T16: Implement IT

ARMeilleure/Decoders/Decoder.cs

@@ -195,21 +195,31 @@ namespace ARMeilleure.Decoders
             ulong          limitAddress)
         {
             ulong address = block.Address;
+            int inITBlock = 0;
 
             OpCode opCode;
 
             do
             {
-                if (address >= limitAddress)
+                if (address >= limitAddress && inITBlock == 0)
                 {
                     break;
                 }
 
-                opCode = DecodeOpCode(memory, address, mode);
+                opCode = DecodeOpCode(memory, address, mode, inITBlock > 0);
 
                 block.OpCodes.Add(opCode);
 
                 address += (ulong)opCode.OpCodeSizeInBytes;
+
+                if (opCode is OpCodeT16IfThen it)
+                {
+                    inITBlock = it.IfThenBlockSize;
+                }
+                else if (inITBlock > 0)
+                {
+                    inITBlock--;
+                }
             }
             while (!(IsBranch(opCode) || IsException(opCode)));
 
@@ -315,7 +325,7 @@ namespace ARMeilleure.Decoders
                    opCode.Instruction.Name == InstName.Und;
         }
 
-        public static OpCode DecodeOpCode(IMemoryManager memory, ulong address, ExecutionMode mode, bool inITBlock = false)
+        public static OpCode DecodeOpCode(IMemoryManager memory, ulong address, ExecutionMode mode, bool inITBlock)
         {
             int opCode = memory.Read<int>(address);
 

ARMeilleure/Decoders/OpCodeT16IfThen.cs

@@ -0,0 +1,34 @@
+using System.Collections.Generic;
+using System.Reflection.Emit;
+
+namespace ARMeilleure.Decoders
+{
+    class OpCodeT16IfThen : OpCodeT16
+    {
+        public Condition[] IfThenBlockConds { get; }
+
+        public int IfThenBlockSize { get { return IfThenBlockConds.Length; } }
+
+        public new static OpCode Create(InstDescriptor inst, ulong address, int opCode, bool inITBlock) => new OpCodeT16IfThen(inst, address, opCode, inITBlock);
+
+        public OpCodeT16IfThen(InstDescriptor inst, ulong address, int opCode, bool inITBlock) : base(inst, address, opCode, inITBlock)
+        {
+            List<Condition> conds = new();
+
+            int cond = (opCode >> 4) & 0xf;
+            int mask = opCode & 0xf;
+
+            conds.Add((Condition)cond);
+
+            while ((mask & 7) != 0)
+            {
+                int newLsb = (mask >> 3) & 1;
+                cond = (cond & 0xe) | newLsb;
+                mask <<= 1;
+                conds.Add((Condition)cond);
+            }
+
+            IfThenBlockConds = conds.ToArray();
+        }
+    }
+}

ARMeilleure/Decoders/OpCodeTable.cs

@@ -1037,12 +1037,13 @@ namespace ARMeilleure.Decoders
             SetT16("101110x1xxxxxxxx", InstName.Cbnz,   InstEmit32.Cbnz,    OpCodeT16BImmCmp.Create);
             SetT16("1011110xxxxxxxxx", InstName.Pop,    InstEmit32.Ldm,     OpCodeT16MemStack.Create);
             SetT16("10111111xxxx0000", InstName.Nop,    InstEmit32.Nop,     OpCodeT16.Create);
+            SetT16("10111111xxxx>>>>", InstName.It,     InstEmit32.It,      OpCodeT16IfThen.Create);
             SetT16("11000xxxxxxxxxxx", InstName.Stm,    InstEmit32.Stm,     OpCodeT16MemMult.Create);
             SetT16("11001xxxxxxxxxxx", InstName.Ldm,    InstEmit32.Ldm,     OpCodeT16MemMult.Create);
             SetT16("1101<<<xxxxxxxxx", InstName.B,      InstEmit32.B,       OpCodeT16BImm8.Create);
             SetT16("11011111xxxxxxxx", InstName.Svc,    InstEmit32.Svc,     OpCodeT16Exception.Create);
             SetT16("11100xxxxxxxxxxx", InstName.B,      InstEmit32.B,       OpCodeT16BImm11.Create);
-            #endregion
+#endregion
 
             FillFastLookupTable(InstA32FastLookup, AllInstA32, ToFastLookupIndexA);
             FillFastLookupTable(InstT32FastLookup, AllInstT32, ToFastLookupIndexT);

ARMeilleure/Instructions/InstEmitFlow32.cs

@@ -100,5 +100,12 @@ namespace ARMeilleure.Instructions
                 context.BranchIfFalse(lblTarget, value);
             }
         }
+
+        public static void It(ArmEmitterContext context)
+        {
+            OpCodeT16IfThen op = (OpCodeT16IfThen)context.CurrOp;
+
+            context.IfThenBlockState = op.IfThenBlockConds;
+        }
     }
 }

ARMeilleure/Instructions/InstName.cs

@@ -48,6 +48,7 @@ namespace ARMeilleure.Instructions
         Extr,
         Hint,
         Isb,
+        It,
         Ldar,
         Ldaxp,
         Ldaxr,

ARMeilleure/Translation/ArmEmitterContext.cs

@@ -9,6 +9,7 @@ using ARMeilleure.State;
 using ARMeilleure.Translation.PTC;
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Reflection;
 using static ARMeilleure.IntermediateRepresentation.Operand.Factory;
 
@@ -54,6 +55,10 @@ namespace ARMeilleure.Translation
         public bool HighCq { get; }
         public Aarch32Mode Mode { get; }
 
+        public bool IsInIfThenBlock { get { return IfThenBlockState.Length > 0; } }
+        public Condition CurrentIfThenBlockCond { get { return IfThenBlockState[0]; } }
+        public Condition[] IfThenBlockState { get; set; }
+
         public ArmEmitterContext(
             IMemoryManager memory,
             EntryTable<uint> countTable,
@@ -196,5 +201,13 @@ namespace ARMeilleure.Translation
 
             return default;
         }
+
+        public void AdvanceIfThenBlockState()
+        {
+            if (IsInIfThenBlock)
+            {
+                IfThenBlockState = IfThenBlockState.Skip(1).ToArray();
+            }
+        }
     }
 }

ARMeilleure/Translation/Translator.cs

@@ -380,6 +380,15 @@ namespace ARMeilleure.Translation
 
                         Operand lblPredicateSkip = default;
 
+                        if (context.IsInIfThenBlock)
+                        {
+                            lblPredicateSkip = Label();
+
+                            InstEmitFlowHelper.EmitCondBranch(context, lblPredicateSkip, context.CurrentIfThenBlockCond.Invert());
+
+                            context.AdvanceIfThenBlockState();
+                        }
+
                         if (opCode is OpCode32 op && op.Cond < Condition.Al)
                         {
                             lblPredicateSkip = Label();