[mypyc] Fix division of negative tagged int (#11168)

The rounding was incorrect for some negative values, because of a bug
related to the tagged integer logic. For example, -5 // 2 evaluated to
-4 instead of -3 (ouch). Change the rounding implementation to not use
shifted integers.

Also add more exhaustive testing and fix a broken integer test case.

Author: JukkaL

mypyc/lib-rt/int_ops.c

@@ -190,16 +190,17 @@ CPyTagged CPyTagged_Multiply(CPyTagged left, CPyTagged right) {
 }
 
 CPyTagged CPyTagged_FloorDivide(CPyTagged left, CPyTagged right) {
-    if (CPyTagged_CheckShort(left) && CPyTagged_CheckShort(right)
+    if (CPyTagged_CheckShort(left)
+        && CPyTagged_CheckShort(right)
         && !CPyTagged_MaybeFloorDivideFault(left, right)) {
-        Py_ssize_t result = ((Py_ssize_t)left / CPyTagged_ShortAsSsize_t(right)) & ~1;
+        Py_ssize_t result = CPyTagged_ShortAsSsize_t(left) / CPyTagged_ShortAsSsize_t(right);
         if (((Py_ssize_t)left < 0) != (((Py_ssize_t)right) < 0)) {
-            if (result / 2 * right != left) {
+            if (result * right != left) {
                 // Round down
-                result -= 2;
+                result--;
             }
         }
-        return result;
+        return result << 1;
     }
     PyObject *left_obj = CPyTagged_AsObject(left);
     PyObject *right_obj = CPyTagged_AsObject(right);

mypyc/test-data/fixtures/ir.py

@@ -286,7 +286,8 @@ def next(i: Iterator[T]) -> T: pass
 def next(i: Iterator[T], default: T) -> T: pass
 def hash(o: object) -> int: ...
 def globals() -> Dict[str, Any]: ...
-def setattr(object: Any, name: str, value: Any) -> None: ...
+def getattr(obj: object, name: str) -> Any: ...
+def setattr(obj: object, name: str, value: Any) -> None: ...
 def enumerate(x: Iterable[T]) -> Iterator[Tuple[int, T]]: ...
 @overload
 def zip(x: Iterable[T], y: Iterable[S]) -> Iterator[Tuple[T, S]]: ...

mypyc/test-data/run-integers.test

@@ -131,6 +131,14 @@ assert neg(-9223372036854775807) == 9223372036854775807
 assert neg(9223372036854775808) == -9223372036854775808
 assert neg(-9223372036854775808) == 9223372036854775808
 
+[case testIsinstanceIntAndNotBool]
+def test_isinstance_int_and_not_bool(value: object) -> bool:
+    return isinstance(value, int) and not isinstance(value, bool)
+[file driver.py]
+from native import test_isinstance_int_and_not_bool
+assert test_isinstance_int_and_not_bool(True) == False
+assert test_isinstance_int_and_not_bool(1) == True
+
 [case testIntOps]
 def check_and(x: int, y: int) -> None:
     # eval() can be trusted to calculate expected result
@@ -157,15 +165,6 @@ def check_bitwise(x: int, y: int) -> None:
             check_or(ll, rr)
             check_xor(ll, rr)
 
-[case testIsinstanceIntAndNotBool]
-def test_isinstance_int_and_not_bool(value: object) -> bool:
-    return isinstance(value, int) and not isinstance(value, bool)
-[file driver.py]
-from native import test_isinstance_int_and_not_bool
-assert test_isinstance_int_and_not_bool(True) == False
-assert test_isinstance_int_and_not_bool(1) == True
-
-
 SHIFT = 30
 DIGIT0a = 615729753
 DIGIT0b = 832796681
@@ -198,6 +197,10 @@ def test_and_or_xor() -> None:
     check_bitwise(BIG_SHORT, DIGIT0a + DIGIT1a + DIGIT2a)
     check_bitwise(BIG_SHORT, DIGIT0a + DIGIT1a + DIGIT2a + DIGIT50)
 
+    for x in range(-25, 25):
+        for y in range(-25, 25):
+            check_bitwise(x, y)
+
 def test_bitwise_inplace() -> None:
     # Basic sanity checks; these should use the same code as the non-in-place variants
     for x, y in (DIGIT0a, DIGIT1a), (DIGIT2a, DIGIT0a + DIGIT2b):
@@ -328,3 +331,15 @@ def test_int_as_bool() -> None:
     for x in 1, 55, -1, -7, 1 << 50, 1 << 101, -(1 << 50), -(1 << 101):
         assert is_true(x)
         assert not is_false(x)
+
+def test_divide() -> None:
+    for x in range(-100, 100):
+        for y in range(-100, 100):
+            if y != 0:
+                assert x // y == getattr(x, "__floordiv__")(y)
+
+def test_mod() -> None:
+    for x in range(-100, 100):
+        for y in range(-100, 100):
+            if y != 0:
+                assert x % y == getattr(x, "__mod__")(y)