switch detection

[williballenthin]

samples:

• cc688ff3a525bac5e1241d13fae8d97a:10001EA1

[williballenthin]

32-bit added in 3e378a4b218e60efe8bf6f771543354ca5cd78e5

[williballenthin]

in mimi64, function 0x140056250 has a massive switch jmp at 0x1400562BF

[williballenthin]

some programs will place the jump tables contiguously, so need to be able to detect if the targets are already part of a prior jump table. if this is the case, then we need to remove the existing references. likewise, we should stop reading a jump table when encountering entries that already have references.

for example, given the following:

  jtable_1:
    j1
    j2
    j3
    j4
  jtable_2:
    j5
    j6
    j7
    j8

the cases:

1. consider that jtable_1 is already defined, and we want to now add jtable_2. need to remove the entries j5 - j8 from jtable_1 and add them to jtable_2.
2. consider that jtable_2 is already defined and we want to now add jtable_1. need to add only up to j4 and not continue across j5 and above.

note: we could probably have these two cases happening at the same time (a sandwich). so, we probably want to find the end of the logical array first, then find any prior tables, and finally update/add the xrefs.

[williballenthin]

external refs:

• https://github.com/vivisect/vivisect/pull/251
• https://github.com/vivisect/vivisect/pull/247#issuecomment-527244982