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task4 submission
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‎hw4/DSE.toml‎

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benchmarks = '../benchmarks/**/*.bril'
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extract = 'total_dyn_inst: (\d+)'
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timeout=60
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[runs.baseline]
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pipeline = [
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"bril2json",
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"brili -p {args}",
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]
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[runs.dead_store_elimination]
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pipeline = [
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"bril2json",
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"python3 dead_store_elimination.py",
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"brili -p {args}",
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]

‎hw4/dead_store_elimination.py‎

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import sys
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import json
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from collections import defaultdict, deque
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from form_blocks import form_blocks
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from util import flatten
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def construct_cfg(blocks):
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labels = []
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block_map = {}
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for idx, block in enumerate(blocks):
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if 'label' in block[0]:
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label = block[0]['label']
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else:
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label = f'<bb{idx}>'
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labels.append(label)
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block_map[label] = block
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cfg = {label: [] for label in labels}
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for idx, block in enumerate(blocks):
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label = labels[idx]
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last_instr = block[-1] if block else None
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if last_instr and 'op' in last_instr:
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op = last_instr['op']
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if op == 'br':
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cfg[label].extend(last_instr['labels'])
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elif op == 'jmp':
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cfg[label].append(last_instr['labels'][0])
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else:
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if idx + 1 < len(blocks):
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cfg[label].append(labels[idx + 1])
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else:
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if idx + 1 < len(blocks):
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cfg[label].append(labels[idx + 1])
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return cfg, labels
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def alias_analysis(blocks, cfg, labels, func_args, alloc_sites):
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block_map = dict(zip(labels, blocks))
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in_state = {label: {} for label in labels}
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out_state = {label: {} for label in labels}
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# Initialize the analysis state
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init_state = {}
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for arg in func_args:
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init_state[arg] = set(['unknown'])
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worklist = deque(labels)
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while worklist:
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label = worklist.popleft()
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block = block_map[label]
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in_map = {}
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preds = [pred for pred in cfg if label in cfg[pred]]
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if preds:
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for pred in preds:
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pred_out = out_state[pred]
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for var in pred_out:
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in_map.setdefault(var, set()).update(pred_out[var])
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else:
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in_map = {var: locs.copy() for var, locs in init_state.items()}
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# **Add this line to update in_state**
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in_state[label] = in_map.copy()
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old_out = out_state[label]
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out_map = analyze_block(block, in_map, alloc_sites)
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out_state[label] = out_map
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if out_map != old_out:
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for succ in cfg[label]:
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if succ not in worklist:
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worklist.append(succ)
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# print(f"[Alias Analysis] Block: {label}, In-State: {in_map}")
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# print(f"[Alias Analysis] Block: {label}, Out-State: {out_map}")
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return in_state, out_state
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def analyze_block(block, in_map, alloc_sites):
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state = {var: locs.copy() for var, locs in in_map.items()}
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for instr in block:
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if 'op' in instr:
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op = instr['op']
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dest = instr.get('dest')
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args = instr.get('args', [])
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if op == 'alloc':
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# x = alloc n: x points to this allocation
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alloc_site = alloc_sites[id(instr)]
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state[dest] = set([alloc_site])
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elif op == 'id':
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y = args[0]
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if y in state:
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# Only update if y is in state
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state[dest] = state[y].copy()
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elif op == 'ptradd':
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p = args[0]
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if p in state:
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# Only update if p is in state
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state[dest] = state[p].copy()
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elif op == 'load':
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# x = load p: x points to all memory locations
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state[dest] = set(['unknown'])
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elif op == 'call':
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# Function calls can change pointers conservatively
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state[dest] = set(['unknown'])
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# Do not update state for non-pointer variables
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return state
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def memory_liveness_analysis(blocks, cfg, labels, alias_info):
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block_map = dict(zip(labels, blocks))
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live_in = {label: set() for label in labels}
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live_out = {label: set() for label in labels}
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changed = True
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while changed:
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changed = False
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for label in reversed(labels):
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block = block_map[label]
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alias_maps = alias_info[label]
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out_set = set()
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succs = cfg.get(label, [])
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for succ in succs:
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out_set.update(live_in[succ])
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old_in = live_in[label].copy()
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live_out[label] = out_set.copy()
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in_set = analyze_memory_uses(block, live_out[label], alias_maps)
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live_in[label] = in_set
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if live_in[label] != old_in:
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changed = True
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# print(f"[Liveness] Block: {label}, Live-In: {live_in[label]}")
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# print(f"[Liveness] Block: {label}, Live-Out: {live_out[label]}")
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return live_in, live_out
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def analyze_memory_uses(block, live_out_set, alias_maps):
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live_set = live_out_set.copy()
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for idx in reversed(range(len(block))):
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instr = block[idx]
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alias_map = alias_maps[idx]
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if 'op' in instr:
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op = instr['op']
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args = instr.get('args', [])
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if op == 'ret':
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if args:
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ret_var = args[0]
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pts = alias_map.get(ret_var, set())
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live_set.update(pts)
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elif op == 'store':
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p = args[0]
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pts = alias_map.get(p, set())
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# print(f"[Store Operation] Address: {p}, Points-To: {pts}, Live-Set Before: {live_set}")
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live_set.update(pts)
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elif op == 'load':
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p = args[0]
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pts = alias_map.get(p, set())
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live_set.update(pts)
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elif op == 'free':
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p = args[0]
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pts = alias_map.get(p, set())
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live_set -= pts
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elif op == 'call':
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for arg in args:
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pts = alias_map.get(arg, set())
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live_set.update(pts)
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return live_set
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def remove_dead_stores(func, alias_info, live_out):
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blocks = list(form_blocks(func['instrs']))
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cfg, labels = construct_cfg(blocks)
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block_map = dict(zip(labels, blocks))
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for label in labels:
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block = block_map[label]
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alias_maps = alias_info[label]
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live_vars = live_out[label].copy()
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new_block = []
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for idx in reversed(range(len(block))):
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instr = block[idx]
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alias_map = alias_maps[idx]
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if 'op' in instr and instr['op'] == 'store':
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p = instr['args'][0]
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pts = alias_map.get(p, set())
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if pts.isdisjoint(live_vars) and 'unknown' not in pts and 'unknown' not in live_vars:
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# print(f"[Remove Decision] Store Instruction: {instr}, Points-To: {pts}, Live Vars: {live_vars}")
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# Store is dead, eliminate it
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continue
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# print(f"[Keep Decision] Store Instruction: {instr}, Points-To: {pts}, Live Vars: {live_vars}")
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if 'op' in instr:
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op = instr['op']
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args = instr.get('args', [])
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if op == 'load':
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p = args[0]
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pts = alias_map.get(p, set())
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live_vars.update(pts)
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elif op == 'free':
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p = args[0]
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pts = alias_map.get(p, set())
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live_vars -= pts
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elif op == 'ret':
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if args:
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ret_var = args[0]
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pts = alias_map.get(ret_var, set())
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live_vars.update(pts)
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elif op == 'call':
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for arg in args:
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pts = alias_map.get(arg, set())
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live_vars.update(pts)
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new_block.append(instr)
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block[:] = reversed(new_block)
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func['instrs'] = flatten([block_map[label] for label in labels])
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def collect_alloc_sites(func):
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alloc_sites = {}
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counter = 0
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for instr in func['instrs']:
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if 'op' in instr and instr['op'] == 'alloc':
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alloc_sites[id(instr)] = f'alloc_{counter}'
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counter += 1
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return alloc_sites
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def get_func_args(func):
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args = []
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for arg in func.get('args', []):
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args.append(arg['name'])
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return args
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def optimize_function(func):
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blocks = list(form_blocks(func['instrs']))
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cfg, labels = construct_cfg(blocks)
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alloc_sites = collect_alloc_sites(func)
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func_args = get_func_args(func)
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# Perform alias analysis
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in_alias, out_alias = alias_analysis(blocks, cfg, labels, func_args, alloc_sites)
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# Get alias info at each instruction
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alias_info = {}
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block_map = dict(zip(labels, blocks))
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# print("labels:", labels)
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for label in labels:
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block = block_map[label]
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state = {var: locs.copy() for var, locs in in_alias.get(label, {}).items()}
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alias_maps = []
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for instr in block:
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alias_maps.append(state.copy())
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if 'op' in instr:
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op = instr['op']
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dest = instr.get('dest')
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args = instr.get('args', [])
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if op == 'alloc':
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alloc_site = alloc_sites[id(instr)]
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state[dest] = set([alloc_site])
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elif op == 'id':
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y = args[0]
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state[dest] = state.get(y, set()).copy()
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elif op == 'ptradd':
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p = args[0]
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state[dest] = state.get(p, set()).copy()
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elif op == 'load':
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state[dest] = set(['unknown'])
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elif op == 'call':
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state[dest] = set(['unknown'])
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alias_info[label] = alias_maps # Store the list of alias maps
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# Perform memory liveness analysis
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live_in, live_out = memory_liveness_analysis(blocks, cfg, labels, alias_info)
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# Remove dead stores
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remove_dead_stores(func, alias_info, live_out)
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def main():
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program = json.load(sys.stdin)
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for func in program['functions']:
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optimize_function(func)
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# print(program)
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json.dump(program, sys.stdout, indent=2)
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if __name__ == '__main__':
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main()

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