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//===- LiveIntervalUnion.cpp - Live interval union data structure ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/LiveIntervalUnion.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SparseBitVector.h"
#include "llvm/CodeGen/LiveInterval.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdlib>
using namespace llvm;
#define DEBUG_TYPE "regalloc"
// Merge a LiveInterval's segments. Guarantee no overlaps.
void LiveIntervalUnion::unify(LiveInterval &VirtReg, const LiveRange &Range) {
if (Range.empty())
return;
++Tag;
// Insert each of the virtual register's live segments into the map.
LiveRange::const_iterator RegPos = Range.begin();
LiveRange::const_iterator RegEnd = Range.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, const LiveRange &Range) {
if (Range.empty())
return;
++Tag;
// Remove each of the virtual register's live segments from the map.
LiveRange::const_iterator RegPos = Range.begin();
LiveRange::const_iterator RegEnd = Range.end();
SegmentIter SegPos = Segments.find(RegPos->start);
while (true) {
assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");
SegPos.erase();
if (!SegPos.valid())
return;
// Skip all segments that may have been coalesced.
RegPos = Range.advanceTo(RegPos, SegPos.start());
if (RegPos == RegEnd)
return;
SegPos.advanceTo(RegPos->start);
}
}
void
LiveIntervalUnion::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {
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 {
return is_contained(InterferingVRegs, VirtReg);
}
// 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 (LR->empty() || LiveUnion->empty()) {
SeenAllInterferences = true;
return 0;
}
// In most cases, the union will start before LR.
LRI = LR->begin();
LiveUnionI.setMap(LiveUnion->getMap());
LiveUnionI.find(LRI->start);
}
LiveRange::const_iterator LREnd = LR->end();
LiveInterval *RecentReg = nullptr;
while (LiveUnionI.valid()) {
assert(LRI != LREnd && "Reached end of LR");
// Check for overlapping interference.
while (LRI->start < LiveUnionI.stop() && LRI->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 LRI.
assert(LRI->end <= LiveUnionI.start() && "Expected non-overlap");
// Advance the iterator that ends first.
LRI = LR->advanceTo(LRI, LiveUnionI.start());
if (LRI == LREnd)
break;
// Detect overlap, handle above.
if (LRI->start < LiveUnionI.stop())
continue;
// Still not overlapping. Catch up LiveUnionI.
LiveUnionI.advanceTo(LRI->start);
}
SeenAllInterferences = true;
return InterferingVRegs.size();
}
void LiveIntervalUnion::Array::init(LiveIntervalUnion::Allocator &Alloc,
unsigned NSize) {
// Reuse existing allocation.
if (NSize == Size)
return;
clear();
Size = NSize;
LIUs = static_cast<LiveIntervalUnion*>(
safe_malloc(sizeof(LiveIntervalUnion)*NSize));
for (unsigned i = 0; i != Size; ++i)
new(LIUs + i) LiveIntervalUnion(Alloc);
}
void LiveIntervalUnion::Array::clear() {
if (!LIUs)
return;
for (unsigned i = 0; i != Size; ++i)
LIUs[i].~LiveIntervalUnion();
free(LIUs);
Size = 0;
LIUs = nullptr;
}
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