llvm-6502/lib/CodeGen/SplitKit.h
Jakob Stoklund Olesen 5eb308b944 Lazily defer duplicating the live interval we are splitting until we know it is
necessary.

Sometimes, live range splitting doesn't shrink the current interval, but simply
changes some instructions to use a new interval. That makes the original more
suitable for spilling. In this case, we don't need to duplicate the original.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110481 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-06 22:17:33 +00:00

227 lines
7.7 KiB
C++

//===---------- 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.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/SlotIndexes.h"
namespace llvm {
class LiveInterval;
class LiveIntervals;
class MachineInstr;
class MachineLoop;
class MachineLoopInfo;
class MachineRegisterInfo;
class TargetInstrInfo;
class VirtRegMap;
class VNInfo;
/// SplitAnalysis - Analyze a LiveInterval, looking for live range splitting
/// opportunities.
class SplitAnalysis {
const MachineFunction &mf_;
const LiveIntervals &lis_;
const MachineLoopInfo &loops_;
const TargetInstrInfo &tii_;
// Current live interval.
const LiveInterval *curli_;
// 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_;
// Loops where the curent interval is used.
typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
LoopPtrSet usingLoops_;
// 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);
const LiveInterval *getCurLI() { return curli_; }
/// clear - clear all data structures so SplitAnalysis is ready to analyze a
/// new interval.
void clear();
typedef SmallPtrSet<const MachineBasicBlock*, 16> BlockPtrSet;
// 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();
}
};
// 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);
/// getBestSplitLoop - Return the loop where curli may best be split to a
/// separate register, or NULL.
const MachineLoop *getBestSplitLoop();
};
/// 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 rewrite().
///
class SplitEditor {
SplitAnalysis &sa_;
LiveIntervals &lis_;
VirtRegMap &vrm_;
MachineRegisterInfo &mri_;
const TargetInstrInfo &tii_;
/// curli_ - The immutable interval we are currently splitting.
const LiveInterval *const curli_;
/// 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_.
LiveInterval *dupli_;
/// Currently open LiveInterval.
LiveInterval *openli_;
/// createInterval - Create a new virtual register and LiveInterval with same
/// register class and spill slot as curli.
LiveInterval *createInterval();
/// getDupLI - Ensure dupli is created and return it.
LiveInterval *getDupLI();
/// valueMap_ - Map values in dupli to values in openIntv. These are direct 1-1
/// mappings, and do not include values created by inserted copies.
DenseMap<const VNInfo*, VNInfo*> valueMap_;
/// mapValue - Return the openIntv value that corresponds to the given curli
/// value.
VNInfo *mapValue(const VNInfo *curliVNI);
/// A dupli value is live through openIntv.
bool liveThrough_;
/// All the new intervals created for this split are added to intervals_.
std::vector<LiveInterval*> &intervals_;
/// The index into intervals_ of the first interval we added. There may be
/// others from before we got it.
unsigned firstInterval;
/// Insert a COPY instruction curli -> li. Allocate a new value from li
/// defined by the COPY
VNInfo *insertCopy(LiveInterval &LI,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I);
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&,
std::vector<LiveInterval*> &newIntervals);
/// getAnalysis - Get the corresponding analysis.
SplitAnalysis &getAnalysis() { return sa_; }
/// Create a new virtual register and live interval.
void openIntv();
/// enterIntvAtEnd - Enter openli at the end of MBB.
/// PhiMBB is a successor inside openli where a PHI value is created.
/// Currently, all entries must share the same PhiMBB.
void enterIntvAtEnd(MachineBasicBlock &MBB, MachineBasicBlock &PhiMBB);
/// 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);
/// 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();
/// rewrite - after all the new live ranges have been created, rewrite
/// instructions using curli to use the new intervals.
void rewrite();
// ===--- High level methods ---===
/// splitAroundLoop - Split curli into a separate live interval inside
/// the loop. Return true if curli has been completely replaced, false if
/// curli is still intact, and needs to be spilled or split further.
bool splitAroundLoop(const MachineLoop*);
};
}