Merge pull request #1421 from o1-labs/feature/mips/bltz

Implement `bltz`
o1-labs · Dec 6, 2023 · c0b61fa · c0b61fa
2 parents d4895dd + b39a95e
commit c0b61fa
Showing 1 changed file with 19 additions and 1 deletion.
diff --git a/optimism/src/mips/interpreter.rs b/optimism/src/mips/interpreter.rs
@@ -948,7 +948,25 @@ pub fn interpret_itype<Env: InterpreterEnv>(env: &mut Env, instr: ITypeInstructi
         }
         ITypeInstruction::BranchLeqZero => (),
         ITypeInstruction::BranchGtZero => (),
-        ITypeInstruction::BranchLtZero => (),
+        ITypeInstruction::BranchLtZero => {
+            let offset = env.sign_extend(&(immediate * Env::constant(1 << 2)), 18);
+            let rs = env.read_register(&rs);
+            let less_than = {
+                // FIXME: Requires constraints
+                let pos = env.alloc_scratch();
+                unsafe { env.test_less_than_signed(&rs, &Env::constant(0), pos) }
+            };
+            let offset =
+                (Env::constant(1) - less_than.clone()) * Env::constant(4) + less_than * offset;
+            let addr = {
+                let pos = env.alloc_scratch();
+                env.copy(&(next_instruction_pointer.clone() + offset), pos)
+            };
+            env.set_instruction_pointer(next_instruction_pointer);
+            env.set_next_instruction_pointer(addr);
+            // REMOVEME: when all itype instructions are implemented.
+            return;
+        }
         ITypeInstruction::BranchGeqZero => (),
         ITypeInstruction::AddImmediate => {
             let register_rs = env.read_register(&rs);