[llvm-dev] mapping a returned struct (from IR) to std::vector<GenericValue>

[koffie drinker via llvm-dev]

Hi all,

I'm working on a run time that allows you to run code on the fly. My
language allows users to define custom structs.

Once I have generated a func that returns a struct, I would like to map the
function result back to a std::vector<GenericValue> to be used in the c++
part. For normal return types (char, ints, double) its easy to cast to
their function pointer and execute and wrap the results.

// for double f();
auto func = (double (*f)()) engine->getFunctionAddress("f");
double result = func();

// how to do this for exampleStruct {double, double}, where example struct
is defined by the user
// exampleStruct f();
// we can't do auto func = (exampleStruct (*f)())
engine->getFunctionAddress("f");
// since example struct is defined by the user inside the
runtime/interpreter
??

How can I cast a function that returns a user defined struct ? I know the
layout of the struct, but the struct layout might be different in the IR vs
C++? I know I could alloc memory in the func and return a ptr to a struct
(returned as void* ), and use that as an offset to read the struct values,
but I would like to avoid using a ptr in this case. What would be the right
approach in ths case?

I tried to look into t he executionengine::runFunction but, they are
incomplete.
I'm using llvm 3.7 btw.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20151230/0a23109e/attachment.html>