From a22b30c2942c68a1d31dc20e2f3ee199a749fa23 Mon Sep 17 00:00:00 2001
From: arthurchan35 <arthurchan35@gmail.com>
Date: Mon, 12 Nov 2018 06:04:54 +0800
Subject: [PATCH] add blx_reg for A32

---
 ChocolArm64/Decoders32/A32OpCodeBReg.cs       | 14 +++++
 .../Instructions32/A32InstInterpretFlow.cs    | 53 +++++++++++++++++--
 ChocolArm64/OpCodeTable.cs                    |  1 +
 3 files changed, 65 insertions(+), 3 deletions(-)
 create mode 100644 ChocolArm64/Decoders32/A32OpCodeBReg.cs

diff --git a/ChocolArm64/Decoders32/A32OpCodeBReg.cs b/ChocolArm64/Decoders32/A32OpCodeBReg.cs
new file mode 100644
index 0000000000..eee555c034
--- /dev/null
+++ b/ChocolArm64/Decoders32/A32OpCodeBReg.cs
@@ -0,0 +1,14 @@
+using ChocolArm64.Instructions;
+
+namespace ChocolArm64.Decoders32
+{
+    class A32OpCodeBReg : A32OpCode
+    {
+        public int Rm { get; private set; }
+
+        public A32OpCodeBReg(Inst inst, long position, int opCode) : base(inst, position, opCode)
+        {
+            Rm = (opCode >> 0) & 0xf;
+        }
+    }
+}
\ No newline at end of file
diff --git a/ChocolArm64/Instructions32/A32InstInterpretFlow.cs b/ChocolArm64/Instructions32/A32InstInterpretFlow.cs
index cdf7e4c6af..b839a6d402 100644
--- a/ChocolArm64/Instructions32/A32InstInterpretFlow.cs
+++ b/ChocolArm64/Instructions32/A32InstInterpretFlow.cs
@@ -21,15 +21,23 @@ namespace ChocolArm64.Instructions32
 
         public static void Bl(CpuThreadState state, MemoryManager memory, OpCode64 opCode)
         {
-            Blx(state, memory, opCode, false);
+            Blx_Imm(state, memory, opCode, false);
         }
 
         public static void Blx(CpuThreadState state, MemoryManager memory, OpCode64 opCode)
         {
-            Blx(state, memory, opCode, true);
+            switch (opCode)
+            {
+                case A32OpCodeBImmAl op:
+                    Blx_Imm(state, memory, op, true);
+                    break;
+                case A32OpCodeBReg op:
+                    Blx_Reg(state, memory, op);
+                    break;
+            }
         }
 
-        public static void Blx(CpuThreadState state, MemoryManager memory, OpCode64 opCode, bool x)
+        private static void Blx_Imm(CpuThreadState state, MemoryManager memory, OpCode64 opCode, bool x)
         {
             A32OpCodeBImmAl op = (A32OpCodeBImmAl)opCode;
 
@@ -60,11 +68,50 @@ namespace ChocolArm64.Instructions32
             }
         }
 
+        private static void Blx_Reg(CpuThreadState state, MemoryManager memory, OpCode64 opCode)
+        {
+            A32OpCodeBReg op = (A32OpCodeBReg)opCode;
+            if (IsConditionTrue(state, op.Cond))
+            {
+                uint pc = GetPc(state);
+                if (state.Thumb)
+                {
+                    state.R14 = (pc - 2U) | 1;
+                }
+                else
+                {
+                    state.R14 = pc - 4U;
+                }
+                BXWritePC(state, GetReg(state, op.Rm));
+            }
+        }
+
         private static void BranchWritePc(CpuThreadState state, uint pc)
         {
             state.R15 = state.Thumb
                 ? pc & ~1U
                 : pc & ~3U;
         }
+
+        private static void BXWritePC(CpuThreadState state, uint pc)
+        {
+            if ((pc & 1U) == 1)
+            {
+                state.Thumb = true;
+                state.R15 = pc & ~1U;
+            }
+            else
+            {
+                state.Thumb = false;
+                // For branches to an unaligned PC counter in A32 state, the processor takes the branch
+                // and does one of:
+                // * Forces the address to be aligned
+                // * Leaves the PC unaligned, meaning the target generates a PC Alignment fault.
+                if ((pc & 2U) == 2 /*&& ConstrainUnpredictableBool()*/)
+                {
+                    state.R15 = pc & ~2U;
+                }
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/ChocolArm64/OpCodeTable.cs b/ChocolArm64/OpCodeTable.cs
index 6b1a724d55..263823ab59 100644
--- a/ChocolArm64/OpCodeTable.cs
+++ b/ChocolArm64/OpCodeTable.cs
@@ -17,6 +17,7 @@ namespace ChocolArm64
             SetA32("<<<<1010xxxxxxxxxxxxxxxxxxxxxxxx", A32InstInterpret.B,      typeof(A32OpCodeBImmAl));
             SetA32("<<<<1011xxxxxxxxxxxxxxxxxxxxxxxx", A32InstInterpret.Bl,     typeof(A32OpCodeBImmAl));
             SetA32("1111101xxxxxxxxxxxxxxxxxxxxxxxxx", A32InstInterpret.Blx,    typeof(A32OpCodeBImmAl));
+            SetA32("<<<<000100101111111111110011xxxx", A32InstInterpret.Blx,    typeof(A32OpCodeBReg));
 #endregion
 
 #region "OpCode Table (AArch64)"