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//===---------- 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"
namespace llvm {
class LiveInterval;
class LiveIntervals;
class MachineBasicBlock;
class MachineInstr;
class MachineFunction;
class MachineFunctionPass;
class MachineLoop;
class MachineLoopInfo;
class TargetInstrInfo;
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);
/// 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();
};
/// splitAroundLoop - Try to split curli into a separate live interval inside
/// the loop. Retun true on success.
bool splitAroundLoop(SplitAnalysis&, const MachineLoop*);
}
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