From ee5f5a2ec41ed426440346ff47339b63c2cf7c1d Mon Sep 17 00:00:00 2001
From: taitep <taitep@taitep.se>
Date: Tue, 7 Oct 2025 20:23:59 +0200
Subject: [PATCH] FIRST INSTRUCTION WORKING

---
 src/instructions.rs           | 26 ++++++++++++++++----------
 src/instructions/gen_tools.rs | 22 ++++++++++++++++++++++
 src/instructions/opcodes.rs   |  6 ++++++
 src/instructions/rvi.rs       | 28 ++++++++++++++++++++++++++++
 4 files changed, 72 insertions(+), 10 deletions(-)
 create mode 100644 src/instructions/gen_tools.rs
 create mode 100644 src/instructions/opcodes.rs
 create mode 100644 src/instructions/rvi.rs

diff --git a/src/instructions.rs b/src/instructions.rs
index ed264f9..fc005e9 100644
--- a/src/instructions.rs
+++ b/src/instructions.rs
@@ -1,7 +1,16 @@
 use once_cell::sync::Lazy;
 
-static INSTRUCTIONS: Lazy<[Option<OpcodeHandler>; 32]> = Lazy::new(|| {
-    let mut instructions = std::array::from_fn(|_i| None);
+mod gen_tools;
+mod opcodes;
+mod rvi;
+
+static INSTRUCTIONS: Lazy<[OpcodeHandler; 32]> = Lazy::new(|| {
+    let mut instructions = std::array::from_fn(|_i| OpcodeHandler {
+        handler: None,
+        splitter: None,
+    });
+
+    rvi::add_instrs(&mut instructions);
 
     instructions
 });
@@ -26,10 +35,7 @@ struct OpcodeHandler {
 
 pub fn find_runner(instruction: Instruction) -> Option<Runner> {
     let opcode_handler = &INSTRUCTIONS[instruction.opcode_noncompressed() as usize];
-    match opcode_handler {
-        Some(h) => h.find_runner(instruction),
-        None => None,
-    }
+    opcode_handler.find_runner(instruction)
 }
 
 impl OpcodeHandler {
@@ -43,16 +49,16 @@ impl OpcodeHandler {
 }
 
 enum Splitter {
-    Funct3Splitter(Box<[Option<OpcodeHandler>; 8]>),
+    Funct3Splitter(Box<[OpcodeHandler; 8]>),
     GeneralSplitter(Box<[GeneralSplitterEntry]>),
 }
 
 impl Splitter {
     fn find_runner(&self, instruction: Instruction) -> Option<Runner> {
         match self {
-            Splitter::Funct3Splitter(f3s) => f3s[instruction.funct3() as usize]
-                .as_ref()
-                .and_then(|h| h.find_runner(instruction)),
+            Splitter::Funct3Splitter(f3s) => {
+                f3s[instruction.funct3() as usize].find_runner(instruction)
+            }
             Splitter::GeneralSplitter(entries) => {
                 for entry in entries {
                     if instruction.0 & entry.mask == entry.value {
diff --git a/src/instructions/gen_tools.rs b/src/instructions/gen_tools.rs
new file mode 100644
index 0000000..ad9ad62
--- /dev/null
+++ b/src/instructions/gen_tools.rs
@@ -0,0 +1,22 @@
+use std::hint::unreachable_unchecked;
+
+use crate::instructions::{OpcodeHandler, Splitter};
+
+pub fn insert_funct3_splitter(splitter: &mut Option<Splitter>) -> &mut [OpcodeHandler; 8] {
+    match splitter {
+        Some(Splitter::Funct3Splitter(s)) => s.as_mut(),
+        Some(_) => panic!("Unexpected splitter variant"),
+        None => {
+            *splitter = Some(Splitter::Funct3Splitter(Box::new(std::array::from_fn(
+                |_i| OpcodeHandler {
+                    handler: None,
+                    splitter: None,
+                },
+            ))));
+            match splitter {
+                Some(Splitter::Funct3Splitter(s)) => s.as_mut(),
+                _ => unsafe { unreachable_unchecked() },
+            }
+        }
+    }
+}
diff --git a/src/instructions/opcodes.rs b/src/instructions/opcodes.rs
new file mode 100644
index 0000000..33f824d
--- /dev/null
+++ b/src/instructions/opcodes.rs
@@ -0,0 +1,6 @@
+//! Includes opcodes, funct3 values, and match/mask values.
+//! Opcodes (unless compressed) have the last 2 bits stripped off as they are always 1s for non-compressed instructions.
+
+pub(super) const OP_IMM: u8 = 0b00100;
+
+pub(super) const FUNCT3_ADDI: u8 = 0x0;
diff --git a/src/instructions/rvi.rs b/src/instructions/rvi.rs
new file mode 100644
index 0000000..8e7dade
--- /dev/null
+++ b/src/instructions/rvi.rs
@@ -0,0 +1,28 @@
+use crate::{
+    core::{Core, InstructionResult},
+    decode::Instruction,
+    instructions::{
+        OpcodeHandler,
+        gen_tools::insert_funct3_splitter,
+        opcodes::{FUNCT3_ADDI, OP_IMM},
+    },
+};
+
+pub(super) fn add_instrs(list: &mut [OpcodeHandler; 32]) {
+    let funct3_split_op_imm = insert_funct3_splitter(&mut list[OP_IMM as usize].splitter);
+    funct3_split_op_imm[FUNCT3_ADDI as usize].handler =
+        Some(super::InstructionHandler { runner: addi });
+}
+
+fn addi(core: &mut Core, instr: Instruction) -> InstructionResult {
+    eprintln!("Running ADDI");
+
+    core.reg_write(
+        instr.rd(),
+        core.reg_read(instr.rs1()).wrapping_add(instr.imm_i()),
+    );
+
+    core.pc = core.pc.wrapping_add(4);
+
+    InstructionResult::Normal
+}