From 691e4139fa920d4ce103e13f63af5a480faf7e5c Mon Sep 17 00:00:00 2001
From: bunnei <bunneidev@gmail.com>
Date: Tue, 2 Aug 2016 19:52:17 -0400
Subject: [PATCH] arm: Implement B/BL/BX instructions.

---
 src/CMakeLists.txt                            |  1 +
 src/frontend/decoder/arm.h                    |  6 +-
 .../translate/translate_arm/branch.cpp        | 65 +++++++++++++++++++
 .../translate/translate_arm/translate_arm.h   |  8 +++
 4 files changed, 77 insertions(+), 3 deletions(-)
 create mode 100644 src/frontend/translate/translate_arm/branch.cpp

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0f160e42..31331121 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -16,6 +16,7 @@ set(SRCS
     frontend/ir/ir_emitter.cpp
     frontend/translate/translate.cpp
     frontend/translate/translate_arm.cpp
+    frontend/translate/translate_arm/branch.cpp
     frontend/translate/translate_arm/data_processing.cpp
     frontend/translate/translate_arm/exception_generating.cpp
     frontend/translate/translate_arm/extension.cpp
diff --git a/src/frontend/decoder/arm.h b/src/frontend/decoder/arm.h
index e8bbe5d8..0367b8d8 100644
--- a/src/frontend/decoder/arm.h
+++ b/src/frontend/decoder/arm.h
@@ -66,9 +66,9 @@ boost::optional<const ArmMatcher<V>&> DecodeArm(u32 instruction) {
         // Branch instructions
         //INST(&V::arm_BLX_imm,     "BLX (imm)",           "1111101hvvvvvvvvvvvvvvvvvvvvvvvv"), // v5
         //INST(&V::arm_BLX_reg,     "BLX (reg)",           "cccc000100101111111111110011mmmm"), // v5
-        //INST(&V::arm_B,           "B",                   "cccc1010vvvvvvvvvvvvvvvvvvvvvvvv"), // all
-        //INST(&V::arm_BL,          "BL",                  "cccc1011vvvvvvvvvvvvvvvvvvvvvvvv"), // all
-        //INST(&V::arm_BX,          "BX",                  "cccc000100101111111111110001mmmm"), // v4T
+        INST(&V::arm_B,           "B",                   "cccc1010vvvvvvvvvvvvvvvvvvvvvvvv"), // all
+        INST(&V::arm_BL,          "BL",                  "cccc1011vvvvvvvvvvvvvvvvvvvvvvvv"), // all
+        INST(&V::arm_BX,          "BX",                  "cccc000100101111111111110001mmmm"), // v4T
         //INST(&V::arm_BXJ,         "BXJ",                 "cccc000100101111111111110010mmmm"), // v5J
 
         // Coprocessor instructions
diff --git a/src/frontend/translate/translate_arm/branch.cpp b/src/frontend/translate/translate_arm/branch.cpp
new file mode 100644
index 00000000..c2703d71
--- /dev/null
+++ b/src/frontend/translate/translate_arm/branch.cpp
@@ -0,0 +1,65 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2016 MerryMage
+ * This software may be used and distributed according to the terms of the GNU
+ * General Public License version 2 or any later version.
+ */
+
+#include "common/bit_util.h"
+
+#include "translate_arm.h"
+
+namespace Dynarmic {
+namespace Arm {
+
+bool ArmTranslatorVisitor::arm_B(Cond cond, Imm24 imm24)
+{
+    s32 imm32 = Common::SignExtend<26, s32>(imm24 << 2) + 8;
+    // B <cond> <label>
+    if (ConditionPassed(cond))
+    {
+        auto new_location = ir.current_location.AdvancePC(imm32);
+        ir.SetTerm(IR::Term::LinkBlock{ new_location });
+        return false;
+    }
+    return true;
+}
+
+bool ArmTranslatorVisitor::arm_BL(Cond cond, Imm24 imm24)
+{
+    s32 imm32 = Common::SignExtend<26, s32>(imm24 << 2) + 8;
+    // BL <cond> <label>
+    if (ConditionPassed(cond))
+    {
+        ir.SetRegister(Reg::LR, ir.Imm32(ir.current_location.PC() + 4));
+        auto new_location = ir.current_location.AdvancePC(imm32);
+        ir.SetTerm(IR::Term::LinkBlock{ new_location });
+        return false;
+    }
+    return true;
+}
+
+bool ArmTranslatorVisitor::arm_BLX_imm(Cond cond, Imm24 imm24)
+{
+    return InterpretThisInstruction();
+}
+
+bool ArmTranslatorVisitor::arm_BLX_reg(Cond cond, Reg m) {
+    return InterpretThisInstruction();
+}
+
+bool ArmTranslatorVisitor::arm_BX(Cond cond, Reg m) {
+    // BX <cond> <Rm>
+    if (ConditionPassed(cond)) {
+        ir.BXWritePC(ir.GetRegister(m));
+        ir.SetTerm(IR::Term::ReturnToDispatch{});
+        return false;
+    }
+    return true;
+}
+
+bool ArmTranslatorVisitor::arm_BXJ(Cond cond, Reg m) {
+    return InterpretThisInstruction();
+}
+
+} // namespace Arm
+} // namespace Dynarmic
diff --git a/src/frontend/translate/translate_arm/translate_arm.h b/src/frontend/translate/translate_arm/translate_arm.h
index f24a6e0b..12bd6499 100644
--- a/src/frontend/translate/translate_arm/translate_arm.h
+++ b/src/frontend/translate/translate_arm/translate_arm.h
@@ -62,6 +62,14 @@ struct ArmTranslatorVisitor final {
     IREmitter::ResultAndCarry EmitRegShift(IR::Value value, ShiftType type, IR::Value amount, IR::Value carry_in);
     IR::Value SignZeroExtendRor(Reg m, SignExtendRotation rotate);
 
+    // Branch instructions
+    bool arm_B(Cond cond, Imm24 imm24);
+    bool arm_BL(Cond cond, Imm24 imm24);
+    bool arm_BLX_imm(Cond cond, Imm24 imm24);
+    bool arm_BLX_reg(Cond cond, Reg m);
+    bool arm_BX(Cond cond, Reg m);
+    bool arm_BXJ(Cond cond, Reg m);
+
     // Data processing instructions
     bool arm_ADC_imm(Cond cond, bool S, Reg n, Reg d, int rotate, Imm8 imm8);
     bool arm_ADC_reg(Cond cond, bool S, Reg n, Reg d, Imm5 imm5, ShiftType shift, Reg m);