using System;
using System.Collections.Generic;
namespace ChocolArm64.Translation
{
class RegisterUsage
{
public const long CallerSavedIntRegistersMask = 0x7fL << 9;
public const long PStateNzcvFlagsMask = 0xfL << 60;
public const long CallerSavedVecRegistersMask = 0xffffL << 16;
private class PathIo
{
private Dictionary<ILBlock, long> _allInputs;
private Dictionary<ILBlock, long> _cmnOutputs;
private long _allOutputs;
public PathIo()
{
_allInputs = new Dictionary<ILBlock, long>();
_cmnOutputs = new Dictionary<ILBlock, long>();
}
public void Set(ILBlock entry, long inputs, long outputs)
{
if (!_allInputs.TryAdd(entry, inputs))
{
_allInputs[entry] |= inputs;
}
if (!_cmnOutputs.TryAdd(entry, outputs))
{
_cmnOutputs[entry] &= outputs;
}
_allOutputs |= outputs;
}
public long GetInputs(ILBlock entry)
{
if (_allInputs.TryGetValue(entry, out long inputs))
{
//We also need to read the registers that may not be written
//by all paths that can reach a exit point, to ensure that
//the local variable will not remain uninitialized depending
//on the flow path taken.
return inputs | (_allOutputs & ~_cmnOutputs[entry]);
}
return 0;
}
public long GetOutputs()
{
return _allOutputs;
}
}
private Dictionary<ILBlock, PathIo> _intPaths;
private Dictionary<ILBlock, PathIo> _vecPaths;
private struct BlockIo : IEquatable<BlockIo>
{
public ILBlock Block { get; }
public ILBlock Entry { get; }
public long IntInputs { get; set; }
public long VecInputs { get; set; }
public long IntOutputs { get; set; }
public long VecOutputs { get; set; }
public BlockIo(ILBlock block, ILBlock entry)
{
Block = block;
Entry = entry;
IntInputs = IntOutputs = 0;
VecInputs = VecOutputs = 0;
}
public BlockIo(
ILBlock block,
ILBlock entry,
long intInputs,
long vecInputs,
long intOutputs,
long vecOutputs) : this(block, entry)
{
IntInputs = intInputs;
VecInputs = vecInputs;
IntOutputs = intOutputs;
VecOutputs = vecOutputs;
}
public override bool Equals(object obj)
{
if (!(obj is BlockIo other))
{
return false;
}
return Equals(other);
}
public bool Equals(BlockIo other)
{
return other.Block == Block &&
other.Entry == Entry &&
other.IntInputs == IntInputs &&
other.VecInputs == VecInputs &&
other.IntOutputs == IntOutputs &&
other.VecOutputs == VecOutputs;
}
public override int GetHashCode()
{
return HashCode.Combine(Block, Entry, IntInputs, VecInputs, IntOutputs, VecOutputs);
}
public static bool operator ==(BlockIo lhs, BlockIo rhs)
{
return lhs.Equals(rhs);
}
public static bool operator !=(BlockIo lhs, BlockIo rhs)
{
return !(lhs == rhs);
}
}
public RegisterUsage()
{
_intPaths = new Dictionary<ILBlock, PathIo>();
_vecPaths = new Dictionary<ILBlock, PathIo>();
}
public void BuildUses(ILBlock entry)
{
//This will go through all possible paths on the graph,
//and store all inputs/outputs for each block. A register
//that was previously written to already is not considered an input.
//When a block can be reached by more than one path, then the
//output from all paths needs to be set for this block, and
//only outputs present in all of the parent blocks can be considered
//when doing input elimination. Each block chain has a entry, that's where
//the code starts executing. They are present on the subroutine start point,
//and on call return points too (address written to X30 by BL).
HashSet<BlockIo> visited = new HashSet<BlockIo>();
Queue<BlockIo> unvisited = new Queue<BlockIo>();
void Enqueue(BlockIo block)
{
if (visited.Add(block))
{
unvisited.Enqueue(block);
}
}
Enqueue(new BlockIo(entry, entry));
while (unvisited.Count > 0)
{
BlockIo current = unvisited.Dequeue();
current.IntInputs |= current.Block.IntInputs & ~current.IntOutputs;
current.VecInputs |= current.Block.VecInputs & ~current.VecOutputs;
current.IntOutputs |= current.Block.IntOutputs;
current.VecOutputs |= current.Block.VecOutputs;
//Check if this is a exit block
//(a block that returns or calls another sub).
if ((current.Block.Next == null &&
current.Block.Branch == null) || current.Block.HasStateStore)
{
if (!_intPaths.TryGetValue(current.Block, out PathIo intPath))
{
_intPaths.Add(current.Block, intPath = new PathIo());
}
if (!_vecPaths.TryGetValue(current.Block, out PathIo vecPath))
{
_vecPaths.Add(current.Block, vecPath = new PathIo());
}
intPath.Set(current.Entry, current.IntInputs, current.IntOutputs);
vecPath.Set(current.Entry, current.VecInputs, current.VecOutputs);
}
void EnqueueFromCurrent(ILBlock block, bool retTarget)
{
BlockIo blockIo;
if (retTarget)
{
blockIo = new BlockIo(block, block);
}
else
{
blockIo = new BlockIo(
block,
current.Entry,
current.IntInputs,
current.VecInputs,
current.IntOutputs,
current.VecOutputs);
}
Enqueue(blockIo);
}
if (current.Block.Next != null)
{
EnqueueFromCurrent(current.Block.Next, current.Block.HasStateStore);
}
if (current.Block.Branch != null)
{
EnqueueFromCurrent(current.Block.Branch, false);
}
}
}
public long GetIntInputs(ILBlock entry) => GetInputsImpl(entry, _intPaths.Values);
public long GetVecInputs(ILBlock entry) => GetInputsImpl(entry, _vecPaths.Values);
private long GetInputsImpl(ILBlock entry, IEnumerable<PathIo> values)
{
long inputs = 0;
foreach (PathIo path in values)
{
inputs |= path.GetInputs(entry);
}
return inputs;
}
public long GetIntNotInputs(ILBlock entry) => GetNotInputsImpl(entry, _intPaths.Values);
public long GetVecNotInputs(ILBlock entry) => GetNotInputsImpl(entry, _vecPaths.Values);
private long GetNotInputsImpl(ILBlock entry, IEnumerable<PathIo> values)
{
//Returns a mask with registers that are written to
//before being read. Only those registers that are
//written in all paths, and is not read before being
//written to on those paths, should be set on the mask.
long mask = -1L;
foreach (PathIo path in values)
{
mask &= path.GetOutputs() & ~path.GetInputs(entry);
}
return mask;
}
public long GetIntOutputs(ILBlock block) => _intPaths[block].GetOutputs();
public long GetVecOutputs(ILBlock block) => _vecPaths[block].GetOutputs();
public static long ClearCallerSavedIntRegs(long mask, bool isAarch64)
{
//TODO: ARM32 support.
if (isAarch64)
{
mask &= ~(CallerSavedIntRegistersMask | PStateNzcvFlagsMask);
}
return mask;
}
public static long ClearCallerSavedVecRegs(long mask, bool isAarch64)
{
//TODO: ARM32 support.
if (isAarch64)
{
mask &= ~CallerSavedVecRegistersMask;
}
return mask;
}
}
}