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//===-- InterferenceCache.cpp - Caching per-block interference ---------*--===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// InterferenceCache remembers per-block interference in LiveIntervalUnions.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "InterferenceCache.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
using namespace llvm;
// Static member used for null interference cursors.
InterferenceCache::BlockInterference InterferenceCache::Cursor::NoInterference;
void InterferenceCache::init(MachineFunction *mf,
LiveIntervalUnion *liuarray,
SlotIndexes *indexes,
LiveIntervals *lis,
const TargetRegisterInfo *tri) {
MF = mf;
LIUArray = liuarray;
TRI = tri;
PhysRegEntries.assign(TRI->getNumRegs(), 0);
for (unsigned i = 0; i != CacheEntries; ++i)
Entries[i].clear(mf, indexes, lis);
}
InterferenceCache::Entry *InterferenceCache::get(unsigned PhysReg) {
unsigned E = PhysRegEntries[PhysReg];
if (E < CacheEntries && Entries[E].getPhysReg() == PhysReg) {
if (!Entries[E].valid(LIUArray, TRI))
Entries[E].revalidate();
return &Entries[E];
}
// No valid entry exists, pick the next round-robin entry.
E = RoundRobin;
if (++RoundRobin == CacheEntries)
RoundRobin = 0;
for (unsigned i = 0; i != CacheEntries; ++i) {
// Skip entries that are in use.
if (Entries[E].hasRefs()) {
if (++E == CacheEntries)
E = 0;
continue;
}
Entries[E].reset(PhysReg, LIUArray, TRI, MF);
PhysRegEntries[PhysReg] = E;
return &Entries[E];
}
llvm_unreachable("Ran out of interference cache entries.");
}
/// revalidate - LIU contents have changed, update tags.
void InterferenceCache::Entry::revalidate() {
// Invalidate all block entries.
++Tag;
// Invalidate all iterators.
PrevPos = SlotIndex();
for (unsigned i = 0, e = Aliases.size(); i != e; ++i)
Aliases[i].second = Aliases[i].first->getTag();
}
void InterferenceCache::Entry::reset(unsigned physReg,
LiveIntervalUnion *LIUArray,
const TargetRegisterInfo *TRI,
const MachineFunction *MF) {
assert(!hasRefs() && "Cannot reset cache entry with references");
// LIU's changed, invalidate cache.
++Tag;
PhysReg = physReg;
Blocks.resize(MF->getNumBlockIDs());
Aliases.clear();
for (const unsigned *AS = TRI->getOverlaps(PhysReg); *AS; ++AS) {
LiveIntervalUnion *LIU = LIUArray + *AS;
Aliases.push_back(std::make_pair(LIU, LIU->getTag()));
}
// Reset iterators.
PrevPos = SlotIndex();
unsigned e = Aliases.size();
Iters.resize(e);
for (unsigned i = 0; i != e; ++i)
Iters[i].setMap(Aliases[i].first->getMap());
}
bool InterferenceCache::Entry::valid(LiveIntervalUnion *LIUArray,
const TargetRegisterInfo *TRI) {
unsigned i = 0, e = Aliases.size();
for (const unsigned *AS = TRI->getOverlaps(PhysReg); *AS; ++AS, ++i) {
LiveIntervalUnion *LIU = LIUArray + *AS;
if (i == e || Aliases[i].first != LIU)
return false;
if (LIU->changedSince(Aliases[i].second))
return false;
}
return i == e;
}
void InterferenceCache::Entry::update(unsigned MBBNum) {
SlotIndex Start, Stop;
tie(Start, Stop) = Indexes->getMBBRange(MBBNum);
// Use advanceTo only when possible.
if (PrevPos != Start) {
if (!PrevPos.isValid() || Start < PrevPos)
for (unsigned i = 0, e = Iters.size(); i != e; ++i)
Iters[i].find(Start);
else
for (unsigned i = 0, e = Iters.size(); i != e; ++i)
Iters[i].advanceTo(Start);
PrevPos = Start;
}
MachineFunction::const_iterator MFI = MF->getBlockNumbered(MBBNum);
BlockInterference *BI = &Blocks[MBBNum];
ArrayRef<SlotIndex> RegMaskSlots;
ArrayRef<const uint32_t*> RegMaskBits;
for (;;) {
BI->Tag = Tag;
BI->First = BI->Last = SlotIndex();
// Check for first interference.
for (unsigned i = 0, e = Iters.size(); i != e; ++i) {
Iter &I = Iters[i];
if (!I.valid())
continue;
SlotIndex StartI = I.start();
if (StartI >= Stop)
continue;
if (!BI->First.isValid() || StartI < BI->First)
BI->First = StartI;
}
// Also check for register mask interference.
RegMaskSlots = LIS->getRegMaskSlotsInBlock(MBBNum);
RegMaskBits = LIS->getRegMaskBitsInBlock(MBBNum);
SlotIndex Limit = BI->First.isValid() ? BI->First : Stop;
for (unsigned i = 0, e = RegMaskSlots.size();
i != e && RegMaskSlots[i] < Limit; ++i)
if (MachineOperand::clobbersPhysReg(RegMaskBits[i], PhysReg)) {
// Register mask i clobbers PhysReg before the LIU interference.
BI->First = RegMaskSlots[i];
break;
}
PrevPos = Stop;
if (BI->First.isValid())
break;
// No interference in this block? Go ahead and precompute the next block.
if (++MFI == MF->end())
return;
MBBNum = MFI->getNumber();
BI = &Blocks[MBBNum];
if (BI->Tag == Tag)
return;
tie(Start, Stop) = Indexes->getMBBRange(MBBNum);
}
// Check for last interference in block.
for (unsigned i = 0, e = Iters.size(); i != e; ++i) {
Iter &I = Iters[i];
if (!I.valid() || I.start() >= Stop)
continue;
I.advanceTo(Stop);
bool Backup = !I.valid() || I.start() >= Stop;
if (Backup)
--I;
SlotIndex StopI = I.stop();
if (!BI->Last.isValid() || StopI > BI->Last)
BI->Last = StopI;
if (Backup)
++I;
}
// Also check for register mask interference.
SlotIndex Limit = BI->Last.isValid() ? BI->Last : Start;
for (unsigned i = RegMaskSlots.size();
i && RegMaskSlots[i-1].getDeadSlot() > Limit; --i)
if (MachineOperand::clobbersPhysReg(RegMaskBits[i-1], PhysReg)) {
// Register mask i-1 clobbers PhysReg after the LIU interference.
// Model the regmask clobber as a dead def.
BI->Last = RegMaskSlots[i-1].getDeadSlot();
break;
}
}
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