Barrel shifted operands sometimes crash the transpiler

[Shai-Aviv]

Consider the following input:

    .arch armv8-a
    .file   "bug.c"
    .text
    .align  2
    .global main
    .type   main, %function
main:
    add w0, w0, w0, lsl 1
    ret
    .size   main, .-main
    .ident  "GCC: (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0"
    .section    .note.GNU-stack,"",@progbits

On my machine (Ubuntu 18.04 LTS running in Docker on RHEL 7.5), the output of arm2riscv.py for this input is distributed as follows:

• 55% of times - the output is okay, no errors:

  .file   "bug.c"
        .section .tdata
  REG_BANK:
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
  .text
  .align  2
  .global main
  .type   main, %function
  main:
  la  s5, REG_BANK
  slliw   s10, a0, 1
  addw    a0, a0, s10
  ret
  .size   main, .-main
  .ident  "GCC: (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0"
  .section    .note.GNU-stack,"",@progbits
  

• 23% of times - I get this error:

  Traceback (most recent call last):
  File "./arm2riscv.py", line 89, in <module>
    buffer.append(instructions[op](op, [tmpreg, shifts['shift_reg'], shifts['shift_by']]))
  File "/home/shayaviv/arm2riscv/aarch64_instructions.py", line 49, in __init__
    self.specific_regs = safe_pullregs(operands)
  File "/home/shayaviv/arm2riscv/instr_helpers.py", line 18, in safe_pullregs
    if 'register' in o.keys():
  AttributeError: 'NoneType' object has no attribute 'keys'

• 22% of times - I get a partial output:

  .file   "bug.c"
        .section .tdata
  REG_BANK:
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
        .dword 0
  .text
  .align  2
  .global main
  .type   main, %function
  main:
  la  s5, REG_BANK

  followed by this error:

  Traceback (most recent call last):
  File "./arm2riscv.py", line 125, in <module>
    line.emit_riscv()
  File "/home/shayaviv/arm2riscv/aarch64_instructions.py", line 176, in emit_riscv
    dest, s1, s2 = self.get_args()
  ValueError: too many values to unpack (expected 3)

I suspect that the bug has something to do with the random ordering of keys in Python's dict or set types, but I'm only guessing.

[schorrm]

In Python 3.6+ dict keys aren't randomly ordered, and I didn't use sets at all, so I'm really not sure what happened here. Trying to figure out.

[schorrm]

Tracked it down, it occurs at the grammar phase. Now to fix this.

[Shai-Aviv]

What a swift response! Thank you

[schorrm]

Fixed some issues with rules priorities, I think it should be addressed now (I just ran this about 30 times without a crash).