the specified endpoint. To do this, we should
/// merge and eliminate all ranges that this will overlap with. The iterator is
/// not invalidated.
void LiveInterval::extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd) {
assert(I != ranges.end() && "Not a valid interval!");
// Search for the first interval that we can't merge with.
Ranges::iterator MergeTo = next(I);
for (; MergeTo != ranges.end() && NewEnd >= MergeTo->end; ++MergeTo)
/*empty*/;
// If NewEnd was in the middle of an interval, make sure to get its endpoint.
I->end = std::max(NewEnd, prior(MergeTo)->end);
// Erase any dead ranges
ranges.erase(next(I), MergeTo);
}
/// extendIntervalStartTo - This method is used when we want to extend the range
/// specified by I to start at the specified endpoint. To do this, we should
/// merge and eliminate all ranges that this will overlap with.
LiveInterval::Ranges::iterator
LiveInterval::extendIntervalStartTo(Ranges::iterator I, unsigned NewStart) {
assert(I != ranges.end() && "Not a valid interval!");
// Search for the first interval that we can't merge with.
Ranges::iterator MergeTo = I;
do {
if (MergeTo == ranges.begin()) {
I->start = NewStart;
return I;
}
--MergeTo;
} while (NewStart <= MergeTo->start);
// If we start in the middle of another interval, just delete a range and
// extend that interval.
if (MergeTo->end >= NewStart) {
MergeTo->end = I->end;
} else {
// Otherwise, extend the interval right after.
++MergeTo;
MergeTo->start = NewStart;
MergeTo->end = I->end;
}
ranges.erase(next(MergeTo), next(I));
return MergeTo;
}
LiveInterval::Ranges::iterator
LiveInterval::addRangeFrom(LiveRange LR, Ranges::iterator From) {
unsigned Start = LR.start, End = LR.end;
Ranges::iterator it = std::upper_bound(From, ranges.end(), Start);
// If the inserted interval starts in the middle or right at the end of
// another interval, just extend that interval to contain the range of LR.
if (it != ranges.begin()) {
Ranges::iterator B = prior(it);
if (B->start <= Start && B->end >= Start) {
extendIntervalEndTo(B, End);
return B;
}
}
// Otherwise, if this range ends in the middle of, or right next to, another
// interval, merge it into that interval.
if (it != ranges.end() && it->start <= End)
return extendIntervalStartTo(it, Start);
// Otherwise, this is just a new range that doesn't interact with anything.
// Insert it.
return ranges.insert(it, LR);
}
void LiveInterval::join(const LiveInterval& other) {
isDefinedOnce &= other.isDefinedOnce;
// Join the ranges of other into the ranges of this interval.
Ranges::iterator cur = ranges.begin();
for (Ranges::const_iterator i = other.ranges.begin(),
e = other.ranges.end(); i != e; ++i)
cur = addRangeFrom(*i, cur);
weight += other.weight;
}
std::ostream& llvm::operator<<(std::ostream& os, const LiveRange &LR) {
return os << "[" << LR.start << "," << LR.end << ")";
}
std::ostream& llvm::operator<<(std::ostream& os, const LiveInterval& li) {
os << "%reg" << li.reg << ',' << li.weight;
if (li.empty())
return os << "EMPTY";
os << " = ";
for (LiveInterval::Ranges::const_iterator i = li.ranges.begin(),
e = li.ranges.end(); i != e; ++i)
os << *i;
return os;
}
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