Update LLVM backend to use arbitrary precision integer for createEnumerator debug info

[andrewrk]

Currently if an enum tag has greater than 63 bits, we cannot create correct debug info for it.
http://lists.llvm.org/pipermail/llvm-dev/2017-December/119475.html

For example, these two enums have incorrect debug info for the tag values.

const Foo = enum (u64) {
    A = 18446744073709551615,
    B = 1,
    C = 2,
};

const Bar = enum(u128) {
    A = 340282366920938463463374607431768211455,
    B = 1,
    C = 2,
};

LLVM's API needs to be updated to allow an APInt instead of int64_t for the tag value.

[LemonBoy]

Here's the patch you were waiting for ;)

[andrewrk]

Wow, that looks like it took a lot of work. Thanks!

[data-man]

Here's the patch you were waiting for ;)

It would be great if this patch will be included to release 9.0
Please remind LLVM team! :)

[andrewrk]

Hmm, the patch never got merged. I'm not sure what step we failed to take to get it into master branch. I sent an email to the llvm-dev mailing list just now.

[camconn]

Sorry to necro bump, but it appears that @LemonBoy's patch has landed in the LLVM 11.0.1 release candidate.