[PATCH][x86_64] Convert indirect call via GOT to direct when possible

[Cary Coutant]

>> 2. HJ, given an R_X86_64_GOTPCRELX relocation, is it still necessary
>> to check the opcode during Scan::global()? Doesn't the relocation
>> guarantee that it's an appropriate instruction for the transformation?
>> I think in both cases, we could skip fetching the section contents if
>> we have this relocation.
>
> Doesn't gold make different decision based on opcode, like
> branch vs non-branch?

Only during actual relocation, when we necessarily have the section
contents already available. During relocation scanning, it would be
nice to avoid reading the section contents.

-cary