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perf(tui): restore steps -- 8.8% less time #46

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Merged
sql-hkr merged 1 commit into from
Oct 26, 2026
Merged

perf(tui): restore steps -- 8.8% less time #46

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128 changes: 70 additions & 58 deletions src/tiny8/tui.py
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Original file line number Diff line number Diff line change
Expand Up @@ -71,13 +71,15 @@ def __init__(

def record(self, step: int) -> None:
"""Store a CPU snapshot at the given step."""
if step not in self.snapshots and len(self.snapshots) < self.max_snapshots:
self.snapshots[step] = self.cpu.snapshot()
if not self.checkpoint_steps or step > self.checkpoint_steps[-1]:
self.checkpoint_steps.append(step)
snapshots = self.snapshots
if step not in snapshots and len(snapshots) < self.max_snapshots:
snapshots[step] = self.cpu.snapshot()
checkpoint_steps = self.checkpoint_steps
if not checkpoint_steps or step > checkpoint_steps[-1]:
checkpoint_steps.append(step)
else:
idx = bisect.bisect_right(self.checkpoint_steps, step)
self.checkpoint_steps.insert(idx, step)
idx = bisect.bisect_right(checkpoint_steps, step)
checkpoint_steps.insert(idx, step)

def record_if_interval(self, step: int) -> None:
"""Record snapshot if step is a multiple of interval."""
Expand All @@ -89,71 +91,78 @@ def restore_exact_step(self, target_step: int) -> bool:
if target_step < 0 or not self.checkpoint_steps:
return False

cpu = self.cpu
checkpoint_steps = self.checkpoint_steps
snapshots = self.snapshots
detect_loop = self.detect_loop
step = cpu.step
record = self.record

# If target_step is beyond currently recorded checkpoints, dynamically extend cache
if target_step > self.checkpoint_steps[-1] and not self.infinite_loop_detected:
latest_step = self.checkpoint_steps[-1]
self.cpu.restore_snapshot(self.snapshots[latest_step])
self.cpu.running = 0 <= self.cpu.pc < len(self.cpu.program)
old_trace = self.cpu.trace_enabled
self.cpu.trace_enabled = False
if target_step > checkpoint_steps[-1] and not self.infinite_loop_detected:
latest_step = checkpoint_steps[-1]
cpu.restore_snapshot(snapshots[latest_step])
cpu.running = 0 <= cpu.pc < len(cpu.program)
old_trace = cpu.trace_enabled
cpu.trace_enabled = False
try:
while self.cpu.running and self.cpu.step_count < target_step:
if self.detect_loop():
self.cpu.running = False
while cpu.running and cpu.step_count < target_step:
if detect_loop():
cpu.running = False
break
if not self.cpu.step(record_trace=False):
self.cpu.running = False
if not step(record_trace=False):
cpu.running = False
break
if self.cpu.step_count % self.interval == 0:
self.record(self.cpu.step_count)
if self.cpu.step_count not in self.snapshots:
self.record(self.cpu.step_count)
if cpu.step_count % self.interval == 0:
record(cpu.step_count)
if cpu.step_count not in snapshots:
record(cpu.step_count)
finally:
self.cpu.trace_enabled = old_trace
cpu.trace_enabled = old_trace

# Find closest checkpoint <= target_step
idx = bisect.bisect_right(self.checkpoint_steps, target_step) - 1
idx = bisect.bisect_right(checkpoint_steps, target_step) - 1
if idx < 0:
base_step = self.checkpoint_steps[0]
base_step = checkpoint_steps[0]
else:
base_step = self.checkpoint_steps[idx]
base_step = checkpoint_steps[idx]

self.cpu.restore_snapshot(self.snapshots[base_step])
self.cpu.running = 0 <= self.cpu.pc < len(self.cpu.program)
cpu.restore_snapshot(snapshots[base_step])
cpu.running = 0 <= cpu.pc < len(cpu.program)
self.infinite_loop_detected = False
self.loop_reason = ""
if self.detect_loop():
self.cpu.running = False
self.cpu.step_trace.clear()
if detect_loop():
cpu.running = False
cpu.step_trace.clear()

# Step forward remaining steps (at most self.interval - 1 steps)
steps_to_advance = max(0, target_step - base_step) if self.cpu.running else 0
steps_to_advance = max(0, target_step - base_step) if cpu.running else 0
for _ in range(steps_to_advance):
if self.detect_loop():
self.cpu.running = False
if detect_loop():
cpu.running = False
break
if not self.cpu.step():
self.cpu.running = False
if not step():
cpu.running = False
break

# Ensure step_trace has at least the current step representation
if not self.cpu.step_trace:
if not cpu.step_trace:
cur_instr = ""
if 0 <= self.cpu.pc < len(self.cpu.program):
instr, ops = self.cpu.program[self.cpu.pc]
if 0 <= cpu.pc < len(cpu.program):
instr, ops = cpu.program[cpu.pc]
cur_instr = (
f"{instr} " + ", ".join(str(o) for o in ops) if ops else instr
)
self.cpu.step_trace.append(
cpu.step_trace.append(
{
"step": self.cpu.step_count,
"pc": self.cpu.pc,
"step": cpu.step_count,
"pc": cpu.pc,
"instr": cur_instr,
"regs": list(self.cpu.regs),
"mem": dict(self.cpu.mem.nonzero_ram),
"sreg": self.cpu.sreg,
"sp": self.cpu.sp,
"source_line": self.cpu.pc_to_line.get(self.cpu.pc, -1),
"regs": list(cpu.regs),
"mem": dict(cpu.mem.nonzero_ram),
"sreg": cpu.sreg,
"sp": cpu.sp,
"source_line": cpu.pc_to_line.get(cpu.pc, -1),
}
)
return True
Expand All @@ -170,14 +179,16 @@ def invalidate_after(self, step: int) -> None:

def detect_loop(self, window_size: int = 256) -> bool:
"""Detect infinite loop (e.g. self-jump HALT or cycling registers/PC)."""
cur_pc = self.cpu.pc
if 0 <= cur_pc < len(self.cpu.program):
instr, operands = self.cpu.program[cur_pc]
cpu = self.cpu
cur_pc = cpu.pc
program = cpu.program
if 0 <= cur_pc < len(program):
instr, operands = program[cur_pc]
if instr in ("RJMP", "JMP") and operands:
op = operands[0]
target_pc: int | None = None
if isinstance(op, str):
target_pc = self.cpu.labels.get(op)
target_pc = cpu.labels.get(op)
elif isinstance(op, int):
if instr == "RJMP":
if op in (-1, 0):
Expand All @@ -188,24 +199,25 @@ def detect_loop(self, window_size: int = 256) -> bool:
target_pc = op
if target_pc == cur_pc:
self.infinite_loop_detected = True
self.loop_reason = f"HALT spin loop detected at PC=0x{cur_pc:04X} (step {self.cpu.step_count})"
self.loop_reason = f"HALT spin loop detected at PC=0x{cur_pc:04X} (step {cpu.step_count})"
return True
elif instr in ("HLT", "BREAK"):
self.infinite_loop_detected = True
self.loop_reason = f"HALT instruction encountered at PC=0x{cur_pc:04X}"
return True

sig = (cur_pc, self.cpu.sreg, tuple(self.cpu.regs))
if sig in self._history_signatures:
prev_step = self._history_signatures[sig]
diff = self.cpu.step_count - prev_step
sig = (cur_pc, cpu.sreg, tuple(cpu.regs))
history = self._history_signatures
prev_step = history.get(sig)
if prev_step is not None:
diff = cpu.step_count - prev_step
if 0 < diff <= window_size:
self.infinite_loop_detected = True
self.loop_reason = f"Cycle loop detected: repeats every {diff} steps at PC=0x{cur_pc:04X}"
return True
self._history_signatures[sig] = self.cpu.step_count
if len(self._history_signatures) > 3000:
self._history_signatures.clear()
history[sig] = cpu.step_count
if len(history) > 3000:
history.clear()
return False

def precompute(
Expand Down
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