dynamic ISA change specification: runtime option for new opcodes

_From [derek.br...@gmail.com](https://code.google.com/u/117968039472581148324/) on February 24, 2009 14:51:17_

this was PR 278248

To avoid DR failing on the latest ISA changes we should consider adding
runtime options that can be used as workarounds.

An event on an invalid opcode is not good enough: if we get the length
wrong we can mess up later on. Need a way to specify ISA changes up front.

We'd need some kind of language. For example, for adding support for the
3-byte-opcode SSSE3 instructions we might support an option like this:

-opcode "0x0f 0x38 \* modrm"

Both fast and slow decode paths would have to honor the option before the
built-in decode tables.

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=57_