/// <summary>
/// Save the state in the low register back to the original register when a save is needed.
/// The save code is inserted directly before the given target instruction.
/// </summary>
public void SaveToOriginalAndClear(Instruction target, BasicBlock block, MethodBody body, RegisterSpillingMap map)
{
if (wideStart != null)
{
wideStart.SaveToOriginalAndClear(target, block, body, map);
}
else
{
if (SaveToOriginalNeeded)
{
var original = OriginalRegister;
// Fix target to insert before
if (target.OpCode.IsMoveResult())
{
do
{
target = target.GetPrevious(body.Instructions);
} while (target.OpCode == OpCodes.Nop);
}
// Insert save code
var move = CreateMove(LowRegister, original, type);
block.InsertBefore(target, move);
// Save end in mapping
Mapping.LastInstruction = move;
// Record mapping
map.Add(Mapping);
}
Clear();
}
}
/// <summary>
/// Allocate a low register and map it to the given original register.
/// </summary>
private LowRegisterState AllocateLowRegister(Instruction ins, Register register, MethodBody body)
{
// Prepare
var type = GetType(register);
var isWide = (type == RType.Wide);
var regsNeeded = isWide ? 2 : 1;
LowRegisterState regState = null;
HashSet <Register> allRegistersUsedInIns = null;
while (true)
{
// Try to allocate free spilling register
regState = lowRegisters.FirstOrDefault(x => x.IsFreeFor(type));
if (regState != null)
{
break; // Found a free low register
}
// No spilling register is available.
// Free another register first
// If wide, free 2 registers
if (nextSpillIndex + regsNeeded > lowRegisters.Length)
{
nextSpillIndex = 0;
}
regState = lowRegisters[nextSpillIndex];
var regStateNext = isWide ? lowRegisters[nextSpillIndex + 1] : null;
// Update index so we take another the next time
nextSpillIndex = (nextSpillIndex + regsNeeded) % (lowRegisters.Length - 1);
// Do not allocate registers already used in the current instruction
allRegistersUsedInIns = allRegistersUsedInIns ?? GetAllUsedRegisters(ins);
if (allRegistersUsedInIns.Contains(regState.LowRegister))
{
continue;
}
if ((regStateNext != null) && allRegistersUsedInIns.Contains(regStateNext.LowRegister))
{
continue;
}
// Save sReg back to original register
var map = mapper.RegisterSpillingMap;
regState.SaveToOriginalAndClear(ins, block, body, map);
if (regStateNext != null)
{
regStateNext.SaveToOriginalAndClear(ins, block, body, map);
}
}
// Add mapping
regState.SetInUseBy(register, type);
return(regState);
}