From c6da147d505020fe5d7ca3b505d412d42cb599e3 Mon Sep 17 00:00:00 2001
From: taitep <taitep@taitep.se>
Date: Tue, 23 Dec 2025 09:51:53 +0100
Subject: [PATCH] Implement BLT

---
 src/instructions.rs     |  1 +
 src/instructions/rvi.rs | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/src/instructions.rs b/src/instructions.rs
index 72ce3d2..2297994 100644
--- a/src/instructions.rs
+++ b/src/instructions.rs
@@ -53,6 +53,7 @@ pub(crate) fn find_and_exec(instr: Instruction, core: &mut Core) -> Option<Instr
             // BRANCH
             0b000 => Some(rvi::beq(core, instr)),
             0b001 => Some(rvi::bne(core, instr)),
+            0b100 => Some(rvi::blt(core, instr)),
             0b110 => Some(rvi::bltu(core, instr)),
             0b111 => Some(rvi::bgeu(core, instr)),
             _ => None,
diff --git a/src/instructions/rvi.rs b/src/instructions/rvi.rs
index 7d57ce6..c5ddaaa 100644
--- a/src/instructions/rvi.rs
+++ b/src/instructions/rvi.rs
@@ -93,12 +93,19 @@ pub fn auipc(core: &mut Core, instr: Instruction) -> InstructionResult {
 
 pub fn jal(core: &mut Core, instr: Instruction) -> InstructionResult {
     core.reg_write(instr.rd(), core.pc.wrapping_add(4));
+    eprintln!("set x{} to {:x}", instr.rd(), core.pc.wrapping_add(4));
     core.pc = core.pc.wrapping_add(instr.imm_j());
     InstructionResult::Normal
 }
 
 pub fn jalr(core: &mut Core, instr: Instruction) -> InstructionResult {
     core.reg_write(instr.rd(), core.pc.wrapping_add(4));
+    eprintln!(
+        "origin: {:x}, reg: x{}={:x}",
+        core.pc,
+        instr.rs1(),
+        core.reg_read(instr.rs1())
+    );
     core.pc = core.reg_read(instr.rs1()).wrapping_add(instr.imm_i());
     InstructionResult::Normal
 }
@@ -123,6 +130,16 @@ pub fn bne(core: &mut Core, instr: Instruction) -> InstructionResult {
     InstructionResult::Normal
 }
 
+pub fn blt(core: &mut Core, instr: Instruction) -> InstructionResult {
+    if (core.reg_read(instr.rs1()) as i64) < (core.reg_read(instr.rs2()) as i64) {
+        core.pc = core.pc.wrapping_add(instr.imm_b());
+    } else {
+        core.advance_pc();
+    }
+
+    InstructionResult::Normal
+}
+
 pub fn bgeu(core: &mut Core, instr: Instruction) -> InstructionResult {
     if core.reg_read(instr.rs1()) >= core.reg_read(instr.rs2()) {
         core.pc = core.pc.wrapping_add(instr.imm_b());