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llvm/lib/CodeGen/LiveVariables.cpp

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//===-- LiveVariables.cpp - Live Variable Analysis for Machine Code -------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the LiveVariable analysis pass. For each machine
// instruction in the function, this pass calculates the set of registers that
// are immediately dead after the instruction (i.e., the instruction calculates
// the value, but it is never used) and the set of registers that are used by
// the instruction, but are never used after the instruction (i.e., they are
// killed).
//
// This class computes live variables using are sparse implementation based on
// the machine code SSA form. This class computes live variable information for
// each virtual and _register allocatable_ physical register in a function. It
// uses the dominance properties of SSA form to efficiently compute live
// variables for virtual registers, and assumes that physical registers are only
// live within a single basic block (allowing it to do a single local analysis
// to resolve physical register lifetimes in each basic block). If a physical
// register is not register allocatable, it is not tracked. This is useful for
// things like the stack pointer and condition codes.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/LiveVariables.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Config/alloca.h"
#include <algorithm>
using namespace llvm;
char LiveVariables::ID = 0;
static RegisterPass<LiveVariables> X("livevars", "Live Variable Analysis");
void LiveVariables::VarInfo::dump() const {
cerr << " Alive in blocks: ";
for (unsigned i = 0, e = AliveBlocks.size(); i != e; ++i)
if (AliveBlocks[i]) cerr << i << ", ";
cerr << " Used in blocks: ";
for (unsigned i = 0, e = UsedBlocks.size(); i != e; ++i)
if (UsedBlocks[i]) cerr << i << ", ";
cerr << "\n Killed by:";
if (Kills.empty())
cerr << " No instructions.\n";
else {
for (unsigned i = 0, e = Kills.size(); i != e; ++i)
cerr << "\n #" << i << ": " << *Kills[i];
cerr << "\n";
}
}
/// getVarInfo - Get (possibly creating) a VarInfo object for the given vreg.
LiveVariables::VarInfo &LiveVariables::getVarInfo(unsigned RegIdx) {
assert(TargetRegisterInfo::isVirtualRegister(RegIdx) &&
"getVarInfo: not a virtual register!");
RegIdx -= TargetRegisterInfo::FirstVirtualRegister;
if (RegIdx >= VirtRegInfo.size()) {
if (RegIdx >= 2*VirtRegInfo.size())
VirtRegInfo.resize(RegIdx*2);
else
VirtRegInfo.resize(2*VirtRegInfo.size());
}
VarInfo &VI = VirtRegInfo[RegIdx];
VI.AliveBlocks.resize(MF->getNumBlockIDs());
VI.UsedBlocks.resize(MF->getNumBlockIDs());
return VI;
}
void LiveVariables::MarkVirtRegAliveInBlock(VarInfo& VRInfo,
MachineBasicBlock *DefBlock,
MachineBasicBlock *MBB,
std::vector<MachineBasicBlock*> &WorkList) {
unsigned BBNum = MBB->getNumber();
// Check to see if this basic block is one of the killing blocks. If so,
// remove it.
for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i)
if (VRInfo.Kills[i]->getParent() == MBB) {
VRInfo.Kills.erase(VRInfo.Kills.begin()+i); // Erase entry
break;
}
if (MBB == DefBlock) return; // Terminate recursion
if (VRInfo.AliveBlocks[BBNum])
return; // We already know the block is live
// Mark the variable known alive in this bb
VRInfo.AliveBlocks[BBNum] = true;
for (MachineBasicBlock::const_pred_reverse_iterator PI = MBB->pred_rbegin(),
E = MBB->pred_rend(); PI != E; ++PI)
WorkList.push_back(*PI);
}
void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo,
MachineBasicBlock *DefBlock,
MachineBasicBlock *MBB) {
std::vector<MachineBasicBlock*> WorkList;
MarkVirtRegAliveInBlock(VRInfo, DefBlock, MBB, WorkList);
while (!WorkList.empty()) {
MachineBasicBlock *Pred = WorkList.back();
WorkList.pop_back();
MarkVirtRegAliveInBlock(VRInfo, DefBlock, Pred, WorkList);
}
}
void LiveVariables::HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB,
MachineInstr *MI) {
assert(MRI->getVRegDef(reg) && "Register use before def!");
unsigned BBNum = MBB->getNumber();
VarInfo& VRInfo = getVarInfo(reg);
VRInfo.UsedBlocks[BBNum] = true;
VRInfo.NumUses++;
// Check to see if this basic block is already a kill block.
if (!VRInfo.Kills.empty() && VRInfo.Kills.back()->getParent() == MBB) {
// Yes, this register is killed in this basic block already. Increase the
// live range by updating the kill instruction.
VRInfo.Kills.back() = MI;
return;
}
#ifndef NDEBUG
for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i)
assert(VRInfo.Kills[i]->getParent() != MBB && "entry should be at end!");
#endif
assert(MBB != MRI->getVRegDef(reg)->getParent() &&
"Should have kill for defblock!");
// Add a new kill entry for this basic block. If this virtual register is
// already marked as alive in this basic block, that means it is alive in at
// least one of the successor blocks, it's not a kill.
if (!VRInfo.AliveBlocks[BBNum])
VRInfo.Kills.push_back(MI);
// Update all dominating blocks to mark them as "known live".
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
E = MBB->pred_end(); PI != E; ++PI)
MarkVirtRegAliveInBlock(VRInfo, MRI->getVRegDef(reg)->getParent(), *PI);
}
/// HandlePhysRegUse - Turn previous partial def's into read/mod/writes. Add
/// implicit defs to a machine instruction if there was an earlier def of its
/// super-register.
void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
// Turn previous partial def's into read/mod/write.
for (unsigned i = 0, e = PhysRegPartDef[Reg].size(); i != e; ++i) {
MachineInstr *Def = PhysRegPartDef[Reg][i];
// First one is just a def. This means the use is reading some undef bits.
if (i != 0)
Def->addOperand(MachineOperand::CreateReg(Reg,
false /*IsDef*/,
true /*IsImp*/,
true /*IsKill*/));
Def->addOperand(MachineOperand::CreateReg(Reg,
true /*IsDef*/,
true /*IsImp*/));
}
PhysRegPartDef[Reg].clear();
// There was an earlier def of a super-register. Add implicit def to that MI.
//
// A: EAX = ...
// B: ... = AX
//
// Add implicit def to A.
if (PhysRegInfo[Reg] && PhysRegInfo[Reg] != PhysRegPartUse[Reg] &&
!PhysRegUsed[Reg]) {
MachineInstr *Def = PhysRegInfo[Reg];
if (!Def->modifiesRegister(Reg))
Def->addOperand(MachineOperand::CreateReg(Reg,
true /*IsDef*/,
true /*IsImp*/));
}
// There is a now a proper use, forget about the last partial use.
PhysRegPartUse[Reg] = NULL;
PhysRegInfo[Reg] = MI;
PhysRegUsed[Reg] = true;
// Now reset the use information for the sub-registers.
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
PhysRegPartUse[SubReg] = NULL;
PhysRegInfo[SubReg] = MI;
PhysRegUsed[SubReg] = true;
}
for (const unsigned *SuperRegs = TRI->getSuperRegisters(Reg);
unsigned SuperReg = *SuperRegs; ++SuperRegs) {
// Remember the partial use of this super-register if it was previously
// defined.
bool HasPrevDef = PhysRegInfo[SuperReg] != NULL;
if (!HasPrevDef)
// No need to go up more levels. A def of a register also sets its sub-
// registers. So if PhysRegInfo[SuperReg] is NULL, it means SuperReg's
// super-registers are not previously defined.
for (const unsigned *SSRegs = TRI->getSuperRegisters(SuperReg);
unsigned SSReg = *SSRegs; ++SSRegs)
if (PhysRegInfo[SSReg] != NULL) {
HasPrevDef = true;
break;
}
if (HasPrevDef) {
PhysRegInfo[SuperReg] = MI;
PhysRegPartUse[SuperReg] = MI;
}
}
}
/// addRegisterKills - For all of a register's sub-registers that are killed in
/// at this machine instruction, mark them as "killed". (If the machine operand
/// isn't found, add it first.)
void LiveVariables::addRegisterKills(unsigned Reg, MachineInstr *MI,
SmallSet<unsigned, 4> &SubKills) {
if (SubKills.count(Reg) == 0) {
MI->addRegisterKilled(Reg, TRI, true);
return;
}
for (const unsigned *SubRegs = TRI->getImmediateSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs)
addRegisterKills(SubReg, MI, SubKills);
}
/// HandlePhysRegKill - The recursive version of HandlePhysRegKill. Returns true
/// if:
///
/// - The register has no sub-registers and the machine instruction is the
/// last def/use of the register, or
/// - The register has sub-registers and none of them are killed elsewhere.
///
/// SubKills is filled with the set of sub-registers that are killed elsewhere.
bool LiveVariables::HandlePhysRegKill(unsigned Reg, const MachineInstr *RefMI,
SmallSet<unsigned, 4> &SubKills) {
const unsigned *SubRegs = TRI->getImmediateSubRegisters(Reg);
for (; unsigned SubReg = *SubRegs; ++SubRegs) {
const MachineInstr *LastRef = PhysRegInfo[SubReg];
if (LastRef != RefMI ||
!HandlePhysRegKill(SubReg, RefMI, SubKills))
SubKills.insert(SubReg);
}
if (*SubRegs == 0) {
// No sub-registers, just check if reg is killed by RefMI.
if (PhysRegInfo[Reg] == RefMI && PhysRegInfo[Reg]->readsRegister(Reg)) {
return true;
}
} else if (SubKills.empty()) {
// None of the sub-registers are killed elsewhere.
return true;
}
return false;
}
/// HandlePhysRegKill - Returns true if the whole register is killed in the
/// machine instruction. If only some of its sub-registers are killed in this
/// machine instruction, then mark those as killed and return false.
bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *RefMI) {
SmallSet<unsigned, 4> SubKills;
if (HandlePhysRegKill(Reg, RefMI, SubKills)) {
// This machine instruction kills this register.
RefMI->addRegisterKilled(Reg, TRI, true);
return true;
}
// Some sub-registers are killed by another machine instruction.
for (const unsigned *SubRegs = TRI->getImmediateSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs)
addRegisterKills(SubReg, RefMI, SubKills);
return false;
}
/// hasRegisterUseBelow - Return true if the specified register is used after
/// the current instruction and before it's next definition.
bool LiveVariables::hasRegisterUseBelow(unsigned Reg,
MachineBasicBlock::iterator I,
MachineBasicBlock *MBB) {
if (I == MBB->end())
return false;
// First find out if there are any uses / defs below.
bool hasDistInfo = true;
unsigned CurDist = DistanceMap[I];
SmallVector<MachineInstr*, 4> Uses;
SmallVector<MachineInstr*, 4> Defs;
for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(Reg),
RE = MRI->reg_end(); RI != RE; ++RI) {
MachineOperand &UDO = RI.getOperand();
MachineInstr *UDMI = &*RI;
if (UDMI->getParent() != MBB)
continue;
DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI);
bool isBelow = false;
if (DI == DistanceMap.end()) {
// Must be below if it hasn't been assigned a distance yet.
isBelow = true;
hasDistInfo = false;
} else if (DI->second > CurDist)
isBelow = true;
if (isBelow) {
if (UDO.isUse())
Uses.push_back(UDMI);
if (UDO.isDef())
Defs.push_back(UDMI);
}
}
if (Uses.empty())
// No uses below.
return false;
else if (!Uses.empty() && Defs.empty())
// There are uses below but no defs below.
return true;
// There are both uses and defs below. We need to know which comes first.
if (!hasDistInfo) {
// Complete DistanceMap for this MBB. This information is computed only
// once per MBB.
++I;
++CurDist;
for (MachineBasicBlock::iterator E = MBB->end(); I != E; ++I, ++CurDist)
DistanceMap.insert(std::make_pair(I, CurDist));
}
unsigned EarliestUse = CurDist;
for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
unsigned Dist = DistanceMap[Uses[i]];
if (Dist < EarliestUse)
EarliestUse = Dist;
}
for (unsigned i = 0, e = Defs.size(); i != e; ++i) {
unsigned Dist = DistanceMap[Defs[i]];
if (Dist < EarliestUse)
// The register is defined before its first use below.
return false;
}
return true;
}
void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
// Does this kill a previous version of this register?
if (MachineInstr *LastRef = PhysRegInfo[Reg]) {
if (PhysRegUsed[Reg]) {
if (!HandlePhysRegKill(Reg, LastRef)) {
if (PhysRegPartUse[Reg])
PhysRegPartUse[Reg]->addRegisterKilled(Reg, TRI, true);
}
} else if (PhysRegPartUse[Reg]) {
// Add implicit use / kill to last partial use.
PhysRegPartUse[Reg]->addRegisterKilled(Reg, TRI, true);
} else if (LastRef != MI) {
// Defined, but not used. However, watch out for cases where a super-reg
// is also defined on the same MI.
LastRef->addRegisterDead(Reg, TRI);
}
}
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (MachineInstr *LastRef = PhysRegInfo[SubReg]) {
if (PhysRegUsed[SubReg]) {
if (!HandlePhysRegKill(SubReg, LastRef)) {
if (PhysRegPartUse[SubReg])
PhysRegPartUse[SubReg]->addRegisterKilled(SubReg, TRI, true);
}
} else if (PhysRegPartUse[SubReg]) {
// Add implicit use / kill to last use of a sub-register.
PhysRegPartUse[SubReg]->addRegisterKilled(SubReg, TRI, true);
} else if (LastRef != MI) {
// This must be a def of the subreg on the same MI.
LastRef->addRegisterDead(SubReg, TRI);
}
}
}
if (MI) {
for (const unsigned *SuperRegs = TRI->getSuperRegisters(Reg);
unsigned SuperReg = *SuperRegs; ++SuperRegs) {
if (PhysRegInfo[SuperReg] && PhysRegInfo[SuperReg] != MI) {
// The larger register is previously defined. Now a smaller part is
// being re-defined. Treat it as read/mod/write if there are uses
// below.
// EAX =
// AX = EAX<imp-use,kill>, EAX<imp-def>
// ...
/// = EAX
if (MI && hasRegisterUseBelow(SuperReg, MI, MI->getParent())) {
MI->addOperand(MachineOperand::CreateReg(SuperReg, false/*IsDef*/,
true/*IsImp*/,true/*IsKill*/));
MI->addOperand(MachineOperand::CreateReg(SuperReg, true/*IsDef*/,
true/*IsImp*/));
PhysRegInfo[SuperReg] = MI;
} else {
PhysRegInfo[SuperReg]->addRegisterKilled(SuperReg, TRI, true);
PhysRegInfo[SuperReg] = NULL;
}
PhysRegUsed[SuperReg] = false;
PhysRegPartUse[SuperReg] = NULL;
} else {
// Remember this partial def.
PhysRegPartDef[SuperReg].push_back(MI);
}
}
PhysRegInfo[Reg] = MI;
PhysRegUsed[Reg] = false;
PhysRegPartDef[Reg].clear();
PhysRegPartUse[Reg] = NULL;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
PhysRegInfo[SubReg] = MI;
PhysRegUsed[SubReg] = false;
PhysRegPartDef[SubReg].clear();
PhysRegPartUse[SubReg] = NULL;
}
}
}
bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
MF = &mf;
MRI = &mf.getRegInfo();
TRI = MF->getTarget().getRegisterInfo();
ReservedRegisters = TRI->getReservedRegs(mf);
unsigned NumRegs = TRI->getNumRegs();
PhysRegInfo = new MachineInstr*[NumRegs];
PhysRegUsed = new bool[NumRegs];
PhysRegPartUse = new MachineInstr*[NumRegs];
PhysRegPartDef = new SmallVector<MachineInstr*,4>[NumRegs];
PHIVarInfo = new SmallVector<unsigned, 4>[MF->getNumBlockIDs()];
std::fill(PhysRegInfo, PhysRegInfo + NumRegs, (MachineInstr*)0);
std::fill(PhysRegUsed, PhysRegUsed + NumRegs, false);
std::fill(PhysRegPartUse, PhysRegPartUse + NumRegs, (MachineInstr*)0);
/// Get some space for a respectable number of registers.
VirtRegInfo.resize(64);
analyzePHINodes(mf);
// Calculate live variable information in depth first order on the CFG of the
// function. This guarantees that we will see the definition of a virtual
// register before its uses due to dominance properties of SSA (except for PHI
// nodes, which are treated as a special case).
MachineBasicBlock *Entry = MF->begin();
SmallPtrSet<MachineBasicBlock*,16> Visited;
for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
DFI != E; ++DFI) {
MachineBasicBlock *MBB = *DFI;
// Mark live-in registers as live-in.
for (MachineBasicBlock::const_livein_iterator II = MBB->livein_begin(),
EE = MBB->livein_end(); II != EE; ++II) {
assert(TargetRegisterInfo::isPhysicalRegister(*II) &&
"Cannot have a live-in virtual register!");
HandlePhysRegDef(*II, 0);
}
// Loop over all of the instructions, processing them.
DistanceMap.clear();
unsigned Dist = 0;
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
I != E; ++I) {
MachineInstr *MI = I;
DistanceMap.insert(std::make_pair(MI, Dist++));
// Process all of the operands of the instruction...
unsigned NumOperandsToProcess = MI->getNumOperands();
// Unless it is a PHI node. In this case, ONLY process the DEF, not any
// of the uses. They will be handled in other basic blocks.
if (MI->getOpcode() == TargetInstrInfo::PHI)
NumOperandsToProcess = 1;
// Process all uses.
for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isRegister() && MO.isUse() && MO.getReg()) {
unsigned MOReg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(MOReg))
HandleVirtRegUse(MOReg, MBB, MI);
else if (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
!ReservedRegisters[MOReg])
HandlePhysRegUse(MOReg, MI);
}
}
// Process all defs.
for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isRegister() && MO.isDef() && MO.getReg()) {
unsigned MOReg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(MOReg)) {
VarInfo &VRInfo = getVarInfo(MOReg);
if (VRInfo.AliveBlocks.none())
// If vr is not alive in any block, then defaults to dead.
VRInfo.Kills.push_back(MI);
} else if (TargetRegisterInfo::isPhysicalRegister(MOReg) &&
!ReservedRegisters[MOReg]) {
HandlePhysRegDef(MOReg, MI);
}
}
}
}
// Handle any virtual assignments from PHI nodes which might be at the
// bottom of this basic block. We check all of our successor blocks to see
// if they have PHI nodes, and if so, we simulate an assignment at the end
// of the current block.
if (!PHIVarInfo[MBB->getNumber()].empty()) {
SmallVector<unsigned, 4>& VarInfoVec = PHIVarInfo[MBB->getNumber()];
for (SmallVector<unsigned, 4>::iterator I = VarInfoVec.begin(),
E = VarInfoVec.end(); I != E; ++I)
// Mark it alive only in the block we are representing.
MarkVirtRegAliveInBlock(getVarInfo(*I),MRI->getVRegDef(*I)->getParent(),
MBB);
}
// Finally, if the last instruction in the block is a return, make sure to
// mark it as using all of the live-out values in the function.
if (!MBB->empty() && MBB->back().getDesc().isReturn()) {
MachineInstr *Ret = &MBB->back();
for (MachineRegisterInfo::liveout_iterator
I = MF->getRegInfo().liveout_begin(),
E = MF->getRegInfo().liveout_end(); I != E; ++I) {
assert(TargetRegisterInfo::isPhysicalRegister(*I) &&
"Cannot have a live-in virtual register!");
HandlePhysRegUse(*I, Ret);
// Add live-out registers as implicit uses.
if (!Ret->readsRegister(*I))
Ret->addOperand(MachineOperand::CreateReg(*I, false, true));
}
}
// Loop over PhysRegInfo, killing any registers that are available at the
// end of the basic block. This also resets the PhysRegInfo map.
for (unsigned i = 0; i != NumRegs; ++i)
if (PhysRegInfo[i])
HandlePhysRegDef(i, 0);
// Clear some states between BB's. These are purely local information.
for (unsigned i = 0; i != NumRegs; ++i)
PhysRegPartDef[i].clear();
std::fill(PhysRegInfo, PhysRegInfo + NumRegs, (MachineInstr*)0);
std::fill(PhysRegUsed, PhysRegUsed + NumRegs, false);
std::fill(PhysRegPartUse, PhysRegPartUse + NumRegs, (MachineInstr*)0);
}
// Convert and transfer the dead / killed information we have gathered into
// VirtRegInfo onto MI's.
for (unsigned i = 0, e1 = VirtRegInfo.size(); i != e1; ++i)
for (unsigned j = 0, e2 = VirtRegInfo[i].Kills.size(); j != e2; ++j)
if (VirtRegInfo[i].Kills[j] ==
MRI->getVRegDef(i + TargetRegisterInfo::FirstVirtualRegister))
VirtRegInfo[i]
.Kills[j]->addRegisterDead(i +
TargetRegisterInfo::FirstVirtualRegister,
TRI);
else
VirtRegInfo[i]
.Kills[j]->addRegisterKilled(i +
TargetRegisterInfo::FirstVirtualRegister,
TRI);
// Check to make sure there are no unreachable blocks in the MC CFG for the
// function. If so, it is due to a bug in the instruction selector or some
// other part of the code generator if this happens.
#ifndef NDEBUG
for(MachineFunction::iterator i = MF->begin(), e = MF->end(); i != e; ++i)
assert(Visited.count(&*i) != 0 && "unreachable basic block found");
#endif
delete[] PhysRegInfo;
delete[] PhysRegUsed;
delete[] PhysRegPartUse;
delete[] PhysRegPartDef;
delete[] PHIVarInfo;
return false;
}
/// instructionChanged - When the address of an instruction changes, this method
/// should be called so that live variables can update its internal data
/// structures. This removes the records for OldMI, transfering them to the
/// records for NewMI.
void LiveVariables::instructionChanged(MachineInstr *OldMI,
MachineInstr *NewMI) {
// If the instruction defines any virtual registers, update the VarInfo,
// kill and dead information for the instruction.
for (unsigned i = 0, e = OldMI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = OldMI->getOperand(i);
if (MO.isRegister() && MO.getReg() &&
TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
unsigned Reg = MO.getReg();
VarInfo &VI = getVarInfo(Reg);
if (MO.isDef()) {
if (MO.isDead()) {
MO.setIsDead(false);
addVirtualRegisterDead(Reg, NewMI);
}
}
if (MO.isKill()) {
MO.setIsKill(false);
addVirtualRegisterKilled(Reg, NewMI);
}
// If this is a kill of the value, update the VI kills list.
if (VI.removeKill(OldMI))
VI.Kills.push_back(NewMI); // Yes, there was a kill of it
}
}
}
/// removeVirtualRegistersKilled - Remove all killed info for the specified
/// instruction.
void LiveVariables::removeVirtualRegistersKilled(MachineInstr *MI) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegister() && MO.isKill()) {
MO.setIsKill(false);
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
bool removed = getVarInfo(Reg).removeKill(MI);
assert(removed && "kill not in register's VarInfo?");
}
}
}
}
/// removeVirtualRegistersDead - Remove all of the dead registers for the
/// specified instruction from the live variable information.
void LiveVariables::removeVirtualRegistersDead(MachineInstr *MI) {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (MO.isRegister() && MO.isDead()) {
MO.setIsDead(false);
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
bool removed = getVarInfo(Reg).removeKill(MI);
assert(removed && "kill not in register's VarInfo?");
}
}
}
}
/// analyzePHINodes - Gather information about the PHI nodes in here. In
/// particular, we want to map the variable information of a virtual register
/// which is used in a PHI node. We map that to the BB the vreg is coming from.
///
void LiveVariables::analyzePHINodes(const MachineFunction& Fn) {
for (MachineFunction::const_iterator I = Fn.begin(), E = Fn.end();
I != E; ++I)
for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end();
BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()]
.push_back(BBI->getOperand(i).getReg());
}
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