def _transform(self, node):
overflow = 1 << self.cellsize
tr = Transformer(node)
for i, cur in tr:
if not isinstance(cur, While): continue
if not isinstance(cur.cond, MemNotEqual): continue
target = cur.cond.target
value = cur.cond.value
if len(cur) == 1 and isinstance(cur[0], MovePointer):
tr.replace(SeekMemory(target, cur[0].offset, value))
continue
if cur.offsets() != 0: continue
flag = True # whether Repeat[] is applicable
cell = Expr()
mode = 0 # 0:adjust, 1:set, -1:unknown
for inode in cur:
if isinstance(inode, SetMemory):
if inode.offset == target:
if inode.delta.simple():
cell += inode.delta
else:
cell = inode.value
mode = 1
else:
if not inode.pure():
flag = False
if inode.offsets() != 0:
flag = False
mode = -1
updates = inode.postupdates().unsure
if None in updates or target in updates:
flag = False
mode = -1
refs = inode.postreferences().unsure - inode.postupdates().sure
if None in refs or target in refs:
flag = False # references target, cannot use Repeat[]
if mode < 0 or not cell.simple(): continue
delta = (value - int(cell)) % overflow
if mode > 0:
if delta == 0:
# XXX SetMemory is added temporarily; we should implement
# SSA-based optimizer and it will recognize them across basic blocks
tr.replace(If(cur.cond, cur[:]), SetMemory(target, value))
else:
infloop = While(Always())
if not cur.pure(): # e.g. +[.[-]+]
infloop.extend(cur)
tr.replace(infloop)
elif flag:
# let w be the overflow value, which is 256 for char etc.
# then there are three cases in the following code:
# i = 0; for (j = 0; i != x; ++j) i += m;
#
# 1. if m = 0, it loops forever.
# 2. otherwise, the condition j * m = x (mod w) must hold.
# let u * m + v * w = gcd(m,w), and
# 1) if x is not a multiple of gcd(m,w), it loops forever.
# 2) otherwise it terminates and j = u * (x / gcd(m,w)).
#
# we can calculate u and gcd(m,w) in the compile time, but
# x is not (yet). so we shall add simple check for now.
if delta == 0:
tr.replace(While(Always()))
continue
u, v, gcd = _gcdex(delta, overflow)
diff = Expr[target] - value
count = (u % overflow) * (diff // gcd)
inodes = [
inode for inode in cur
if not (isinstance(inode, SetMemory)
and inode.offset == target)
]
result = []
if gcd > 1:
# no need to check if x is a multiple of gcd(m,w) (=1).
result.append(
If(NotEqual(diff % gcd, 0), [While(Always())]))
if inodes:
# don't emit Repeat[] if [-] or [+] is given.
result.append(Repeat(count, inodes))
result.append(SetMemory(target, value))
tr.replace(*result)
return cleanup(node)
def _transform(self, node):
unusedcells = {} # cell -> node which last updated this cell
unusednodes = set()
unusedmoves = []
offsets = 0
tr = Transformer(node)
for i, cur in tr:
ioffsets = cur.offsets()
if ioffsets is None:
unusedcells.clear()
unusednodes.clear()
else:
offsets += ioffsets
pure = cur.pure() and cur.returns()
if pure: # to remove non-I/O nodes independent to memory cells
unusedmoves.append(i)
irefs = cur.postreferences().unsure
iupdates = cur.postupdates().sure
removable = pure and ioffsets == 0
if irefs or iupdates:
# any pointer moves before this cell cannot be removed
del unusedmoves[:]
# delete references to all nodes which updates the cell which
# this node can reference, thus cannot be removed.
if None in irefs:
unusedcells.clear()
unusednodes.clear()
else:
for j in irefs:
j += offsets
try:
unusednodes.discard(unusedcells.pop(j))
except:
pass
# now removes all nodes which cell updates have been never
# referenced, and is to be (certainly) updated by this node.
iupdates.discard(None)
for j in iupdates:
j += offsets
try:
oldi = unusedcells[j]
unusednodes.remove(oldi) # will raise exception if none
node[oldi] = Nop()
except:
pass
if removable:
unusedcells[j] = i
unusednodes.add(i)
if isinstance(node, Program):
for i in unusednodes:
node[i] = Nop()
for i in unusedmoves:
node[i] = Nop()
return cleanup(node)
def _transform(self, node):
overflow = 1 << self.cellsize
tr = Transformer(node)
for i, cur in tr:
if not isinstance(cur, While):
continue
if not isinstance(cur.cond, MemNotEqual):
continue
target = cur.cond.target
value = cur.cond.value
if len(cur) == 1 and isinstance(cur[0], MovePointer):
tr.replace(SeekMemory(target, cur[0].offset, value))
continue
if cur.offsets() != 0:
continue
flag = True # whether Repeat[] is applicable
cell = Expr()
mode = 0 # 0:adjust, 1:set, -1:unknown
for inode in cur:
if isinstance(inode, SetMemory):
if inode.offset == target:
if inode.delta.simple():
cell += inode.delta
else:
cell = inode.value
mode = 1
else:
if not inode.pure():
flag = False
if inode.offsets() != 0:
flag = False
mode = -1
updates = inode.postupdates().unsure
if None in updates or target in updates:
flag = False
mode = -1
refs = inode.postreferences().unsure - inode.postupdates().sure
if None in refs or target in refs:
flag = False # references target, cannot use Repeat[]
if mode < 0 or not cell.simple():
continue
delta = (value - int(cell)) % overflow
if mode > 0:
if delta == 0:
# XXX SetMemory is added temporarily; we should implement
# SSA-based optimizer and it will recognize them across basic blocks
tr.replace(If(cur.cond, cur[:]), SetMemory(target, value))
else:
infloop = While(Always())
if not cur.pure(): # e.g. +[.[-]+]
infloop.extend(cur)
tr.replace(infloop)
elif flag:
# let w be the overflow value, which is 256 for char etc.
# then there are three cases in the following code:
# i = 0; for (j = 0; i != x; ++j) i += m;
#
# 1. if m = 0, it loops forever.
# 2. otherwise, the condition j * m = x (mod w) must hold.
# let u * m + v * w = gcd(m,w), and
# 1) if x is not a multiple of gcd(m,w), it loops forever.
# 2) otherwise it terminates and j = u * (x / gcd(m,w)).
#
# we can calculate u and gcd(m,w) in the compile time, but
# x is not (yet). so we shall add simple check for now.
if delta == 0:
tr.replace(While(Always()))
continue
u, v, gcd = _gcdex(delta, overflow)
diff = Expr[target] - value
count = (u % overflow) * (diff // gcd)
inodes = [inode for inode in cur if not (isinstance(inode, SetMemory) and inode.offset == target)]
result = []
if gcd > 1:
# no need to check if x is a multiple of gcd(m,w) (=1).
result.append(If(NotEqual(diff % gcd, 0), [While(Always())]))
if inodes:
# don't emit Repeat[] if [-] or [+] is given.
result.append(Repeat(count, inodes))
result.append(SetMemory(target, value))
tr.replace(*result)
return cleanup(node)
def _transform(self, node):
backrefs = {}
usedrefs = {}
substs = {} # only for simple one, unless some vars are not current
tr = Transformer(node)
for i, cur in tr:
cur.withmemory(substs)
alters = mergable = False
offset = None
refs = []
if isinstance(cur, Nop):
pass
elif isinstance(cur, SetMemory):
alters = mergable = True
offset = cur.offset
if cur.value.simple():
substs[offset] = cur.value
elif cur.delta.simple():
if offset in substs:
substs[offset] += cur.delta
if substs[offset].simple():
# replace with equivalent SetMemory node.
cur = SetMemory(offset, substs[offset])
tr.replace(cur)
else:
del substs[offset]
else:
try:
del substs[offset]
except:
pass
elif isinstance(cur, Input):
alters = True
offset = cur.offset
try:
del substs[offset]
except:
pass
elif isinstance(cur, Output):
pass
else: # MovePointer, While etc.
backrefs.clear()
usedrefs.clear()
substs.clear()
if isinstance(cur, (While, If)) and isinstance(
cur.cond, MemNotEqual):
substs[cur.cond.target] = cur.cond.value
elif isinstance(cur, SeekMemory):
substs[cur.target] = cur.value
refs = cur.postreferences().unsure
merged = False
if alters:
if not mergable:
# prohibit next merging attempt.
try:
del backrefs[offset]
except:
pass
else:
# we can merge node[target] and node[i] if:
# - no operation has changed cell k between them. (thus such target
# is backrefs[offset], as it is updated after change)
# - no operation has referenced the target cell between them.
# node[target] itself could reference that cell.
# - no operation has changed cell(s) referenced by value.
# similar to above, node[target] is excluded from this rule.
if offset in backrefs:
target = backrefs[offset]
if target >= usedrefs.get(offset, -1) and \
all(target >= backrefs.get(ioffset, -1) for ioffset in refs):
assume = {offset: node[target].value}
node[target].value = cur.value.withmemory(assume)
tr.replace()
merged = True
if not merged:
backrefs[offset] = i
if not merged:
target = i
for ioffset in refs:
usedrefs[ioffset] = target
return cleanup(node)
