initial cpu structure :thonk:

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>
2023-08-27 21:40:55 +05:30
parent ad64b1e8d1
commit 84c68a4e00
20 changed files with 449 additions and 42 deletions
--- a/src/cpu/cpu.cc
+++ b/src/cpu/cpu.cc
@@ -1,6 +1,104 @@
 #include "cpu.hh"
-#include <iostream>
+#include "cpu/utility.hh"
+#include <algorithm>
+#include <cstdio>

-namespace cpu {
-void run() { std::cout << "Hello from inside the CPU" << std::endl; }
-} // namespace cpu
+/* change modes */
+void
+Cpu::chg_mode(Mode from, Mode to) {
+    if (from == to)
+        return;
+
+/* TODO: replace visible registers with view once I understand how to
+ * concatenate views */
+#define STORE_BANKED(mode, MODE)                                               \
+    std::copy(gpr + GPR_##MODE##_BANKED_FIRST,                                 \
+              gpr + GPR_##MODE##_BANKED_FIRST + GPR_##MODE##_BANKED_COUNT,     \
+              gpr_banked.mode)
+
+    switch (from) {
+        case Mode::Fiq:
+            STORE_BANKED(fiq, FIQ);
+            spsr_banked.fiq = spsr;
+            break;
+
+        case Mode::Supervisor:
+            STORE_BANKED(svc, SVC);
+            spsr_banked.svc = spsr;
+            break;
+
+        case Mode::Abort:
+            STORE_BANKED(abt, ABT);
+            spsr_banked.abt = spsr;
+            break;
+
+        case Mode::Irq:
+            STORE_BANKED(irq, IRQ);
+            spsr_banked.irq = spsr;
+            break;
+
+        case Mode::Undefined:
+            STORE_BANKED(und, UND);
+            spsr_banked.und = spsr;
+            break;
+
+        case Mode::User:
+        case Mode::System:
+            STORE_BANKED(old, SYS_USR);
+            break;
+    }
+
+#define RESTORE_BANKED(mode, MODE)                                             \
+    std::copy(gpr_banked.mode,                                                 \
+              gpr_banked.mode + GPR_##MODE##_BANKED_COUNT,                     \
+              gpr + GPR_##MODE##_BANKED_FIRST)
+
+    switch (to) {
+        case Mode::Fiq:
+            RESTORE_BANKED(fiq, FIQ);
+            spsr = spsr_banked.fiq;
+            break;
+
+        case Mode::Supervisor:
+            RESTORE_BANKED(svc, SVC);
+            spsr = spsr_banked.svc;
+            break;
+
+        case Mode::Abort:
+            RESTORE_BANKED(abt, ABT);
+            spsr = spsr_banked.abt;
+            break;
+
+        case Mode::Irq:
+            RESTORE_BANKED(irq, IRQ);
+            spsr = spsr_banked.irq;
+            break;
+
+        case Mode::Undefined:
+            RESTORE_BANKED(und, UND);
+            spsr = spsr_banked.und;
+            break;
+
+        case Mode::User:
+        case Mode::System:
+            STORE_BANKED(old, SYS_USR);
+            break;
+    }
+
+#undef RESTORE_BANKED
+
+    cpsr.set_mode(to);
+}
+
+//  set register
+inline uint32_t&
+Cpu::operator[](size_t idx) {
+    // avoid unneeded complexity like index checks
+    return gpr[idx];
+}
+
+// get register
+inline const uint32_t&
+Cpu::operator[](size_t idx) const {
+    return gpr[idx];
+}