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Fix unused storage slots (#2439)
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* fix: don't alloc slots for repeated nonreentrancy keys

this is not a semantic bug but an optimization bug since we allocate
more slots than we actually need, leading to "holes" in the slot
allocator -- slots which are allocated but unused.

* make the test for nonreentrant slots harder
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charles-cooper authored Oct 25, 2021
1 parent 3931ba4 commit eae0eaf
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Showing 2 changed files with 45 additions and 24 deletions.
29 changes: 21 additions & 8 deletions tests/cli/outputs/test_storage_layout.py
Original file line number Diff line number Diff line change
@@ -1,26 +1,39 @@
from vyper.compiler import compile_code


def test_method_identifiers():
def test_storage_layout():
code = """
foo: HashMap[address, uint256]
baz: Bytes[65]
bar: uint256
@external
@nonreentrant("foo")
def public_foo():
def public_foo1():
pass
@external
@nonreentrant("foo")
def public_foo2():
pass
@internal
@nonreentrant("bar")
def _bar():
pass
# mix it up a little
baz: Bytes[65]
bar: uint256
@external
@nonreentrant("bar")
def public_bar():
pass
@external
@nonreentrant("foo")
def public_foo3():
pass
"""

out = compile_code(
Expand All @@ -30,12 +43,12 @@ def public_bar():

assert out["layout"] == {
"nonreentrant.foo": {"type": "nonreentrant lock", "location": "storage", "slot": 0},
"nonreentrant.bar": {"type": "nonreentrant lock", "location": "storage", "slot": 2},
"nonreentrant.bar": {"type": "nonreentrant lock", "location": "storage", "slot": 1},
"foo": {
"type": "HashMap[address, uint256][address, uint256]",
"location": "storage",
"slot": 3,
"slot": 2,
},
"baz": {"type": "Bytes[65]", "location": "storage", "slot": 4},
"bar": {"type": "uint256", "location": "storage", "slot": 8},
"baz": {"type": "Bytes[65]", "location": "storage", "slot": 3},
"bar": {"type": "uint256", "location": "storage", "slot": 7},
}
40 changes: 24 additions & 16 deletions vyper/semantics/validation/data_positions.py
Original file line number Diff line number Diff line change
Expand Up @@ -32,22 +32,30 @@ def set_storage_slots(vyper_module: vy_ast.Module) -> StorageLayout:

for node in vyper_module.get_children(vy_ast.FunctionDef):
type_ = node._metadata["type"]
if type_.nonreentrant is not None:
type_.set_reentrancy_key_position(StorageSlot(storage_slot))

# TODO this could have better typing but leave it untyped until
# we nail down the format better
variable_name = f"nonreentrant.{type_.nonreentrant}"
ret[variable_name] = {
"type": "nonreentrant lock",
"location": "storage",
"slot": storage_slot,
}

# TODO use one byte - or bit - per reentrancy key
# requires either an extra SLOAD or caching the value of the
# location in memory at entrance
storage_slot += 1
if type_.nonreentrant is None:
continue

variable_name = f"nonreentrant.{type_.nonreentrant}"

# a nonreentrant key can appear many times in a module but it
# only takes one slot. ignore it after the first time we see it.
if variable_name in ret:
continue

type_.set_reentrancy_key_position(StorageSlot(storage_slot))

# TODO this could have better typing but leave it untyped until
# we nail down the format better
ret[variable_name] = {
"type": "nonreentrant lock",
"location": "storage",
"slot": storage_slot,
}

# TODO use one byte - or bit - per reentrancy key
# requires either an extra SLOAD or caching the value of the
# location in memory at entrance
storage_slot += 1

for node in vyper_module.get_children(vy_ast.AnnAssign):
type_ = node.target._metadata["type"]
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