llvm-6502/lib/CodeGen/SimpleRegisterCoalescing.h
Dan Gohman a70dca156f Factor out LiveIntervalAnalysis' code to determine whether an instruction
is trivially rematerializable and integrate it into
TargetInstrInfo::isTriviallyReMaterializable. This way, all places that
need to know whether an instruction is rematerializable will get the
same answer.

This enables the useful parts of the aggressive-remat option by
default -- using AliasAnalysis to determine whether a memory location
is invariant, and removes the questionable parts -- rematting operations
with virtual register inputs that may not be live everywhere.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83687 91177308-0d34-0410-b5e6-96231b3b80d8
2009-10-09 23:27:56 +00:00

252 lines
11 KiB
C++

//===-- SimpleRegisterCoalescing.h - Register Coalescing --------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements a simple register copy coalescing phase.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_SIMPLE_REGISTER_COALESCING_H
#define LLVM_CODEGEN_SIMPLE_REGISTER_COALESCING_H
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/ADT/BitVector.h"
namespace llvm {
class SimpleRegisterCoalescing;
class LiveVariables;
class TargetRegisterInfo;
class TargetInstrInfo;
class VirtRegMap;
class MachineLoopInfo;
/// CopyRec - Representation for copy instructions in coalescer queue.
///
struct CopyRec {
MachineInstr *MI;
unsigned LoopDepth;
CopyRec(MachineInstr *mi, unsigned depth)
: MI(mi), LoopDepth(depth) {};
};
class SimpleRegisterCoalescing : public MachineFunctionPass,
public RegisterCoalescer {
MachineFunction* mf_;
MachineRegisterInfo* mri_;
const TargetMachine* tm_;
const TargetRegisterInfo* tri_;
const TargetInstrInfo* tii_;
LiveIntervals *li_;
const MachineLoopInfo* loopInfo;
AliasAnalysis *AA;
BitVector allocatableRegs_;
DenseMap<const TargetRegisterClass*, BitVector> allocatableRCRegs_;
/// JoinedCopies - Keep track of copies eliminated due to coalescing.
///
SmallPtrSet<MachineInstr*, 32> JoinedCopies;
/// ReMatCopies - Keep track of copies eliminated due to remat.
///
SmallPtrSet<MachineInstr*, 32> ReMatCopies;
/// ReMatDefs - Keep track of definition instructions which have
/// been remat'ed.
SmallPtrSet<MachineInstr*, 8> ReMatDefs;
public:
static char ID; // Pass identifcation, replacement for typeid
SimpleRegisterCoalescing() : MachineFunctionPass(&ID) {}
struct InstrSlots {
enum {
LOAD = 0,
USE = 1,
DEF = 2,
STORE = 3,
NUM = 4
};
};
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
virtual void releaseMemory();
/// runOnMachineFunction - pass entry point
virtual bool runOnMachineFunction(MachineFunction&);
bool coalesceFunction(MachineFunction &mf, RegallocQuery &) {
// This runs as an independent pass, so don't do anything.
return false;
};
/// print - Implement the dump method.
virtual void print(raw_ostream &O, const Module* = 0) const;
private:
/// joinIntervals - join compatible live intervals
void joinIntervals();
/// CopyCoalesceInMBB - Coalesce copies in the specified MBB, putting
/// copies that cannot yet be coalesced into the "TryAgain" list.
void CopyCoalesceInMBB(MachineBasicBlock *MBB,
std::vector<CopyRec> &TryAgain);
/// JoinCopy - Attempt to join intervals corresponding to SrcReg/DstReg,
/// which are the src/dst of the copy instruction CopyMI. This returns true
/// if the copy was successfully coalesced away. If it is not currently
/// possible to coalesce this interval, but it may be possible if other
/// things get coalesced, then it returns true by reference in 'Again'.
bool JoinCopy(CopyRec &TheCopy, bool &Again);
/// JoinIntervals - Attempt to join these two intervals. On failure, this
/// returns false. Otherwise, if one of the intervals being joined is a
/// physreg, this method always canonicalizes DestInt to be it. The output
/// "SrcInt" will not have been modified, so we can use this information
/// below to update aliases.
bool JoinIntervals(LiveInterval &LHS, LiveInterval &RHS, bool &Swapped);
/// SimpleJoin - Attempt to join the specified interval into this one. The
/// caller of this method must guarantee that the RHS only contains a single
/// value number and that the RHS is not defined by a copy from this
/// interval. This returns false if the intervals are not joinable, or it
/// joins them and returns true.
bool SimpleJoin(LiveInterval &LHS, LiveInterval &RHS);
/// Return true if the two specified registers belong to different register
/// classes. The registers may be either phys or virt regs.
bool differingRegisterClasses(unsigned RegA, unsigned RegB) const;
/// AdjustCopiesBackFrom - We found a non-trivially-coalescable copy. If
/// the source value number is defined by a copy from the destination reg
/// see if we can merge these two destination reg valno# into a single
/// value number, eliminating a copy.
bool AdjustCopiesBackFrom(LiveInterval &IntA, LiveInterval &IntB,
MachineInstr *CopyMI);
/// HasOtherReachingDefs - Return true if there are definitions of IntB
/// other than BValNo val# that can reach uses of AValno val# of IntA.
bool HasOtherReachingDefs(LiveInterval &IntA, LiveInterval &IntB,
VNInfo *AValNo, VNInfo *BValNo);
/// RemoveCopyByCommutingDef - We found a non-trivially-coalescable copy.
/// If the source value number is defined by a commutable instruction and
/// its other operand is coalesced to the copy dest register, see if we
/// can transform the copy into a noop by commuting the definition.
bool RemoveCopyByCommutingDef(LiveInterval &IntA, LiveInterval &IntB,
MachineInstr *CopyMI);
/// TrimLiveIntervalToLastUse - If there is a last use in the same basic
/// block as the copy instruction, trim the ive interval to the last use
/// and return true.
bool TrimLiveIntervalToLastUse(LiveIndex CopyIdx,
MachineBasicBlock *CopyMBB,
LiveInterval &li, const LiveRange *LR);
/// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
/// computation, replace the copy by rematerialize the definition.
bool ReMaterializeTrivialDef(LiveInterval &SrcInt, unsigned DstReg,
unsigned DstSubIdx, MachineInstr *CopyMI);
/// CanCoalesceWithImpDef - Returns true if the specified copy instruction
/// from an implicit def to another register can be coalesced away.
bool CanCoalesceWithImpDef(MachineInstr *CopyMI,
LiveInterval &li, LiveInterval &ImpLi) const;
/// TurnCopiesFromValNoToImpDefs - The specified value# is defined by an
/// implicit_def and it is being removed. Turn all copies from this value#
/// into implicit_defs.
void TurnCopiesFromValNoToImpDefs(LiveInterval &li, VNInfo *VNI);
/// isWinToJoinVRWithSrcPhysReg - Return true if it's worth while to join a
/// a virtual destination register with physical source register.
bool isWinToJoinVRWithSrcPhysReg(MachineInstr *CopyMI,
MachineBasicBlock *CopyMBB,
LiveInterval &DstInt, LiveInterval &SrcInt);
/// isWinToJoinVRWithDstPhysReg - Return true if it's worth while to join a
/// copy from a virtual source register to a physical destination register.
bool isWinToJoinVRWithDstPhysReg(MachineInstr *CopyMI,
MachineBasicBlock *CopyMBB,
LiveInterval &DstInt, LiveInterval &SrcInt);
/// isWinToJoinCrossClass - Return true if it's profitable to coalesce
/// two virtual registers from different register classes.
bool isWinToJoinCrossClass(unsigned LargeReg, unsigned SmallReg,
unsigned Threshold);
/// HasIncompatibleSubRegDefUse - If we are trying to coalesce a virtual
/// register with a physical register, check if any of the virtual register
/// operand is a sub-register use or def. If so, make sure it won't result
/// in an illegal extract_subreg or insert_subreg instruction.
bool HasIncompatibleSubRegDefUse(MachineInstr *CopyMI,
unsigned VirtReg, unsigned PhysReg);
/// CanJoinExtractSubRegToPhysReg - Return true if it's possible to coalesce
/// an extract_subreg where dst is a physical register, e.g.
/// cl = EXTRACT_SUBREG reg1024, 1
bool CanJoinExtractSubRegToPhysReg(unsigned DstReg, unsigned SrcReg,
unsigned SubIdx, unsigned &RealDstReg);
/// CanJoinInsertSubRegToPhysReg - Return true if it's possible to coalesce
/// an insert_subreg where src is a physical register, e.g.
/// reg1024 = INSERT_SUBREG reg1024, c1, 0
bool CanJoinInsertSubRegToPhysReg(unsigned DstReg, unsigned SrcReg,
unsigned SubIdx, unsigned &RealDstReg);
/// RangeIsDefinedByCopyFromReg - Return true if the specified live range of
/// the specified live interval is defined by a copy from the specified
/// register.
bool RangeIsDefinedByCopyFromReg(LiveInterval &li, LiveRange *LR,
unsigned Reg);
/// UpdateRegDefsUses - Replace all defs and uses of SrcReg to DstReg and
/// update the subregister number if it is not zero. If DstReg is a
/// physical register and the existing subregister number of the def / use
/// being updated is not zero, make sure to set it to the correct physical
/// subregister.
void UpdateRegDefsUses(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
/// RemoveUnnecessaryKills - Remove kill markers that are no longer accurate
/// due to live range lengthening as the result of coalescing.
void RemoveUnnecessaryKills(unsigned Reg, LiveInterval &LI);
/// ShortenDeadCopyLiveRange - Shorten a live range defined by a dead copy.
/// Return true if live interval is removed.
bool ShortenDeadCopyLiveRange(LiveInterval &li, MachineInstr *CopyMI);
/// ShortenDeadCopyLiveRange - Shorten a live range as it's artificially
/// extended by a dead copy. Mark the last use (if any) of the val# as kill
/// as ends the live range there. If there isn't another use, then this
/// live range is dead. Return true if live interval is removed.
bool ShortenDeadCopySrcLiveRange(LiveInterval &li, MachineInstr *CopyMI);
/// RemoveDeadDef - If a def of a live interval is now determined dead,
/// remove the val# it defines. If the live interval becomes empty, remove
/// it as well.
bool RemoveDeadDef(LiveInterval &li, MachineInstr *DefMI);
/// lastRegisterUse - Returns the last use of the specific register between
/// cycles Start and End or NULL if there are no uses.
MachineOperand *lastRegisterUse(LiveIndex Start,
LiveIndex End, unsigned Reg,
LiveIndex &LastUseIdx) const;
/// CalculateSpillWeights - Compute spill weights for all virtual register
/// live intervals.
void CalculateSpillWeights();
void printRegName(unsigned reg) const;
};
} // End llvm namespace
#endif