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to use register units instead of registers. reviewed by Jakob Stoklund Olesen. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214798 91177308-0d34-0410-b5e6-96231b3b80d8
195 lines
6.6 KiB
C++
195 lines
6.6 KiB
C++
//===-- RegisterScavenging.h - Machine register scavenging ------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares the machine register scavenger class. It can provide
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// information such as unused register at any point in a machine basic block.
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// It also provides a mechanism to make registers availbale by evicting them
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// to spill slots.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_REGISTERSCAVENGING_H
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#define LLVM_CODEGEN_REGISTERSCAVENGING_H
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#include "llvm/ADT/BitVector.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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namespace llvm {
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class MachineRegisterInfo;
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class TargetRegisterInfo;
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class TargetInstrInfo;
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class TargetRegisterClass;
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class RegScavenger {
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const TargetRegisterInfo *TRI;
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const TargetInstrInfo *TII;
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MachineRegisterInfo* MRI;
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MachineBasicBlock *MBB;
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MachineBasicBlock::iterator MBBI;
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unsigned NumRegUnits;
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/// Tracking - True if RegScavenger is currently tracking the liveness of
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/// registers.
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bool Tracking;
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/// Information on scavenged registers (held in a spill slot).
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struct ScavengedInfo {
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ScavengedInfo(int FI = -1) : FrameIndex(FI), Reg(0), Restore(nullptr) {}
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/// A spill slot used for scavenging a register post register allocation.
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int FrameIndex;
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/// If non-zero, the specific register is currently being
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/// scavenged. That is, it is spilled to this scavenging stack slot.
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unsigned Reg;
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/// The instruction that restores the scavenged register from stack.
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const MachineInstr *Restore;
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};
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/// A vector of information on scavenged registers.
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SmallVector<ScavengedInfo, 2> Scavenged;
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/// RegUnitsAvailable - The current state of each reg unit immediatelly
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/// before MBBI. One bit per register unit. If bit is not set it means any
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/// register containing that register unit is currently being used.
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BitVector RegUnitsAvailable;
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// These BitVectors are only used internally to forward(). They are members
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// to avoid frequent reallocations.
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BitVector KillRegUnits, DefRegUnits;
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BitVector TmpRegUnits;
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public:
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RegScavenger()
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: MBB(nullptr), NumRegUnits(0), Tracking(false) {}
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/// enterBasicBlock - Start tracking liveness from the begin of the specific
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/// basic block.
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void enterBasicBlock(MachineBasicBlock *mbb);
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/// initRegState - allow resetting register state info for multiple
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/// passes over/within the same function.
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void initRegState();
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/// forward - Move the internal MBB iterator and update register states.
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void forward();
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/// forward - Move the internal MBB iterator and update register states until
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/// it has processed the specific iterator.
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void forward(MachineBasicBlock::iterator I) {
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if (!Tracking && MBB->begin() != I) forward();
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while (MBBI != I) forward();
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}
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/// Invert the behavior of forward() on the current instruction (undo the
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/// changes to the available registers made by forward()).
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void unprocess();
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/// Unprocess instructions until you reach the provided iterator.
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void unprocess(MachineBasicBlock::iterator I) {
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while (MBBI != I) unprocess();
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}
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/// skipTo - Move the internal MBB iterator but do not update register states.
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void skipTo(MachineBasicBlock::iterator I) {
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if (I == MachineBasicBlock::iterator(nullptr))
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Tracking = false;
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MBBI = I;
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}
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MachineBasicBlock::iterator getCurrentPosition() const {
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return MBBI;
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}
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/// isRegUsed - return if a specific register is currently used.
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bool isRegUsed(unsigned Reg, bool includeReserved = true) const;
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/// getRegsAvailable - Return all available registers in the register class
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/// in Mask.
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BitVector getRegsAvailable(const TargetRegisterClass *RC);
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/// FindUnusedReg - Find a unused register of the specified register class.
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/// Return 0 if none is found.
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unsigned FindUnusedReg(const TargetRegisterClass *RegClass) const;
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/// Add a scavenging frame index.
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void addScavengingFrameIndex(int FI) {
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Scavenged.push_back(ScavengedInfo(FI));
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}
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/// Query whether a frame index is a scavenging frame index.
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bool isScavengingFrameIndex(int FI) const {
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for (SmallVectorImpl<ScavengedInfo>::const_iterator I = Scavenged.begin(),
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IE = Scavenged.end(); I != IE; ++I)
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if (I->FrameIndex == FI)
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return true;
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return false;
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}
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/// Get an array of scavenging frame indices.
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void getScavengingFrameIndices(SmallVectorImpl<int> &A) const {
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for (SmallVectorImpl<ScavengedInfo>::const_iterator I = Scavenged.begin(),
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IE = Scavenged.end(); I != IE; ++I)
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if (I->FrameIndex >= 0)
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A.push_back(I->FrameIndex);
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}
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/// scavengeRegister - Make a register of the specific register class
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/// available and do the appropriate bookkeeping. SPAdj is the stack
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/// adjustment due to call frame, it's passed along to eliminateFrameIndex().
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/// Returns the scavenged register.
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unsigned scavengeRegister(const TargetRegisterClass *RegClass,
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MachineBasicBlock::iterator I, int SPAdj);
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unsigned scavengeRegister(const TargetRegisterClass *RegClass, int SPAdj) {
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return scavengeRegister(RegClass, MBBI, SPAdj);
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}
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/// setRegUsed - Tell the scavenger a register is used.
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///
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void setRegUsed(unsigned Reg);
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private:
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/// isReserved - Returns true if a register is reserved. It is never "unused".
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bool isReserved(unsigned Reg) const { return MRI->isReserved(Reg); }
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/// setUsed / setUnused - Mark the state of one or a number of register units.
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///
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void setUsed(BitVector &RegUnits) {
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RegUnitsAvailable.reset(RegUnits);
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}
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void setUnused(BitVector &RegUnits) {
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RegUnitsAvailable |= RegUnits;
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}
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/// Processes the current instruction and fill the KillRegUnits and
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/// DefRegUnits bit vectors.
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void determineKillsAndDefs();
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/// Add all Reg Units that Reg contains to BV.
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void addRegUnits(BitVector &BV, unsigned Reg);
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/// findSurvivorReg - Return the candidate register that is unused for the
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/// longest after StartMI. UseMI is set to the instruction where the search
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/// stopped.
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///
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/// No more than InstrLimit instructions are inspected.
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unsigned findSurvivorReg(MachineBasicBlock::iterator StartMI,
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BitVector &Candidates,
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unsigned InstrLimit,
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MachineBasicBlock::iterator &UseMI);
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};
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} // End llvm namespace
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#endif
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