[PATCH] Add an option to allow JumpInstrTables to set unnamed_addr and jumptable on all address-taken functions

[Tom Roeder]

On Tue, Jun 24, 2014 at 12:00 PM, Tom Roeder <tmroeder at google.com> wrote:
> On Mon, Jun 23, 2014 at 12:18 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
>> Tom Roeder wrote:
>>> I don't see why this should have anything to do with a front end
>>> component, though it might make sense eventually to have a high-level
>>> flag like that in clang that sets a lower-level flag. Currently, I
>>> just pass flags directly to LTO through clang with
>>>
>>> -Wl,--plugin-opt=-jump-table-type=arity
>>
>>
>> Mostly I want to have a single place to decide whether we're going to do the
>> jump table transform or not. The reason it goes in the frontend is because
>> it actually changes language semantics, the frontend may want to emit
>> different IR, or may want to warn the user that "&func1 == my_funcptr" isn't
>> going to work when CFI is on. If you did have it in the frontend, I don't
>> see why you would also need a plugin option.
>
> That makes sense; I'll look into it.

It looks fairly straightfoward to add the option in clang; however,
after thinking about it some more, I think that even with a frontend
option, there still needs to be a way to trigger CFI from the back end
directly, since there needs to be some way to write CFI regression
tests in LLVM directly without using clang.