x86-64: tighten convert-load-reloc checking

Even if the assembler avoids using relaxable relocations for
inapplicable insns, such relocations can still appear for other reasons.
Be more thorough in the opcode checking we do, to avoid bogusly altering
other insns.

Furthermore correct an opcode mask (even if with the added condition
that's now fully benign).
4 files changed