[LLVMdev] How to get llvm bitcode executed

[Duncan Sands]

Hi Xialong,

> I have a program that uses C++ STL a lot. To have the source code for
> STL functions, I undefined "_GLIBCXX_EXTERN_TEMPLATE" in
> c++config.h. In spite of this, after compilation (via clang) and
> linking (via llvm-ld), the resulting bitcode contains a few declared
> functions (with no definitions).
>
> My question is: In the scenario where some function definitions are
> missing in a llvm bitcode, can we get a way to run this module via llc
> or lli? Or is there any way to make these function definitions
> available in the llvm bitcode?

with lli, you should be able to do it by adding
   -load=libstdc++.so
to the lli command line (maybe with a full path).  With llc, use g++
to the linking.  For example, if llc turned bitcode.bc into bitcode.s,
do
   g++ -o bitcode bitcode.s
since g++ automagically passes libstdc++ to the linker.  You can also
use the system linker directly, adding the missing libraries.

>
> Specifically, these missing functions are as below:
>
>    declare i8* @llvm.eh.exception() nounwind readonly

This is an LLVM intrinsic, so isn't really missing.

>    declare i32 @__gxx_personality_v0(...)

This should be in libstdc++.

>    declare i32 @llvm.eh.selector(i8*, i8*, ...) nounwind
>    declare void @llvm.eh.resume(i8*, i32)

LLVM intrinsics.

>    declare void @_ZSt9terminatev()

This should be in libstdc++.

>    declare i32 @memcmp(i8*, i8*, i64)

In libc (libc.so) which should be pulled in by libstdc++.

>    declare i64 @llvm.expect.i64(i64, i64) nounwind readnone

LLVM intrinsic.

>    declare void @_ZSt19__throw_logic_errorPKc(i8*) noreturn
>    declare i8* @__cxa_begin_catch(i8*)
>    declare void @__cxa_rethrow()
>    declare void @__cxa_end_catch()
>    declare void @__cxa_call_unexpected(i8*)
>    declare void @_ZdlPv(i8*) nounwind
>    declare void @_ZSt20__throw_length_errorPKc(i8*) noreturn
>    declare void @_ZSt17__throw_bad_allocv() noreturn
>    declare noalias i8* @_Znwm(i64)

These should all be in libstdc++.

>    declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
>    declare void @llvm.memmove.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i32, i1) nounwind
>    declare i32 @llvm.atomic.load.add.i32.p0i32(i32* nocapture, i32) nounwind
>    declare void @llvm.memory.barrier(i1, i1, i1, i1, i1) nounwind

LLVM intrinsics.

>    declare void @_ZSt20__throw_out_of_rangePKc(i8*) noreturn

This should be in libstdc++.

>    declare i64 @strlen(i8*)
>    declare void @abort()

In libc (libc.so) which should be pulled in by libstdc++.

Ciao, Duncan.

>
>
> Xiaolong
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