6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-21 02:29:22 +00:00
Code Issues Projects Releases Wiki Activity
d0cf2585a0
llvm-6502/lib/CodeGen/SplitKit.cpp
Jakob Stoklund Olesen 8d0963f72c Add EdgeBundles to SplitKit. 
Edge bundles is an annotation on the CFG that turns it into a bipartite directed
graph where each basic block is connected to an outgoing and an ingoing bundle.
These bundles are useful for identifying regions of the CFG for live range
splitting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122301 91177308-0d34-0410-b5e6-96231b3b80d8
2010-12-21 01:50:21 +00:00

1298 lines
47 KiB
C++
Raw Blame History

//===---------- SplitKit.cpp - Toolkit for splitting live ranges ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the SplitAnalysis class as well as mutator functions for
// live range splitting.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "SplitKit.h"
#include "LiveRangeEdit.h"
#include "VirtRegMap.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GraphWriter.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
static cl::opt<bool>
AllowSplit("spiller-splits-edges",
cl::desc("Allow critical edge splitting during spilling"));
//===----------------------------------------------------------------------===//
// Edge Bundles
//===----------------------------------------------------------------------===//
/// compute - Compute the edge bundles for MF. Bundles depend only on the CFG.
void EdgeBundles::compute(const MachineFunction *mf) {
MF = mf;
EC.clear();
EC.grow(2 * MF->size());
for (MachineFunction::const_iterator I = MF->begin(), E = MF->end(); I != E;
++I) {
const MachineBasicBlock &MBB = *I;
unsigned OutE = 2 * MBB.getNumber() + 1;
// Join the outgoing bundle with the ingoing bundles of all successors.
for (MachineBasicBlock::const_succ_iterator SI = MBB.succ_begin(),
SE = MBB.succ_end(); SI != SE; ++SI)
EC.join(OutE, 2 * (*SI)->getNumber());
}
EC.compress();
}
/// view - Visualize the annotated bipartite CFG with Graphviz.
void EdgeBundles::view() const {
ViewGraph(*this, "EdgeBundles");
}
/// Specialize WriteGraph, the standard implementation won't work.
raw_ostream &llvm::WriteGraph(raw_ostream &O, const EdgeBundles &G,
bool ShortNames,
const std::string &Title) {
const MachineFunction *MF = G.getMachineFunction();
O << "digraph {\n";
for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
I != E; ++I) {
unsigned BB = I->getNumber();
O << "\t\"BB#" << BB << "\" [ shape=box ]\n"
<< '\t' << G.getBundle(BB, false) << " -> \"BB#" << BB << "\"\n"
<< "\t\"BB#" << BB << "\" -> " << G.getBundle(BB, true) << '\n';
}
O << "}\n";
return O;
}
//===----------------------------------------------------------------------===//
// Split Analysis
//===----------------------------------------------------------------------===//
SplitAnalysis::SplitAnalysis(const MachineFunction &mf,
const LiveIntervals &lis,
const MachineLoopInfo &mli)
: mf_(mf),
lis_(lis),
loops_(mli),
tii_(*mf.getTarget().getInstrInfo()),
curli_(0) {}
void SplitAnalysis::clear() {
usingInstrs_.clear();
usingBlocks_.clear();
usingLoops_.clear();
curli_ = 0;
}
bool SplitAnalysis::canAnalyzeBranch(const MachineBasicBlock *MBB) {
MachineBasicBlock *T, *F;
SmallVector<MachineOperand, 4> Cond;
return !tii_.AnalyzeBranch(const_cast<MachineBasicBlock&>(*MBB), T, F, Cond);
}
/// analyzeUses - Count instructions, basic blocks, and loops using curli.
void SplitAnalysis::analyzeUses() {
const MachineRegisterInfo &MRI = mf_.getRegInfo();
for (MachineRegisterInfo::reg_iterator I = MRI.reg_begin(curli_->reg);
MachineInstr *MI = I.skipInstruction();) {
if (MI->isDebugValue() || !usingInstrs_.insert(MI))
continue;
MachineBasicBlock *MBB = MI->getParent();
if (usingBlocks_[MBB]++)
continue;
for (MachineLoop *Loop = loops_.getLoopFor(MBB); Loop;
Loop = Loop->getParentLoop())
usingLoops_[Loop]++;
}
DEBUG(dbgs() << " counted "
<< usingInstrs_.size() << " instrs, "
<< usingBlocks_.size() << " blocks, "
<< usingLoops_.size() << " loops.\n");
}
void SplitAnalysis::print(const BlockPtrSet &B, raw_ostream &OS) const {
for (BlockPtrSet::const_iterator I = B.begin(), E = B.end(); I != E; ++I) {
unsigned count = usingBlocks_.lookup(*I);
OS << " BB#" << (*I)->getNumber();
if (count)
OS << '(' << count << ')';
}
}
// Get three sets of basic blocks surrounding a loop: Blocks inside the loop,
// predecessor blocks, and exit blocks.
void SplitAnalysis::getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks) {
Blocks.clear();
// Blocks in the loop.
Blocks.Loop.insert(Loop->block_begin(), Loop->block_end());
// Predecessor blocks.
const MachineBasicBlock *Header = Loop->getHeader();
for (MachineBasicBlock::const_pred_iterator I = Header->pred_begin(),
E = Header->pred_end(); I != E; ++I)
if (!Blocks.Loop.count(*I))
Blocks.Preds.insert(*I);
// Exit blocks.
for (MachineLoop::block_iterator I = Loop->block_begin(),
E = Loop->block_end(); I != E; ++I) {
const MachineBasicBlock *MBB = *I;
for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
SE = MBB->succ_end(); SI != SE; ++SI)
if (!Blocks.Loop.count(*SI))
Blocks.Exits.insert(*SI);
}
}
void SplitAnalysis::print(const LoopBlocks &B, raw_ostream &OS) const {
OS << "Loop:";
print(B.Loop, OS);
OS << ", preds:";
print(B.Preds, OS);
OS << ", exits:";
print(B.Exits, OS);
}
/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
/// and around the Loop.
SplitAnalysis::LoopPeripheralUse SplitAnalysis::
analyzeLoopPeripheralUse(const SplitAnalysis::LoopBlocks &Blocks) {
LoopPeripheralUse use = ContainedInLoop;
for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
I != E; ++I) {
const MachineBasicBlock *MBB = I->first;
// Is this a peripheral block?
if (use < MultiPeripheral &&
(Blocks.Preds.count(MBB) || Blocks.Exits.count(MBB))) {
if (I->second > 1) use = MultiPeripheral;
else use = SinglePeripheral;
continue;
}
// Is it a loop block?
if (Blocks.Loop.count(MBB))
continue;
// It must be an unrelated block.
DEBUG(dbgs() << ", outside: BB#" << MBB->getNumber());
return OutsideLoop;
}
return use;
}
/// getCriticalExits - It may be necessary to partially break critical edges
/// leaving the loop if an exit block has predecessors from outside the loop
/// periphery.
void SplitAnalysis::getCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalExits) {
CriticalExits.clear();
// A critical exit block has curli live-in, and has a predecessor that is not
// in the loop nor a loop predecessor. For such an exit block, the edges
// carrying the new variable must be moved to a new pre-exit block.
for (BlockPtrSet::iterator I = Blocks.Exits.begin(), E = Blocks.Exits.end();
I != E; ++I) {
const MachineBasicBlock *Exit = *I;
// A single-predecessor exit block is definitely not a critical edge.
if (Exit->pred_size() == 1)
continue;
// This exit may not have curli live in at all. No need to split.
if (!lis_.isLiveInToMBB(*curli_, Exit))
continue;
// Does this exit block have a predecessor that is not a loop block or loop
// predecessor?
for (MachineBasicBlock::const_pred_iterator PI = Exit->pred_begin(),
PE = Exit->pred_end(); PI != PE; ++PI) {
const MachineBasicBlock *Pred = *PI;
if (Blocks.Loop.count(Pred) || Blocks.Preds.count(Pred))
continue;
// This is a critical exit block, and we need to split the exit edge.
CriticalExits.insert(Exit);
break;
}
}
}
void SplitAnalysis::getCriticalPreds(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalPreds) {
CriticalPreds.clear();
// A critical predecessor block has curli live-out, and has a successor that
// has curli live-in and is not in the loop nor a loop exit block. For such a
// predecessor block, we must carry the value in both the 'inside' and
// 'outside' registers.
for (BlockPtrSet::iterator I = Blocks.Preds.begin(), E = Blocks.Preds.end();
I != E; ++I) {
const MachineBasicBlock *Pred = *I;
// Definitely not a critical edge.
if (Pred->succ_size() == 1)
continue;
// This block may not have curli live out at all if there is a PHI.
if (!lis_.isLiveOutOfMBB(*curli_, Pred))
continue;
// Does this block have a successor outside the loop?
for (MachineBasicBlock::const_pred_iterator SI = Pred->succ_begin(),
SE = Pred->succ_end(); SI != SE; ++SI) {
const MachineBasicBlock *Succ = *SI;
if (Blocks.Loop.count(Succ) || Blocks.Exits.count(Succ))
continue;
if (!lis_.isLiveInToMBB(*curli_, Succ))
continue;
// This is a critical predecessor block.
CriticalPreds.insert(Pred);
break;
}
}
}
/// canSplitCriticalExits - Return true if it is possible to insert new exit
/// blocks before the blocks in CriticalExits.
bool
SplitAnalysis::canSplitCriticalExits(const SplitAnalysis::LoopBlocks &Blocks,
BlockPtrSet &CriticalExits) {
// If we don't allow critical edge splitting, require no critical exits.
if (!AllowSplit)
return CriticalExits.empty();
for (BlockPtrSet::iterator I = CriticalExits.begin(), E = CriticalExits.end();
I != E; ++I) {
const MachineBasicBlock *Succ = *I;
// We want to insert a new pre-exit MBB before Succ, and change all the
// in-loop blocks to branch to the pre-exit instead of Succ.
// Check that all the in-loop predecessors can be changed.
for (MachineBasicBlock::const_pred_iterator PI = Succ->pred_begin(),
PE = Succ->pred_end(); PI != PE; ++PI) {
const MachineBasicBlock *Pred = *PI;
// The external predecessors won't be altered.
if (!Blocks.Loop.count(Pred) && !Blocks.Preds.count(Pred))
continue;
if (!canAnalyzeBranch(Pred))
return false;
}
// If Succ's layout predecessor falls through, that too must be analyzable.
// We need to insert the pre-exit block in the gap.
MachineFunction::const_iterator MFI = Succ;
if (MFI == mf_.begin())
continue;
if (!canAnalyzeBranch(--MFI))
return false;
}
// No problems found.
return true;
}
void SplitAnalysis::analyze(const LiveInterval *li) {
clear();
curli_ = li;
analyzeUses();
}
void SplitAnalysis::getSplitLoops(LoopPtrSet &Loops) {
assert(curli_ && "Call analyze() before getSplitLoops");
if (usingLoops_.empty())
return;
LoopBlocks Blocks;
BlockPtrSet CriticalExits;
// We split around loops where curli is used outside the periphery.
for (LoopCountMap::const_iterator I = usingLoops_.begin(),
E = usingLoops_.end(); I != E; ++I) {
const MachineLoop *Loop = I->first;
getLoopBlocks(Loop, Blocks);
DEBUG({ dbgs() << " "; print(Blocks, dbgs()); });
switch(analyzeLoopPeripheralUse(Blocks)) {
case OutsideLoop:
break;
case MultiPeripheral:
// FIXME: We could split a live range with multiple uses in a peripheral
// block and still make progress. However, it is possible that splitting
// another live range will insert copies into a peripheral block, and
// there is a small chance we can enter an infinite loop, inserting copies
// forever.
// For safety, stick to splitting live ranges with uses outside the
// periphery.
DEBUG(dbgs() << ": multiple peripheral uses");
break;
case ContainedInLoop:
DEBUG(dbgs() << ": fully contained\n");
continue;
case SinglePeripheral:
DEBUG(dbgs() << ": single peripheral use\n");
continue;
}
// Will it be possible to split around this loop?
getCriticalExits(Blocks, CriticalExits);
DEBUG(dbgs() << ": " << CriticalExits.size() << " critical exits\n");
if (!canSplitCriticalExits(Blocks, CriticalExits))
continue;
// This is a possible split.
Loops.insert(Loop);
}
DEBUG(dbgs() << " getSplitLoops found " << Loops.size()
<< " candidate loops.\n");
}
const MachineLoop *SplitAnalysis::getBestSplitLoop() {
LoopPtrSet Loops;
getSplitLoops(Loops);
if (Loops.empty())
return 0;
// Pick the earliest loop.
// FIXME: Are there other heuristics to consider?
const MachineLoop *Best = 0;
SlotIndex BestIdx;
for (LoopPtrSet::const_iterator I = Loops.begin(), E = Loops.end(); I != E;
++I) {
SlotIndex Idx = lis_.getMBBStartIdx((*I)->getHeader());
if (!Best || Idx < BestIdx)
Best = *I, BestIdx = Idx;
}
DEBUG(dbgs() << " getBestSplitLoop found " << *Best);
return Best;
}
/// isBypassLoop - Return true if curli is live through Loop and has no uses
/// inside the loop. Bypass loops are candidates for splitting because it can
/// prevent interference inside the loop.
bool SplitAnalysis::isBypassLoop(const MachineLoop *Loop) {
// If curli is live into the loop header and there are no uses in the loop, it
// must be live in the entire loop and live on at least one exiting edge.
return !usingLoops_.count(Loop) &&
lis_.isLiveInToMBB(*curli_, Loop->getHeader());
}
/// getBypassLoops - Get all the maximal bypass loops. These are the bypass
/// loops whose parent is not a bypass loop.
void SplitAnalysis::getBypassLoops(LoopPtrSet &BypassLoops) {
SmallVector<MachineLoop*, 8> Todo(loops_.begin(), loops_.end());
while (!Todo.empty()) {
MachineLoop *Loop = Todo.pop_back_val();
if (!usingLoops_.count(Loop)) {
// This is either a bypass loop or completely irrelevant.
if (lis_.isLiveInToMBB(*curli_, Loop->getHeader()))
BypassLoops.insert(Loop);
// Either way, skip the child loops.
continue;
}
// The child loops may be bypass loops.
Todo.append(Loop->begin(), Loop->end());
}
}
//===----------------------------------------------------------------------===//
// LiveIntervalMap
//===----------------------------------------------------------------------===//
// Work around the fact that the std::pair constructors are broken for pointer
// pairs in some implementations. makeVV(x, 0) works.
static inline std::pair<const VNInfo*, VNInfo*>
makeVV(const VNInfo *a, VNInfo *b) {
return std::make_pair(a, b);
}
void LiveIntervalMap::reset(LiveInterval *li) {
li_ = li;
valueMap_.clear();
liveOutCache_.clear();
}
bool LiveIntervalMap::isComplexMapped(const VNInfo *ParentVNI) const {
ValueMap::const_iterator i = valueMap_.find(ParentVNI);
return i != valueMap_.end() && i->second == 0;
}
// defValue - Introduce a li_ def for ParentVNI that could be later than
// ParentVNI->def.
VNInfo *LiveIntervalMap::defValue(const VNInfo *ParentVNI, SlotIndex Idx) {
assert(li_ && "call reset first");
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
// Create a new value.
VNInfo *VNI = li_->getNextValue(Idx, 0, lis_.getVNInfoAllocator());
// Preserve the PHIDef bit.
if (ParentVNI->isPHIDef() && Idx == ParentVNI->def)
VNI->setIsPHIDef(true);
// Use insert for lookup, so we can add missing values with a second lookup.
std::pair<ValueMap::iterator,bool> InsP =
valueMap_.insert(makeVV(ParentVNI, Idx == ParentVNI->def ? VNI : 0));
// This is now a complex def. Mark with a NULL in valueMap.
if (!InsP.second)
InsP.first->second = 0;
return VNI;
}
// mapValue - Find the mapped value for ParentVNI at Idx.
// Potentially create phi-def values.
VNInfo *LiveIntervalMap::mapValue(const VNInfo *ParentVNI, SlotIndex Idx,
bool *simple) {
assert(li_ && "call reset first");
assert(ParentVNI && "Mapping NULL value");
assert(Idx.isValid() && "Invalid SlotIndex");
assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
// Use insert for lookup, so we can add missing values with a second lookup.
std::pair<ValueMap::iterator,bool> InsP =
valueMap_.insert(makeVV(ParentVNI, 0));
// This was an unknown value. Create a simple mapping.
if (InsP.second) {
if (simple) *simple = true;
return InsP.first->second = li_->createValueCopy(ParentVNI,
lis_.getVNInfoAllocator());
}
// This was a simple mapped value.
if (InsP.first->second) {
if (simple) *simple = true;
return InsP.first->second;
}
// This is a complex mapped value. There may be multiple defs, and we may need
// to create phi-defs.
if (simple) *simple = false;
MachineBasicBlock *IdxMBB = lis_.getMBBFromIndex(Idx);
assert(IdxMBB && "No MBB at Idx");
// Is there a def in the same MBB we can extend?
if (VNInfo *VNI = extendTo(IdxMBB, Idx))
return VNI;
// Now for the fun part. We know that ParentVNI potentially has multiple defs,
// and we may need to create even more phi-defs to preserve VNInfo SSA form.
// Perform a search for all predecessor blocks where we know the dominating
// VNInfo. Insert phi-def VNInfos along the path back to IdxMBB.
DEBUG(dbgs() << "\n Reaching defs for BB#" << IdxMBB->getNumber()
<< " at " << Idx << " in " << *li_ << '\n');
// Blocks where li_ should be live-in.
SmallVector<MachineDomTreeNode*, 16> LiveIn;
LiveIn.push_back(mdt_[IdxMBB]);
// Using liveOutCache_ as a visited set, perform a BFS for all reaching defs.
for (unsigned i = 0; i != LiveIn.size(); ++i) {
MachineBasicBlock *MBB = LiveIn[i]->getBlock();
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
MachineBasicBlock *Pred = *PI;
// Is this a known live-out block?
std::pair<LiveOutMap::iterator,bool> LOIP =
liveOutCache_.insert(std::make_pair(Pred, LiveOutPair()));
// Yes, we have been here before.
if (!LOIP.second) {
DEBUG(if (VNInfo *VNI = LOIP.first->second.first)
dbgs() << " known valno #" << VNI->id
<< " at BB#" << Pred->getNumber() << '\n');
continue;
}
// Does Pred provide a live-out value?
SlotIndex Last = lis_.getMBBEndIdx(Pred).getPrevSlot();
if (VNInfo *VNI = extendTo(Pred, Last)) {
MachineBasicBlock *DefMBB = lis_.getMBBFromIndex(VNI->def);
DEBUG(dbgs() << " found valno #" << VNI->id
<< " from BB#" << DefMBB->getNumber()
<< " at BB#" << Pred->getNumber() << '\n');
LiveOutPair &LOP = LOIP.first->second;
LOP.first = VNI;
LOP.second = mdt_[DefMBB];
continue;
}
// No, we need a live-in value for Pred as well
if (Pred != IdxMBB)
LiveIn.push_back(mdt_[Pred]);
}
}
// We may need to add phi-def values to preserve the SSA form.
// This is essentially the same iterative algorithm that SSAUpdater uses,
// except we already have a dominator tree, so we don't have to recompute it.
VNInfo *IdxVNI = 0;
unsigned Changes;
do {
Changes = 0;
DEBUG(dbgs() << " Iterating over " << LiveIn.size() << " blocks.\n");
// Propagate live-out values down the dominator tree, inserting phi-defs when
// necessary. Since LiveIn was created by a BFS, going backwards makes it more
// likely for us to visit immediate dominators before their children.
for (unsigned i = LiveIn.size(); i; --i) {
MachineDomTreeNode *Node = LiveIn[i-1];
MachineBasicBlock *MBB = Node->getBlock();
MachineDomTreeNode *IDom = Node->getIDom();
LiveOutPair IDomValue;
// We need a live-in value to a block with no immediate dominator?
// This is probably an unreachable block that has survived somehow.
bool needPHI = !IDom;
// Get the IDom live-out value.
if (!needPHI) {
LiveOutMap::iterator I = liveOutCache_.find(IDom->getBlock());
if (I != liveOutCache_.end())
IDomValue = I->second;
else
// If IDom is outside our set of live-out blocks, there must be new
// defs, and we need a phi-def here.
needPHI = true;
}
// IDom dominates all of our predecessors, but it may not be the immediate
// dominator. Check if any of them have live-out values that are properly
// dominated by IDom. If so, we need a phi-def here.
if (!needPHI) {
for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
PE = MBB->pred_end(); PI != PE; ++PI) {
LiveOutPair Value = liveOutCache_[*PI];
if (!Value.first || Value.first == IDomValue.first)
continue;
// This predecessor is carrying something other than IDomValue.
// It could be because IDomValue hasn't propagated yet, or it could be
// because MBB is in the dominance frontier of that value.
if (mdt_.dominates(IDom, Value.second)) {
needPHI = true;
break;
}
}
}
// Create a phi-def if required.
if (needPHI) {
++Changes;
SlotIndex Start = lis_.getMBBStartIdx(MBB);
VNInfo *VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator());
VNI->setIsPHIDef(true);
DEBUG(dbgs() << " - BB#" << MBB->getNumber()
<< " phi-def #" << VNI->id << " at " << Start << '\n');
// We no longer need li_ to be live-in.
LiveIn.erase(LiveIn.begin()+(i-1));
// Blocks in LiveIn are either IdxMBB, or have a value live-through.
if (MBB == IdxMBB)
IdxVNI = VNI;
// Check if we need to update live-out info.
LiveOutMap::iterator I = liveOutCache_.find(MBB);
if (I == liveOutCache_.end() || I->second.second == Node) {
// We already have a live-out defined in MBB, so this must be IdxMBB.
assert(MBB == IdxMBB && "Adding phi-def to known live-out");
li_->addRange(LiveRange(Start, Idx.getNextSlot(), VNI));
} else {
// This phi-def is also live-out, so color the whole block.
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
I->second = LiveOutPair(VNI, Node);
}
} else if (IDomValue.first) {
// No phi-def here. Remember incoming value for IdxMBB.
if (MBB == IdxMBB)
IdxVNI = IDomValue.first;
// Propagate IDomValue if needed:
// MBB is live-out and doesn't define its own value.
LiveOutMap::iterator I = liveOutCache_.find(MBB);
if (I != liveOutCache_.end() && I->second.second != Node &&
I->second.first != IDomValue.first) {
++Changes;
I->second = IDomValue;
DEBUG(dbgs() << " - BB#" << MBB->getNumber()
<< " idom valno #" << IDomValue.first->id
<< " from BB#" << IDom->getBlock()->getNumber() << '\n');
}
}
}
DEBUG(dbgs() << " - made " << Changes << " changes.\n");
} while (Changes);
assert(IdxVNI && "Didn't find value for Idx");
#ifndef NDEBUG
// Check the liveOutCache_ invariants.
for (LiveOutMap::iterator I = liveOutCache_.begin(), E = liveOutCache_.end();
I != E; ++I) {
assert(I->first && "Null MBB entry in cache");
assert(I->second.first && "Null VNInfo in cache");
assert(I->second.second && "Null DomTreeNode in cache");
if (I->second.second->getBlock() == I->first)
continue;
for (MachineBasicBlock::pred_iterator PI = I->first->pred_begin(),
PE = I->first->pred_end(); PI != PE; ++PI)
assert(liveOutCache_.lookup(*PI) == I->second && "Bad invariant");
}
#endif
// Since we went through the trouble of a full BFS visiting all reaching defs,
// the values in LiveIn are now accurate. No more phi-defs are needed
// for these blocks, so we can color the live ranges.
// This makes the next mapValue call much faster.
for (unsigned i = 0, e = LiveIn.size(); i != e; ++i) {
MachineBasicBlock *MBB = LiveIn[i]->getBlock();
SlotIndex Start = lis_.getMBBStartIdx(MBB);
if (MBB == IdxMBB) {
li_->addRange(LiveRange(Start, Idx.getNextSlot(), IdxVNI));
continue;
}
// Anything in LiveIn other than IdxMBB is live-through.
VNInfo *VNI = liveOutCache_.lookup(MBB).first;
assert(VNI && "Missing block value");
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
}
return IdxVNI;
}
// extendTo - Find the last li_ value defined in MBB at or before Idx. The
// parentli_ is assumed to be live at Idx. Extend the live range to Idx.
// Return the found VNInfo, or NULL.
VNInfo *LiveIntervalMap::extendTo(const MachineBasicBlock *MBB, SlotIndex Idx) {
assert(li_ && "call reset first");
LiveInterval::iterator I = std::upper_bound(li_->begin(), li_->end(), Idx);
if (I == li_->begin())
return 0;
--I;
if (I->end <= lis_.getMBBStartIdx(MBB))
return 0;
if (I->end <= Idx)
I->end = Idx.getNextSlot();
return I->valno;
}
// addSimpleRange - Add a simple range from parentli_ to li_.
// ParentVNI must be live in the [Start;End) interval.
void LiveIntervalMap::addSimpleRange(SlotIndex Start, SlotIndex End,
const VNInfo *ParentVNI) {
assert(li_ && "call reset first");
bool simple;
VNInfo *VNI = mapValue(ParentVNI, Start, &simple);
// A simple mapping is easy.
if (simple) {
li_->addRange(LiveRange(Start, End, VNI));
return;
}
// ParentVNI is a complex value. We must map per MBB.
MachineFunction::iterator MBB = lis_.getMBBFromIndex(Start);
MachineFunction::iterator MBBE = lis_.getMBBFromIndex(End.getPrevSlot());
if (MBB == MBBE) {
li_->addRange(LiveRange(Start, End, VNI));
return;
}
// First block.
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB), VNI));
// Run sequence of full blocks.
for (++MBB; MBB != MBBE; ++MBB) {
Start = lis_.getMBBStartIdx(MBB);
li_->addRange(LiveRange(Start, lis_.getMBBEndIdx(MBB),
mapValue(ParentVNI, Start)));
}
// Final block.
Start = lis_.getMBBStartIdx(MBB);
if (Start != End)
li_->addRange(LiveRange(Start, End, mapValue(ParentVNI, Start)));
}
/// addRange - Add live ranges to li_ where [Start;End) intersects parentli_.
/// All needed values whose def is not inside [Start;End) must be defined
/// beforehand so mapValue will work.
void LiveIntervalMap::addRange(SlotIndex Start, SlotIndex End) {
assert(li_ && "call reset first");
LiveInterval::const_iterator B = parentli_.begin(), E = parentli_.end();
LiveInterval::const_iterator I = std::lower_bound(B, E, Start);
// Check if --I begins before Start and overlaps.
if (I != B) {
--I;
if (I->end > Start)
addSimpleRange(Start, std::min(End, I->end), I->valno);
++I;
}
// The remaining ranges begin after Start.
for (;I != E && I->start < End; ++I)
addSimpleRange(I->start, std::min(End, I->end), I->valno);
}
//===----------------------------------------------------------------------===//
// Split Editor
//===----------------------------------------------------------------------===//
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
SplitEditor::SplitEditor(SplitAnalysis &sa,
LiveIntervals &lis,
VirtRegMap &vrm,
MachineDominatorTree &mdt,
LiveRangeEdit &edit)
: sa_(sa), lis_(lis), vrm_(vrm),
mri_(vrm.getMachineFunction().getRegInfo()),
tii_(*vrm.getMachineFunction().getTarget().getInstrInfo()),
tri_(*vrm.getMachineFunction().getTarget().getRegisterInfo()),
edit_(edit),
dupli_(lis_, mdt, edit.getParent()),
openli_(lis_, mdt, edit.getParent())
{
// We don't need an AliasAnalysis since we will only be performing
// cheap-as-a-copy remats anyway.
edit_.anyRematerializable(lis_, tii_, 0);
}
bool SplitEditor::intervalsLiveAt(SlotIndex Idx) const {
for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I)
if (*I != dupli_.getLI() && (*I)->liveAt(Idx))
return true;
return false;
}
VNInfo *SplitEditor::defFromParent(LiveIntervalMap &Reg,
VNInfo *ParentVNI,
SlotIndex UseIdx,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
VNInfo *VNI = 0;
MachineInstr *CopyMI = 0;
SlotIndex Def;
// Attempt cheap-as-a-copy rematerialization.
LiveRangeEdit::Remat RM(ParentVNI);
if (edit_.canRematerializeAt(RM, UseIdx, true, lis_)) {
Def = edit_.rematerializeAt(MBB, I, Reg.getLI()->reg, RM,
lis_, tii_, tri_);
} else {
// Can't remat, just insert a copy from parent.
CopyMI = BuildMI(MBB, I, DebugLoc(), tii_.get(TargetOpcode::COPY),
Reg.getLI()->reg).addReg(edit_.getReg());
Def = lis_.InsertMachineInstrInMaps(CopyMI).getDefIndex();
}
// Define the value in Reg.
VNI = Reg.defValue(ParentVNI, Def);
VNI->setCopy(CopyMI);
// Add minimal liveness for the new value.
if (UseIdx < Def)
UseIdx = Def;
Reg.getLI()->addRange(LiveRange(Def, UseIdx.getNextSlot(), VNI));
return VNI;
}
/// Create a new virtual register and live interval.
void SplitEditor::openIntv() {
assert(!openli_.getLI() && "Previous LI not closed before openIntv");
if (!dupli_.getLI())
dupli_.reset(&edit_.create(mri_, lis_, vrm_));
openli_.reset(&edit_.create(mri_, lis_, vrm_));
}
/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
/// not live before Idx, a COPY is not inserted.
void SplitEditor::enterIntvBefore(SlotIndex Idx) {
assert(openli_.getLI() && "openIntv not called before enterIntvBefore");
Idx = Idx.getUseIndex();
DEBUG(dbgs() << " enterIntvBefore " << Idx);
VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
truncatedValues.insert(ParentVNI);
MachineInstr *MI = lis_.getInstructionFromIndex(Idx);
assert(MI && "enterIntvBefore called with invalid index");
defFromParent(openli_, ParentVNI, Idx, *MI->getParent(), MI);
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// enterIntvAtEnd - Enter openli at the end of MBB.
void SplitEditor::enterIntvAtEnd(MachineBasicBlock &MBB) {
assert(openli_.getLI() && "openIntv not called before enterIntvAtEnd");
SlotIndex End = lis_.getMBBEndIdx(&MBB).getPrevSlot();
DEBUG(dbgs() << " enterIntvAtEnd BB#" << MBB.getNumber() << ", " << End);
VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(End);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
truncatedValues.insert(ParentVNI);
defFromParent(openli_, ParentVNI, End, MBB, MBB.getFirstTerminator());
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// useIntv - indicate that all instructions in MBB should use openli.
void SplitEditor::useIntv(const MachineBasicBlock &MBB) {
useIntv(lis_.getMBBStartIdx(&MBB), lis_.getMBBEndIdx(&MBB));
}
void SplitEditor::useIntv(SlotIndex Start, SlotIndex End) {
assert(openli_.getLI() && "openIntv not called before useIntv");
openli_.addRange(Start, End);
DEBUG(dbgs() << " use [" << Start << ';' << End << "): "
<< *openli_.getLI() << '\n');
}
/// leaveIntvAfter - Leave openli after the instruction at Idx.
void SplitEditor::leaveIntvAfter(SlotIndex Idx) {
assert(openli_.getLI() && "openIntv not called before leaveIntvAfter");
DEBUG(dbgs() << " leaveIntvAfter " << Idx);
// The interval must be live beyond the instruction at Idx.
Idx = Idx.getBoundaryIndex();
VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Idx);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
DEBUG(dbgs() << ": valno " << ParentVNI->id);
MachineBasicBlock::iterator MII = lis_.getInstructionFromIndex(Idx);
VNInfo *VNI = defFromParent(dupli_, ParentVNI, Idx,
*MII->getParent(), llvm::next(MII));
// Make sure that openli is properly extended from Idx to the new copy.
// FIXME: This shouldn't be necessary for remats.
openli_.addSimpleRange(Idx, VNI->def, ParentVNI);
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// leaveIntvAtTop - Leave the interval at the top of MBB.
/// Currently, only one value can leave the interval.
void SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
assert(openli_.getLI() && "openIntv not called before leaveIntvAtTop");
SlotIndex Start = lis_.getMBBStartIdx(&MBB);
DEBUG(dbgs() << " leaveIntvAtTop BB#" << MBB.getNumber() << ", " << Start);
VNInfo *ParentVNI = edit_.getParent().getVNInfoAt(Start);
if (!ParentVNI) {
DEBUG(dbgs() << ": not live\n");
return;
}
VNInfo *VNI = defFromParent(dupli_, ParentVNI, Start, MBB,
MBB.SkipPHIsAndLabels(MBB.begin()));
// Finally we must make sure that openli is properly extended from Start to
// the new copy.
openli_.addSimpleRange(Start, VNI->def, ParentVNI);
DEBUG(dbgs() << ": " << *openli_.getLI() << '\n');
}
/// closeIntv - Indicate that we are done editing the currently open
/// LiveInterval, and ranges can be trimmed.
void SplitEditor::closeIntv() {
assert(openli_.getLI() && "openIntv not called before closeIntv");
DEBUG(dbgs() << " closeIntv cleaning up\n");
DEBUG(dbgs() << " open " << *openli_.getLI() << '\n');
openli_.reset(0);
}
/// rewrite - Rewrite all uses of reg to use the new registers.
void SplitEditor::rewrite(unsigned reg) {
for (MachineRegisterInfo::reg_iterator RI = mri_.reg_begin(reg),
RE = mri_.reg_end(); RI != RE;) {
MachineOperand &MO = RI.getOperand();
unsigned OpNum = RI.getOperandNo();
MachineInstr *MI = MO.getParent();
++RI;
if (MI->isDebugValue()) {
DEBUG(dbgs() << "Zapping " << *MI);
// FIXME: We can do much better with debug values.
MO.setReg(0);
continue;
}
SlotIndex Idx = lis_.getInstructionIndex(MI);
Idx = MO.isUse() ? Idx.getUseIndex() : Idx.getDefIndex();
LiveInterval *LI = 0;
for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E;
++I) {
LiveInterval *testli = *I;
if (testli->liveAt(Idx)) {
LI = testli;
break;
}
}
DEBUG(dbgs() << " rewr BB#" << MI->getParent()->getNumber() << '\t'<< Idx);
assert(LI && "No register was live at use");
MO.setReg(LI->reg);
if (MO.isUse() && !MI->isRegTiedToDefOperand(OpNum))
MO.setIsKill(LI->killedAt(Idx.getDefIndex()));
DEBUG(dbgs() << '\t' << *MI);
}
}
void
SplitEditor::addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI) {
// Build vector of iterator pairs from the intervals.
typedef std::pair<LiveInterval::const_iterator,
LiveInterval::const_iterator> IIPair;
SmallVector<IIPair, 8> Iters;
for (LiveRangeEdit::iterator LI = edit_.begin(), LE = edit_.end(); LI != LE;
++LI) {
if (*LI == dupli_.getLI())
continue;
LiveInterval::const_iterator I = (*LI)->find(Start);
LiveInterval::const_iterator E = (*LI)->end();
if (I != E)
Iters.push_back(std::make_pair(I, E));
}
SlotIndex sidx = Start;
// Break [Start;End) into segments that don't overlap any intervals.
for (;;) {
SlotIndex next = sidx, eidx = End;
// Find overlapping intervals.
for (unsigned i = 0; i != Iters.size() && sidx < eidx; ++i) {
LiveInterval::const_iterator I = Iters[i].first;
// Interval I is overlapping [sidx;eidx). Trim sidx.
if (I->start <= sidx) {
sidx = I->end;
// Move to the next run, remove iters when all are consumed.
I = ++Iters[i].first;
if (I == Iters[i].second) {
Iters.erase(Iters.begin() + i);
--i;
continue;
}
}
// Trim eidx too if needed.
if (I->start >= eidx)
continue;
eidx = I->start;
next = I->end;
}
// Now, [sidx;eidx) doesn't overlap anything in intervals_.
if (sidx < eidx)
dupli_.addSimpleRange(sidx, eidx, VNI);
// If the interval end was truncated, we can try again from next.
if (next <= sidx)
break;
sidx = next;
}
}
void SplitEditor::computeRemainder() {
// First we need to fill in the live ranges in dupli.
// If values were redefined, we need a full recoloring with SSA update.
// If values were truncated, we only need to truncate the ranges.
// If values were partially rematted, we should shrink to uses.
// If values were fully rematted, they should be omitted.
// FIXME: If a single value is redefined, just move the def and truncate.
LiveInterval &parent = edit_.getParent();
// Values that are fully contained in the split intervals.
SmallPtrSet<const VNInfo*, 8> deadValues;
// Map all curli values that should have live defs in dupli.
for (LiveInterval::const_vni_iterator I = parent.vni_begin(),
E = parent.vni_end(); I != E; ++I) {
const VNInfo *VNI = *I;
// Don't transfer unused values to the new intervals.
if (VNI->isUnused())
continue;
// Original def is contained in the split intervals.
if (intervalsLiveAt(VNI->def)) {
// Did this value escape?
if (dupli_.isMapped(VNI))
truncatedValues.insert(VNI);
else
deadValues.insert(VNI);
continue;
}
// Add minimal live range at the definition.
VNInfo *DVNI = dupli_.defValue(VNI, VNI->def);
dupli_.getLI()->addRange(LiveRange(VNI->def, VNI->def.getNextSlot(), DVNI));
}
// Add all ranges to dupli.
for (LiveInterval::const_iterator I = parent.begin(), E = parent.end();
I != E; ++I) {
const LiveRange &LR = *I;
if (truncatedValues.count(LR.valno)) {
// recolor after removing intervals_.
addTruncSimpleRange(LR.start, LR.end, LR.valno);
} else if (!deadValues.count(LR.valno)) {
// recolor without truncation.
dupli_.addSimpleRange(LR.start, LR.end, LR.valno);
}
}
// Extend dupli_ to be live out of any critical loop predecessors.
// This means we have multiple registers live out of those blocks.
// The alternative would be to split the critical edges.
if (criticalPreds_.empty())
return;
for (SplitAnalysis::BlockPtrSet::iterator I = criticalPreds_.begin(),
E = criticalPreds_.end(); I != E; ++I)
dupli_.extendTo(*I, lis_.getMBBEndIdx(*I).getPrevSlot());
criticalPreds_.clear();
}
void SplitEditor::finish() {
assert(!openli_.getLI() && "Previous LI not closed before rewrite");
assert(dupli_.getLI() && "No dupli for rewrite. Noop spilt?");
// Complete dupli liveness.
computeRemainder();
// Get rid of unused values and set phi-kill flags.
for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I)
(*I)->RenumberValues(lis_);
// Rewrite instructions.
rewrite(edit_.getReg());
// Now check if any registers were separated into multiple components.
ConnectedVNInfoEqClasses ConEQ(lis_);
for (unsigned i = 0, e = edit_.size(); i != e; ++i) {
// Don't use iterators, they are invalidated by create() below.
LiveInterval *li = edit_.get(i);
unsigned NumComp = ConEQ.Classify(li);
if (NumComp <= 1)
continue;
DEBUG(dbgs() << " " << NumComp << " components: " << *li << '\n');
SmallVector<LiveInterval*, 8> dups;
dups.push_back(li);
for (unsigned i = 1; i != NumComp; ++i)
dups.push_back(&edit_.create(mri_, lis_, vrm_));
ConEQ.Distribute(&dups[0]);
// Rewrite uses to the new regs.
rewrite(li->reg);
}
// Calculate spill weight and allocation hints for new intervals.
VirtRegAuxInfo vrai(vrm_.getMachineFunction(), lis_, sa_.loops_);
for (LiveRangeEdit::iterator I = edit_.begin(), E = edit_.end(); I != E; ++I){
LiveInterval &li = **I;
vrai.CalculateRegClass(li.reg);
vrai.CalculateWeightAndHint(li);
DEBUG(dbgs() << " new interval " << mri_.getRegClass(li.reg)->getName()
<< ":" << li << '\n');
}
}
//===----------------------------------------------------------------------===//
// Loop Splitting
//===----------------------------------------------------------------------===//
void SplitEditor::splitAroundLoop(const MachineLoop *Loop) {
SplitAnalysis::LoopBlocks Blocks;
sa_.getLoopBlocks(Loop, Blocks);
DEBUG({
dbgs() << " splitAround"; sa_.print(Blocks, dbgs()); dbgs() << '\n';
});
// Break critical edges as needed.
SplitAnalysis::BlockPtrSet CriticalExits;
sa_.getCriticalExits(Blocks, CriticalExits);
assert(CriticalExits.empty() && "Cannot break critical exits yet");
// Get critical predecessors so computeRemainder can deal with them.
sa_.getCriticalPreds(Blocks, criticalPreds_);
// Create new live interval for the loop.
openIntv();
// Insert copies in the predecessors if live-in to the header.
if (lis_.isLiveInToMBB(edit_.getParent(), Loop->getHeader())) {
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Preds.begin(),
E = Blocks.Preds.end(); I != E; ++I) {
MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
enterIntvAtEnd(MBB);
}
}
// Switch all loop blocks.
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Loop.begin(),
E = Blocks.Loop.end(); I != E; ++I)
useIntv(**I);
// Insert back copies in the exit blocks.
for (SplitAnalysis::BlockPtrSet::iterator I = Blocks.Exits.begin(),
E = Blocks.Exits.end(); I != E; ++I) {
MachineBasicBlock &MBB = const_cast<MachineBasicBlock&>(**I);
leaveIntvAtTop(MBB);
}
// Done.
closeIntv();
finish();
}
//===----------------------------------------------------------------------===//
// Single Block Splitting
//===----------------------------------------------------------------------===//
/// getMultiUseBlocks - if curli has more than one use in a basic block, it
/// may be an advantage to split curli for the duration of the block.
bool SplitAnalysis::getMultiUseBlocks(BlockPtrSet &Blocks) {
// If curli is local to one block, there is no point to splitting it.
if (usingBlocks_.size() <= 1)
return false;
// Add blocks with multiple uses.
for (BlockCountMap::iterator I = usingBlocks_.begin(), E = usingBlocks_.end();
I != E; ++I)
switch (I->second) {
case 0:
case 1:
continue;
case 2: {
// When there are only two uses and curli is both live in and live out,
// we don't really win anything by isolating the block since we would be
// inserting two copies.
// The remaing register would still have two uses in the block. (Unless it
// separates into disconnected components).
if (lis_.isLiveInToMBB(*curli_, I->first) &&
lis_.isLiveOutOfMBB(*curli_, I->first))
continue;
} // Fall through.
default:
Blocks.insert(I->first);
}
return !Blocks.empty();
}
/// splitSingleBlocks - Split curli into a separate live interval inside each
/// basic block in Blocks.
void SplitEditor::splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks) {
DEBUG(dbgs() << " splitSingleBlocks for " << Blocks.size() << " blocks.\n");
// Determine the first and last instruction using curli in each block.
typedef std::pair<SlotIndex,SlotIndex> IndexPair;
typedef DenseMap<const MachineBasicBlock*,IndexPair> IndexPairMap;
IndexPairMap MBBRange;
for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
E = sa_.usingInstrs_.end(); I != E; ++I) {
const MachineBasicBlock *MBB = (*I)->getParent();
if (!Blocks.count(MBB))
continue;
SlotIndex Idx = lis_.getInstructionIndex(*I);
DEBUG(dbgs() << " BB#" << MBB->getNumber() << '\t' << Idx << '\t' << **I);
IndexPair &IP = MBBRange[MBB];
if (!IP.first.isValid() || Idx < IP.first)
IP.first = Idx;
if (!IP.second.isValid() || Idx > IP.second)
IP.second = Idx;
}
// Create a new interval for each block.
for (SplitAnalysis::BlockPtrSet::const_iterator I = Blocks.begin(),
E = Blocks.end(); I != E; ++I) {
IndexPair &IP = MBBRange[*I];
DEBUG(dbgs() << " splitting for BB#" << (*I)->getNumber() << ": ["
<< IP.first << ';' << IP.second << ")\n");
assert(IP.first.isValid() && IP.second.isValid());
openIntv();
enterIntvBefore(IP.first);
useIntv(IP.first.getBaseIndex(), IP.second.getBoundaryIndex());
leaveIntvAfter(IP.second);
closeIntv();
}
finish();
}
//===----------------------------------------------------------------------===//
// Sub Block Splitting
//===----------------------------------------------------------------------===//
/// getBlockForInsideSplit - If curli is contained inside a single basic block,
/// and it wou pay to subdivide the interval inside that block, return it.
/// Otherwise return NULL. The returned block can be passed to
/// SplitEditor::splitInsideBlock.
const MachineBasicBlock *SplitAnalysis::getBlockForInsideSplit() {
// The interval must be exclusive to one block.
if (usingBlocks_.size() != 1)
return 0;
// Don't to this for less than 4 instructions. We want to be sure that
// splitting actually reduces the instruction count per interval.
if (usingInstrs_.size() < 4)
return 0;
return usingBlocks_.begin()->first;
}
/// splitInsideBlock - Split curli into multiple intervals inside MBB.
void SplitEditor::splitInsideBlock(const MachineBasicBlock *MBB) {
SmallVector<SlotIndex, 32> Uses;
Uses.reserve(sa_.usingInstrs_.size());
for (SplitAnalysis::InstrPtrSet::const_iterator I = sa_.usingInstrs_.begin(),
E = sa_.usingInstrs_.end(); I != E; ++I)
if ((*I)->getParent() == MBB)
Uses.push_back(lis_.getInstructionIndex(*I));
DEBUG(dbgs() << " splitInsideBlock BB#" << MBB->getNumber() << " for "
<< Uses.size() << " instructions.\n");
assert(Uses.size() >= 3 && "Need at least 3 instructions");
array_pod_sort(Uses.begin(), Uses.end());
// Simple algorithm: Find the largest gap between uses as determined by slot
// indices. Create new intervals for instructions before the gap and after the
// gap.
unsigned bestPos = 0;
int bestGap = 0;
DEBUG(dbgs() << " dist (" << Uses[0]);
for (unsigned i = 1, e = Uses.size(); i != e; ++i) {
int g = Uses[i-1].distance(Uses[i]);
DEBUG(dbgs() << ") -" << g << "- (" << Uses[i]);
if (g > bestGap)
bestPos = i, bestGap = g;
}
DEBUG(dbgs() << "), best: -" << bestGap << "-\n");
// bestPos points to the first use after the best gap.
assert(bestPos > 0 && "Invalid gap");
// FIXME: Don't create intervals for low densities.
// First interval before the gap. Don't create single-instr intervals.
if (bestPos > 1) {
openIntv();
enterIntvBefore(Uses.front());
useIntv(Uses.front().getBaseIndex(), Uses[bestPos-1].getBoundaryIndex());
leaveIntvAfter(Uses[bestPos-1]);
closeIntv();
}
// Second interval after the gap.
if (bestPos < Uses.size()-1) {
openIntv();
enterIntvBefore(Uses[bestPos]);
useIntv(Uses[bestPos].getBaseIndex(), Uses.back().getBoundaryIndex());
leaveIntvAfter(Uses.back());
closeIntv();
}
finish();
}
Reference in New Issue View Git Blame Copy Permalink