riscii

commit e7aa518e36013753a72d3343b1b4c1c24840f6f6
parent 1b01ffcdd654ab25eb2da6f7a8eff5873ffb9b7f
Author: Ryan Jeffrey <ryan@ryanmj.xyz>
Date:   Tue,  7 Jun 2022 11:56:16 -0700

Register stub

Diffstat:
A
src/register.rs
 | 
65
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 65 insertions(+), 0 deletions(-)
diff --git a/src/register.rs b/src/register.rs
@@ -0,0 +1,65 @@
+/// RISC II register system.
+/// (C) Ryan Jeffrey <ryan@ryanmj.xyz>, 2022
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or (at
+// your option) any later version.
+
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+/// The number of register windows the RISCII supports.
+const NUM_WINDOWS: usize = 6;
+/// The number of local registers per window.
+const NUM_LOCALS: usize = 10;
+/// The number of registers shared with the previous register window (input arguments).
+const NUM_SHARED_PREV: usize = 6;
+/// The number of registers shared with the next register window (output arguments).
+const NUM_SHARED_NEXT: usize = 6;
+/// The number of registers per window.
+const WINDOW_SIZE: usize = NUM_LOCALS + NUM_SHARED_PREV + NUM_SHARED_NEXT;
+/// Number of global registers.
+const NUM_GLOBALS: usize = 10;
+
+// Struct definitions.
+
+/// A RISC II 32bit register.
+struct Register(u32);
+
+/// The CPU's register state.
+struct State {
+    /// Current window pointer, index of the currently active window.
+    cwp: Register,
+    /// Saved window pointer, the index of the youngest window saved in memory.
+    swp: Register,
+    /// Global registers.
+    globals: [Register; NUM_GLOBALS],
+    /// Register window stack.
+    locals: [Register; NUM_WINDOWS * (NUM_LOCALS + NUM_SHARED_NEXT)],
+}
+
+// Struct implementations.
+
+impl State {
+    pub fn new() -> State {
+        State {
+            cwp: 0,
+            swp: 0,
+            globals: [0; NUM_GLOBALS],
+            locals: [0; NUM_WINDOWS * (NUM_LOCALS + NUM_SHARED_NEXT)],
+        }
+    }
+
+    fn inc_cwp(&self) {
+        self.cwp += 1;
+        while self.cwp >= self.swp {
+            // TODO save the top window into memory.
+            self.swp += 1;
+        }
+    }
+}