A32: Implement ASIMD VSWP

A trivial one to implement, this just swaps the contents of two
registers in place.

src/frontend/A32/translate/impl/asimd_two_regs_misc.cpp

@@ -0,0 +1,43 @@
+/* This file is part of the dynarmic project.
+ * Copyright (c) 2020 MerryMage
+ * SPDX-License-Identifier: 0BSD
+ */
+
+#include "common/bit_util.h"
+
+#include "frontend/A32/translate/impl/translate_arm.h"
+
+namespace Dynarmic::A32 {
+namespace {
+ExtReg ToExtRegD(size_t base, bool bit) {
+    return ExtReg::D0 + (base + (bit ? 16 : 0));
+}
+} // Anonymous namespace
+
+bool ArmTranslatorVisitor::asimd_VSWP(bool D, size_t Vd, bool Q, bool M, size_t Vm) {
+    if (Q && (Common::Bit<0>(Vd) || Common::Bit<0>(Vm))) {
+        return UndefinedInstruction();
+    }
+
+    // Swapping the same register results in the same contents.
+    const auto d = ToExtRegD(Vd, D);
+    const auto m = ToExtRegD(Vm, M);
+    if (d == m) {
+        return true;
+    }
+
+    const size_t regs = Q ? 2 : 1;
+    for (size_t i = 0; i < regs; i++) {
+        const auto d_index = d + i;
+        const auto m_index = m + i;
+
+        const auto reg_d = ir.GetExtendedRegister(d_index);
+        const auto reg_m = ir.GetExtendedRegister(m_index);
+
+        ir.SetExtendedRegister(m_index, reg_d);
+        ir.SetExtendedRegister(d_index, reg_m);
+    }
+
+    return true;
+}
+} // namespace Dynarmic::A32