Add modulo constant folding (#411)

* Add modulo constant folding * black --------- Co-authored-by: Steffen Enders <steffen.enders@fkie.fraunhofer.de>
fkie-cad · Jun 19, 2024 · 800a3c1 · 800a3c1
1 parent ba2a67a
commit 800a3c1
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Showing 2 changed files with 25 additions and 2 deletions.
diff --git a/decompiler/pipeline/controlflowanalysis/expression_simplification/constant_folding.py b/decompiler/pipeline/controlflowanalysis/expression_simplification/constant_folding.py
@@ -65,7 +65,12 @@ def constant_fold(operation: OperationType, constants: list[Constant], result_ty
     )
 
 
-def _constant_fold_arithmetic_binary(constants: list[Constant], fun: Callable[[int, int], int], norm_sign: Optional[bool] = None) -> int:
+def _constant_fold_arithmetic_binary(
+    constants: list[Constant],
+    fun: Callable[[int, int], int],
+    norm_sign: Optional[bool] = None,
+    allow_mismatched_sizes: bool = False,
+) -> int:
     """
     Fold an arithmetic binary operation with constants as operands.
 
@@ -84,7 +89,7 @@ def _constant_fold_arithmetic_binary(constants: list[Constant], fun: Callable[[i
 
     if len(constants) != 2:
         raise IncompatibleOperandCount(f"Expected exactly 2 constants to fold, got {len(constants)}.")
-    if not all(constant.type.size == constants[0].type.size for constant in constants):
+    if not allow_mismatched_sizes and not all(constant.type.size == constants[0].type.size for constant in constants):
         raise UnsupportedMismatchedSizes(f"Can not fold constants with different sizes: {[constant.type for constant in constants]}")
 
     left, right = constants
@@ -137,13 +142,19 @@ def _constant_fold_shift(constants: list[Constant], fun: Callable[[int, int], in
     return fun(normalize_int(left.value, left.type.size, norm_signed), right.value)
 
 
+def remainder(n, d):
+    return (-1 if n < 0 else 1) * (n % d)
+
+
 _OPERATION_TO_FOLD_FUNCTION: dict[OperationType, Callable[[list[Constant]], int]] = {
     OperationType.minus: partial(_constant_fold_arithmetic_binary, fun=operator.sub),
     OperationType.plus: partial(_constant_fold_arithmetic_binary, fun=operator.add),
     OperationType.multiply: partial(_constant_fold_arithmetic_binary, fun=operator.mul, norm_sign=True),
     OperationType.multiply_us: partial(_constant_fold_arithmetic_binary, fun=operator.mul, norm_sign=False),
     OperationType.divide: partial(_constant_fold_arithmetic_binary, fun=operator.floordiv, norm_sign=True),
     OperationType.divide_us: partial(_constant_fold_arithmetic_binary, fun=operator.floordiv, norm_sign=False),
+    OperationType.modulo: partial(_constant_fold_arithmetic_binary, fun=remainder, norm_sign=True, allow_mismatched_sizes=True),
+    OperationType.modulo_us: partial(_constant_fold_arithmetic_binary, fun=operator.mod, norm_sign=False, allow_mismatched_sizes=True),
     OperationType.negate: partial(_constant_fold_arithmetic_unary, fun=operator.neg),
     OperationType.left_shift: partial(_constant_fold_shift, fun=operator.lshift, signed=True),
     OperationType.right_shift: partial(_constant_fold_shift, fun=operator.rshift, signed=True),

diff --git a/tests/pipeline/controlflowanalysis/expression_simplification/test_constant_folding.py b/tests/pipeline/controlflowanalysis/expression_simplification/test_constant_folding.py
@@ -93,6 +93,18 @@ def test_constant_fold_invalid_value_type(
         (OperationType.divide_us, [_c_i32(3), _c_i16(4)], Integer.int32_t(), None, pytest.raises(UnsupportedMismatchedSizes)),
         (OperationType.divide_us, [_c_i32(3)], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),
         (OperationType.divide_us, [_c_i32(3), _c_i32(3), _c_i32(3)], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),
+        (OperationType.modulo, [_c_i32(13), _c_i32(4)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo, [_c_i32(-2147483647), _c_i32(2)], Integer.int32_t(), _c_i32(-1), nullcontext()),
+        (OperationType.modulo, [_c_u32(4), _c_i32(3)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo, [_c_i32(4), _c_i16(3)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo, [_c_i32(3)], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),
+        (OperationType.modulo, [_c_i32(3), _c_i32(3), _c_i32(3)], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),
+        (OperationType.modulo_us, [_c_i32(13), _c_i32(4)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo_us, [_c_i32(-2147483647), _c_i32(2)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo_us, [_c_u32(4), _c_i32(3)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo_us, [_c_i32(4), _c_i16(3)], Integer.int32_t(), _c_i32(1), nullcontext()),
+        (OperationType.modulo_us, [_c_i32(3)], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),
+        (OperationType.modulo_us, [_c_i32(3), _c_i32(3), _c_i32(3)], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),
         (OperationType.negate, [_c_i32(3)], Integer.int32_t(), _c_i32(-3), nullcontext()),
         (OperationType.negate, [_c_i32(-2147483648)], Integer.int32_t(), _c_i32(-2147483648), nullcontext()),
         (OperationType.negate, [], Integer.int32_t(), None, pytest.raises(IncompatibleOperandCount)),