• name: mallocs
  • description: Remove mallocs
  • command-line: –translation-backendopt-mallocs
  • command-line for negation: –no-translation-backendopt-mallocs
  • option type: boolean option
  • default: True

This optimization enables “malloc removal”, which “explodes” allocations of structures which do not escape from the function they are allocated in into one or more additional local variables.

An example. Consider this rather unlikely seeming code:

class C:
def f(y):
    c = C()
    c.x = y
    return c.x

Malloc removal will spot that the C object can never leave f and replace the above with code like this:

def f(y):
    _c__x = y
    return _c__x

It is rare for code to be directly written in a way that allows this optimization to be useful, but inlining often results in opportunities for its use (and indeed, this is one of the main reasons PyPy does its own inlining rather than relying on the C compilers).

For much more information about this and other optimizations you can read section 4.1 of the technical report on “Massive Parallelism and Translation Aspects” which you can find on the Technical reports page.