llvm-6502/lib/CodeGen/SplitKit.h
Jakob Stoklund Olesen cfa7134a9c Basic rematerialization during splitting.
Whenever splitting wants to insert a copy, it checks if the value can be
rematerialized cheaply instead.

Missing features:
- Delete instructions when all uses have been rematerialized.
- Truncate live ranges to the remaining uses after rematerialization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118702 91177308-0d34-0410-b5e6-96231b3b80d8
2010-11-10 19:31:50 +00:00

367 lines
14 KiB
C++

//===-------- SplitKit.cpp - Toolkit for splitting live ranges --*- C++ -*-===//
//
// 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.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/SlotIndexes.h"
namespace llvm {
class LiveInterval;
class LiveIntervals;
class LiveRangeEdit;
class MachineInstr;
class MachineLoop;
class MachineLoopInfo;
class MachineRegisterInfo;
class TargetInstrInfo;
class TargetRegisterInfo;
class VirtRegMap;
class VNInfo;
class raw_ostream;
/// At some point we should just include MachineDominators.h:
class MachineDominatorTree;
template <class NodeT> class DomTreeNodeBase;
typedef DomTreeNodeBase<MachineBasicBlock> MachineDomTreeNode;
/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
/// opportunities.
class SplitAnalysis {
public:
const MachineFunction &mf_;
const LiveIntervals &lis_;
const MachineLoopInfo &loops_;
const TargetInstrInfo &tii_;
// Instructions using the the current register.
typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
InstrPtrSet usingInstrs_;
// The number of instructions using curli in each basic block.
typedef DenseMap<const MachineBasicBlock*, unsigned> BlockCountMap;
BlockCountMap usingBlocks_;
// The number of basic block using curli in each loop.
typedef DenseMap<const MachineLoop*, unsigned> LoopCountMap;
LoopCountMap usingLoops_;
private:
// Current live interval.
const LiveInterval *curli_;
// Sumarize statistics by counting instructions using curli_.
void analyzeUses();
/// canAnalyzeBranch - Return true if MBB ends in a branch that can be
/// analyzed.
bool canAnalyzeBranch(const MachineBasicBlock *MBB);
public:
SplitAnalysis(const MachineFunction &mf, const LiveIntervals &lis,
const MachineLoopInfo &mli);
/// analyze - set curli to the specified interval, and analyze how it may be
/// split.
void analyze(const LiveInterval *li);
/// clear - clear all data structures so SplitAnalysis is ready to analyze a
/// new interval.
void clear();
typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
// Print a set of blocks with use counts.
void print(const BlockPtrSet&, raw_ostream&) const;
// Sets of basic blocks surrounding a machine loop.
struct LoopBlocks {
BlockPtrSet Loop; // Blocks in the loop.
BlockPtrSet Preds; // Loop predecessor blocks.
BlockPtrSet Exits; // Loop exit blocks.
void clear() {
Loop.clear();
Preds.clear();
Exits.clear();
}
};
// Print loop blocks with use counts.
void print(const LoopBlocks&, raw_ostream&) const;
// Calculate the block sets surrounding the loop.
void getLoopBlocks(const MachineLoop *Loop, LoopBlocks &Blocks);
/// LoopPeripheralUse - how is a variable used in and around a loop?
/// Peripheral blocks are the loop predecessors and exit blocks.
enum LoopPeripheralUse {
ContainedInLoop, // All uses are inside the loop.
SinglePeripheral, // At most one instruction per peripheral block.
MultiPeripheral, // Multiple instructions in some peripheral blocks.
OutsideLoop // Uses outside loop periphery.
};
/// analyzeLoopPeripheralUse - Return an enum describing how curli_ is used in
/// and around the Loop.
LoopPeripheralUse analyzeLoopPeripheralUse(const LoopBlocks&);
/// getCriticalExits - It may be necessary to partially break critical edges
/// leaving the loop if an exit block has phi uses of curli. Collect the exit
/// blocks that need special treatment into CriticalExits.
void getCriticalExits(const LoopBlocks &Blocks, BlockPtrSet &CriticalExits);
/// canSplitCriticalExits - Return true if it is possible to insert new exit
/// blocks before the blocks in CriticalExits.
bool canSplitCriticalExits(const LoopBlocks &Blocks,
BlockPtrSet &CriticalExits);
/// getCriticalPreds - Get the set of loop predecessors with critical edges to
/// blocks outside the loop that have curli live in. We don't have to break
/// these edges, but they do require special treatment.
void getCriticalPreds(const LoopBlocks &Blocks, BlockPtrSet &CriticalPreds);
/// getBestSplitLoop - Return the loop where curli may best be split to a
/// separate register, or NULL.
const MachineLoop *getBestSplitLoop();
/// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
/// having curli split to a new live interval. Return true if Blocks can be
/// passed to SplitEditor::splitSingleBlocks.
bool getMultiUseBlocks(BlockPtrSet &Blocks);
/// 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 *getBlockForInsideSplit();
};
/// LiveIntervalMap - Map values from a large LiveInterval into a small
/// interval that is a subset. Insert phi-def values as needed. This class is
/// used by SplitEditor to create new smaller LiveIntervals.
///
/// parentli_ is the larger interval, li_ is the subset interval. Every value
/// in li_ corresponds to exactly one value in parentli_, and the live range
/// of the value is contained within the live range of the parentli_ value.
/// Values in parentli_ may map to any number of openli_ values, including 0.
class LiveIntervalMap {
LiveIntervals &lis_;
MachineDominatorTree &mdt_;
// The parent interval is never changed.
const LiveInterval &parentli_;
// The child interval's values are fully contained inside parentli_ values.
LiveInterval *li_;
typedef DenseMap<const VNInfo*, VNInfo*> ValueMap;
// Map parentli_ values to simple values in li_ that are defined at the same
// SlotIndex, or NULL for parentli_ values that have complex li_ defs.
// Note there is a difference between values mapping to NULL (complex), and
// values not present (unknown/unmapped).
ValueMap valueMap_;
typedef std::pair<VNInfo*, MachineDomTreeNode*> LiveOutPair;
typedef DenseMap<MachineBasicBlock*,LiveOutPair> LiveOutMap;
// liveOutCache_ - Map each basic block where li_ is live out to the live-out
// value and its defining block. One of these conditions shall be true:
//
// 1. !liveOutCache_.count(MBB)
// 2. liveOutCache_[MBB].second.getNode() == MBB
// 3. forall P in preds(MBB): liveOutCache_[P] == liveOutCache_[MBB]
//
// This is only a cache, the values can be computed as:
//
// VNI = li_->getVNInfoAt(lis_.getMBBEndIdx(MBB))
// Node = mbt_[lis_.getMBBFromIndex(VNI->def)]
//
// The cache is also used as a visiteed set by mapValue().
LiveOutMap liveOutCache_;
public:
LiveIntervalMap(LiveIntervals &lis,
MachineDominatorTree &mdt,
const LiveInterval &parentli)
: lis_(lis), mdt_(mdt), parentli_(parentli), li_(0) {}
/// reset - clear all data structures and start a new live interval.
void reset(LiveInterval *);
/// getLI - return the current live interval.
LiveInterval *getLI() const { return li_; }
/// defValue - define a value in li_ from the parentli_ value VNI and Idx.
/// Idx does not have to be ParentVNI->def, but it must be contained within
/// ParentVNI's live range in parentli_.
/// Return the new li_ value.
VNInfo *defValue(const VNInfo *ParentVNI, SlotIndex Idx);
/// mapValue - map ParentVNI to the corresponding li_ value at Idx. It is
/// assumed that ParentVNI is live at Idx.
/// If ParentVNI has not been defined by defValue, it is assumed that
/// ParentVNI->def dominates Idx.
/// If ParentVNI has been defined by defValue one or more times, a value that
/// dominates Idx will be returned. This may require creating extra phi-def
/// values and adding live ranges to li_.
/// If simple is not NULL, *simple will indicate if ParentVNI is a simply
/// mapped value.
VNInfo *mapValue(const VNInfo *ParentVNI, SlotIndex Idx, bool *simple = 0);
// 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 include
// Idx. Return the found VNInfo, or NULL.
VNInfo *extendTo(const MachineBasicBlock *MBB, SlotIndex Idx);
/// isMapped - Return true is ParentVNI is a known mapped value. It may be a
/// simple 1-1 mapping or a complex mapping to later defs.
bool isMapped(const VNInfo *ParentVNI) const {
return valueMap_.count(ParentVNI);
}
/// isComplexMapped - Return true if ParentVNI has received new definitions
/// with defValue.
bool isComplexMapped(const VNInfo *ParentVNI) const;
// addSimpleRange - Add a simple range from parentli_ to li_.
// ParentVNI must be live in the [Start;End) interval.
void addSimpleRange(SlotIndex Start, SlotIndex End, const VNInfo *ParentVNI);
/// 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 addRange(SlotIndex Start, SlotIndex End);
};
/// SplitEditor - Edit machine code and LiveIntervals for live range
/// splitting.
///
/// - Create a SplitEditor from a SplitAnalysis.
/// - Start a new live interval with openIntv.
/// - Mark the places where the new interval is entered using enterIntv*
/// - Mark the ranges where the new interval is used with useIntv*
/// - Mark the places where the interval is exited with exitIntv*.
/// - Finish the current interval with closeIntv and repeat from 2.
/// - Rewrite instructions with finish().
///
class SplitEditor {
SplitAnalysis &sa_;
LiveIntervals &lis_;
VirtRegMap &vrm_;
MachineRegisterInfo &mri_;
const TargetInstrInfo &tii_;
const TargetRegisterInfo &tri_;
/// edit_ - The current parent register and new intervals created.
LiveRangeEdit &edit_;
/// dupli_ - Created as a copy of curli_, ranges are carved out as new
/// intervals get added through openIntv / closeIntv. This is used to avoid
/// editing curli_.
LiveIntervalMap dupli_;
/// Currently open LiveInterval.
LiveIntervalMap openli_;
/// defFromParent - Define Reg from ParentVNI at UseIdx using either
/// rematerialization or a COPY from parent. Return the new value.
VNInfo *defFromParent(LiveIntervalMap &Reg,
VNInfo *ParentVNI,
SlotIndex UseIdx,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I);
/// intervalsLiveAt - Return true if any member of intervals_ is live at Idx.
bool intervalsLiveAt(SlotIndex Idx) const;
/// Values in curli whose live range has been truncated when entering an open
/// li.
SmallPtrSet<const VNInfo*, 8> truncatedValues;
/// addTruncSimpleRange - Add the given simple range to dupli_ after
/// truncating any overlap with intervals_.
void addTruncSimpleRange(SlotIndex Start, SlotIndex End, VNInfo *VNI);
/// criticalPreds_ - Set of basic blocks where both dupli and openli should be
/// live out because of a critical edge.
SplitAnalysis::BlockPtrSet criticalPreds_;
/// computeRemainder - Compute the dupli liveness as the complement of all the
/// new intervals.
void computeRemainder();
/// rewrite - Rewrite all uses of reg to use the new registers.
void rewrite(unsigned reg);
public:
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
/// Newly created intervals will be appended to newIntervals.
SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
MachineDominatorTree&, LiveRangeEdit&);
/// getAnalysis - Get the corresponding analysis.
SplitAnalysis &getAnalysis() { return sa_; }
/// Create a new virtual register and live interval.
void openIntv();
/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
/// not live before Idx, a COPY is not inserted.
void enterIntvBefore(SlotIndex Idx);
/// enterIntvAtEnd - Enter openli at the end of MBB.
void enterIntvAtEnd(MachineBasicBlock &MBB);
/// useIntv - indicate that all instructions in MBB should use openli.
void useIntv(const MachineBasicBlock &MBB);
/// useIntv - indicate that all instructions in range should use openli.
void useIntv(SlotIndex Start, SlotIndex End);
/// leaveIntvAfter - Leave openli after the instruction at Idx.
void leaveIntvAfter(SlotIndex Idx);
/// leaveIntvAtTop - Leave the interval at the top of MBB.
/// Currently, only one value can leave the interval.
void leaveIntvAtTop(MachineBasicBlock &MBB);
/// closeIntv - Indicate that we are done editing the currently open
/// LiveInterval, and ranges can be trimmed.
void closeIntv();
/// finish - after all the new live ranges have been created, compute the
/// remaining live range, and rewrite instructions to use the new registers.
void finish();
// ===--- High level methods ---===
/// splitAroundLoop - Split curli into a separate live interval inside
/// the loop.
void splitAroundLoop(const MachineLoop*);
/// splitSingleBlocks - Split curli into a separate live interval inside each
/// basic block in Blocks.
void splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
/// splitInsideBlock - Split curli into multiple intervals inside MBB.
void splitInsideBlock(const MachineBasicBlock *);
};
}