initial cpu structure :thonk:

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

src/cpu/psr.hh

@@ -0,0 +1,55 @@
+#pragma once
+
+#include "bits.hh"
+#include "utility.hh"
+#include <cstdint>
+
+static constexpr uint32_t PSR_CLEAR_RESERVED = 0xf00000ff;
+static constexpr uint32_t PSR_CLEAR_MODE     = 0x0b00000;
+
+class Psr {
+    uint32_t psr;
+
+  public:
+    // clear the reserved bits i.e, [8:27]
+    Psr(uint32_t raw) { psr = raw & PSR_CLEAR_RESERVED; }
+
+    // Mode : [4:0]
+    Mode mode() const { return static_cast<Mode>(psr & ~PSR_CLEAR_MODE); }
+    void set_mode(Mode mode) {
+        psr &= PSR_CLEAR_MODE;
+        psr |= static_cast<uint32_t>(mode);
+    }
+
+    // State : [5]
+    bool state() const { return get_nth_bit(psr, 5); }
+    void set_state(State state) {
+        chg_nth_bit(psr, 5, static_cast<bool>(state));
+    }
+
+#define GET_SET_NTH_BIT_FUNCTIONS(name, n)                                     \
+    bool name() const { return get_nth_bit(psr, n); }                          \
+    void set_##name(bool val) { chg_nth_bit(psr, n, val); }
+
+    // FIQ disable : [6]
+    GET_SET_NTH_BIT_FUNCTIONS(fiq_disabled, 6)
+
+    // IRQ disable : [7]
+    GET_SET_NTH_BIT_FUNCTIONS(irq_disabled, 7)
+
+    // Reserved bits : [27:8]
+
+    // Overflow flag : [28]
+    GET_SET_NTH_BIT_FUNCTIONS(v, 28);
+
+    // Carry flag : [29]
+    GET_SET_NTH_BIT_FUNCTIONS(c, 29);
+
+    // Zero flag : [30]
+    GET_SET_NTH_BIT_FUNCTIONS(z, 30);
+
+    // Negative flag : [30]
+    GET_SET_NTH_BIT_FUNCTIONS(n, 31);
+
+#undef GET_SET_NTH_BIT_FUNCTIONS
+};