215 lines · cpp
1//===- LiveIntervalUnion.cpp - Live interval union data structure ---------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// LiveIntervalUnion represents a coalesced set of live intervals. This may be10// used during coalescing to represent a congruence class, or during register11// allocation to model liveness of a physical register.12//13//===----------------------------------------------------------------------===//14 15#include "llvm/CodeGen/LiveIntervalUnion.h"16#include "llvm/ADT/STLExtras.h"17#include "llvm/CodeGen/LiveInterval.h"18#include "llvm/CodeGen/TargetRegisterInfo.h"19#include "llvm/Support/raw_ostream.h"20#include <cassert>21#include <cstdlib>22 23using namespace llvm;24 25#define DEBUG_TYPE "regalloc"26 27// Merge a LiveInterval's segments. Guarantee no overlaps.28void LiveIntervalUnion::unify(const LiveInterval &VirtReg,29 const LiveRange &Range) {30 if (Range.empty())31 return;32 ++Tag;33 34 // Insert each of the virtual register's live segments into the map.35 LiveRange::const_iterator RegPos = Range.begin();36 LiveRange::const_iterator RegEnd = Range.end();37 SegmentIter SegPos = Segments.find(RegPos->start);38 39 while (SegPos.valid()) {40 SegPos.insert(RegPos->start, RegPos->end, &VirtReg);41 if (++RegPos == RegEnd)42 return;43 SegPos.advanceTo(RegPos->start);44 }45 46 // We have reached the end of Segments, so it is no longer necessary to search47 // for the insertion position.48 // It is faster to insert the end first.49 --RegEnd;50 SegPos.insert(RegEnd->start, RegEnd->end, &VirtReg);51 for (; RegPos != RegEnd; ++RegPos, ++SegPos)52 SegPos.insert(RegPos->start, RegPos->end, &VirtReg);53}54 55// Remove a live virtual register's segments from this union.56void LiveIntervalUnion::extract(const LiveInterval &VirtReg,57 const LiveRange &Range) {58 if (Range.empty())59 return;60 ++Tag;61 62 // Remove each of the virtual register's live segments from the map.63 LiveRange::const_iterator RegPos = Range.begin();64 LiveRange::const_iterator RegEnd = Range.end();65 SegmentIter SegPos = Segments.find(RegPos->start);66 67 while (true) {68 assert(SegPos.value() == &VirtReg && "Inconsistent LiveInterval");69 SegPos.erase();70 if (!SegPos.valid())71 return;72 73 // Skip all segments that may have been coalesced.74 RegPos = Range.advanceTo(RegPos, SegPos.start());75 if (RegPos == RegEnd)76 return;77 78 SegPos.advanceTo(RegPos->start);79 }80}81 82void83LiveIntervalUnion::print(raw_ostream &OS, const TargetRegisterInfo *TRI) const {84 if (empty()) {85 OS << " empty\n";86 return;87 }88 for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {89 OS << " [" << SI.start() << ' ' << SI.stop()90 << "):" << printReg(SI.value()->reg(), TRI);91 }92 OS << '\n';93}94 95#ifndef NDEBUG96// Verify the live intervals in this union and add them to the visited set.97void LiveIntervalUnion::verify(LiveVirtRegBitSet& VisitedVRegs) {98 for (SegmentIter SI = Segments.begin(); SI.valid(); ++SI)99 VisitedVRegs.set(SI.value()->reg().id());100}101#endif //!NDEBUG102 103const LiveInterval *LiveIntervalUnion::getOneVReg() const {104 if (empty())105 return nullptr;106 for (LiveSegments::const_iterator SI = Segments.begin(); SI.valid(); ++SI) {107 // return the first valid live interval108 return SI.value();109 }110 return nullptr;111}112 113// Scan the vector of interfering virtual registers in this union. Assume it's114// quite small.115bool LiveIntervalUnion::Query::isSeenInterference(116 const LiveInterval *VirtReg) const {117 return is_contained(InterferingVRegs, VirtReg);118}119 120// Collect virtual registers in this union that interfere with this121// query's live virtual register.122//123// The query state is one of:124//125// 1. CheckedFirstInterference == false: Iterators are uninitialized.126// 2. SeenAllInterferences == true: InterferingVRegs complete, iterators unused.127// 3. Iterators left at the last seen intersection.128//129unsigned130LiveIntervalUnion::Query::collectInterferingVRegs(unsigned MaxInterferingRegs) {131 // Fast path return if we already have the desired information.132 if (SeenAllInterferences || InterferingVRegs.size() >= MaxInterferingRegs)133 return InterferingVRegs.size();134 135 // Set up iterators on the first call.136 if (!CheckedFirstInterference) {137 CheckedFirstInterference = true;138 139 // Quickly skip interference check for empty sets.140 if (LR->empty() || LiveUnion->empty()) {141 SeenAllInterferences = true;142 return 0;143 }144 145 // In most cases, the union will start before LR.146 LRI = LR->begin();147 LiveUnionI.setMap(LiveUnion->getMap());148 LiveUnionI.find(LRI->start);149 }150 151 LiveRange::const_iterator LREnd = LR->end();152 const LiveInterval *RecentReg = nullptr;153 while (LiveUnionI.valid()) {154 assert(LRI != LREnd && "Reached end of LR");155 156 // Check for overlapping interference.157 while (LRI->start < LiveUnionI.stop() && LRI->end > LiveUnionI.start()) {158 // This is an overlap, record the interfering register.159 const LiveInterval *VReg = LiveUnionI.value();160 if (VReg != RecentReg && !isSeenInterference(VReg)) {161 RecentReg = VReg;162 InterferingVRegs.push_back(VReg);163 if (InterferingVRegs.size() >= MaxInterferingRegs)164 return InterferingVRegs.size();165 }166 // This LiveUnion segment is no longer interesting.167 if (!(++LiveUnionI).valid()) {168 SeenAllInterferences = true;169 return InterferingVRegs.size();170 }171 }172 173 // The iterators are now not overlapping, LiveUnionI has been advanced174 // beyond LRI.175 assert(LRI->end <= LiveUnionI.start() && "Expected non-overlap");176 177 // Advance the iterator that ends first.178 LRI = LR->advanceTo(LRI, LiveUnionI.start());179 if (LRI == LREnd)180 break;181 182 // Detect overlap, handle above.183 if (LRI->start < LiveUnionI.stop())184 continue;185 186 // Still not overlapping. Catch up LiveUnionI.187 LiveUnionI.advanceTo(LRI->start);188 }189 SeenAllInterferences = true;190 return InterferingVRegs.size();191}192 193void LiveIntervalUnion::Array::init(LiveIntervalUnion::Allocator &Alloc,194 unsigned NSize) {195 // Reuse existing allocation.196 if (NSize == Size)197 return;198 clear();199 Size = NSize;200 LIUs = static_cast<LiveIntervalUnion*>(201 safe_malloc(sizeof(LiveIntervalUnion)*NSize));202 for (unsigned i = 0; i != Size; ++i)203 new(LIUs + i) LiveIntervalUnion(Alloc);204}205 206void LiveIntervalUnion::Array::clear() {207 if (!LIUs)208 return;209 for (unsigned i = 0; i != Size; ++i)210 LIUs[i].~LiveIntervalUnion();211 free(LIUs);212 Size = 0;213 LIUs = nullptr;214}215