Merge pull request #2861 from o1-labs/sai/branch-gteu

implementation for branch greater than equal unsigned

o1vm/src/interpreters/riscv32im/interpreter.rs

@@ -2352,7 +2352,27 @@ pub fn interpret_sbtype<Env: InterpreterEnv>(env: &mut Env, instr: SBInstruction
             env.set_next_instruction_pointer(addr);
         }
         SBInstruction::BranchGreaterThanEqualUnsigned => {
-            unimplemented!("BranchGreaterThanEqualUnsigned")
+            // bgeu: if (x[rs1] >=u 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(&local_rs1, &local_rs2, rd_scratch) };
+            let offset =
+                less_than.clone() * Env::constant(4) + (Env::constant(1) - less_than) * imm0_12;
+
+            // greater than equal is the negation of less than
+            let addr = {
+                let res_scratch = env.alloc_scratch();
+                let overflow_scratch = env.alloc_scratch();
+                let (res, _overflow) = unsafe {
+                    env.add_witness(&instruction_pointer, &offset, res_scratch, overflow_scratch)
+                };
+                res
+            };
+
+            env.set_instruction_pointer(next_instruction_pointer);
+            env.set_next_instruction_pointer(addr);
         }
     };
 }