[LLVMdev] Issues in converting C++ code to C using llvm and llc

[Duncan Sands]

Hi Raj,

> I came to know from a friend that using LLVM insfrastucture one can convert C++
> programs to C. I needed this for my cross-compiler because we don't have support
> for C++ compilation in our cross-compiler.

as described in the release notes, the C backend is deprecated and in any case
doesn't work properly.

Ciao, Duncan.

>
> I tried following:
> http://llvm.org/docs/FAQ.html#translatecxx
>
> While I can generate .bc its llc which gives error. Then I also tried "clang" as
> oppose to llvm-g++.
>
> Here is what I want to accomplish: I have a simple c++ prog which I want to
> convert to c using llvm
> -----------------------------------------------------------------
>
> For example
> -------------------------------------------------------------------------
> c++ orig file: test_orig.cpp
> -----
> #include<iostream>
> int main()
> {
>    std::cout << "hello world from C++\n";
>    return 0;
> }
> ---------------------------------
> c orig file: test_orig.c
> -----
> #include<stdio>
> int main()
> {
>    printf("Hello workd from C\n");
>    return 0;
> }
> -------------------------------------
> I used following commands
>
> % clang -c -emit-llvm test_orig./*EXT*/ -o test_orig.bc
> or
> % llvm-g++ -c -emit-llvm test_orig./*EXT*/ -o test_orig.bc
>
>
> % llc -march=c test_orig.bc -o test_new.c
>
> and then I simply used gcc to compile test_new.c
> gcc test_new.c
>
> When /*EXT*/ is .c then everything works fine however when it is .cpp then when
> I try to recompile the test_new.c using gcc it says undefiend references to
> std::cout, std::basic_ostream, std::ios_base
>
> I thought that llvm should be able to convert "cout" to "printf" or equivalent.
> Also how does llvm handles the libraries which are not part of std C but are in C++.
> -----------------------------------------
>
> When I tried to compile my original benchmarks (They are from PARSEC suite)
> I see this error
>
> LLVM_ERROR: code generator does not support intrinsic function
> "llvm.umul.with.overflow.i32"
>
> How can I avoid this. I am running things on 64-bit Intel machine loaded with
> CentOS 5.x
>
> Any help/pointers to solve the above issues would be highly appriciated.
>
> Thanks,
> -Raj
>
>
>
>
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