[bin2llvmir] AARCH64 C++ Class constructor generates @__decompiler_undefined_function_0

when running a retdec-decompiler.py --no-memory-limit --backend-no-opts on a ELF binary built for AARCH64/FreeBSD, I get several @__decompiler_undefined_function_0 being injected at the beginning of class functions

```
File format : ELF
File class : 64-bit
File type : DLL
Architecture : ARM AARCH64
Endianness : Little endian
Entry point address : 0
Entry point offset : 0x788
Entry point section name : .text
Entry point section index: 1
Bytes on entry point : 00000000080000004d4f443030bdc600f85fc70038d2311178e8a90054b9ad00f85fc700f30f1ef8fd7b01a9fd430091ffc3
Detected tool : gc (compiler), 33 from 191 significant nibbles (17.2775%)
```

Here is a disassembled C++ class constructor :
```
movn x8, #0xffff, lsl #16
movk x8, #0x5c0
stp x8, xzr, [x0]
str wzr, [x0, #0x10]
ret
```
That seems to perform some variable initializations, x0 is supposed to be the object location, hence the stores relative to it.
But on the LLVM IR I get :
```
%0 = call i64 @__decompiler_undefined_function_0()
%1 = inttoptr i64 %0 to i64*, !insn.addr !482175
store i64 -4294965824, i64* %1, align 8, !insn.addr !482175
%2 = add i64 %0, 8, !insn.addr !482175
%3 = inttoptr i64 %2 to i64*, !insn.addr !482175
store i64 0, i64* %3, align 8, !insn.addr !482175
%4 = add i64 %0, 16, !insn.addr !482176
%5 = inttoptr i64 %4 to i32*, !insn.addr !482176
store i32 0, i32* %5, align 4, !insn.addr !482176
ret i64 %0, !insn.addr !482177
```
Which get transformed in C :
```
int64_t result; // 0x48465c
// 0x48465c
*(int64_t *)result = -0xfffffa40;
*(int64_t *)(result + 8) = 0;
*(int32_t *)(result + 16) = 0;
return result;
```

It seems to me retdec can't detect the reference to the object and uses absolute offsets instead. I'm quite new to the project, so I'm not sure where to start (and I could have missed something in the setup 😉 )
What do you reckon ?

Reproduce the AARCH64/FreeBSD case with retdec-decompiler.py --no-memory-limit --backend-no-opts and inspect the bin2llvmir output for the shown constructor. Trace how the constructor’s x0 object pointer becomes __decompiler_undefined_function_0 and compare the generated LLVM IR with the disassembly. Done means the object-relative stores no longer use an undefined absolute base.

Written by the indexing model from the issue text.