[LLVMdev] [RFC] OpenMP Representation in LLVM IR

[dag at cray.com]

Andrey Bokhanko <andreybokhanko at gmail.com> writes:

>> Again, I only skimmed the document, but I was left with the question,
>> "why not just make calls to runtime routines?"
>
> Granted, this is the easiest and cheapest way to support OpenMP...
> that throws away the whole notion of "optimizing compilation" and
> "front-end / back-end decoupling".

How?  Nothing prevents the use of an intermediate layor to handle
high-level transformation.

> Wait a sec... LLVM IR is meant to be portable and supporting
> "life-long program analysis and transformation". Locking it with
> target machine's OpenMP runtime calls from the very beginning is not
> the best way to acheive these goals. Same with physical registers --
> this must be the reason why they invented virtual ones several decades
> ago.

Sure, I understand the whys of the proposal and I understand that
intrisics can be valuable.  I don't want to lose the low-level nature of
LLVM and these proposals (not just parallelization, but GPU IR,
eval-style inline bitcode, etc.) are starting to feel like
mission-creep.

That's all.  I'm not forcibly objecting to anything.  Just passing on
thoughts.

> The reasons are listed in "Function Outlining" section of my proposal.
> You simply dimissed them with:

I apologize for offending you.  That was certainly not my intent.

                             -David