[Openmp-commits] [PATCH] D75581: [libomptarget][amdgcn] Implement get_wtime

[Jon Chesterfield via Phabricator via Openmp-commits]

JonChesterfield marked an inline comment as done.
JonChesterfield added inline comments.


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Comment at: openmp/libomptarget/deviceRTLs/amdgcn/src/target_impl.hip:50
+  return ((double)1.0 / 745000000.0) * t;
 }
 
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grokos wrote:
> JonChesterfield wrote:
> > I don't have a source for the magic number. It's from before my time. I can offer that rough checks from running applications look ok, and that it has been shipping as part of aomp for ages without user complaints.
> At least can you add a comment about what this magic number is (obviously the clock speed in Hz, but it would be nice to have some sort of documentation)? Or (even better) use a macro because this frequency may change in future chips?
The isa docs offer that the clock operates as if at a fixed frequency. It seems plausible that the various amdgcn chips would all have a timer running at the same rate, but I'd also be happier with a reference on that.

I'll ask around. It would be useful to know whether the scaling factor should be different for different chips.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D75581/new/

https://reviews.llvm.org/D75581