llvm-6502/lib/CodeGen/SplitKit.h
Jakob Stoklund Olesen f0179004e9 Add SplitEditor to SplitKit. This class will be used to edit live intervals and
rewrite instructions for live range splitting.

Still work in progress.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109469 91177308-0d34-0410-b5e6-96231b3b80d8
2010-07-26 23:44:11 +00:00

203 lines
6.8 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.
///
/// 1. Create a SplitEditor from a SplitAnalysis. This will create a new
/// LiveInterval, dupli, that is identical to SA.curli.
/// 2. Start a new live interval with openLI.
/// 3. Insert copies to the new interval with copyTo* and mark the ranges where
/// it should be used with use*.
/// 4. Insert back-copies with copyFromLI.
/// 5. Finish the current LI with closeLI and repeat from 2.
/// 6. Rewrite instructions with rewrite().
///
class SplitEditor {
SplitAnalysis &sa_;
LiveIntervals &lis_;
VirtRegMap &vrm_;
MachineRegisterInfo &mri_;
const TargetInstrInfo &tii_;
/// dupli_ - Created as a copy of sa_.curli_, ranges are carved out as new
/// intervals get added through openLI / closeLI.
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();
/// valueMap_ - Map values in dupli to values in openli. These are direct 1-1
/// mappings, and do not include values created by inserted copies.
DenseMap<VNInfo*,VNInfo*> valueMap_;
/// mapValue - Return the openli value that corresponds to the given dupli
/// value.
VNInfo *mapValue(VNInfo *dupliVNI);
public:
/// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
SplitEditor(SplitAnalysis&, LiveIntervals&, VirtRegMap&);
/// getAnalysis - Get the corresponding analysis.
SplitAnalysis &getAnalysis() { return sa_; }
/// Create a new virtual register and live interval to be used by following
/// use* and copy* calls.
void openLI();
/// copyToPHI - Insert a copy to openli at the end of A, and catch it with a
/// PHI def at the beginning of the successor B. This call is ignored if dupli
/// is not live out of A.
void copyToPHI(MachineBasicBlock &A, MachineBasicBlock &B);
/// useLI - indicate that all instructions in MBB should use openli.
void useLI(const MachineBasicBlock &MBB);
/// useLI - indicate that all instructions in range should use openli.
void useLI(SlotIndex Start, SlotIndex End);
/// copyFromLI - Insert a copy back to dupli from openli at position I.
/// This also marks the remainder of MBB as not used by openli.
SlotIndex copyFromLI(MachineBasicBlock &MBB, MachineBasicBlock::iterator I);
/// closeLI - Indicate that we are done editing the currently open
/// LiveInterval, and ranges can be trimmed.
void closeLI();
/// 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.
void splitAroundLoop(const MachineLoop*);
};
}