mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-16 11:30:51 +00:00
b371f457b0
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34428 91177308-0d34-0410-b5e6-96231b3b80d8
448 lines
16 KiB
C++
448 lines
16 KiB
C++
//===-- LiveVariables.cpp - Live Variable Analysis for Machine Code -------===//
|
|
//
|
|
// 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 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/Target/MRegisterInfo.h"
|
|
#include "llvm/Target/TargetInstrInfo.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
#include "llvm/ADT/DepthFirstIterator.h"
|
|
#include "llvm/ADT/STLExtras.h"
|
|
#include "llvm/Config/alloca.h"
|
|
#include <algorithm>
|
|
using namespace llvm;
|
|
|
|
static RegisterPass<LiveVariables> X("livevars", "Live Variable Analysis");
|
|
|
|
void LiveVariables::VarInfo::dump() const {
|
|
cerr << "Register Defined by: ";
|
|
if (DefInst)
|
|
cerr << *DefInst;
|
|
else
|
|
cerr << "<null>\n";
|
|
cerr << " Alive in blocks: ";
|
|
for (unsigned i = 0, e = AliveBlocks.size(); i != e; ++i)
|
|
if (AliveBlocks[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";
|
|
}
|
|
}
|
|
|
|
LiveVariables::VarInfo &LiveVariables::getVarInfo(unsigned RegIdx) {
|
|
assert(MRegisterInfo::isVirtualRegister(RegIdx) &&
|
|
"getVarInfo: not a virtual register!");
|
|
RegIdx -= MRegisterInfo::FirstVirtualRegister;
|
|
if (RegIdx >= VirtRegInfo.size()) {
|
|
if (RegIdx >= 2*VirtRegInfo.size())
|
|
VirtRegInfo.resize(RegIdx*2);
|
|
else
|
|
VirtRegInfo.resize(2*VirtRegInfo.size());
|
|
}
|
|
return VirtRegInfo[RegIdx];
|
|
}
|
|
|
|
bool LiveVariables::KillsRegister(MachineInstr *MI, unsigned Reg) const {
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isReg() && MO.isKill()) {
|
|
if (RegInfo->regsOverlap(Reg, MO.getReg()))
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool LiveVariables::RegisterDefIsDead(MachineInstr *MI, unsigned Reg) const {
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isReg() && MO.isDead())
|
|
if (RegInfo->regsOverlap(Reg, MO.getReg()))
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool LiveVariables::ModifiesRegister(MachineInstr *MI, unsigned Reg) const {
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isReg() && MO.isDef()) {
|
|
if (RegInfo->regsOverlap(Reg, MO.getReg()))
|
|
return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
|
|
void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo,
|
|
MachineBasicBlock *MBB) {
|
|
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 == VRInfo.DefInst->getParent()) return; // Terminate recursion
|
|
|
|
if (VRInfo.AliveBlocks.size() <= BBNum)
|
|
VRInfo.AliveBlocks.resize(BBNum+1); // Make space...
|
|
|
|
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_iterator PI = MBB->pred_begin(),
|
|
E = MBB->pred_end(); PI != E; ++PI)
|
|
MarkVirtRegAliveInBlock(VRInfo, *PI);
|
|
}
|
|
|
|
void LiveVariables::HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB,
|
|
MachineInstr *MI) {
|
|
assert(VRInfo.DefInst && "Register use before def!");
|
|
|
|
// 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 != VRInfo.DefInst->getParent() &&
|
|
"Should have kill for defblock!");
|
|
|
|
// Add a new kill entry for this basic block.
|
|
VRInfo.Kills.push_back(MI);
|
|
|
|
// Update all dominating blocks to mark them known live.
|
|
for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
|
|
E = MBB->pred_end(); PI != E; ++PI)
|
|
MarkVirtRegAliveInBlock(VRInfo, *PI);
|
|
}
|
|
|
|
void LiveVariables::addRegisterKilled(unsigned IncomingReg, MachineInstr *MI) {
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isReg() && MO.isUse() && MO.getReg() == IncomingReg) {
|
|
MO.setIsKill();
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
void LiveVariables::addRegisterDead(unsigned IncomingReg, MachineInstr *MI) {
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isReg() && MO.isDef() && MO.getReg() == IncomingReg) {
|
|
MO.setIsDead();
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
|
|
PhysRegInfo[Reg] = MI;
|
|
PhysRegUsed[Reg] = true;
|
|
|
|
for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
|
|
unsigned Alias = *AliasSet; ++AliasSet) {
|
|
PhysRegInfo[Alias] = MI;
|
|
PhysRegUsed[Alias] = true;
|
|
}
|
|
}
|
|
|
|
void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
|
|
// Does this kill a previous version of this register?
|
|
if (MachineInstr *LastUse = PhysRegInfo[Reg]) {
|
|
if (PhysRegUsed[Reg])
|
|
addRegisterKilled(Reg, LastUse);
|
|
else
|
|
addRegisterDead(Reg, LastUse);
|
|
}
|
|
PhysRegInfo[Reg] = MI;
|
|
PhysRegUsed[Reg] = false;
|
|
|
|
for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
|
|
unsigned Alias = *AliasSet; ++AliasSet) {
|
|
if (MachineInstr *LastUse = PhysRegInfo[Alias]) {
|
|
if (PhysRegUsed[Alias])
|
|
addRegisterKilled(Alias, LastUse);
|
|
else
|
|
addRegisterDead(Alias, LastUse);
|
|
}
|
|
PhysRegInfo[Alias] = MI;
|
|
PhysRegUsed[Alias] = false;
|
|
}
|
|
}
|
|
|
|
bool LiveVariables::runOnMachineFunction(MachineFunction &MF) {
|
|
const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
|
|
RegInfo = MF.getTarget().getRegisterInfo();
|
|
assert(RegInfo && "Target doesn't have register information?");
|
|
|
|
ReservedRegisters = RegInfo->getReservedRegs(MF);
|
|
|
|
// PhysRegInfo - Keep track of which instruction was the last use of a
|
|
// physical register. This is a purely local property, because all physical
|
|
// register references as presumed dead across basic blocks.
|
|
//
|
|
PhysRegInfo = (MachineInstr**)alloca(sizeof(MachineInstr*) *
|
|
RegInfo->getNumRegs());
|
|
PhysRegUsed = (bool*)alloca(sizeof(bool)*RegInfo->getNumRegs());
|
|
std::fill(PhysRegInfo, PhysRegInfo+RegInfo->getNumRegs(), (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();
|
|
std::set<MachineBasicBlock*> Visited;
|
|
for (df_ext_iterator<MachineBasicBlock*> 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(MRegisterInfo::isPhysicalRegister(*II) &&
|
|
"Cannot have a live-in virtual register!");
|
|
HandlePhysRegDef(*II, 0);
|
|
}
|
|
|
|
// Loop over all of the instructions, processing them.
|
|
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
|
|
I != E; ++I) {
|
|
MachineInstr *MI = I;
|
|
|
|
// 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) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isRegister() && MO.isUse() && MO.getReg()) {
|
|
if (MRegisterInfo::isVirtualRegister(MO.getReg())){
|
|
HandleVirtRegUse(getVarInfo(MO.getReg()), MBB, MI);
|
|
} else if (MRegisterInfo::isPhysicalRegister(MO.getReg()) &&
|
|
!ReservedRegisters[MO.getReg()]) {
|
|
HandlePhysRegUse(MO.getReg(), MI);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Process all defs...
|
|
for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
|
|
MachineOperand &MO = MI->getOperand(i);
|
|
if (MO.isRegister() && MO.isDef() && MO.getReg()) {
|
|
if (MRegisterInfo::isVirtualRegister(MO.getReg())) {
|
|
VarInfo &VRInfo = getVarInfo(MO.getReg());
|
|
|
|
assert(VRInfo.DefInst == 0 && "Variable multiply defined!");
|
|
VRInfo.DefInst = MI;
|
|
// Defaults to dead
|
|
VRInfo.Kills.push_back(MI);
|
|
} else if (MRegisterInfo::isPhysicalRegister(MO.getReg()) &&
|
|
!ReservedRegisters[MO.getReg()]) {
|
|
HandlePhysRegDef(MO.getReg(), 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].empty()) {
|
|
std::vector<unsigned>& VarInfoVec = PHIVarInfo[MBB];
|
|
|
|
for (std::vector<unsigned>::iterator I = VarInfoVec.begin(),
|
|
E = VarInfoVec.end(); I != E; ++I) {
|
|
VarInfo& VRInfo = getVarInfo(*I);
|
|
assert(VRInfo.DefInst && "Register use before def (or no def)!");
|
|
|
|
// Only mark it alive only in the block we are representing.
|
|
MarkVirtRegAliveInBlock(VRInfo, 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() && TII.isReturn(MBB->back().getOpcode())) {
|
|
MachineInstr *Ret = &MBB->back();
|
|
for (MachineFunction::liveout_iterator I = MF.liveout_begin(),
|
|
E = MF.liveout_end(); I != E; ++I) {
|
|
assert(MRegisterInfo::isPhysicalRegister(*I) &&
|
|
"Cannot have a live-in virtual register!");
|
|
HandlePhysRegUse(*I, Ret);
|
|
// Add live-out registers as implicit uses.
|
|
Ret->addRegOperand(*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, e = RegInfo->getNumRegs(); i != e; ++i)
|
|
if (PhysRegInfo[i])
|
|
HandlePhysRegDef(i, 0);
|
|
}
|
|
|
|
// Convert and transfer the dead / killed information we have gathered into
|
|
// VirtRegInfo onto MI's.
|
|
//
|
|
for (unsigned i = 0, e = VirtRegInfo.size(); i != e; ++i)
|
|
for (unsigned j = 0, e = VirtRegInfo[i].Kills.size(); j != e; ++j) {
|
|
if (VirtRegInfo[i].Kills[j] == VirtRegInfo[i].DefInst)
|
|
addRegisterDead(i + MRegisterInfo::FirstVirtualRegister,
|
|
VirtRegInfo[i].Kills[j]);
|
|
else
|
|
addRegisterKilled(i + MRegisterInfo::FirstVirtualRegister,
|
|
VirtRegInfo[i].Kills[j]);
|
|
}
|
|
|
|
// 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
|
|
|
|
PHIVarInfo.clear();
|
|
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() &&
|
|
MRegisterInfo::isVirtualRegister(MO.getReg())) {
|
|
unsigned Reg = MO.getReg();
|
|
VarInfo &VI = getVarInfo(Reg);
|
|
if (MO.isDef()) {
|
|
if (MO.isDead()) {
|
|
MO.unsetIsDead();
|
|
addVirtualRegisterDead(Reg, NewMI);
|
|
}
|
|
// Update the defining instruction.
|
|
if (VI.DefInst == OldMI)
|
|
VI.DefInst = NewMI;
|
|
}
|
|
if (MO.isUse()) {
|
|
if (MO.isKill()) {
|
|
MO.unsetIsKill();
|
|
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.isReg() && MO.isKill()) {
|
|
MO.unsetIsKill();
|
|
unsigned Reg = MO.getReg();
|
|
if (MRegisterInfo::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.isReg() && MO.isDead()) {
|
|
MO.unsetIsDead();
|
|
unsigned Reg = MO.getReg();
|
|
if (MRegisterInfo::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).getMachineBasicBlock()].
|
|
push_back(BBI->getOperand(i).getReg());
|
|
}
|