The problem is that for x86 the way the opcodes are defined (both Intel and AT&T syntax) suggests a much more orthogonal instruction set than it is (in x86-64 i

The problem is that for x86 the way the opcodes are defined (both Intel and AT&T syntax) suggests a much more orthogonal instruction set than it is (in x86-64 it is even worse). So I consider the problem that you tell in your second paragraph as the classical problem of hitting the walls of a leaky abstraction (full disclosure: for some private side project that I work on I try to develop a way to mitigate this problem; don't ask me about details yet).