//
// 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 file was developed by Duraid Madina and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
+// This file implements the RABigBlock class
+//
+//===----------------------------------------------------------------------===//
+
// 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
#include "llvm/ADT/IndexedMap.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include <algorithm>
using namespace llvm;
bigBlockRegAlloc("bigblock", " Big-block register allocator",
createBigBlockRegisterAllocator);
+/// VRegKeyInfo - Defines magic values required to use VirtRegs as DenseMap
+/// keys.
struct VRegKeyInfo {
static inline unsigned getEmptyKey() { return -1U; }
static inline unsigned getTombstoneKey() { return -2U; }
+ static bool isEqual(unsigned LHS, unsigned RHS) { return LHS == RHS; }
static unsigned getHashValue(const unsigned &Key) { return Key; }
};
+
+/// 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)
+///
class VISIBILITY_HIDDEN RABigBlock : public MachineFunctionPass {
public:
static char ID;
RABigBlock() : MachineFunctionPass((intptr_t)&ID) {}
private:
+ /// TM - For getting at TargetMachine info
+ ///
const TargetMachine *TM;
+
+ /// MF - Our generic MachineFunction pointer
+ ///
MachineFunction *MF;
+
+ /// RegInfo - For dealing with machine register info (aliases, folds
+ /// etc)
const MRegisterInfo *RegInfo;
+
+ /// LV - Our generic LiveVariables pointer
+ ///
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;
+ typedef SmallVector<unsigned, 2> VRegTimes;
+
+ /// VRegReadTable - maps VRegs in a BB to the set of times they are read
+ ///
+ DenseMap<unsigned, VRegTimes*, VRegKeyInfo> VRegReadTable;
- // StackSlotForVirtReg - Maps virtual regs to the frame index where these
- // values are spilled.
- std::map<unsigned, int> StackSlotForVirtReg;
+ /// VRegReadIdx - keeps track of the "current time" in terms of
+ /// positions in VRegReadTable
+ DenseMap<unsigned, unsigned , VRegKeyInfo> VRegReadIdx;
- // Virt2PhysRegMap - This map contains entries for each virtual register
- // that is currently available in a physical register.
+ /// StackSlotForVirtReg - Maps virtual regs to the frame index where these
+ /// values are spilled.
+ IndexedMap<unsigned, VirtReg2IndexFunctor> StackSlotForVirtReg;
+
+ /// Virt2PhysRegMap - This map contains entries for each virtual register
+ /// that is currently available in a physical register.
IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
+ /// 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;
+
+ /// 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<int> VirtRegModified;
+
+ /// MBBLastInsnTime - the number of the the last instruction in MBB
+ ///
+ int MBBLastInsnTime;
+
+ /// MBBCurTime - the number of the the instruction being currently processed
+ ///
+ int MBBCurTime;
+
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;
+ unsigned &getVirt2StackSlot(unsigned VirtReg) {
+ return StackSlotForVirtReg[VirtReg];
+ }
+ /// markVirtRegModified - Lets us flip bits in the VirtRegModified bitset
+ ///
void markVirtRegModified(unsigned Reg, bool Val = true) {
assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
Reg -= MRegisterInfo::FirstVirtualRegister;
- if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
+ if (VirtRegModified.size() <= Reg)
+ VirtRegModified.resize(Reg+1);
VirtRegModified[Reg] = Val;
}
+ /// isVirtRegModified - Lets us query the VirtRegModified bitset
+ ///
bool isVirtRegModified(unsigned Reg) const {
assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
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:
+ /// getPassName - returns the BigBlock allocator's name
+ ///
virtual const char *getPassName() const {
return "BigBlock Register Allocator";
}
+ /// getAnalaysisUsage - declares the required analyses
+ ///
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<LiveVariables>();
AU.addRequiredID(PHIEliminationID);
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
///
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...
/// 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);
+ int FrameIdx = getVirt2StackSlot(VirtReg);
- if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
- return I->second; // Already has space allocated?
+ if (FrameIdx)
+ return FrameIdx - 1; // Already has space allocated?
// Allocate a new stack object for this spill location...
- int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
+ FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
RC->getAlignment());
// Assign the slot...
- StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
+ getVirt2StackSlot(VirtReg) = FrameIdx + 1;
return FrameIdx;
}
///
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);
}
*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
+ if (PhysRegsUsed[*AliasSet])
spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
}
}
// it holds VirtReg.
PhysRegsUsed[PhysReg] = VirtReg;
getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
- PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
}
return true;
}
-
-//////// FIX THIS:
+
/// getFreeReg - Look to see if there is a free register available in the
/// specified register class. If not, 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.
// read at the most distant point in time.
if (PhysReg == 0) {
unsigned delay=0, longest_delay=0;
- SmallVector<unsigned, 2> *ReadTimes;
+ VRegTimes* ReadTimes;
- unsigned curTime = InsnTimes[I];
+ unsigned curTime = MBBCurTime;
// for all physical regs in the RC,
for(TargetRegisterClass::iterator pReg = RC->begin();
// 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(ReadTimes && !ReadTimes->empty()) {
+ unsigned& pt = VRegReadIdx[PhysRegsUsed[*pReg]];
+ while(pt < ReadTimes->size() && (*ReadTimes)[pt] < curTime) {
+ ++pt;
+ }
+
+ if(pt < ReadTimes->size())
+ delay = (*ReadTimes)[pt] - curTime;
+ else
+ delay = MBBLastInsnTime + 1 - curTime;
+ } else {
+ // This register is only defined, but never
+ // read in this MBB. Therefore the next read
+ // happens after the end of this MBB
+ delay = MBBLastInsnTime + 1 - curTime;
+ }
+
if(delay > longest_delay) {
longest_delay = delay;
}
}
}
+
+ if(PhysReg == 0) { // ok, now we're desperate. We couldn't choose
+ // a register to spill by looking through the
+ // read timetable, so now we just spill the
+ // first allocatable register we find.
+
+ // for all physical regs in the RC,
+ for(TargetRegisterClass::iterator pReg = RC->begin();
+ pReg != RC->end(); ++pReg) {
+ // if we find a register we can spill
+ if(PhysRegsUsed[*pReg]>=-1)
+ PhysReg = *pReg; // choose it to be spilled
+ }
+ }
- assert(PhysReg && "couldn't grab a register from the table?");
- // TODO: assert that RC->contains(PhysReg) / handle aliased registers
+ assert(PhysReg && "couldn't choose a register to spill :( ");
+ // 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);
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);
+ // ..and add them to the read table.
+ VRegTimes* &Times = VRegReadTable[MO.getReg()];
+ if(!VRegReadTable[MO.getReg()]) {
+ Times = new VRegTimes;
+ VRegReadIdx[MO.getReg()] = 0;
+ }
+ Times->push_back(ReadTime);
}
}
}
+ MBBLastInsnTime = ReadTime;
+
+ for(DenseMap<unsigned, VRegTimes*, VRegKeyInfo>::iterator Reads = VRegReadTable.begin();
+ Reads != VRegReadTable.end(); ++Reads) {
+ if(Reads->second) {
+ DOUT << "Reads[" << Reads->first << "]=" << Reads->second->size() << "\n";
+ }
+ }
+}
+
+/// isReadModWriteImplicitKill - True if this is an implicit kill for a
+/// read/mod/write register, i.e. update partial register.
+static bool isReadModWriteImplicitKill(MachineInstr *MI, unsigned Reg) {
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ if (MO.isRegister() && MO.getReg() == Reg && MO.isImplicit() &&
+ MO.isDef() && !MO.isDead())
+ return true;
+ }
+ return false;
}
+/// isReadModWriteImplicitDef - True if this is an implicit def for a
+/// read/mod/write register, i.e. update partial register.
+static bool isReadModWriteImplicitDef(MachineInstr *MI, unsigned Reg) {
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ if (MO.isRegister() && MO.getReg() == Reg && MO.isImplicit() &&
+ !MO.isDef() && MO.isKill())
+ return true;
+ }
+ return false;
+}
+
+
void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
// loop over each instruction
MachineBasicBlock::iterator MII = MBB.begin();
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);
+ for (const unsigned *AliasSet = RegInfo->getSubRegisters(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.
+ MBBCurTime = -1;
while (MII != MBB.end()) {
MachineInstr *MI = MII++;
+ MBBCurTime++;
const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());
- DEBUG(DOUT << "\nStarting RegAlloc of: " << *MI;
+ DEBUG(DOUT << "\nTime=" << MBBCurTime << " Starting RegAlloc of: " << *MI;
DOUT << " Regs have values: ";
for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
<< ",%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());
+ if (MO.isRegister() && MO.isKill()) {
+ if (!MO.isImplicit())
+ Kills.push_back(MO.getReg());
+ else if (!isReadModWriteImplicitKill(MI, MO.getReg()))
+ // These are extra physical register kills when a sub-register
+ // is defined (def of a sub-register is a read/mod/write of the
+ // larger registers). Ignore.
+ Kills.push_back(MO.getReg());
+ }
}
// Get the used operands into registers. This has the potential to spill
} else if (PhysRegsUsed[PhysReg] == -2) {
// Unallocatable register dead, ignore.
continue;
+ } else {
+ assert(!PhysRegsUsed[PhysReg] || PhysRegsUsed[PhysReg] == -1 &&
+ "Silently clearing a virtual register?");
}
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);
+ for (const unsigned *AliasSet = RegInfo->getSubRegisters(PhysReg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
DOUT << " Last use of "
MRegisterInfo::isPhysicalRegister(MO.getReg())) {
unsigned Reg = MO.getReg();
if (PhysRegsUsed[Reg] == -2) continue; // Something like ESP.
-
+ // These are extra physical register defs when a sub-register
+ // is defined (def of a sub-register is a read/mod/write of the
+ // larger registers). Ignore.
+ if (isReadModWriteImplicitDef(MI, MO.getReg())) continue;
+
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);
+ for (const unsigned *AliasSet = RegInfo->getSubRegisters(Reg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
- PhysRegsUseOrder.push_back(*AliasSet);
PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
MF->setPhysRegUsed(*AliasSet);
}
for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
*ImplicitDefs; ++ImplicitDefs) {
unsigned Reg = *ImplicitDefs;
- bool IsNonAllocatable = PhysRegsUsed[Reg] == -2;
- if (!IsNonAllocatable) {
+ if (PhysRegsUsed[Reg] != -2) {
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);
+ for (const unsigned *AliasSet = RegInfo->getSubRegisters(Reg);
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
- if (!IsNonAllocatable) {
- PhysRegsUseOrder.push_back(*AliasSet);
- PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
- }
+ PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
MF->setPhysRegUsed(*AliasSet);
}
}
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
// initialize the virtual->physical register map to have a 'null'
// mapping for all virtual registers
Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
+ StackSlotForVirtReg.grow(MF->getSSARegMap()->getLastVirtReg());
+ VirtRegModified.resize(MF->getSSARegMap()->getLastVirtReg() - MRegisterInfo::FirstVirtualRegister + 1,0);
// Loop over all of the basic blocks, eliminating virtual register references
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
projects / oota-llvm.git / blobdiff