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//===-- LiveIntervalUnion.cpp - Live interval union data structure --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// LiveIntervalUnion represents a coalesced set of live intervals. This may be
// used during coalescing to represent a congruence class, or during register
// allocation to model liveness of a physical register.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "LiveIntervalUnion.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/CodeGen/MachineLoopRanges.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
// Merge a LiveInterval's segments. Guarantee no overlaps.
void LiveIntervalUnion::unify(LiveInterval &VirtReg) {
if (VirtReg.empty())
return;
++Tag;
// Insert each of the virtual register's live segments into the map.
LiveInterval::iterator RegPos = VirtReg.begin();
LiveInterval::iterator RegEnd = VirtReg.end();
SegmentIter SegPos = Segments.find(RegPos->start);
while (SegPos.valid()) {
SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
if (++RegPos == RegEnd)
return;
SegPos.advanceTo(RegPos->start);
}
// We have reached the end of Segments, so it is no longer necessary to search
// for the insertion position.
// It is faster to insert the end first.
--RegEnd;
SegPos.insert(RegEnd->start, RegEnd->end, &VirtReg);
for (; RegPos != RegEnd; ++RegPos, ++SegPos)
SegPos.insert(RegPos->start, RegPos->end, &VirtReg);
}
// Remove a live virtual register's segments from this union.
void LiveIntervalUnion::extract(LiveInterval &VirtReg) {
if (VirtReg.empty())
return;
++Tag;
// Remove each of the virtual register's live segments from the map.
LiveInterval::iterator RegPos = VirtReg.begin();
LiveInterval::iterator RegEnd = VirtReg.end();
SegmentIter SegPos = Segments.find(RegPos->start);
for (;;) {
assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");
SegPos.erase();
if (!SegPos.valid())
return;
// Skip all segments that may have been coalesced.
RegPos = VirtReg.advanceTo(RegPos, SegPos.start());
if (RegPos == RegEnd)
return;
SegPos.advanceTo(RegPos->start);
}
}
void
LiveIntervalUnion::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {
OS << "LIU " << PrintReg(RepReg, TRI);
if (empty()) {
OS << " empty\n";
return;
}
for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {
OS << " [" << SI.start() << ' ' << SI.stop() << "):"
<< PrintReg(SI.value()->reg, TRI);
}
OS << '\n';
}
#ifndef NDEBUG
// Verify the live intervals in this union and add them to the visited set.
void LiveIntervalUnion::verify(LiveVirtRegBitSet& VisitedVRegs) {
for (SegmentIter SI = Segments.begin(); SI.valid(); ++SI)
VisitedVRegs.set(SI.value()->reg);
}
#endif //!NDEBUG
// Scan the vector of interfering virtual registers in this union. Assume it's
// quite small.
bool LiveIntervalUnion::Query::isSeenInterference(LiveInterval *VirtReg) const {
SmallVectorImpl<LiveInterval*>::const_iterator I =
std::find(InterferingVRegs.begin(), InterferingVRegs.end(), VirtReg);
return I != InterferingVRegs.end();
}
// Collect virtual registers in this union that interfere with this
// query's live virtual register.
//
// The query state is one of:
//
// 1. CheckedFirstInterference == false: Iterators are uninitialized.
// 2. SeenAllInterferences == true: InterferingVRegs complete, iterators unused.
// 3. Iterators left at the last seen intersection.
//
unsigned LiveIntervalUnion::Query::
collectInterferingVRegs(unsigned MaxInterferingRegs) {
// Fast path return if we already have the desired information.
if (SeenAllInterferences || InterferingVRegs.size() >= MaxInterferingRegs)
return InterferingVRegs.size();
// Set up iterators on the first call.
if (!CheckedFirstInterference) {
CheckedFirstInterference = true;
// Quickly skip interference check for empty sets.
if (VirtReg->empty() || LiveUnion->empty()) {
SeenAllInterferences = true;
return 0;
}
// In most cases, the union will start before VirtReg.
VirtRegI = VirtReg->begin();
LiveUnionI.setMap(LiveUnion->getMap());
LiveUnionI.find(VirtRegI->start);
}
LiveInterval::iterator VirtRegEnd = VirtReg->end();
LiveInterval *RecentReg = 0;
while (LiveUnionI.valid()) {
assert(VirtRegI != VirtRegEnd && "Reached end of VirtReg");
// Check for overlapping interference.
while (VirtRegI->start < LiveUnionI.stop() &&
VirtRegI->end > LiveUnionI.start()) {
// This is an overlap, record the interfering register.
LiveInterval *VReg = LiveUnionI.value();
if (VReg != RecentReg && !isSeenInterference(VReg)) {
RecentReg = VReg;
InterferingVRegs.push_back(VReg);
if (InterferingVRegs.size() >= MaxInterferingRegs)
return InterferingVRegs.size();
}
// This LiveUnion segment is no longer interesting.
if (!(++LiveUnionI).valid()) {
SeenAllInterferences = true;
return InterferingVRegs.size();
}
}
// The iterators are now not overlapping, LiveUnionI has been advanced
// beyond VirtRegI.
assert(VirtRegI->end <= LiveUnionI.start() && "Expected non-overlap");
// Advance the iterator that ends first.
VirtRegI = VirtReg->advanceTo(VirtRegI, LiveUnionI.start());
if (VirtRegI == VirtRegEnd)
break;
// Detect overlap, handle above.
if (VirtRegI->start < LiveUnionI.stop())
continue;
// Still not overlapping. Catch up LiveUnionI.
LiveUnionI.advanceTo(VirtRegI->start);
}
SeenAllInterferences = true;
return InterferingVRegs.size();
}
bool LiveIntervalUnion::Query::checkLoopInterference(MachineLoopRange *Loop) {
// VirtReg is likely live throughout the loop, so start by checking LIU-Loop
// overlaps.
IntervalMapOverlaps<LiveIntervalUnion::Map, MachineLoopRange::Map>
Overlaps(LiveUnion->getMap(), Loop->getMap());
if (!Overlaps.valid())
return false;
// The loop is overlapping an LIU assignment. Check VirtReg as well.
LiveInterval::iterator VRI = VirtReg->find(Overlaps.start());
for (;;) {
if (VRI == VirtReg->end())
return false;
if (VRI->start < Overlaps.stop())
return true;
Overlaps.advanceTo(VRI->start);
if (!Overlaps.valid())
return false;
if (Overlaps.start() < VRI->end)
return true;
VRI = VirtReg->advanceTo(VRI, Overlaps.start());
}
}
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