From f6b3406669ea06d38f7248f356a6948c67c6593d Mon Sep 17 00:00:00 2001
From: mrmr1993 <mr_1993@hotmail.co.uk>
Date: Tue, 5 Dec 2023 23:44:57 +0000
Subject: [PATCH] Implement `and`

---
 optimism/src/mips/interpreter.rs | 27 ++++++++++++++++++++++++++-
 optimism/src/mips/witness.rs     | 11 +++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/optimism/src/mips/interpreter.rs b/optimism/src/mips/interpreter.rs
index 5bbfee7a3b..aaf2320efc 100644
--- a/optimism/src/mips/interpreter.rs
+++ b/optimism/src/mips/interpreter.rs
@@ -589,6 +589,19 @@ pub trait InterpreterEnv {
         position: Self::Position,
     ) -> Self::Variable;
 
+    /// Returns `x or y`, storing the result in `position`.
+    ///
+    /// # Safety
+    ///
+    /// There are no constraints on the returned value; callers must manually add constraints to
+    /// ensure that it is correctly constructed.
+    unsafe fn and_witness(
+        &mut self,
+        x: &Self::Variable,
+        y: &Self::Variable,
+        position: Self::Position,
+    ) -> Self::Variable;
+
     /// Returns `x or y`, storing the result in `position`.
     ///
     /// # Safety
@@ -784,7 +797,19 @@ pub fn interpret_rtype<Env: InterpreterEnv>(env: &mut Env, instr: RTypeInstructi
         }
         RTypeInstruction::Sub => (),
         RTypeInstruction::SubUnsigned => (),
-        RTypeInstruction::And => (),
+        RTypeInstruction::And => {
+            let rs = env.read_register(&rs);
+            let rt = env.read_register(&rt);
+            let res = {
+                // FIXME: Constrain
+                let pos = env.alloc_scratch();
+                unsafe { env.and_witness(&rs, &rt, pos) }
+            };
+            env.write_register(&rd, res);
+            env.set_instruction_pointer(next_instruction_pointer.clone());
+            env.set_next_instruction_pointer(next_instruction_pointer + Env::constant(4u32));
+            return;
+        }
         RTypeInstruction::Or => {
             let rs = env.read_register(&rs);
             let rt = env.read_register(&rt);
diff --git a/optimism/src/mips/witness.rs b/optimism/src/mips/witness.rs
index 1ac0217dd4..2c2fad8264 100644
--- a/optimism/src/mips/witness.rs
+++ b/optimism/src/mips/witness.rs
@@ -277,6 +277,17 @@ impl<Fp: Field> InterpreterEnv for Env<Fp> {
         res
     }
 
+    unsafe fn and_witness(
+        &mut self,
+        x: &Self::Variable,
+        y: &Self::Variable,
+        position: Self::Position,
+    ) -> Self::Variable {
+        let res = x & y;
+        self.write_column(position, res.into());
+        res
+    }
+
     unsafe fn or_witness(
         &mut self,
         x: &Self::Variable,