llvm-6502/lib/CodeGen/MachineRegisterInfo.cpp
2010-05-24 21:33:37 +00:00

303 lines
11 KiB
C++

//===-- lib/Codegen/MachineRegisterInfo.cpp -------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implementation of the MachineRegisterInfo class.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
MachineRegisterInfo::MachineRegisterInfo(const TargetRegisterInfo &TRI) {
VRegInfo.reserve(256);
RegAllocHints.reserve(256);
RegClass2VRegMap.resize(TRI.getNumRegClasses()+1); // RC ID starts at 1.
UsedPhysRegs.resize(TRI.getNumRegs());
// Create the physreg use/def lists.
PhysRegUseDefLists = new MachineOperand*[TRI.getNumRegs()];
memset(PhysRegUseDefLists, 0, sizeof(MachineOperand*)*TRI.getNumRegs());
}
MachineRegisterInfo::~MachineRegisterInfo() {
#ifndef NDEBUG
for (unsigned i = 0, e = VRegInfo.size(); i != e; ++i)
assert(VRegInfo[i].second == 0 && "Vreg use list non-empty still?");
for (unsigned i = 0, e = UsedPhysRegs.size(); i != e; ++i)
assert(!PhysRegUseDefLists[i] &&
"PhysRegUseDefLists has entries after all instructions are deleted");
#endif
delete [] PhysRegUseDefLists;
}
/// setRegClass - Set the register class of the specified virtual register.
///
void
MachineRegisterInfo::setRegClass(unsigned Reg, const TargetRegisterClass *RC) {
unsigned VR = Reg;
Reg -= TargetRegisterInfo::FirstVirtualRegister;
assert(Reg < VRegInfo.size() && "Invalid vreg!");
const TargetRegisterClass *OldRC = VRegInfo[Reg].first;
VRegInfo[Reg].first = RC;
// Remove from old register class's vregs list. This may be slow but
// fortunately this operation is rarely needed.
std::vector<unsigned> &VRegs = RegClass2VRegMap[OldRC->getID()];
std::vector<unsigned>::iterator I=std::find(VRegs.begin(), VRegs.end(), VR);
VRegs.erase(I);
// Add to new register class's vregs list.
RegClass2VRegMap[RC->getID()].push_back(VR);
}
/// createVirtualRegister - Create and return a new virtual register in the
/// function with the specified register class.
///
unsigned
MachineRegisterInfo::createVirtualRegister(const TargetRegisterClass *RegClass){
assert(RegClass && "Cannot create register without RegClass!");
// Add a reg, but keep track of whether the vector reallocated or not.
void *ArrayBase = VRegInfo.empty() ? 0 : &VRegInfo[0];
VRegInfo.push_back(std::make_pair(RegClass, (MachineOperand*)0));
RegAllocHints.push_back(std::make_pair(0, 0));
if (!((&VRegInfo[0] == ArrayBase || VRegInfo.size() == 1)))
// The vector reallocated, handle this now.
HandleVRegListReallocation();
unsigned VR = getLastVirtReg();
RegClass2VRegMap[RegClass->getID()].push_back(VR);
return VR;
}
/// HandleVRegListReallocation - We just added a virtual register to the
/// VRegInfo info list and it reallocated. Update the use/def lists info
/// pointers.
void MachineRegisterInfo::HandleVRegListReallocation() {
// The back pointers for the vreg lists point into the previous vector.
// Update them to point to their correct slots.
for (unsigned i = 0, e = VRegInfo.size(); i != e; ++i) {
MachineOperand *List = VRegInfo[i].second;
if (!List) continue;
// Update the back-pointer to be accurate once more.
List->Contents.Reg.Prev = &VRegInfo[i].second;
}
}
/// replaceRegWith - Replace all instances of FromReg with ToReg in the
/// machine function. This is like llvm-level X->replaceAllUsesWith(Y),
/// except that it also changes any definitions of the register as well.
void MachineRegisterInfo::replaceRegWith(unsigned FromReg, unsigned ToReg) {
assert(FromReg != ToReg && "Cannot replace a reg with itself");
// TODO: This could be more efficient by bulk changing the operands.
for (reg_iterator I = reg_begin(FromReg), E = reg_end(); I != E; ) {
MachineOperand &O = I.getOperand();
++I;
O.setReg(ToReg);
}
}
/// getVRegDef - Return the machine instr that defines the specified virtual
/// register or null if none is found. This assumes that the code is in SSA
/// form, so there should only be one definition.
MachineInstr *MachineRegisterInfo::getVRegDef(unsigned Reg) const {
assert(Reg-TargetRegisterInfo::FirstVirtualRegister < VRegInfo.size() &&
"Invalid vreg!");
// Since we are in SSA form, we can use the first definition.
if (!def_empty(Reg))
return &*def_begin(Reg);
return 0;
}
bool MachineRegisterInfo::hasOneUse(unsigned RegNo) const {
use_iterator UI = use_begin(RegNo);
if (UI == use_end())
return false;
return ++UI == use_end();
}
bool MachineRegisterInfo::hasOneNonDBGUse(unsigned RegNo) const {
use_nodbg_iterator UI = use_nodbg_begin(RegNo);
if (UI == use_nodbg_end())
return false;
return ++UI == use_nodbg_end();
}
/// clearKillFlags - Iterate over all the uses of the given register and
/// clear the kill flag from the MachineOperand. This function is used by
/// optimization passes which extend register lifetimes and need only
/// preserve conservative kill flag information.
void MachineRegisterInfo::clearKillFlags(unsigned Reg) const {
for (use_iterator UI = use_begin(Reg), UE = use_end(); UI != UE; ++UI)
UI.getOperand().setIsKill(false);
}
bool MachineRegisterInfo::isLiveIn(unsigned Reg) const {
for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
if (I->first == Reg || I->second == Reg)
return true;
return false;
}
bool MachineRegisterInfo::isLiveOut(unsigned Reg) const {
for (liveout_iterator I = liveout_begin(), E = liveout_end(); I != E; ++I)
if (*I == Reg)
return true;
return false;
}
/// getLiveInPhysReg - If VReg is a live-in virtual register, return the
/// corresponding live-in physical register.
unsigned MachineRegisterInfo::getLiveInPhysReg(unsigned VReg) const {
for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
if (I->second == VReg)
return I->first;
return 0;
}
/// getLiveInVirtReg - If PReg is a live-in physical register, return the
/// corresponding live-in physical register.
unsigned MachineRegisterInfo::getLiveInVirtReg(unsigned PReg) const {
for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
if (I->first == PReg)
return I->second;
return 0;
}
static cl::opt<bool>
SchedLiveInCopies("schedule-livein-copies", cl::Hidden,
cl::desc("Schedule copies of livein registers"),
cl::init(false));
/// EmitLiveInCopy - Emit a copy for a live in physical register. If the
/// physical register has only a single copy use, then coalesced the copy
/// if possible.
static void EmitLiveInCopy(MachineBasicBlock *MBB,
MachineBasicBlock::iterator &InsertPos,
unsigned VirtReg, unsigned PhysReg,
const TargetRegisterClass *RC,
DenseMap<MachineInstr*, unsigned> &CopyRegMap,
const MachineRegisterInfo &MRI,
const TargetRegisterInfo &TRI,
const TargetInstrInfo &TII) {
unsigned NumUses = 0;
MachineInstr *UseMI = NULL;
for (MachineRegisterInfo::use_iterator UI = MRI.use_begin(VirtReg),
UE = MRI.use_end(); UI != UE; ++UI) {
UseMI = &*UI;
if (++NumUses > 1)
break;
}
// If the number of uses is not one, or the use is not a move instruction,
// don't coalesce. Also, only coalesce away a virtual register to virtual
// register copy.
bool Coalesced = false;
unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
if (NumUses == 1 &&
TII.isMoveInstr(*UseMI, SrcReg, DstReg, SrcSubReg, DstSubReg) &&
TargetRegisterInfo::isVirtualRegister(DstReg)) {
VirtReg = DstReg;
Coalesced = true;
}
// Now find an ideal location to insert the copy.
MachineBasicBlock::iterator Pos = InsertPos;
while (Pos != MBB->begin()) {
MachineInstr *PrevMI = prior(Pos);
DenseMap<MachineInstr*, unsigned>::iterator RI = CopyRegMap.find(PrevMI);
// copyRegToReg might emit multiple instructions to do a copy.
unsigned CopyDstReg = (RI == CopyRegMap.end()) ? 0 : RI->second;
if (CopyDstReg && !TRI.regsOverlap(CopyDstReg, PhysReg))
// This is what the BB looks like right now:
// r1024 = mov r0
// ...
// r1 = mov r1024
//
// We want to insert "r1025 = mov r1". Inserting this copy below the
// move to r1024 makes it impossible for that move to be coalesced.
//
// r1025 = mov r1
// r1024 = mov r0
// ...
// r1 = mov 1024
// r2 = mov 1025
break; // Woot! Found a good location.
--Pos;
}
bool Emitted = TII.copyRegToReg(*MBB, Pos, VirtReg, PhysReg, RC, RC,
DebugLoc());
assert(Emitted && "Unable to issue a live-in copy instruction!\n");
(void) Emitted;
CopyRegMap.insert(std::make_pair(prior(Pos), VirtReg));
if (Coalesced) {
if (&*InsertPos == UseMI) ++InsertPos;
MBB->erase(UseMI);
}
}
/// EmitLiveInCopies - Emit copies to initialize livein virtual registers
/// into the given entry block.
void
MachineRegisterInfo::EmitLiveInCopies(MachineBasicBlock *EntryMBB,
const TargetRegisterInfo &TRI,
const TargetInstrInfo &TII) {
if (SchedLiveInCopies) {
// Emit the copies at a heuristically-determined location in the block.
DenseMap<MachineInstr*, unsigned> CopyRegMap;
MachineBasicBlock::iterator InsertPos = EntryMBB->begin();
for (MachineRegisterInfo::livein_iterator LI = livein_begin(),
E = livein_end(); LI != E; ++LI)
if (LI->second) {
const TargetRegisterClass *RC = getRegClass(LI->second);
EmitLiveInCopy(EntryMBB, InsertPos, LI->second, LI->first,
RC, CopyRegMap, *this, TRI, TII);
}
} else {
// Emit the copies into the top of the block.
for (MachineRegisterInfo::livein_iterator LI = livein_begin(),
E = livein_end(); LI != E; ++LI)
if (LI->second) {
const TargetRegisterClass *RC = getRegClass(LI->second);
bool Emitted = TII.copyRegToReg(*EntryMBB, EntryMBB->begin(),
LI->second, LI->first, RC, RC,
DebugLoc());
assert(Emitted && "Unable to issue a live-in copy instruction!\n");
(void) Emitted;
}
}
// Add function live-ins to entry block live-in set.
for (MachineRegisterInfo::livein_iterator I = livein_begin(),
E = livein_end(); I != E; ++I)
EntryMBB->addLiveIn(I->first);
}
void MachineRegisterInfo::closePhysRegsUsed(const TargetRegisterInfo &TRI) {
for (int i = UsedPhysRegs.find_first(); i >= 0;
i = UsedPhysRegs.find_next(i))
for (const unsigned *SS = TRI.getSubRegisters(i);
unsigned SubReg = *SS; ++SS)
if (SubReg > unsigned(i))
UsedPhysRegs.set(SubReg);
}
#ifndef NDEBUG
void MachineRegisterInfo::dumpUses(unsigned Reg) const {
for (use_iterator I = use_begin(Reg), E = use_end(); I != E; ++I)
I.getOperand().getParent()->dump();
}
#endif