ChocolArm64/Decoders/Decoder.cs
Alex Barney 25e6a2e0ea Misc cleanup (#708)
* Fix typos

* Remove unneeded using statements

* Enforce var style more

* Remove redundant qualifiers

* Fix some indentation

* Disable naming warnings on files with external enum names

* Fix build

* Mass find & replace for comments with no spacing

* Standardize todo capitalization and for/if spacing
2019-07-02 04:39:22 +02:00

379 lines
12 KiB
C#

using ChocolArm64.Instructions;
using ChocolArm64.Memory;
using ChocolArm64.State;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Reflection.Emit;
namespace ChocolArm64.Decoders
{
static class Decoder
{
private delegate object OpActivator(Inst inst, long position, int opCode);
private static ConcurrentDictionary<Type, OpActivator> _opActivators;
static Decoder()
{
_opActivators = new ConcurrentDictionary<Type, OpActivator>();
}
public static Block[] DecodeBasicBlock(MemoryManager memory, ulong address, ExecutionMode mode)
{
Block block = new Block(address);
FillBlock(memory, mode, block, ulong.MaxValue);
OpCode64 lastOp = block.GetLastOp();
if (IsBranch(lastOp) && !IsCall(lastOp) && lastOp is IOpCodeBImm op)
{
// It's possible that the branch on this block lands on the middle of the block.
// This is more common on tight loops. In this case, we can improve the codegen
// a bit by changing the CFG and either making the branch point to the same block
// (which indicates that the block is a loop that jumps back to the start), and the
// other possible case is a jump somewhere on the middle of the block, which is
// also a loop, but in this case we need to split the block in half.
if ((ulong)op.Imm == address)
{
block.Branch = block;
}
else if ((ulong)op.Imm > address &&
(ulong)op.Imm < block.EndAddress)
{
Block rightBlock = new Block((ulong)op.Imm);
block.Split(rightBlock);
return new Block[] { block, rightBlock };
}
}
return new Block[] { block };
}
public static Block[] DecodeSubroutine(MemoryManager memory, ulong address, ExecutionMode mode)
{
List<Block> blocks = new List<Block>();
Queue<Block> workQueue = new Queue<Block>();
Dictionary<ulong, Block> visited = new Dictionary<ulong, Block>();
Block GetBlock(ulong blkAddress)
{
if (!visited.TryGetValue(blkAddress, out Block block))
{
block = new Block(blkAddress);
workQueue.Enqueue(block);
visited.Add(blkAddress, block);
}
return block;
}
GetBlock(address);
while (workQueue.TryDequeue(out Block currBlock))
{
// Check if the current block is inside another block.
if (BinarySearch(blocks, currBlock.Address, out int nBlkIndex))
{
Block nBlock = blocks[nBlkIndex];
if (nBlock.Address == currBlock.Address)
{
throw new InvalidOperationException("Found duplicate block address on the list.");
}
nBlock.Split(currBlock);
blocks.Insert(nBlkIndex + 1, currBlock);
continue;
}
// If we have a block after the current one, set the limit address.
ulong limitAddress = ulong.MaxValue;
if (nBlkIndex != blocks.Count)
{
Block nBlock = blocks[nBlkIndex];
int nextIndex = nBlkIndex + 1;
if (nBlock.Address < currBlock.Address && nextIndex < blocks.Count)
{
limitAddress = blocks[nextIndex].Address;
}
else if (nBlock.Address > currBlock.Address)
{
limitAddress = blocks[nBlkIndex].Address;
}
}
FillBlock(memory, mode, currBlock, limitAddress);
if (currBlock.OpCodes.Count != 0)
{
// Set child blocks. "Branch" is the block the branch instruction
// points to (when taken), "Next" is the block at the next address,
// executed when the branch is not taken. For Unconditional Branches
// (except BL/BLR that are sub calls) or end of executable, Next is null.
OpCode64 lastOp = currBlock.GetLastOp();
bool isCall = IsCall(lastOp);
if (lastOp is IOpCodeBImm op && !isCall)
{
currBlock.Branch = GetBlock((ulong)op.Imm);
}
if (!IsUnconditionalBranch(lastOp) || isCall)
{
currBlock.Next = GetBlock(currBlock.EndAddress);
}
}
// Insert the new block on the list (sorted by address).
if (blocks.Count != 0)
{
Block nBlock = blocks[nBlkIndex];
blocks.Insert(nBlkIndex + (nBlock.Address < currBlock.Address ? 1 : 0), currBlock);
}
else
{
blocks.Add(currBlock);
}
}
return blocks.ToArray();
}
private static bool BinarySearch(List<Block> blocks, ulong address, out int index)
{
index = 0;
int left = 0;
int right = blocks.Count - 1;
while (left <= right)
{
int size = right - left;
int middle = left + (size >> 1);
Block block = blocks[middle];
index = middle;
if (address >= block.Address && address < block.EndAddress)
{
return true;
}
if (address < block.Address)
{
right = middle - 1;
}
else
{
left = middle + 1;
}
}
return false;
}
private static void FillBlock(
MemoryManager memory,
ExecutionMode mode,
Block block,
ulong limitAddress)
{
ulong address = block.Address;
OpCode64 opCode;
do
{
if (address >= limitAddress)
{
break;
}
opCode = DecodeOpCode(memory, address, mode);
block.OpCodes.Add(opCode);
address += (ulong)opCode.OpCodeSizeInBytes;
}
while (!(IsBranch(opCode) || IsException(opCode)));
block.EndAddress = address;
}
private static bool IsBranch(OpCode64 opCode)
{
return opCode is OpCodeBImm64 ||
opCode is OpCodeBReg64 || IsAarch32Branch(opCode);
}
private static bool IsUnconditionalBranch(OpCode64 opCode)
{
return opCode is OpCodeBImmAl64 ||
opCode is OpCodeBReg64 || IsAarch32UnconditionalBranch(opCode);
}
private static bool IsAarch32UnconditionalBranch(OpCode64 opCode)
{
if (!(opCode is OpCode32 op))
{
return false;
}
// Note: On ARM32, most instructions have conditional execution,
// so there's no "Always" (unconditional) branch like on ARM64.
// We need to check if the condition is "Always" instead.
return IsAarch32Branch(op) && op.Cond >= Condition.Al;
}
private static bool IsAarch32Branch(OpCode64 opCode)
{
// Note: On ARM32, most ALU operations can write to R15 (PC),
// so we must consider such operations as a branch in potential as well.
if (opCode is IOpCode32Alu opAlu && opAlu.Rd == RegisterAlias.Aarch32Pc)
{
return true;
}
// Same thing for memory operations. We have the cases where PC is a target
// register (Rt == 15 or (mask & (1 << 15)) != 0), and cases where there is
// a write back to PC (wback == true && Rn == 15), however the later may
// be "undefined" depending on the CPU, so compilers should not produce that.
if (opCode is IOpCode32Mem || opCode is IOpCode32MemMult)
{
int rt, rn;
bool wBack, isLoad;
if (opCode is IOpCode32Mem opMem)
{
rt = opMem.Rt;
rn = opMem.Rn;
wBack = opMem.WBack;
isLoad = opMem.IsLoad;
// For the dual load, we also need to take into account the
// case were Rt2 == 15 (PC).
if (rt == 14 && opMem.Emitter == InstEmit32.Ldrd)
{
rt = RegisterAlias.Aarch32Pc;
}
}
else if (opCode is IOpCode32MemMult opMemMult)
{
const int pcMask = 1 << RegisterAlias.Aarch32Pc;
rt = (opMemMult.RegisterMask & pcMask) != 0 ? RegisterAlias.Aarch32Pc : 0;
rn = opMemMult.Rn;
wBack = opMemMult.PostOffset != 0;
isLoad = opMemMult.IsLoad;
}
else
{
throw new NotImplementedException($"The type \"{opCode.GetType().Name}\" is not implemented on the decoder.");
}
if ((rt == RegisterAlias.Aarch32Pc && isLoad) ||
(rn == RegisterAlias.Aarch32Pc && wBack))
{
return true;
}
}
// Explicit branch instructions.
return opCode is IOpCode32BImm ||
opCode is IOpCode32BReg;
}
private static bool IsCall(OpCode64 opCode)
{
// TODO (CQ): ARM32 support.
return opCode.Emitter == InstEmit.Bl ||
opCode.Emitter == InstEmit.Blr;
}
private static bool IsException(OpCode64 opCode)
{
return opCode.Emitter == InstEmit.Brk ||
opCode.Emitter == InstEmit.Svc ||
opCode.Emitter == InstEmit.Und;
}
public static OpCode64 DecodeOpCode(MemoryManager memory, ulong address, ExecutionMode mode)
{
int opCode = memory.ReadInt32((long)address);
Inst inst;
if (mode == ExecutionMode.Aarch64)
{
inst = OpCodeTable.GetInstA64(opCode);
}
else
{
if (mode == ExecutionMode.Aarch32Arm)
{
inst = OpCodeTable.GetInstA32(opCode);
}
else /* if (mode == ExecutionMode.Aarch32Thumb) */
{
inst = OpCodeTable.GetInstT32(opCode);
}
}
OpCode64 decodedOpCode = new OpCode64(Inst.Undefined, (long)address, opCode);
if (inst.Type != null)
{
decodedOpCode = MakeOpCode(inst.Type, inst, (long)address, opCode);
}
return decodedOpCode;
}
private static OpCode64 MakeOpCode(Type type, Inst inst, long position, int opCode)
{
if (type == null)
{
throw new ArgumentNullException(nameof(type));
}
OpActivator createInstance = _opActivators.GetOrAdd(type, CacheOpActivator);
return (OpCode64)createInstance(inst, position, opCode);
}
private static OpActivator CacheOpActivator(Type type)
{
Type[] argTypes = new Type[] { typeof(Inst), typeof(long), typeof(int) };
DynamicMethod mthd = new DynamicMethod($"Make{type.Name}", type, argTypes);
ILGenerator generator = mthd.GetILGenerator();
generator.Emit(OpCodes.Ldarg_0);
generator.Emit(OpCodes.Ldarg_1);
generator.Emit(OpCodes.Ldarg_2);
generator.Emit(OpCodes.Newobj, type.GetConstructor(argTypes));
generator.Emit(OpCodes.Ret);
return (OpActivator)mthd.CreateDelegate(typeof(OpActivator));
}
}
}