From 84ffa12e2e5808febd780fca0e5522bbc2a726b8 Mon Sep 17 00:00:00 2001
From: svv232 <saidcooldude@gmail.com>
Date: Sun, 1 Dec 2024 16:55:52 -0500
Subject: [PATCH] adding instruction for branch lt

---
 .../src/interpreters/riscv32im/interpreter.rs | 28 ++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/o1vm/src/interpreters/riscv32im/interpreter.rs b/o1vm/src/interpreters/riscv32im/interpreter.rs
index 0c9207c21e..ca486910cd 100644
--- a/o1vm/src/interpreters/riscv32im/interpreter.rs
+++ b/o1vm/src/interpreters/riscv32im/interpreter.rs
@@ -2267,7 +2267,33 @@ pub fn interpret_sbtype<Env: InterpreterEnv>(env: &mut Env, instr: SBInstruction
             env.set_next_instruction_pointer(addr);
         }
         SBInstruction::BranchLessThan => {
-            unimplemented!("BranchLessThan")
+                        // blt: if (x[rs1] < x[rs2]) pc += sext(offset)
+                        let local_rs1 = env.read_register(&rs1);
+                        let local_rs2 = env.read_register(&rs2);
+            
+                        let rd_scratch = env.alloc_scratch();
+            
+                        let less_than =
+                            unsafe { env.test_less_than_signed(&local_rs1, &local_rs2, rd_scratch) };
+                        let offset = (less_than.clone()) * imm0_12
+                            + (Env::constant(1) - less_than.clone()) * Env::constant(4);
+            
+                        let addr = {
+                            let res_scratch = env.alloc_scratch();
+                            let overflow_scratch = env.alloc_scratch();
+                            let (res, _overflow) = unsafe {
+                                env.add_witness(
+                                    &next_instruction_pointer,
+                                    &offset,
+                                    res_scratch,
+                                    overflow_scratch,
+                                )
+                            };
+                            // FIXME: Requires a range check
+                            res
+                        };
+                        env.set_instruction_pointer(next_instruction_pointer);
+                        env.set_next_instruction_pointer(addr);
         }
         SBInstruction::BranchGreaterThanEqual => {
             unimplemented!("BranchGreaterThanEqual")