[PATCH] D69785: [OpenMP] Introduce the OpenMP-IR-Builder

[Jon Chesterfield via Phabricator via llvm-commits]

JonChesterfield added inline comments.


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Comment at: llvm/include/llvm/IR/OpenMPKinds.def:186
+///{
+
+#ifndef OMP_IDENT_FLAG
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jdoerfert wrote:
> Meinersbur wrote:
> > jdoerfert wrote:
> > > JonChesterfield wrote:
> > > > Sharing constants between the compiler and the runtime is an interesting subproblem. I think the cleanest solution is the one used by libc, where the compiler generates header files containing the constants which the runtime library includes.
> > > I'd prefer not to tackle this right now but get this done first and revisit the issue later. OK?
> > I don't think this is a good solution. It means that libomp cannot built built anymore without also building clang. Moreover, the values cannot be changed anyway since it would break the ABI.
> > 
> > I'd go the other route: The libomp defines what it's ABI is, the compiler generates code for it. 
> This patch doesn't change what we do, just where. The numbers are hard coded in clang now. Let's start a discussion on the list and if we come up with a different scheme we do it after this landed.
Revisit later sounds good.

@Meinersbur Do you know of an example of a non-llvm compiler using this libomp?

The usual order is build a compiler, then use it to build the runtime libraries, then the whole package can build other stuff. Provided the compiler doesn't need any of the runtime libraries (compiler-rt, maths libraries, libomp etc) itself the system bootstraps cleanly. Especially important when cross compiling and I suspect the gpu targets in openmp have similarly strict requirements on the first compiler.

Closely related to that, I tend to assume that the runtime libraries can be rewritten to best serve their only client - the associated compiler - so if libomp is used by out of tree compilers I'd like to know who we are at risk of breaking.


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https://reviews.llvm.org/D69785