tests: add execution tests

all but data processing

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

src/cpu/cpu-impl.hh

@@ -0,0 +1,57 @@
+#pragma once
+
+#include "bus.hh"
+#include "cpu/arm/instruction.hh"
+#include "cpu/psr.hh"
+
+#include <cstdint>
+
+class CpuImpl {
+  public:
+    CpuImpl(const Bus& bus) noexcept;
+
+    void step();
+    void chg_mode(const Mode to);
+    void exec_arm(const arm::Instruction instruction);
+
+    static constexpr uint8_t GPR_COUNT = 16;
+
+    static constexpr uint8_t GPR_FIQ_FIRST     = 8;
+    static constexpr uint8_t GPR_SVC_FIRST     = 13;
+    static constexpr uint8_t GPR_ABT_FIRST     = 13;
+    static constexpr uint8_t GPR_IRQ_FIRST     = 13;
+    static constexpr uint8_t GPR_UND_FIRST     = 13;
+    static constexpr uint8_t GPR_SYS_USR_FIRST = 8;
+
+    std::shared_ptr<Bus> bus;
+    std::array<uint32_t, GPR_COUNT> gpr; // general purpose registers
+
+    Psr cpsr; // current program status register
+    Psr spsr; // status program status register
+
+    static constexpr uint8_t PC_INDEX = 15;
+    static_assert(PC_INDEX < GPR_COUNT);
+
+    uint32_t& pc = gpr[PC_INDEX];
+
+    bool is_flushed;
+
+    struct {
+        std::array<uint32_t, GPR_COUNT - GPR_FIQ_FIRST - 1> fiq;
+        std::array<uint32_t, GPR_COUNT - GPR_SVC_FIRST - 1> svc;
+        std::array<uint32_t, GPR_COUNT - GPR_ABT_FIRST - 1> abt;
+        std::array<uint32_t, GPR_COUNT - GPR_IRQ_FIRST - 1> irq;
+        std::array<uint32_t, GPR_COUNT - GPR_UND_FIRST - 1> und;
+
+        // visible registers before the mode switch
+        std::array<uint32_t, GPR_COUNT - GPR_SYS_USR_FIRST> old;
+    } gpr_banked; // banked general purpose registers
+
+    struct {
+        Psr fiq;
+        Psr svc;
+        Psr abt;
+        Psr irq;
+        Psr und;
+    } spsr_banked; // banked saved program status registers
+};