Remove new_stack_top_channel from StackBehavior (0xPolygonZero#1296)

evm/src/cpu/bootstrap_kernel.rs

@@ -1,6 +1,7 @@
 //! The initial phase of execution, where the kernel code is hashed while being written to memory.
 //! The hash is then checked against a precomputed kernel hash.
 
+use ethereum_types::U256;
 use itertools::Itertools;
 use plonky2::field::extension::Extendable;
 use plonky2::field::packed::PackedField;
@@ -52,6 +53,13 @@ pub(crate) fn generate_bootstrap_kernel<F: Field>(state: &mut GenerationState<F>
         MemoryAddress::new(0, Segment::Code, 0),
         KERNEL.code.clone(),
     );
+    state.registers.stack_top = KERNEL
+        .code_hash
+        .iter()
+        .enumerate()
+        .fold(0.into(), |acc, (i, &elt)| {
+            acc + (U256::from(elt) << (224 - 32 * i))
+        });
     state.traces.push_cpu(final_cpu_row);
     log::info!("Bootstrapping took {} cycles", state.traces.clock());
 }

evm/src/cpu/cpu_stark.rs

@@ -14,7 +14,6 @@ use super::halt;
 use crate::all_stark::Table;
 use crate::constraint_consumer::{ConstraintConsumer, RecursiveConstraintConsumer};
 use crate::cpu::columns::{COL_MAP, NUM_CPU_COLUMNS};
-use crate::cpu::membus::NUM_GP_CHANNELS;
 use crate::cpu::{
     bootstrap_kernel, contextops, control_flow, decode, dup_swap, gas, jumps, membus, memio,
     modfp254, pc, push0, shift, simple_logic, stack, stack_bounds, syscalls_exceptions,
@@ -41,7 +40,7 @@ pub fn ctl_data_keccak_sponge<F: Field>() -> Vec<Column<F>> {
     let timestamp = Column::linear_combination([(COL_MAP.clock, num_channels)]);
 
     let mut cols = vec![context, segment, virt, len, timestamp];
-    cols.extend(COL_MAP.mem_channels[4].value.map(Column::single));
+    cols.extend(Column::singles_next_row(COL_MAP.mem_channels[0].value));
     cols
 }
 
@@ -54,9 +53,7 @@ pub fn ctl_filter_keccak_sponge<F: Field>() -> Column<F> {
 fn ctl_data_binops<F: Field>() -> Vec<Column<F>> {
     let mut res = Column::singles(COL_MAP.mem_channels[0].value).collect_vec();
     res.extend(Column::singles(COL_MAP.mem_channels[1].value));
-    res.extend(Column::singles(
-        COL_MAP.mem_channels[NUM_GP_CHANNELS - 1].value,
-    ));
+    res.extend(Column::singles_next_row(COL_MAP.mem_channels[0].value));
     res
 }
 
@@ -68,9 +65,7 @@ fn ctl_data_ternops<F: Field>() -> Vec<Column<F>> {
     let mut res = Column::singles(COL_MAP.mem_channels[0].value).collect_vec();
     res.extend(Column::singles(COL_MAP.mem_channels[1].value));
     res.extend(Column::singles(COL_MAP.mem_channels[2].value));
-    res.extend(Column::singles(
-        COL_MAP.mem_channels[NUM_GP_CHANNELS - 1].value,
-    ));
+    res.extend(Column::singles_next_row(COL_MAP.mem_channels[0].value));
     res
 }
 

evm/src/cpu/simple_logic/eq_iszero.rs

@@ -27,13 +27,6 @@ pub fn generate_pinv_diff<F: Field>(val0: U256, val1: U256, lv: &mut CpuColumnsV
     let num_unequal_limbs = izip!(val0_limbs, val1_limbs)
         .map(|(limb0, limb1)| (limb0 != limb1) as usize)
         .sum();
-    let equal = num_unequal_limbs == 0;
-
-    let output = &mut lv.mem_channels[2].value;
-    output[0] = F::from_bool(equal);
-    for limb in &mut output[1..] {
-        *limb = F::ZERO;
-    }
 
     // Form `diff_pinv`.
     // Let `diff = val0 - val1`. Consider `x[i] = diff[i]^-1` if `diff[i] != 0` and 0 otherwise.
@@ -57,7 +50,7 @@ pub fn eval_packed<P: PackedField>(
     let logic = lv.general.logic();
     let input0 = lv.mem_channels[0].value;
     let input1 = lv.mem_channels[1].value;
-    let output = lv.mem_channels[2].value;
+    let output = nv.mem_channels[0].value;
 
     // EQ (0x14) and ISZERO (0x15) are differentiated by their first opcode bit.
     let eq_filter = lv.op.eq_iszero * (P::ONES - lv.opcode_bits[0]);
@@ -117,7 +110,7 @@ pub fn eval_ext_circuit<F: RichField + Extendable<D>, const D: usize>(
     let logic = lv.general.logic();
     let input0 = lv.mem_channels[0].value;
     let input1 = lv.mem_channels[1].value;
-    let output = lv.mem_channels[2].value;
+    let output = nv.mem_channels[0].value;
 
     // EQ (0x14) and ISZERO (0x15) are differentiated by their first opcode bit.
     let eq_filter = builder.mul_extension(lv.op.eq_iszero, lv.opcode_bits[0]);

evm/src/cpu/simple_logic/mod.rs

@@ -14,7 +14,7 @@ pub fn eval_packed<P: PackedField>(
     nv: &CpuColumnsView<P>,
     yield_constr: &mut ConstraintConsumer<P>,
 ) {
-    not::eval_packed(lv, yield_constr);
+    not::eval_packed(lv, nv, yield_constr);
     eq_iszero::eval_packed(lv, nv, yield_constr);
 }
 
@@ -24,6 +24,6 @@ pub fn eval_ext_circuit<F: RichField + Extendable<D>, const D: usize>(
     nv: &CpuColumnsView<ExtensionTarget<D>>,
     yield_constr: &mut RecursiveConstraintConsumer<F, D>,
 ) {
-    not::eval_ext_circuit(builder, lv, yield_constr);
+    not::eval_ext_circuit(builder, lv, nv, yield_constr);
     eq_iszero::eval_ext_circuit(builder, lv, nv, yield_constr);
 }

evm/src/cpu/simple_logic/not.rs

@@ -6,18 +6,18 @@ use plonky2::iop::ext_target::ExtensionTarget;
 
 use crate::constraint_consumer::{ConstraintConsumer, RecursiveConstraintConsumer};
 use crate::cpu::columns::CpuColumnsView;
-use crate::cpu::membus::NUM_GP_CHANNELS;
 
 const LIMB_SIZE: usize = 32;
 const ALL_1_LIMB: u64 = (1 << LIMB_SIZE) - 1;
 
 pub fn eval_packed<P: PackedField>(
     lv: &CpuColumnsView<P>,
+    nv: &CpuColumnsView<P>,
     yield_constr: &mut ConstraintConsumer<P>,
 ) {
     // This is simple: just do output = 0xffffffff - input.
     let input = lv.mem_channels[0].value;
-    let output = lv.mem_channels[NUM_GP_CHANNELS - 1].value;
+    let output = nv.mem_channels[0].value;
     let filter = lv.op.not;
     for (input_limb, output_limb) in input.into_iter().zip(output) {
         yield_constr.constraint(
@@ -29,10 +29,11 @@ pub fn eval_packed<P: PackedField>(
 pub fn eval_ext_circuit<F: RichField + Extendable<D>, const D: usize>(
     builder: &mut plonky2::plonk::circuit_builder::CircuitBuilder<F, D>,
     lv: &CpuColumnsView<ExtensionTarget<D>>,
+    nv: &CpuColumnsView<ExtensionTarget<D>>,
     yield_constr: &mut RecursiveConstraintConsumer<F, D>,
 ) {
     let input = lv.mem_channels[0].value;
-    let output = lv.mem_channels[NUM_GP_CHANNELS - 1].value;
+    let output = nv.mem_channels[0].value;
     let filter = lv.op.not;
     for (input_limb, output_limb) in input.into_iter().zip(output) {
         let constr = builder.add_extension(output_limb, input_limb);

evm/src/cpu/stack.rs

@@ -17,39 +17,33 @@ use crate::memory::segments::Segment;
 pub(crate) struct StackBehavior {
     pub(crate) num_pops: usize,
     pub(crate) pushes: bool,
-    new_top_stack_channel: Option<usize>,
     disable_other_channels: bool,
 }
 
 const BASIC_BINARY_OP: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 2,
     pushes: true,
-    new_top_stack_channel: Some(NUM_GP_CHANNELS - 1),
     disable_other_channels: true,
 });
 const BASIC_TERNARY_OP: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 3,
     pushes: true,
-    new_top_stack_channel: Some(NUM_GP_CHANNELS - 1),
     disable_other_channels: true,
 });
 pub(crate) const JUMP_OP: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 1,
     pushes: false,
-    new_top_stack_channel: None,
     disable_other_channels: false,
 });
 pub(crate) const JUMPI_OP: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 2,
     pushes: false,
-    new_top_stack_channel: None,
     disable_other_channels: false,
 });
 
 pub(crate) const MLOAD_GENERAL_OP: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 3,
     pushes: true,
-    new_top_stack_channel: None,
     disable_other_channels: false,
 });
 
@@ -67,99 +61,84 @@ pub(crate) const STACK_BEHAVIORS: OpsColumnsView<Option<StackBehavior>> = OpsCol
     not: Some(StackBehavior {
         num_pops: 1,
         pushes: true,
-        new_top_stack_channel: Some(NUM_GP_CHANNELS - 1),
         disable_other_channels: true,
     }),
     shift: Some(StackBehavior {
         num_pops: 2,
         pushes: true,
-        new_top_stack_channel: Some(NUM_GP_CHANNELS - 1),
         disable_other_channels: false,
     }),
     keccak_general: Some(StackBehavior {
         num_pops: 4,
         pushes: true,
-        new_top_stack_channel: Some(NUM_GP_CHANNELS - 1),
         disable_other_channels: true,
     }),
     prover_input: None, // TODO
     pop: Some(StackBehavior {
         num_pops: 1,
         pushes: false,
-        new_top_stack_channel: None,
         disable_other_channels: true,
     }),
     jumps: None, // Depends on whether it's a JUMP or a JUMPI.
     pc: Some(StackBehavior {
         num_pops: 0,
         pushes: true,
-        new_top_stack_channel: None,
         disable_other_channels: true,
     }),
     jumpdest: Some(StackBehavior {
         num_pops: 0,
         pushes: false,
-        new_top_stack_channel: None,
         disable_other_channels: true,
     }),
     push0: Some(StackBehavior {
         num_pops: 0,
         pushes: true,
-        new_top_stack_channel: None,
         disable_other_channels: true,
     }),
     push: None, // TODO
     dup_swap: None,
     get_context: Some(StackBehavior {
         num_pops: 0,
         pushes: true,
-        new_top_stack_channel: None,
         disable_other_channels: true,
     }),
     set_context: None, // SET_CONTEXT is special since it involves the old and the new stack.
     mload_32bytes: Some(StackBehavior {
         num_pops: 4,
         pushes: true,
-        new_top_stack_channel: Some(4),
         disable_other_channels: false,
     }),
     mstore_32bytes: Some(StackBehavior {
         num_pops: 5,
         pushes: false,
-        new_top_stack_channel: None,
         disable_other_channels: false,
     }),
     exit_kernel: Some(StackBehavior {
         num_pops: 1,
         pushes: false,
-        new_top_stack_channel: None,
         disable_other_channels: true,
     }),
     m_op_general: None,
     syscall: Some(StackBehavior {
         num_pops: 0,
         pushes: true,
-        new_top_stack_channel: None,
         disable_other_channels: false,
     }),
     exception: Some(StackBehavior {
         num_pops: 0,
         pushes: true,
-        new_top_stack_channel: None,
         disable_other_channels: false,
     }),
 };
 
 pub(crate) const EQ_STACK_BEHAVIOR: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 2,
     pushes: true,
-    new_top_stack_channel: Some(2),
     disable_other_channels: true,
 });
 pub(crate) const IS_ZERO_STACK_BEHAVIOR: Option<StackBehavior> = Some(StackBehavior {
     num_pops: 1,
     pushes: true,
-    new_top_stack_channel: Some(2),
     disable_other_channels: true,
 });
 
@@ -256,18 +235,6 @@ pub(crate) fn eval_packed_one<P: PackedField>(
         }
     }
 
-    // Maybe constrain next stack_top.
-    // These are transition constraints: they don't apply to the last row.
-    if let Some(next_top_ch) = stack_behavior.new_top_stack_channel {
-        for (limb_ch, limb_top) in lv.mem_channels[next_top_ch]
-            .value
-            .iter()
-            .zip(nv.mem_channels[0].value.iter())
-        {
-            yield_constr.constraint_transition(filter * (*limb_ch - *limb_top));
-        }
-    }
-
     // Unused channels
     if stack_behavior.disable_other_channels {
         // The first channel contains (or not) the top od the stack and is constrained elsewhere.
@@ -478,20 +445,6 @@ pub(crate) fn eval_ext_circuit_one<F: RichField + Extendable<D>, const D: usize>
         }
     }
 
-    // Maybe constrain next stack_top.
-    // These are transition constraints: they don't apply to the last row.
-    if let Some(next_top_ch) = stack_behavior.new_top_stack_channel {
-        for (limb_ch, limb_top) in lv.mem_channels[next_top_ch]
-            .value
-            .iter()
-            .zip(nv.mem_channels[0].value.iter())
-        {
-            let diff = builder.sub_extension(*limb_ch, *limb_top);
-            let constr = builder.mul_extension(filter, diff);
-            yield_constr.constraint_transition(builder, constr);
-        }
-    }
-
     // Unused channels
     if stack_behavior.disable_other_channels {
         // The first channel contains (or not) the top od the stack and is constrained elsewhere.