static bool isACalleeSavedRegister(unsigned reg, const TargetRegisterInfo &TRI,
const MachineFunction &MF) {
const MCPhysReg *CSR = TRI.getCalleeSavedRegs(&MF);
for (unsigned i = 0; CSR[i] != 0; ++i)
if (TRI.regsOverlap(reg, CSR[i]))
return true;
return 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);
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);
}
}