[CIR][CIRGen][Builtin] Support __sync_add_and_fetch

[ghehg]

Notable change is to introduce helper function buildBinaryAtomicPost which models on OG's EmitBinaryAtomicPost. Comparing to EmitBinaryAtomicPost, buildBinaryAtomicPost is more concise as OG's EmitBinaryAtomicPost duplicates quite a bit of code from MakeBinaryAtomicValue
Also, didn't implement invert as __sync_add_and_fetch does not need it, but will add it (which is a trivial work) when we implement a builtin that needs it.
Test cases are from OG

[bcardosolopes]

Also, didn't implement invert as __sync_add_and_fetch does not need it

What do you mean?

[bcardosolopes]

*only

[ghehg]

Also, didn't implement invert as __sync_add_and_fetch does not need it

What do you mean?

OG has additional argument invert and code like the following to flip bits of result.

 if (Invert)
    Result =
        CGF.Builder.CreateBinOp(llvm::Instruction::Xor, Result,
                                llvm::ConstantInt::getAllOnesValue(IntType));

I didn't implement them so to keep test coverage , but will implement them when we implement __sync_nand_and_fetch which seems to be only case for this logic.
Or I might just do it at client site as again, __sync_nand_and_fetch seems to be the only use.

[github-actions]

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[bcardosolopes]

I didn't implement them so to keep test coverage

Where's the missing feature assert + comments talking about that in code?

[ghehg]

I didn't implement them so to keep test coverage

Where's the missing feature assert + comments talking about that in code?
You are right, should add missing feature assert + comments when the code is different from OG.

[bcardosolopes]

One minor conflict, but otherwise LGTM