compReturnType: Compute the type of the R return type from a routine

In duncantl/NativeCodeAnalysis: Tools to analyze native code (C/C++) related to R.

Compute the type of the R return type from a routine

Description

This function examines an native/IR (LLVM intermediate representation) Function that returns an R object (SEXP). It examines the native code to find the possible R types that are returned and returns a description for each of these possible types. These types are currently described as scalars, vectors, lists, matrices, NULL, and where possible, the length/dimensions of the vectors/matrices and also from which parameters these were computed.

Note that while the approach is reasonably general, the current implementation works with IR code that has been generated with an optimization level of 1 or higher, not -O0. With -O0, we currently recover some of the information but not necessarily the class and element names. This can be fixed, but just requires some additional steps to be added to the existing code.

Usage

compReturnType(fun, toc = NULL, blocks = getBlocks(fun))

Arguments

fun	the IR Function object whose return type is to be computed
toc	a table-of-contents of different modules so that we can find called functions that might be in other modules
blocks	the basic blocks for the fun object

Details

What we are moving towards is being able to find native code that for example calls ScalarReal and identifying this as a scalar. This works, at least for some cases. When we find native code of the form Rf_allocVector(REALSXP, n), we capture how n is calculated. If this is Rf_nrows(x), we record that this is the number of rows of a data.frame/matrix computed from x. The function also detects lists and determines the types of the elements and also the names of the elements if they are set.

Value

A list with elements for each of the different return paths. The elements describe the R types. These can be scalars, vectors, matrices, NULL, ....

S4 objects are represented by S4Instance.

We will change the nature of the R representations of the type descriptions in the future. For now, this is more proof-of-concept.

Author(s)

DTL

See Also

getRReturnTypes which will probably be removed.

duncantl/NativeCodeAnalysis documentation built on Nov. 20, 2023, 5:44 a.m.