[BUG] RetroWrite does not symbolize RIP-relative addressing and omits the definition of labels

[witbring]

Describe the bug

1. RetroWrite fails on symbolizing RIP-relative addressing. I observed that RetroWrite fails on recovering RIP-relative addressing. As an example, given instruction  ‘leaq fix_syms(%rip), %rsi’ found in addr2line of binutils, RetroWrite reassembled the instruction as ‘leaq 5(%rip), %rsi’.

• Compiler-generated assembly

  
  _bfd_fix_excluded_sec_syms:             
  .cfi_startproc
  movq    %rdi, %rdx
  movq    40(%rsi), %rdi
  leaq    fix_syms(%rip), %rsi
  jmp bfd_link_hash_traverse          # TAILCALL
  .cfi_endproc

fix_syms:
.cfi_startproc pushq %r14

- Binary

00000000000a663f <_bfd_fix_excluded_sec_syms>: a663f: mov %rdi,%rdx a6642: mov 0x28(%rsi),%rdi a6646: lea 0x5(%rip),%rsi # a6652 a664d: jmpq a3ec0

00000000000a6652 : a6652: push %r14

- Reassembler-generated assembly 

.LCa6646: leaq 5(%rip), %rsi

2. RetroWrite omits the definition of some labels. 
Also, I found that RetroWrite sometimes omits some definitions of labels. For example, given the data pointer 0x170c80, RetroWrite symbolized the pointer as '.LC170c80', but RetroWrite misses the definition of the label '.LC170c80'. As a result, it causes a compilation error. 

**Describe how to reproduce the bug**
1. Platform: x86-64.
2. Compiler: Clang v12.0 and GCC v7.5.0
3. Binary: addr2line in binutils-2.31.1