Bitfields don't seem to decompile very well

[jrmuizel]

Given a program like:

struct A {
        int a: 4;
        int b: 4;
        int c;
};

int test(struct A* v) {
        if (v->a == 4) {
                return 1;
        } else {
                return 2;
        }
}

which compiles to

push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    -0x8(%rbp),%rax
movzbl (%rax),%eax
and    $0xf,%eax
cmp    $0x4,%al
jne    1d <test+0x1d>
mov    $0x1,%eax
jmp    22 <test+0x22>
mov    $0x2,%eax
pop    %rbp
retq

When A is defined to contain a bit field the decompiler produces:

undefined8 test(A *param_1)

{
  undefined8 uVar1;
  
  if ((*(byte *)param_1 & 0xf) == 4) {
    uVar1 = 1;
  }
  else {
    uVar1 = 2;
  }
  return uVar1;
}

vs

undefined8 test(Value *param_1)

{
  undefined8 uVar1;
  
  if ((param_1->a_and_b & 0xfU) == 4) {
    uVar1 = 1;
  }
  else {
    uVar1 = 2;
  }
  return uVar1;
}

when the fields are not separated into the appropriate bitfields.

[ryanmkurtz]

Full support for bitfield references within the decompiler is planned for a future release.

[ryanmkurtz]

Duplicate of #647.