Mypyc Object Representation

Mypyc uses a tagged pointer representation for values of type int (CPyTagged), char for booleans, and C structs for tuples. For most other objects mypyc uses the CPython PyObject *.

Python integers that fit in 31/63 bits (depending on whether we are on a 32-bit or 64-bit platform) are represented as C integers (CPyTagged) shifted left by 1. Integers that don't fit in this representation are represented as pointers to a PyObject * (this is always a Python int object) with the least significant bit set. Tagged integer operations are defined in mypyc/lib-rt/int_ops.c and mypyc/lib-rt/CPy.h.

There are also low-level integer types, such as int32 (see mypyc.ir.rtypes), that don't use the tagged representation. These types are not exposed to users, but they are used in generated code.