no-op MIPS

.github/workflows/o1vm-ci.yml

@@ -89,4 +89,4 @@ jobs:
           eval $(opam env)
           cd o1vm
           unzip -q -o /tmp/o1vm-e2e-testing-cache.zip -d ./
-          RUN_WITH_CACHED_DATA="y" FILENAME="env-for-latest-l2-block.sh" O1VM_FLAVOR="pickles" STOP_AT="=3000000" ./run-code.sh
+          RUST_LOG=debug RUN_WITH_CACHED_DATA="y" FILENAME="env-for-latest-l2-block.sh" O1VM_FLAVOR="pickles" STOP_AT="=3000000" ./run-code.sh

o1vm/src/interpreters/mips/column.rs

@@ -47,8 +47,9 @@ pub const SCRATCH_SIZE_INVERSE: usize = 12;
 pub const N_MIPS_REL_COLS: usize = SCRATCH_SIZE + SCRATCH_SIZE_INVERSE + 2;
 
 /// The number of witness columns used to store the instruction selectors.
+/// NOTE: The +1 is coming from the NoOp instruction.
 pub const N_MIPS_SEL_COLS: usize =
-    RTypeInstruction::COUNT + JTypeInstruction::COUNT + ITypeInstruction::COUNT;
+    RTypeInstruction::COUNT + JTypeInstruction::COUNT + ITypeInstruction::COUNT + 1;
 
 /// All the witness columns used in MIPS
 pub const N_MIPS_COLS: usize = N_MIPS_REL_COLS + N_MIPS_SEL_COLS;
@@ -97,6 +98,12 @@ impl From<Instruction> for usize {
             IType(itype) => {
                 N_MIPS_REL_COLS + RTypeInstruction::COUNT + JTypeInstruction::COUNT + itype as usize
             }
+            Instruction::NoOp => {
+                N_MIPS_REL_COLS
+                    + RTypeInstruction::COUNT
+                    + JTypeInstruction::COUNT
+                    + ITypeInstruction::COUNT
+            }
         }
     }
 }

o1vm/src/interpreters/mips/interpreter.rs

@@ -31,6 +31,7 @@ pub enum Instruction {
     RType(RTypeInstruction),
     JType(JTypeInstruction),
     IType(ITypeInstruction),
+    NoOp,
 }
 
 #[derive(
@@ -153,6 +154,7 @@ impl IntoIterator for Instruction {
                 }
                 iter_contents.into_iter()
             }
+            Instruction::NoOp => vec![Instruction::NoOp].into_iter(),
         }
     }
 }
@@ -970,9 +972,34 @@ pub fn interpret_instruction<Env: InterpreterEnv>(env: &mut Env, instr: Instruct
         Instruction::RType(instr) => interpret_rtype(env, instr),
         Instruction::JType(instr) => interpret_jtype(env, instr),
         Instruction::IType(instr) => interpret_itype(env, instr),
+        Instruction::NoOp => interpret_noop(env),
     }
 }
 
+pub fn interpret_noop<Env: InterpreterEnv>(env: &mut Env) {
+    let instruction_pointer = env.get_instruction_pointer();
+    let instruction = {
+        let v0 = env.read_memory(&instruction_pointer);
+        let v1 = env.read_memory(&(instruction_pointer.clone() + Env::constant(1)));
+        let v2 = env.read_memory(&(instruction_pointer.clone() + Env::constant(2)));
+        let v3 = env.read_memory(&(instruction_pointer.clone() + Env::constant(3)));
+        (v0 * Env::constant(1 << 24))
+            + (v1 * Env::constant(1 << 16))
+            + (v2 * Env::constant(1 << 8))
+            + v3
+    };
+    let opcode = {
+        let pos = env.alloc_scratch();
+        unsafe { env.bitmask(&instruction, 32, 26, pos) }
+    };
+
+    env.range_check8(&opcode, 6);
+    env.assert_is_zero(opcode);
+    let next_instruction_pointer = env.get_next_instruction_pointer();
+    env.set_instruction_pointer(next_instruction_pointer.clone());
+    env.set_next_instruction_pointer(next_instruction_pointer + Env::constant(4u32));
+}
+
 pub fn interpret_rtype<Env: InterpreterEnv>(env: &mut Env, instr: RTypeInstruction) {
     let instruction_pointer = env.get_instruction_pointer();
     let next_instruction_pointer = env.get_next_instruction_pointer();

o1vm/src/interpreters/mips/tests.rs

@@ -342,7 +342,8 @@ fn test_regression_selectors_for_instructions() {
         constraints.len() - 1,
         // We could use N_MIPS_SEL_COLS, but sanity check in case this value is
         // changed.
-        RTypeInstruction::COUNT + JTypeInstruction::COUNT + ITypeInstruction::COUNT
+        // the +1 is coming from NoOp instruction
+        RTypeInstruction::COUNT + JTypeInstruction::COUNT + ITypeInstruction::COUNT + 1
     );
     // All instructions are degree 1 or 2.
     constraints

o1vm/src/interpreters/mips/witness.rs

@@ -1076,7 +1076,13 @@ impl<Fp: PrimeField, PreImageOracle: PreImageOracleT> Env<Fp, PreImageOracle> {
         let opcode = {
             match instruction >> 26 {
                 0x00 => match instruction & 0x3F {
-                    0x00 => Instruction::RType(RTypeInstruction::ShiftLeftLogical),
+                    0x00 => {
+                        if instruction == 0 {
+                            Instruction::NoOp
+                        } else {
+                            Instruction::RType(RTypeInstruction::ShiftLeftLogical)
+                        }
+                    }
                     0x02 => Instruction::RType(RTypeInstruction::ShiftRightLogical),
                     0x03 => Instruction::RType(RTypeInstruction::ShiftRightArithmetic),
                     0x04 => Instruction::RType(RTypeInstruction::ShiftLeftLogicalVariable),

o1vm/src/pickles/mod.rs

@@ -31,7 +31,7 @@ pub const DEGREE_QUOTIENT_POLYNOMIAL: u64 = 7;
 
 /// Total number of constraints for all instructions, including the constraints
 /// added for the selectors.
-pub const TOTAL_NUMBER_OF_CONSTRAINTS: usize = 464;
+pub const TOTAL_NUMBER_OF_CONSTRAINTS: usize = 466;
 
 #[cfg(test)]
 mod tests;