From 1af5bef32c9cb58a9677851a7b192b474b1eb110 Mon Sep 17 00:00:00 2001
From: MerryMage <MerryMage@users.noreply.github.com>
Date: Sun, 7 Aug 2016 20:19:37 +0100
Subject: [PATCH] TranslateArm: Implement BLX (imm), BLX (reg) and BXJ

---
 src/frontend/arm_types.h                      |  4 +-
 .../translate/translate_arm/branch.cpp        | 44 +++++++++++--------
 .../translate/translate_arm/translate_arm.h   |  2 +-
 tests/arm/fuzz_arm.cpp                        | 14 ++++++
 4 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/src/frontend/arm_types.h b/src/frontend/arm_types.h
index a4bf94f7..1b419b87 100644
--- a/src/frontend/arm_types.h
+++ b/src/frontend/arm_types.h
@@ -119,8 +119,8 @@ struct LocationDescriptor {
         return LocationDescriptor(new_arm_pc, tflag, eflag, fpscr);
     }
 
-    LocationDescriptor AdvancePC(s32 amount) const {
-        return LocationDescriptor(arm_pc + amount, tflag, eflag, fpscr);
+    LocationDescriptor AdvancePC(int amount) const {
+        return LocationDescriptor(static_cast<u32>(arm_pc + amount), tflag, eflag, fpscr);
     }
 
     LocationDescriptor SetTFlag(bool new_tflag) const {
diff --git a/src/frontend/translate/translate_arm/branch.cpp b/src/frontend/translate/translate_arm/branch.cpp
index c2703d71..4a061b07 100644
--- a/src/frontend/translate/translate_arm/branch.cpp
+++ b/src/frontend/translate/translate_arm/branch.cpp
@@ -11,12 +11,10 @@
 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))
-    {
+bool ArmTranslatorVisitor::arm_B(Cond cond, Imm24 imm24) {
+    u32 imm32 = Common::SignExtend<26, u32>(imm24 << 2) + 8;
+    // B <label>
+    if (ConditionPassed(cond)) {
         auto new_location = ir.current_location.AdvancePC(imm32);
         ir.SetTerm(IR::Term::LinkBlock{ new_location });
         return false;
@@ -24,12 +22,10 @@ bool ArmTranslatorVisitor::arm_B(Cond cond, Imm24 imm24)
     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))
-    {
+bool ArmTranslatorVisitor::arm_BL(Cond cond, Imm24 imm24) {
+    u32 imm32 = Common::SignExtend<26, u32>(imm24 << 2) + 8;
+    // BL <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 });
@@ -38,17 +34,28 @@ bool ArmTranslatorVisitor::arm_BL(Cond cond, Imm24 imm24)
     return true;
 }
 
-bool ArmTranslatorVisitor::arm_BLX_imm(Cond cond, Imm24 imm24)
-{
-    return InterpretThisInstruction();
+bool ArmTranslatorVisitor::arm_BLX_imm(bool H, Imm24 imm24) {
+    u32 imm32 = Common::SignExtend<26, u32>((imm24 << 2)) + (H ? 2 : 0) + 8;
+    // BLX <label>
+    ir.SetRegister(Reg::LR, ir.Imm32(ir.current_location.PC() + 4));
+    auto new_location = ir.current_location.AdvancePC(imm32).SetTFlag(true);
+    ir.SetTerm(IR::Term::LinkBlock{ new_location });
+    return false;
 }
 
 bool ArmTranslatorVisitor::arm_BLX_reg(Cond cond, Reg m) {
-    return InterpretThisInstruction();
+    // BLX <Rm>
+    if (ConditionPassed(cond)) {
+        ir.SetRegister(Reg::LR, ir.Imm32(ir.current_location.PC() + 4));
+        ir.BXWritePC(ir.GetRegister(m));
+        ir.SetTerm(IR::Term::ReturnToDispatch{});
+        return false;
+    }
+    return true;
 }
 
 bool ArmTranslatorVisitor::arm_BX(Cond cond, Reg m) {
-    // BX <cond> <Rm>
+    // BX <Rm>
     if (ConditionPassed(cond)) {
         ir.BXWritePC(ir.GetRegister(m));
         ir.SetTerm(IR::Term::ReturnToDispatch{});
@@ -58,7 +65,8 @@ bool ArmTranslatorVisitor::arm_BX(Cond cond, Reg m) {
 }
 
 bool ArmTranslatorVisitor::arm_BXJ(Cond cond, Reg m) {
-    return InterpretThisInstruction();
+    // Jazelle not supported
+    return arm_BX(cond, m);
 }
 
 } // namespace Arm
diff --git a/src/frontend/translate/translate_arm/translate_arm.h b/src/frontend/translate/translate_arm/translate_arm.h
index 7a247529..05c3ec93 100644
--- a/src/frontend/translate/translate_arm/translate_arm.h
+++ b/src/frontend/translate/translate_arm/translate_arm.h
@@ -65,7 +65,7 @@ struct ArmTranslatorVisitor final {
     // 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_imm(bool H, Imm24 imm24);
     bool arm_BLX_reg(Cond cond, Reg m);
     bool arm_BX(Cond cond, Reg m);
     bool arm_BXJ(Cond cond, Reg m);
diff --git a/tests/arm/fuzz_arm.cpp b/tests/arm/fuzz_arm.cpp
index 4d80f430..10397f70 100644
--- a/tests/arm/fuzz_arm.cpp
+++ b/tests/arm/fuzz_arm.cpp
@@ -560,6 +560,20 @@ TEST_CASE("Fuzz ARM data processing instructions", "[JitX64]") {
     }
 }
 
+TEST_CASE("Fuzz ARM branch instructions", "[JitX64]") {
+    const std::array<InstructionGenerator, 6> instructions = {{
+        InstructionGenerator("1111101hvvvvvvvvvvvvvvvvvvvvvvvv"),
+        InstructionGenerator("cccc000100101111111111110011mmmm"),
+        InstructionGenerator("cccc1010vvvvvvvvvvvvvvvvvvvvvvvv"),
+        InstructionGenerator("cccc1011vvvvvvvvvvvvvvvvvvvvvvvv"),
+        InstructionGenerator("cccc000100101111111111110001mmmm"),
+        InstructionGenerator("cccc000100101111111111110010mmmm"),
+    }};
+    FuzzJitArm(1, 1, 10000, [&instructions]() -> u32 {
+        return instructions[RandInt<size_t>(0, instructions.size() - 1)].Generate();
+    });
+}
+
 TEST_CASE("Fuzz ARM reversal instructions", "[JitX64]") {
     const auto is_valid = [](u32 instr) -> bool {
         // R15 is UNPREDICTABLE