common: instruction encoding via macro and trait ugly hack works

2025-06-15 13:56:45 +01:00
parent 4e1d4d784f
commit 977a621d5f
2 changed files with 127 additions and 66 deletions
@@ -0,0 +1,62 @@
+use crate::common::instructions::Register;
+
+use super::Instruction;
+
+/// Not to be used directly, just call [`Instruction::encode`].
+pub trait Encode {
+    fn encode(self, opcode: u8) -> u32;
+}
+
+/// Encodes a zero argument instruction.
+fn encode_no_args(opcode: u8) -> u32 {
+    let opcode = u32::from(opcode);
+    let sr1 = Register::NoReg as u32;
+    let sr2 = Register::NoReg as u32;
+    let dr = Register::NoReg as u32;
+    let shamt = 0;
+
+    (opcode << 26) | (sr1 << 21) | (sr2 << 16) | (dr << 11) | (shamt << 6)
+}
+
+/// Expands to a match statement that calls encode on instructions that implement [`Encode`]:
+///
+/// # Usage
+///
+/// ```rs
+/// encode_instruction!(self, with_args: [...], no_args: [...], special: [...] )
+/// ```
+macro_rules! encode_instruction {
+    ($self:expr, with_args: [$($variant:ident),+ $(,)?], no_args: [$($no_arg_variant:ident),* $(,)?] $(, special: [$($special:pat => $body:expr),* $(,)?])?) => {
+        match $self {
+            $(
+                Instruction::$variant(args) => args.encode($self.opcode()),
+            )+
+            $(
+                Instruction::$no_arg_variant => encode_no_args($self.opcode()),
+            )*
+            $($(
+                $special => $body,
+            )*)?
+        }
+    };
+}
+
+impl Encode for Instruction {
+    fn encode(self, _: u8) -> u32 {
+        encode_instruction!(
+            self,
+            with_args: [
+                Mov, MovSigned, LoadByte, LoadByteSigned, LoadHalfword,
+                LoadHalfwordSigned, LoadWord, StoreByte, StoreHalfword,
+                StoreWord, LoadLowerImmediate, LoadUpperImmediate, Jump,
+                JumpEq, JumpNeq, JumpGt, JumpGe, JumpLt, JumpLe, Compare,
+                Add, Sub, Increment, Decrement, ShiftLeft, ShiftRight,
+                And, Or, Not, Xor, Nand, Nor, Xnor
+            ],
+            no_args: [Nop, IntReturn, Halt],
+            special: [
+                Self::Interrupt(_) => todo!()
+            ]
+        )
+    }
+}