skip next_access update in fulltracer (#1217)

tested with block num `23817600` e2e (with recursion)

| Component   | Before Time | After Time | Improvement |
|-------------|-------------|------------|-------------|
| reth-block  | 153 s       | 141 s      | ↓ 7.8%      |
| app.prove   | 150 s       | 138 s      | ↓ 8.0%      |

Co-authored-by: xkx <[email protected]>

Author: hero78119

ceno_emul/src/tracer.rs

@@ -8,7 +8,7 @@ use crate::{
 };
 use ceno_rt::WORD_SIZE;
 use smallvec::SmallVec;
-use std::{collections::BTreeMap, fmt, mem};
+use std::{collections::BTreeMap, fmt, mem, sync::Arc};
 
 /// An instruction and its context in an execution trace. That is concrete values of registers and memory.
 ///
@@ -88,6 +88,14 @@ pub trait Tracer {
 
     fn new(platform: &Platform) -> Self;
 
+    fn with_next_accesses(platform: &Platform, next_accesses: Option<Arc<NextCycleAccess>>) -> Self
+    where
+        Self: Sized,
+    {
+        let _ = next_accesses;
+        Self::new(platform)
+    }
+
     fn advance(&mut self) -> Self::Record;
 
     fn is_busy_loop(&self, record: &Self::Record) -> bool;
@@ -541,10 +549,6 @@ pub struct FullTracer {
 
     // keep track of each address that the cycle when they were last accessed.
     latest_accesses: LatestAccesses,
-
-    // keep track of each cycle that accessed addresses in the future with respective future cycles.
-    // format: [current cycle -> Vec<(WordAddr, Cycle)>]
-    next_accesses: NextCycleAccess,
 }
 
 impl FullTracer {
@@ -565,7 +569,6 @@ impl FullTracer {
             },
             platform: platform.clone(),
             latest_accesses: LatestAccesses::new(platform),
-            next_accesses: NextCycleAccess::new(ACCESSED_CHUNK_SIZE),
             max_heap_addr_access: ByteAddr::from(platform.heap.start),
             max_hint_addr_access: ByteAddr::from(platform.hints.start),
         }
@@ -711,21 +714,13 @@ impl FullTracer {
     #[inline(always)]
     pub fn track_access(&mut self, addr: WordAddr, subcycle: Cycle) -> Cycle {
         let cur_cycle = self.record.cycle + subcycle;
-        let prev_cycle = self.latest_accesses.track(addr, cur_cycle);
-        self.next_accesses
-            .get_or_create(prev_cycle as usize)
-            .push((addr, cur_cycle));
-        prev_cycle
+        self.latest_accesses.track(addr, cur_cycle)
     }
 
     pub fn final_accesses(&self) -> &LatestAccesses {
         &self.latest_accesses
     }
 
-    pub fn next_accesses(self) -> NextCycleAccess {
-        self.next_accesses
-    }
-
     /// Return the cycle of the pending instruction (after the last completed step).
     pub fn cycle(&self) -> Cycle {
         self.record.cycle
@@ -1010,7 +1005,7 @@ impl Tracer for FullTracer {
     }
 
     fn into_next_accesses(self) -> NextCycleAccess {
-        self.next_accesses()
+        unimplemented!("FullTracer does not record next access metadata")
     }
 
     fn cycle(&self) -> Cycle {

ceno_emul/src/vm_state.rs

@@ -6,7 +6,7 @@ use crate::{
     platform::Platform,
     rv32im::{Instruction, TrapCause},
     syscalls::{SyscallEffects, handle_syscall},
-    tracer::{Change, FullTracer, Tracer},
+    tracer::{Change, FullTracer, NextCycleAccess, Tracer},
 };
 use anyhow::{Result, anyhow};
 use std::{iter::from_fn, ops::Deref, sync::Arc};
@@ -47,6 +47,14 @@ impl<T: Tracer> VMState<T> {
     pub const REG_COUNT: usize = VM_REG_COUNT;
 
     pub fn new_with_tracer(platform: Platform, program: Arc<Program>) -> Self {
+        Self::new_with_tracer_and_next_accesses(platform, program, None)
+    }
+
+    pub fn new_with_tracer_and_next_accesses(
+        platform: Platform,
+        program: Arc<Program>,
+        next_accesses: Option<Arc<NextCycleAccess>>,
+    ) -> Self {
         let pc = program.entry;
 
         let mut vm = Self {
@@ -59,7 +67,7 @@ impl<T: Tracer> VMState<T> {
             ),
             registers: [0; VM_REG_COUNT],
             halt_state: None,
-            tracer: T::new(&platform),
+            tracer: T::with_next_accesses(&platform, next_accesses),
         };
 
         for (&addr, &value) in &program.image {