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A bunch of fixes to the BigBlock allocator improve compile-time by ~20%

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and code quality by ~2% on my tests.

A big thank you to Roman Levenstein for this patch! See
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070618/050717.html
for more details.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37724 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duraid Madina 2007-06-25 23:46:54 +00:00
parent ba6801e6e7
commit 2e0930cf37
1 changed files with 65 additions and 72 deletions
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135
lib/CodeGen/RegAllocBigBlock.cpp
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@ -40,6 +40,7 @@
#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;
@ -69,15 +70,17 @@ namespace {
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;
// This is a sorted list
typedef SmallVector<unsigned, 2> VRegTimes;
DenseMap<unsigned, VRegTimes*, VRegKeyInfo> VRegReadTable;
DenseMap<unsigned, unsigned , VRegKeyInfo> VRegReadIdx;
// StackSlotForVirtReg - Maps virtual regs to the frame index where these
// values are spilled.
std::map<unsigned, int> StackSlotForVirtReg;
//DenseMap<unsigned, int, VRegKeyInf> StackSlotForVirtReg;
IndexedMap<unsigned, VirtReg2IndexFunctor> StackSlotForVirtReg;
// Virt2PhysRegMap - This map contains entries for each virtual register
// that is currently available in a physical register.
@ -87,6 +90,11 @@ namespace {
return Virt2PhysRegMap[VirtReg];
}
unsigned &getVirt2StackSlot(unsigned VirtReg) {
return StackSlotForVirtReg[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
@ -98,22 +106,19 @@ namespace {
//
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;
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;
void markVirtRegModified(unsigned Reg, bool Val = true) {
assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
@ -129,21 +134,6 @@ namespace {
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";
@ -256,17 +246,17 @@ namespace {
/// 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;
}
@ -276,11 +266,6 @@ int RABigBlock::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC
///
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);
}
@ -362,7 +347,6 @@ void RABigBlock::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
// it holds VirtReg.
PhysRegsUsed[PhysReg] = VirtReg;
getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
}
@ -426,9 +410,9 @@ unsigned RABigBlock::chooseReg(MachineBasicBlock &MBB, MachineInstr *I,
// 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();
@ -436,11 +420,23 @@ unsigned RABigBlock::chooseReg(MachineBasicBlock &MBB, MachineInstr *I,
// 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;
@ -533,24 +529,33 @@ void RABigBlock::FillVRegReadTable(MachineBasicBlock &MBB) {
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);
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";
}
}
}
void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
// loop over each instruction
@ -568,11 +573,9 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
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);
}
@ -581,10 +584,12 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
}
// 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)
@ -592,14 +597,6 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
<< ",%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);
@ -667,11 +664,9 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
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);
}
@ -687,7 +682,6 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
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);
@ -696,7 +690,6 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
*AliasSet; ++AliasSet) {
if (PhysRegsUsed[*AliasSet] != -2) {
if (!IsNonAllocatable) {
PhysRegsUseOrder.push_back(*AliasSet);
PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
}
MF->setPhysRegUsed(*AliasSet);
@ -800,7 +793,6 @@ void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
// 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
@ -827,6 +819,8 @@ bool RABigBlock::runOnMachineFunction(MachineFunction &Fn) {
// 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();
@ -849,4 +843,3 @@ bool RABigBlock::runOnMachineFunction(MachineFunction &Fn) {
FunctionPass *llvm::createBigBlockRegisterAllocator() {
return new RABigBlock();
}