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llvm-6502/lib/CodeGen/LiveVariables.cpp
Jeffrey Yasskin 493a3d015c LiveVariables::VarInfo contains an AliveBlocks BitVector, which has as many 
entries as there are basic blocks in the function.  LiveVariables::getVarInfo
creates a VarInfo struct for every register in the function, leading to
quadratic space use.  This patch changes the BitVector to a SparseBitVector,
which doesn't help the worst-case memory use but does reduce the actual use in
very long functions with short-lived variables.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72426 91177308-0d34-0410-b5e6-96231b3b80d8
2009-05-26 18:27:15 +00:00

696 lines
26 KiB
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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/CodeGen/Passes.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/SmallSet.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::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(UnreachableMachineBlockElimID);
AU.setPreservesAll();
}
void LiveVariables::VarInfo::dump() const {
cerr << " Alive in blocks: ";
for (SparseBitVector<>::iterator I = AliveBlocks.begin(),
E = AliveBlocks.end(); I != E; ++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());
}
return VirtRegInfo[RegIdx];
}
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.test(BBNum))
return; // We already know the block is live
// Mark the variable known alive in this bb
VRInfo.AliveBlocks.set(BBNum);
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.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
// This situation can occur:
//
// ,------.
// | |
// | v
// | t2 = phi ... t1 ...
// | |
// | v
// | t1 = ...
// | ... = ... t1 ...
// | |
// `------'
//
// where there is a use in a PHI node that's a predecessor to the defining
// block. We don't want to mark all predecessors as having the value "alive"
// in this case.
if (MBB == MRI->getVRegDef(reg)->getParent()) return;
// 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.test(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);
}
void LiveVariables::HandleVirtRegDef(unsigned Reg, MachineInstr *MI) {
VarInfo &VRInfo = getVarInfo(Reg);
if (VRInfo.AliveBlocks.empty())
// If vr is not alive in any block, then defaults to dead.
VRInfo.Kills.push_back(MI);
}
/// FindLastPartialDef - Return the last partial def of the specified register.
/// Also returns the sub-register that's defined.
MachineInstr *LiveVariables::FindLastPartialDef(unsigned Reg,
unsigned &PartDefReg) {
unsigned LastDefReg = 0;
unsigned LastDefDist = 0;
MachineInstr *LastDef = NULL;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
MachineInstr *Def = PhysRegDef[SubReg];
if (!Def)
continue;
unsigned Dist = DistanceMap[Def];
if (Dist > LastDefDist) {
LastDefReg = SubReg;
LastDef = Def;
LastDefDist = Dist;
}
}
PartDefReg = LastDefReg;
return LastDef;
}
/// 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) {
// If there was a previous use or a "full" def all is well.
if (!PhysRegDef[Reg] && !PhysRegUse[Reg]) {
// Otherwise, the last sub-register def implicitly defines this register.
// e.g.
// AH =
// AL = ... <imp-def EAX>, <imp-kill AH>
// = AH
// ...
// = EAX
// All of the sub-registers must have been defined before the use of Reg!
unsigned PartDefReg = 0;
MachineInstr *LastPartialDef = FindLastPartialDef(Reg, PartDefReg);
// If LastPartialDef is NULL, it must be using a livein register.
if (LastPartialDef) {
LastPartialDef->addOperand(MachineOperand::CreateReg(Reg, true/*IsDef*/,
true/*IsImp*/));
PhysRegDef[Reg] = LastPartialDef;
SmallSet<unsigned, 8> Processed;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (Processed.count(SubReg))
continue;
if (SubReg == PartDefReg || TRI->isSubRegister(PartDefReg, SubReg))
continue;
// This part of Reg was defined before the last partial def. It's killed
// here.
LastPartialDef->addOperand(MachineOperand::CreateReg(SubReg,
false/*IsDef*/,
true/*IsImp*/));
PhysRegDef[SubReg] = LastPartialDef;
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
Processed.insert(*SS);
}
}
}
// 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 there isn't a use of AX (or EAX) before B.
if (!PhysRegUse[Reg]) {
MachineInstr *Def = PhysRegDef[Reg];
if (Def && !Def->modifiesRegister(Reg))
Def->addOperand(MachineOperand::CreateReg(Reg,
true /*IsDef*/,
true /*IsImp*/));
}
// Remember this use.
PhysRegUse[Reg] = MI;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs)
PhysRegUse[SubReg] = MI;
}
/// 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 = DistanceMap[Uses[0]];
for (unsigned i = 1, 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;
}
bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) {
if (!PhysRegUse[Reg] && !PhysRegDef[Reg])
return false;
MachineInstr *LastRefOrPartRef = PhysRegUse[Reg]
? PhysRegUse[Reg] : PhysRegDef[Reg];
unsigned LastRefOrPartRefDist = DistanceMap[LastRefOrPartRef];
// The whole register is used.
// AL =
// AH =
//
// = AX
// = AL, AX<imp-use, kill>
// AX =
//
// Or whole register is defined, but not used at all.
// AX<dead> =
// ...
// AX =
//
// Or whole register is defined, but only partly used.
// AX<dead> = AL<imp-def>
// = AL<kill>
// AX =
SmallSet<unsigned, 8> PartUses;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (MachineInstr *Use = PhysRegUse[SubReg]) {
PartUses.insert(SubReg);
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
PartUses.insert(*SS);
unsigned Dist = DistanceMap[Use];
if (Dist > LastRefOrPartRefDist) {
LastRefOrPartRefDist = Dist;
LastRefOrPartRef = Use;
}
}
}
if (LastRefOrPartRef == PhysRegDef[Reg] && LastRefOrPartRef != MI)
// If the last reference is the last def, then it's not used at all.
// That is, unless we are currently processing the last reference itself.
LastRefOrPartRef->addRegisterDead(Reg, TRI, true);
/* Partial uses. Mark register def dead and add implicit def of
sub-registers which are used.
FIXME: LiveIntervalAnalysis can't handle this yet!
EAX<dead> = op AL<imp-def>
That is, EAX def is dead but AL def extends pass it.
Enable this after live interval analysis is fixed to improve codegen!
else if (!PhysRegUse[Reg]) {
PhysRegDef[Reg]->addRegisterDead(Reg, TRI, true);
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (PartUses.count(SubReg)) {
PhysRegDef[Reg]->addOperand(MachineOperand::CreateReg(SubReg,
true, true));
LastRefOrPartRef->addRegisterKilled(SubReg, TRI, true);
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
PartUses.erase(*SS);
}
}
} */
else
LastRefOrPartRef->addRegisterKilled(Reg, TRI, true);
return true;
}
void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
// What parts of the register are previously defined?
SmallSet<unsigned, 32> Live;
if (PhysRegDef[Reg] || PhysRegUse[Reg]) {
Live.insert(Reg);
for (const unsigned *SS = TRI->getSubRegisters(Reg); *SS; ++SS)
Live.insert(*SS);
} else {
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
// If a register isn't itself defined, but all parts that make up of it
// are defined, then consider it also defined.
// e.g.
// AL =
// AH =
// = AX
if (PhysRegDef[SubReg] || PhysRegUse[SubReg]) {
Live.insert(SubReg);
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
Live.insert(*SS);
}
}
}
// Start from the largest piece, find the last time any part of the register
// is referenced.
if (!HandlePhysRegKill(Reg, MI)) {
// Only some of the sub-registers are used.
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
if (!Live.count(SubReg))
// Skip if this sub-register isn't defined.
continue;
if (HandlePhysRegKill(SubReg, MI)) {
Live.erase(SubReg);
for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
Live.erase(*SS);
}
}
assert(Live.empty() && "Not all defined registers are killed / dead?");
}
if (MI) {
// Does this extend the live range of a super-register?
SmallSet<unsigned, 8> Processed;
for (const unsigned *SuperRegs = TRI->getSuperRegisters(Reg);
unsigned SuperReg = *SuperRegs; ++SuperRegs) {
if (Processed.count(SuperReg))
continue;
MachineInstr *LastRef = PhysRegUse[SuperReg]
? PhysRegUse[SuperReg] : PhysRegDef[SuperReg];
if (LastRef && LastRef != 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 (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*/));
PhysRegDef[SuperReg] = MI;
PhysRegUse[SuperReg] = NULL;
Processed.insert(SuperReg);
for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) {
PhysRegDef[*SS] = MI;
PhysRegUse[*SS] = NULL;
Processed.insert(*SS);
}
} else {
// Otherwise, the super register is killed.
if (HandlePhysRegKill(SuperReg, MI)) {
PhysRegDef[SuperReg] = NULL;
PhysRegUse[SuperReg] = NULL;
for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) {
PhysRegDef[*SS] = NULL;
PhysRegUse[*SS] = NULL;
Processed.insert(*SS);
}
}
}
}
}
// Remember this def.
PhysRegDef[Reg] = MI;
PhysRegUse[Reg] = NULL;
for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
unsigned SubReg = *SubRegs; ++SubRegs) {
PhysRegDef[SubReg] = MI;
PhysRegUse[SubReg] = NULL;
}
}
}
bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
MF = &mf;
MRI = &mf.getRegInfo();
TRI = MF->getTarget().getRegisterInfo();
ReservedRegisters = TRI->getReservedRegs(mf);
unsigned NumRegs = TRI->getNumRegs();
PhysRegDef = new MachineInstr*[NumRegs];
PhysRegUse = new MachineInstr*[NumRegs];
PHIVarInfo = new SmallVector<unsigned, 4>[MF->getNumBlockIDs()];
std::fill(PhysRegDef, PhysRegDef + NumRegs, (MachineInstr*)0);
std::fill(PhysRegUse, PhysRegUse + 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;
SmallVector<unsigned, 4> UseRegs;
SmallVector<unsigned, 4> DefRegs;
for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg() || MO.getReg() == 0)
continue;
unsigned MOReg = MO.getReg();
if (MO.isUse())
UseRegs.push_back(MOReg);
if (MO.isDef())
DefRegs.push_back(MOReg);
}
// Process all uses.
for (unsigned i = 0, e = UseRegs.size(); i != e; ++i) {
unsigned MOReg = UseRegs[i];
if (TargetRegisterInfo::isVirtualRegister(MOReg))
HandleVirtRegUse(MOReg, MBB, MI);
else if (!ReservedRegisters[MOReg])
HandlePhysRegUse(MOReg, MI);
}
// Process all defs.
for (unsigned i = 0, e = DefRegs.size(); i != e; ++i) {
unsigned MOReg = DefRegs[i];
if (TargetRegisterInfo::isVirtualRegister(MOReg))
HandleVirtRegDef(MOReg, MI);
else if (!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-out 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 PhysRegDef / PhysRegUse, killing any registers that are
// available at the end of the basic block.
for (unsigned i = 0; i != NumRegs; ++i)
if (PhysRegDef[i] || PhysRegUse[i])
HandlePhysRegDef(i, 0);
std::fill(PhysRegDef, PhysRegDef + NumRegs, (MachineInstr*)0);
std::fill(PhysRegUse, PhysRegUse + 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[] PhysRegDef;
delete[] PhysRegUse;
delete[] PHIVarInfo;
return false;
}
/// replaceKillInstruction - Update register kill info by replacing a kill
/// instruction with a new one.
void LiveVariables::replaceKillInstruction(unsigned Reg, MachineInstr *OldMI,
MachineInstr *NewMI) {
VarInfo &VI = getVarInfo(Reg);
std::replace(VI.Kills.begin(), VI.Kills.end(), OldMI, NewMI);
}
/// 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.isReg() && 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?");
removed = true;
}
}
}
}
/// 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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