chore: Modify arm64 instruction formatter and cleanup code for arm64 disassembler

src/BenchmarkDotNet/Disassemblers/Arm64Disassembler.cs

@@ -5,137 +5,6 @@
 
 namespace BenchmarkDotNet.Disassemblers
 {
-    internal struct RegisterValueAccumulator
-    {
-        private enum State
-        {
-            LookingForPattern,
-            ExpectingMovk,
-            ExpectingAdd,
-            LookingForPossibleLdr
-        }
-
-        private State _state;
-        private long _value;
-        private int _expectedMovkShift;
-        private Arm64RegisterId _registerId;
-        private ClrRuntime _runtime;
-
-        public void Init(ClrRuntime runtime)
-        {
-            _state = State.LookingForPattern;
-            _expectedMovkShift = 0;
-            _value = 0;
-            _registerId = Arm64RegisterId.Invalid;
-            _runtime = runtime;
-        }
-
-        public void Feed(Arm64Instruction instruction)
-        {
-            Arm64InstructionDetail details = instruction.Details;
-
-            switch (_state)
-            {
-                case State.LookingForPattern:
-                    if (instruction.Id == Arm64InstructionId.ARM64_INS_MOVZ)
-                    {
-                        _registerId = details.Operands[0].Register.Id;
-                        _value = details.Operands[1].Immediate;
-                        _state = State.ExpectingMovk;
-                        _expectedMovkShift = 16;
-                    }
-                    else if (instruction.Id == Arm64InstructionId.ARM64_INS_ADRP)
-                    {
-                        _registerId = details.Operands[0].Register.Id;
-                        _value = details.Operands[1].Immediate;
-                        _state = State.ExpectingAdd;
-                    }
-                    break;
-                case State.ExpectingMovk:
-                    if (instruction.Id == Arm64InstructionId.ARM64_INS_MOVK &&
-                        details.Operands[0].Register.Id == _registerId &&
-                        details.Operands[1].ShiftOperation == Arm64ShiftOperation.ARM64_SFT_LSL &&
-                        details.Operands[1].ShiftValue == _expectedMovkShift)
-                    {
-                        _value = _value | (instruction.Details.Operands[1].Immediate << details.Operands[1].ShiftValue);
-                        _expectedMovkShift += 16;
-                        break;
-                    }
-                    _state = State.LookingForPossibleLdr;
-                    goto case State.LookingForPossibleLdr;
-                case State.ExpectingAdd:
-                    if (instruction.Id == Arm64InstructionId.ARM64_INS_ADD &&
-                        details.Operands[0].Register.Id == _registerId &&
-                        details.Operands[1].Register.Id == _registerId &&
-                        details.Operands[2].Type == Arm64OperandType.Immediate)
-                    {
-                        _value = _value | instruction.Details.Operands[2].Immediate;
-                        _state = State.LookingForPossibleLdr;
-                    }
-                    break;
-                case State.LookingForPossibleLdr:
-                    if (instruction.Id == Arm64InstructionId.ARM64_INS_LDR &&
-                        details.Operands[1].Type == Arm64OperandType.Memory &&
-                        details.Operands[1].Memory.Base.Id == _registerId && // The source address is in the register we are tracking
-                        details.Operands[1].Memory.Displacement == 0 && // There is no displacement
-                        details.Operands[1].Memory.Index == null) // And there is no extra index register
-                    {
-                        // Simulate the LDR instruction.
-                        long newValue = (long)_runtime.DataTarget.DataReader.ReadPointer((ulong)_value);
-                        _value = newValue;
-                        if (_value == 0)
-                        {
-                            _state = State.LookingForPattern;
-                        }
-                        else
-                        {
-                            // The LDR might have loaded the result in another register
-                            _registerId = details.Operands[0].Register.Id;
-                        }
-                    }
-                    else if (instruction.Id == Arm64InstructionId.ARM64_INS_CBZ ||
-                            instruction.Id == Arm64InstructionId.ARM64_INS_CBNZ ||
-                            instruction.Id == Arm64InstructionId.ARM64_INS_B && details.ConditionCode != Arm64ConditionCode.Invalid)
-                    {
-                        // ignore conditional branches
-                    }
-                    else if (details.BelongsToGroup(Arm64InstructionGroupId.ARM64_GRP_BRANCH_RELATIVE) ||
-                             details.BelongsToGroup(Arm64InstructionGroupId.ARM64_GRP_CALL) ||
-                             details.BelongsToGroup(Arm64InstructionGroupId.ARM64_GRP_JUMP))
-                    {
-                        // We've encountered an unconditional jump or call, the accumulated registers value is not valid anymore
-                        _state = State.LookingForPattern;
-                    }
-                    else if (instruction.Id == Arm64InstructionId.ARM64_INS_MOVZ)
-                    {
-                        // Another constant loading is starting
-                        _state = State.LookingForPattern;
-                        goto case State.LookingForPattern;
-                    }
-                    else
-                    {
-                        // Finally check if the current instruction modified the register that was accumulating the constant
-                        // and reset the state machine in case it did.
-                        foreach (Arm64Register reg in details.AllWrittenRegisters)
-                        {
-                            // Some unexpected instruction overwriting the accumulated register
-                            if (reg.Id == _registerId)
-                            {
-                                _state = State.LookingForPattern;
-                            }
-                        }
-                    }
-                    break;
-            }
-        }
-
-        public bool HasValue => _state == State.ExpectingMovk || _state == State.LookingForPossibleLdr;
-
-        public long Value { get { return _value; } }
-
-        public Arm64RegisterId RegisterId { get { return _registerId; } }
-    }
-
     internal class Arm64Disassembler : ClrMdDisassembler
     {
         protected override IEnumerable<Asm> Decode(byte[] code, ulong startAddress, State state, int depth, ClrMethod currentMethod, DisassemblySyntax syntax)
@@ -147,7 +16,7 @@ protected override IEnumerable<Asm> Decode(byte[] code, ulong startAddress, Stat
                 // disassembled binary code.
                 disassembler.EnableInstructionDetails = true;
                 disassembler.DisassembleSyntax = Map(syntax);
-                RegisterValueAccumulator accumulator = new RegisterValueAccumulator();
+                Arm64RegisterValueAccumulator accumulator = new();
                 accumulator.Init(state.Runtime);
 
                 Arm64Instruction[] instructions = disassembler.Disassemble(code, (long)startAddress);
@@ -324,7 +193,7 @@ private static bool IsLdrLiteral64(uint instr, out int rt, out int offsetBytes)
             return true;
         }
 
-        private static bool TryGetReferencedAddress(Arm64Instruction instruction, RegisterValueAccumulator accumulator, uint pointerSize, out ulong referencedAddress, out bool isReferencedAddressIndirect)
+        private static bool TryGetReferencedAddress(Arm64Instruction instruction, Arm64RegisterValueAccumulator accumulator, uint pointerSize, out ulong referencedAddress, out bool isReferencedAddressIndirect)
         {
             if ((instruction.Id == Arm64InstructionId.ARM64_INS_BR || instruction.Id == Arm64InstructionId.ARM64_INS_BLR) && instruction.Details.Operands[0].Register.Id == accumulator.RegisterId && accumulator.HasValue)
             {

src/BenchmarkDotNet/Disassemblers/Arm64InstructionFormatter.cs

@@ -22,7 +22,8 @@ internal static string Format(Arm64Asm asm, FormatterOptions formatterOptions,
                 FormatInstructionPointer(instruction, formatterOptions, pointerSize, output);
             }
 
-            output.Append(instruction.Mnemonic.ToString().PadRight(formatterOptions.FirstOperandCharIndex));
+            var padRight = Math.Max(formatterOptions.FirstOperandCharIndex, instruction.Mnemonic.Length + 1);
+            output.Append(instruction.Mnemonic.PadRight(padRight));
 
             if (asm.ReferencedAddress.HasValue && !asm.IsReferencedAddressIndirect && symbols.TryGetValue(asm.ReferencedAddress.Value, out var name))
             {

src/BenchmarkDotNet/Disassemblers/Arm64RegisterValueAccumulator.cs

@@ -0,0 +1,135 @@
+using Gee.External.Capstone.Arm64;
+using Microsoft.Diagnostics.Runtime.Interfaces;
+
+namespace BenchmarkDotNet.Disassemblers;
+
+internal struct Arm64RegisterValueAccumulator
+{
+    private enum State
+    {
+        LookingForPattern,
+        ExpectingMovk,
+        ExpectingAdd,
+        LookingForPossibleLdr
+    }
+
+    private State _state;
+    private long _value;
+    private int _expectedMovkShift;
+    private Arm64RegisterId _registerId;
+    private IClrRuntime _runtime;
+
+    public void Init(IClrRuntime runtime)
+    {
+        _state = State.LookingForPattern;
+        _expectedMovkShift = 0;
+        _value = 0;
+        _registerId = Arm64RegisterId.Invalid;
+        _runtime = runtime;
+    }
+
+    public void Feed(Arm64Instruction instruction)
+    {
+        Arm64InstructionDetail details = instruction.Details;
+
+        switch (_state)
+        {
+            case State.LookingForPattern:
+                if (instruction.Id == Arm64InstructionId.ARM64_INS_MOVZ)
+                {
+                    _registerId = details.Operands[0].Register.Id;
+                    _value = details.Operands[1].Immediate;
+                    _state = State.ExpectingMovk;
+                    _expectedMovkShift = 16;
+                }
+                else if (instruction.Id == Arm64InstructionId.ARM64_INS_ADRP)
+                {
+                    _registerId = details.Operands[0].Register.Id;
+                    _value = details.Operands[1].Immediate;
+                    _state = State.ExpectingAdd;
+                }
+                break;
+            case State.ExpectingMovk:
+                if (instruction.Id == Arm64InstructionId.ARM64_INS_MOVK &&
+                    details.Operands[0].Register.Id == _registerId &&
+                    details.Operands[1].ShiftOperation == Arm64ShiftOperation.ARM64_SFT_LSL &&
+                    details.Operands[1].ShiftValue == _expectedMovkShift)
+                {
+                    _value = _value | (instruction.Details.Operands[1].Immediate << details.Operands[1].ShiftValue);
+                    _expectedMovkShift += 16;
+                    break;
+                }
+                _state = State.LookingForPossibleLdr;
+                goto case State.LookingForPossibleLdr;
+            case State.ExpectingAdd:
+                if (instruction.Id == Arm64InstructionId.ARM64_INS_ADD &&
+                    details.Operands[0].Register.Id == _registerId &&
+                    details.Operands[1].Register.Id == _registerId &&
+                    details.Operands[2].Type == Arm64OperandType.Immediate)
+                {
+                    _value = _value | instruction.Details.Operands[2].Immediate;
+                    _state = State.LookingForPossibleLdr;
+                }
+                break;
+            case State.LookingForPossibleLdr:
+                if (instruction.Id == Arm64InstructionId.ARM64_INS_LDR &&
+                    details.Operands[1].Type == Arm64OperandType.Memory &&
+                    details.Operands[1].Memory.Base.Id == _registerId && // The source address is in the register we are tracking
+                    details.Operands[1].Memory.Displacement == 0 && // There is no displacement
+                    details.Operands[1].Memory.Index == null) // And there is no extra index register
+                {
+                    // Simulate the LDR instruction.
+                    long newValue = (long)_runtime.DataTarget.DataReader.ReadPointer((ulong)_value);
+                    _value = newValue;
+                    if (_value == 0)
+                    {
+                        _state = State.LookingForPattern;
+                    }
+                    else
+                    {
+                        // The LDR might have loaded the result in another register
+                        _registerId = details.Operands[0].Register.Id;
+                    }
+                }
+                else if (instruction.Id == Arm64InstructionId.ARM64_INS_CBZ ||
+                        instruction.Id == Arm64InstructionId.ARM64_INS_CBNZ ||
+                        instruction.Id == Arm64InstructionId.ARM64_INS_B && details.ConditionCode != Arm64ConditionCode.Invalid)
+                {
+                    // ignore conditional branches
+                }
+                else if (details.BelongsToGroup(Arm64InstructionGroupId.ARM64_GRP_BRANCH_RELATIVE) ||
+                         details.BelongsToGroup(Arm64InstructionGroupId.ARM64_GRP_CALL) ||
+                         details.BelongsToGroup(Arm64InstructionGroupId.ARM64_GRP_JUMP))
+                {
+                    // We've encountered an unconditional jump or call, the accumulated registers value is not valid anymore
+                    _state = State.LookingForPattern;
+                }
+                else if (instruction.Id == Arm64InstructionId.ARM64_INS_MOVZ)
+                {
+                    // Another constant loading is starting
+                    _state = State.LookingForPattern;
+                    goto case State.LookingForPattern;
+                }
+                else
+                {
+                    // Finally check if the current instruction modified the register that was accumulating the constant
+                    // and reset the state machine in case it did.
+                    foreach (Arm64Register reg in details.AllWrittenRegisters)
+                    {
+                        // Some unexpected instruction overwriting the accumulated register
+                        if (reg.Id == _registerId)
+                        {
+                            _state = State.LookingForPattern;
+                        }
+                    }
+                }
+                break;
+        }
+    }
+
+    public bool HasValue => _state == State.ExpectingMovk || _state == State.LookingForPossibleLdr;
+
+    public long Value { get { return _value; } }
+
+    public Arm64RegisterId RegisterId { get { return _registerId; } }
+}