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check in the BigBlock local register allocator 

llvm-svn: 37703
This commit is contained in:
Duraid Madina 2007-06-22 08:27:12 +00:00
parent f6e21871ad
commit 81a752aa95
3 changed files with 862 additions and 0 deletions
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1
llvm/include/llvm/CodeGen/LinkAllCodegenComponents.h
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@ -30,6 +30,7 @@ namespace {
(void) llvm::createSimpleRegisterAllocator();
(void) llvm::createLocalRegisterAllocator();
(void) llvm::createBigBlockRegisterAllocator();
(void) llvm::createLinearScanRegisterAllocator();
(void) llvm::createBFS_DAGScheduler(NULL, NULL, NULL);

9
llvm/include/llvm/CodeGen/Passes.h
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@ -70,6 +70,15 @@ namespace llvm {
///
FunctionPass *createLocalRegisterAllocator();
/// BigBlockRegisterAllocation Pass - The BigBlock register allocator
/// munches single basic blocks at a time, like the local register
/// allocator. While the BigBlock allocator is a little slower, and uses
/// somewhat more memory than the local register allocator, it tends to
/// yield the best allocations (of any of the allocators) for blocks that
/// have hundreds or thousands of instructions in sequence.
///
FunctionPass *createBigBlockRegisterAllocator();
/// LinearScanRegisterAllocation Pass - This pass implements the linear scan
/// register allocation algorithm, a global register allocator.
///

852
llvm/lib/CodeGen/RegAllocBigBlock.cpp Normal file
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@ -0,0 +1,852 @@
//===- RegAllocBigBlock.cpp - A register allocator for large basic blocks -===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This register allocator is derived from RegAllocLocal.cpp. Like it, this
// allocator works on one basic block at a time, oblivious to others.
// However, the algorithm used here is suited for long blocks of
// instructions - registers are spilled by greedily choosing those holding
// values that will not be needed for the longest amount of time. This works
// particularly well for blocks with 10 or more times as many instructions
// as machine registers, but can be used for general code.
//
//===----------------------------------------------------------------------===//
//
// TODO: - automagically invoke linearscan for (groups of) small BBs?
// - break ties when picking regs? (probably not worth it in a
// JIT context)
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "llvm/BasicBlock.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/RegAllocRegistry.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Compiler.h"
#include "llvm/ADT/IndexedMap.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include <algorithm>
using namespace llvm;
STATISTIC(NumStores, "Number of stores added");
STATISTIC(NumLoads , "Number of loads added");
STATISTIC(NumFolded, "Number of loads/stores folded into instructions");
namespace {
static RegisterRegAlloc
bigBlockRegAlloc("bigblock", " Big-block register allocator",
createBigBlockRegisterAllocator);
struct VRegKeyInfo {
static inline unsigned getEmptyKey() { return -1U; }
static inline unsigned getTombstoneKey() { return -2U; }
static unsigned getHashValue(const unsigned &Key) { return Key; }
};
class VISIBILITY_HIDDEN RABigBlock : public MachineFunctionPass {
public:
static char ID;
RABigBlock() : MachineFunctionPass((intptr_t)&ID) {}
private:
const TargetMachine *TM;
MachineFunction *MF;
const MRegisterInfo *RegInfo;
LiveVariables *LV;
// InsnTimes - maps machine instructions to their "execute times"
std::map<MachineInstr *, unsigned> InsnTimes;
// VRegReadTable - maps VRegs in a BB to the set of times they are read
DenseMap<unsigned, SmallVector<unsigned, 2>*, VRegKeyInfo> VRegReadTable;
// StackSlotForVirtReg - Maps virtual regs to the frame index where these
// values are spilled.
std::map<unsigned, int> StackSlotForVirtReg;
// Virt2PhysRegMap - This map contains entries for each virtual register
// that is currently available in a physical register.
IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
return Virt2PhysRegMap[VirtReg];
}
// PhysRegsUsed - This array is effectively a map, containing entries for
// each physical register that currently has a value (ie, it is in
// Virt2PhysRegMap). The value mapped to is the virtual register
// corresponding to the physical register (the inverse of the
// Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
// because it is used by a future instruction, and to -2 if it is not
// allocatable. If the entry for a physical register is -1, then the
// physical register is "not in the map".
//
std::vector<int> PhysRegsUsed;
// PhysRegsUseOrder - This contains a list of the physical registers that
// currently have a virtual register value in them. This list provides an
// ordering of registers, imposing a reallocation order. This list is only
// used if all registers are allocated and we have to spill one, in which
// case we spill the least recently used register. Entries at the front of
// the list are the least recently used registers, entries at the back are
// the most recently used.
//
std::vector<unsigned> PhysRegsUseOrder;
// VirtRegModified - This bitset contains information about which virtual
// registers need to be spilled back to memory when their registers are
// scavenged. If a virtual register has simply been rematerialized, there
// is no reason to spill it to memory when we need the register back.
//
std::vector<bool> VirtRegModified;
void markVirtRegModified(unsigned Reg, bool Val = true) {
assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
Reg -= MRegisterInfo::FirstVirtualRegister;
if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
VirtRegModified[Reg] = Val;
}
bool isVirtRegModified(unsigned Reg) const {
assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
&& "Illegal virtual register!");
return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
}
void MarkPhysRegRecentlyUsed(unsigned Reg) {
if (PhysRegsUseOrder.empty() ||
PhysRegsUseOrder.back() == Reg) return; // Already most recently used
for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
// Add it to the end of the list
PhysRegsUseOrder.push_back(RegMatch);
if (RegMatch == Reg)
return; // Found an exact match, exit early
}
}
public:
virtual const char *getPassName() const {
return "BigBlock Register Allocator";
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveVariables>();
AU.addRequiredID(PHIEliminationID);
AU.addRequiredID(TwoAddressInstructionPassID);
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
/// runOnMachineFunction - Register allocate the whole function
bool runOnMachineFunction(MachineFunction &Fn);
/// AllocateBasicBlock - Register allocate the specified basic block.
void AllocateBasicBlock(MachineBasicBlock &MBB);
/// FillVRegReadTable - Fill out the table of vreg read times given a BB
void FillVRegReadTable(MachineBasicBlock &MBB);
/// areRegsEqual - This method returns true if the specified registers are
/// related to each other. To do this, it checks to see if they are equal
/// or if the first register is in the alias set of the second register.
///
bool areRegsEqual(unsigned R1, unsigned R2) const {
if (R1 == R2) return true;
for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
*AliasSet; ++AliasSet) {
if (*AliasSet == R1) return true;
}
return false;
}
/// getStackSpaceFor - This returns the frame index of the specified virtual
/// register on the stack, allocating space if necessary.
int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
/// removePhysReg - This method marks the specified physical register as no
/// longer being in use.
///
void removePhysReg(unsigned PhysReg);
/// spillVirtReg - This method spills the value specified by PhysReg into
/// the virtual register slot specified by VirtReg. It then updates the RA
/// data structures to indicate the fact that PhysReg is now available.
///
void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
unsigned VirtReg, unsigned PhysReg);
/// spillPhysReg - This method spills the specified physical register into
/// the virtual register slot associated with it. If OnlyVirtRegs is set to
/// true, then the request is ignored if the physical register does not
/// contain a virtual register.
///
void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
unsigned PhysReg, bool OnlyVirtRegs = false);
/// assignVirtToPhysReg - This method updates local state so that we know
/// that PhysReg is the proper container for VirtReg now. The physical
/// register must not be used for anything else when this is called.
///
void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
/// liberatePhysReg - Make sure the specified physical register is available
/// for use. If there is currently a value in it, it is either moved out of
/// the way or spilled to memory.
///
void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
unsigned PhysReg);
/// isPhysRegAvailable - Return true if the specified physical register is
/// free and available for use. This also includes checking to see if
/// aliased registers are all free...
///
bool isPhysRegAvailable(unsigned PhysReg) const;
/// getFreeReg - Look to see if there is a free register available in the
/// specified register class. If not, return 0.
///
unsigned getFreeReg(const TargetRegisterClass *RC);
/// chooseReg - Pick a physical register to hold the specified
/// virtual register by choosing the one which will be read furthest
/// in the future.
///
unsigned chooseReg(MachineBasicBlock &MBB, MachineInstr *MI,
unsigned VirtReg);
/// reloadVirtReg - This method transforms the specified specified virtual
/// register use to refer to a physical register. This method may do this
/// in one of several ways: if the register is available in a physical
/// register already, it uses that physical register. If the value is not
/// in a physical register, and if there are physical registers available,
/// it loads it into a register. If register pressure is high, and it is
/// possible, it tries to fold the load of the virtual register into the
/// instruction itself. It avoids doing this if register pressure is low to
/// improve the chance that subsequent instructions can use the reloaded
/// value. This method returns the modified instruction.
///
MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
unsigned OpNum);
};
char RABigBlock::ID = 0;
}
/// getStackSpaceFor - This allocates space for the specified virtual register
/// to be held on the stack.
int RABigBlock::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
// Find the location Reg would belong...
std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
return I->second; // Already has space allocated?
// Allocate a new stack object for this spill location...
int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
RC->getAlignment());
// Assign the slot...
StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
return FrameIdx;
}
/// removePhysReg - This method marks the specified physical register as no
/// longer being in use.
///
void RABigBlock::removePhysReg(unsigned PhysReg) {
PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
std::vector<unsigned>::iterator It =
std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
if (It != PhysRegsUseOrder.end())
PhysRegsUseOrder.erase(It);
}
/// spillVirtReg - This method spills the value specified by PhysReg into the
/// virtual register slot specified by VirtReg. It then updates the RA data
/// structures to indicate the fact that PhysReg is now available.
///
void RABigBlock::spillVirtReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
unsigned VirtReg, unsigned PhysReg) {
assert(VirtReg && "Spilling a physical register is illegal!"
" Must not have appropriate kill for the register or use exists beyond"
" the intended one.");
DOUT << " Spilling register " << RegInfo->getName(PhysReg)
<< " containing %reg" << VirtReg;
if (!isVirtRegModified(VirtReg))
DOUT << " which has not been modified, so no store necessary!";
// Otherwise, there is a virtual register corresponding to this physical
// register. We only need to spill it into its stack slot if it has been
// modified.
if (isVirtRegModified(VirtReg)) {
const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
int FrameIndex = getStackSpaceFor(VirtReg, RC);
DOUT << " to stack slot #" << FrameIndex;
RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
++NumStores; // Update statistics
}
getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
DOUT << "\n";
removePhysReg(PhysReg);
}
/// spillPhysReg - This method spills the specified physical register into the
/// virtual register slot associated with it. If OnlyVirtRegs is set to true,
/// then the request is ignored if the physical register does not contain a
/// virtual register.
///
void RABigBlock::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
unsigned PhysReg, bool OnlyVirtRegs) {
if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
assert(PhysRegsUsed[PhysReg] != -2 && "Non allocable reg used!");
if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
} else {
// If the selected register aliases any other registers, we must make
// sure that one of the aliases isn't alive.
for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
*AliasSet; ++AliasSet)
if (PhysRegsUsed[*AliasSet] != -1 && // Spill aliased register.
PhysRegsUsed[*AliasSet] != -2) // If allocatable.
if (PhysRegsUsed[*AliasSet] == 0) {
// This must have been a dead def due to something like this:
// %EAX :=
// := op %AL
// No more use of %EAX, %AH, etc.
// %EAX isn't dead upon definition, but %AH is. However %AH isn't
// an operand of definition MI so it's not marked as such.
DOUT << " Register " << RegInfo->getName(*AliasSet)
<< " [%reg" << *AliasSet
<< "] is never used, removing it frame live list\n";
removePhysReg(*AliasSet);
} else
spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
}
}
/// assignVirtToPhysReg - This method updates local state so that we know
/// that PhysReg is the proper container for VirtReg now. The physical
/// register must not be used for anything else when this is called.
///
void RABigBlock::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
// Update information to note the fact that this register was just used, and
// it holds VirtReg.
PhysRegsUsed[PhysReg] = VirtReg;
getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
}
/// isPhysRegAvailable - Return true if the specified physical register is free
/// and available for use. This also includes checking to see if aliased
/// registers are all free...
///
bool RABigBlock::isPhysRegAvailable(unsigned PhysReg) const {
if (PhysRegsUsed[PhysReg] != -1) return false;
// If the selected register aliases any other allocated registers, it is
// not free!
for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
*AliasSet; ++AliasSet)
if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
return false; // Can't use this reg then.
return true;
}
//////// FIX THIS:
/// getFreeReg - Look to see if there is a free register available in the
/// specified register class. If not, return 0.
///
unsigned RABigBlock::getFreeReg(const TargetRegisterClass *RC) {
// Get iterators defining the range of registers that are valid to allocate in
// this class, which also specifies the preferred allocation order.
TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
for (; RI != RE; ++RI)
if (isPhysRegAvailable(*RI)) { // Is reg unused?
assert(*RI != 0 && "Cannot use register!");
return *RI; // Found an unused register!
}
return 0;
}
/// liberatePhysReg - Make sure the specified physical register is available for
/// use. If there is currently a value in it, it is either moved out of the way
/// or spilled to memory.
///
void RABigBlock::liberatePhysReg(MachineBasicBlock &MBB,
MachineBasicBlock::iterator &I,
unsigned PhysReg) {
spillPhysReg(MBB, I, PhysReg);
}
/// chooseReg - Pick a physical register to hold the specified
/// virtual register by choosing the one whose value will be read
/// furthest in the future.
///
unsigned RABigBlock::chooseReg(MachineBasicBlock &MBB, MachineInstr *I,
unsigned VirtReg) {
const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
// First check to see if we have a free register of the requested type...
unsigned PhysReg = getFreeReg(RC);
// If we didn't find an unused register, find the one which will be
// read at the most distant point in time.
if (PhysReg == 0) {
unsigned delay=0, longest_delay=0;
SmallVector<unsigned, 2> *ReadTimes;
unsigned curTime = InsnTimes[I];
// for all physical regs in the RC,
for(TargetRegisterClass::iterator pReg = RC->begin();
pReg != RC->end(); ++pReg) {
// how long until they're read?
if(PhysRegsUsed[*pReg]>0) { // ignore non-allocatable regs
ReadTimes = VRegReadTable[PhysRegsUsed[*pReg]];
SmallVector<unsigned, 2>::iterator pt =
std::lower_bound(ReadTimes->begin(),
ReadTimes->end(),
curTime);
delay = *pt - curTime;
if(delay > longest_delay) {
longest_delay = delay;
PhysReg = *pReg;
}
}
}
assert(PhysReg && "couldn't grab a register from the table?");
// TODO: assert that RC->contains(PhysReg) / handle aliased registers
// since we needed to look in the table we need to spill this register.
spillPhysReg(MBB, I, PhysReg);
}
// assign the vreg to our chosen physical register
assignVirtToPhysReg(VirtReg, PhysReg);
return PhysReg; // and return it
}
/// reloadVirtReg - This method transforms an instruction with a virtual
/// register use to one that references a physical register. It does this as
/// follows:
///
/// 1) If the register is already in a physical register, it uses it.
/// 2) Otherwise, if there is a free physical register, it uses that.
/// 3) Otherwise, it calls chooseReg() to get the physical register
/// holding the most distantly needed value, generating a spill in
/// the process.
///
/// This method returns the modified instruction.
MachineInstr *RABigBlock::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
unsigned OpNum) {
unsigned VirtReg = MI->getOperand(OpNum).getReg();
// If the virtual register is already available in a physical register,
// just update the instruction and return.
if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
MI->getOperand(OpNum).setReg(PR);
return MI;
}
// Otherwise, if we have free physical registers available to hold the
// value, use them.
const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
unsigned PhysReg = getFreeReg(RC);
int FrameIndex = getStackSpaceFor(VirtReg, RC);
if (PhysReg) { // we have a free register, so use it.
assignVirtToPhysReg(VirtReg, PhysReg);
} else { // no free registers available.
// try to fold the spill into the instruction
if(MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)) {
++NumFolded;
// Since we changed the address of MI, make sure to update live variables
// to know that the new instruction has the properties of the old one.
LV->instructionChanged(MI, FMI);
return MBB.insert(MBB.erase(MI), FMI);
}
// determine which of the physical registers we'll kill off, since we
// couldn't fold.
PhysReg = chooseReg(MBB, MI, VirtReg);
}
// this virtual register is now unmodified (since we just reloaded it)
markVirtRegModified(VirtReg, false);
DOUT << " Reloading %reg" << VirtReg << " into "
<< RegInfo->getName(PhysReg) << "\n";
// Add move instruction(s)
RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
++NumLoads; // Update statistics
MF->setPhysRegUsed(PhysReg);
MI->getOperand(OpNum).setReg(PhysReg); // Assign the input register
return MI;
}
/// Fill out the vreg read timetable. Since ReadTime increases
/// monotonically, the individual readtime sets will be sorted
/// in ascending order.
void RABigBlock::FillVRegReadTable(MachineBasicBlock &MBB) {
// loop over each instruction
MachineBasicBlock::iterator MII;
unsigned ReadTime;
for(ReadTime=0, MII = MBB.begin(); MII != MBB.end(); ++ReadTime, ++MII) {
MachineInstr *MI = MII;
InsnTimes[MI] = ReadTime;
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& MO = MI->getOperand(i);
// look for vreg reads..
if (MO.isRegister() && !MO.isDef() && MO.getReg() &&
MRegisterInfo::isVirtualRegister(MO.getReg())) {
// ..and add them to the read table.
if(!VRegReadTable[MO.getReg()])
VRegReadTable[MO.getReg()] = new SmallVector<unsigned, 2>;
VRegReadTable[MO.getReg()]->push_back(ReadTime);
}
}
}
}
void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
// loop over each instruction
MachineBasicBlock::iterator MII = MBB.begin();
const TargetInstrInfo &TII = *TM->getInstrInfo();
DEBUG(const BasicBlock *LBB = MBB.getBasicBlock();
if (LBB) DOUT << "\nStarting RegAlloc of BB: " << LBB->getName());
// If this is the first basic block in the machine function, add live-in
// registers as active.
if (&MBB == &*MF->begin()) {
for (MachineFunction::livein_iterator I = MF->livein_begin(),
E = MF->livein_end(); I != E; ++I) {
unsigned Reg = I->first;
MF->setPhysRegUsed(Reg);
PhysRegsUsed[Reg] = 0; // It is free and reserved now
PhysRegsUseOrder.push_back(Reg);
for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
PhysRegsUseOrder.push_back(*AliasSet);
PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
MF->setPhysRegUsed(*AliasSet);
}
}
}
}
// Otherwise, sequentially allocate each instruction in the MBB.
while (MII != MBB.end()) {
MachineInstr *MI = MII++;
const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());
DEBUG(DOUT << "\nStarting RegAlloc of: " << *MI;
DOUT << " Regs have values: ";
for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
DOUT << "[" << RegInfo->getName(i)
<< ",%reg" << PhysRegsUsed[i] << "] ";
DOUT << "\n");
// Loop over the implicit uses, making sure that they are at the head of the
// use order list, so they don't get reallocated.
if (TID.ImplicitUses) {
for (const unsigned *ImplicitUses = TID.ImplicitUses;
*ImplicitUses; ++ImplicitUses)
MarkPhysRegRecentlyUsed(*ImplicitUses);
}
SmallVector<unsigned, 8> Kills;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (MO.isRegister() && MO.isKill())
Kills.push_back(MO.getReg());
}
// Get the used operands into registers. This has the potential to spill
// incoming values if we are out of registers. Note that we completely
// ignore physical register uses here. We assume that if an explicit
// physical register is referenced by the instruction, that it is guaranteed
// to be live-in, or the input is badly hosed.
//
for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
MachineOperand& MO = MI->getOperand(i);
// here we are looking for only used operands (never def&use)
if (MO.isRegister() && !MO.isDef() && MO.getReg() && !MO.isImplicit() &&
MRegisterInfo::isVirtualRegister(MO.getReg()))
MI = reloadVirtReg(MBB, MI, i);
}
// If this instruction is the last user of this register, kill the
// value, freeing the register being used, so it doesn't need to be
// spilled to memory.
//
for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
unsigned VirtReg = Kills[i];
unsigned PhysReg = VirtReg;
if (MRegisterInfo::isVirtualRegister(VirtReg)) {
// If the virtual register was never materialized into a register, it
// might not be in the map, but it won't hurt to zero it out anyway.
unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
PhysReg = PhysRegSlot;
PhysRegSlot = 0;
} else if (PhysRegsUsed[PhysReg] == -2) {
// Unallocatable register dead, ignore.
continue;
}
if (PhysReg) {
DOUT << " Last use of " << RegInfo->getName(PhysReg)
<< "[%reg" << VirtReg <<"], removing it from live set\n";
removePhysReg(PhysReg);
for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
DOUT << " Last use of "
<< RegInfo->getName(*AliasSet)
<< "[%reg" << VirtReg <<"], removing it from live set\n";
removePhysReg(*AliasSet);
}
}
}
}
// Loop over all of the operands of the instruction, spilling registers that
// are defined, and marking explicit destinations in the PhysRegsUsed map.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (MO.isRegister() && MO.isDef() && !MO.isImplicit() && MO.getReg() &&
MRegisterInfo::isPhysicalRegister(MO.getReg())) {
unsigned Reg = MO.getReg();
if (PhysRegsUsed[Reg] == -2) continue; // Something like ESP.
MF->setPhysRegUsed(Reg);
spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in reg
PhysRegsUsed[Reg] = 0; // It is free and reserved now
PhysRegsUseOrder.push_back(Reg);
for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
PhysRegsUseOrder.push_back(*AliasSet);
PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
MF->setPhysRegUsed(*AliasSet);
}
}
}
}
// Loop over the implicit defs, spilling them as well.
if (TID.ImplicitDefs) {
for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
*ImplicitDefs; ++ImplicitDefs) {
unsigned Reg = *ImplicitDefs;
bool IsNonAllocatable = PhysRegsUsed[Reg] == -2;
if (!IsNonAllocatable) {
spillPhysReg(MBB, MI, Reg, true);
PhysRegsUseOrder.push_back(Reg);
PhysRegsUsed[Reg] = 0; // It is free and reserved now
}
MF->setPhysRegUsed(Reg);
for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
if (!IsNonAllocatable) {
PhysRegsUseOrder.push_back(*AliasSet);
PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
}
MF->setPhysRegUsed(*AliasSet);
}
}
}
}
SmallVector<unsigned, 8> DeadDefs;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (MO.isRegister() && MO.isDead())
DeadDefs.push_back(MO.getReg());
}
// Okay, we have allocated all of the source operands and spilled any values
// that would be destroyed by defs of this instruction. Loop over the
// explicit defs and assign them to a register, spilling incoming values if
// we need to scavenge a register.
//
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand& MO = MI->getOperand(i);
if (MO.isRegister() && MO.isDef() && MO.getReg() &&
MRegisterInfo::isVirtualRegister(MO.getReg())) {
unsigned DestVirtReg = MO.getReg();
unsigned DestPhysReg;
// If DestVirtReg already has a value, use it.
if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
DestPhysReg = chooseReg(MBB, MI, DestVirtReg);
MF->setPhysRegUsed(DestPhysReg);
markVirtRegModified(DestVirtReg);
MI->getOperand(i).setReg(DestPhysReg); // Assign the output register
}
}
// If this instruction defines any registers that are immediately dead,
// kill them now.
//
for (unsigned i = 0, e = DeadDefs.size(); i != e; ++i) {
unsigned VirtReg = DeadDefs[i];
unsigned PhysReg = VirtReg;
if (MRegisterInfo::isVirtualRegister(VirtReg)) {
unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
PhysReg = PhysRegSlot;
assert(PhysReg != 0);
PhysRegSlot = 0;
} else if (PhysRegsUsed[PhysReg] == -2) {
// Unallocatable register dead, ignore.
continue;
}
if (PhysReg) {
DOUT << " Register " << RegInfo->getName(PhysReg)
<< " [%reg" << VirtReg
<< "] is never used, removing it frame live list\n";
removePhysReg(PhysReg);
for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
DOUT << " Register " << RegInfo->getName(*AliasSet)
<< " [%reg" << *AliasSet
<< "] is never used, removing it frame live list\n";
removePhysReg(*AliasSet);
}
}
}
}
// Finally, if this is a noop copy instruction, zap it.
unsigned SrcReg, DstReg;
if (TII.isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg) {
LV->removeVirtualRegistersKilled(MI);
LV->removeVirtualRegistersDead(MI);
MBB.erase(MI);
}
}
MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
// Spill all physical registers holding virtual registers now.
for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
if (unsigned VirtReg = PhysRegsUsed[i])
spillVirtReg(MBB, MI, VirtReg, i);
else
removePhysReg(i);
#if 0
// This checking code is very expensive.
bool AllOk = true;
for (unsigned i = MRegisterInfo::FirstVirtualRegister,
e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
if (unsigned PR = Virt2PhysRegMap[i]) {
cerr << "Register still mapped: " << i << " -> " << PR << "\n";
AllOk = false;
}
assert(AllOk && "Virtual registers still in phys regs?");
#endif
// Clear any physical register which appear live at the end of the basic
// block, but which do not hold any virtual registers. e.g., the stack
// pointer.
PhysRegsUseOrder.clear();
}
/// runOnMachineFunction - Register allocate the whole function
///
bool RABigBlock::runOnMachineFunction(MachineFunction &Fn) {
DOUT << "Machine Function " << "\n";
MF = &Fn;
TM = &Fn.getTarget();
RegInfo = TM->getRegisterInfo();
LV = &getAnalysis<LiveVariables>();
PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
// At various places we want to efficiently check to see whether a register
// is allocatable. To handle this, we mark all unallocatable registers as
// being pinned down, permanently.
{
BitVector Allocable = RegInfo->getAllocatableSet(Fn);
for (unsigned i = 0, e = Allocable.size(); i != e; ++i)
if (!Allocable[i])
PhysRegsUsed[i] = -2; // Mark the reg unallocable.
}
// initialize the virtual->physical register map to have a 'null'
// mapping for all virtual registers
Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
// Loop over all of the basic blocks, eliminating virtual register references
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
MBB != MBBe; ++MBB) {
// fill out the read timetable
FillVRegReadTable(*MBB);
// use it to allocate the BB
AllocateBasicBlock(*MBB);
// clear it
VRegReadTable.clear();
}
StackSlotForVirtReg.clear();
PhysRegsUsed.clear();
VirtRegModified.clear();
Virt2PhysRegMap.clear();
return true;
}
FunctionPass *llvm::createBigBlockRegisterAllocator() {
return new RABigBlock();
}