dblaikie added inline comments.

================
Comment at: llvm/lib/ProfileData/Coverage/CoverageMappingWriter.cpp:54-60
+  OptionalCompressionScheme = compression::noneIfUnsupported(
+      (Compress && DoInstrProfNameCompression) ? OptionalCompressionScheme
+                                               : llvm::NoneType());
+
+  bool doCompression = bool(OptionalCompressionScheme);
+
+  if (doCompression) {
----------------
ckissane wrote:
> ckissane wrote:
> > ckissane wrote:
> > > dblaikie wrote:
> > > > This still seems like a lot of hoops to jump through - why 
> > > > "noneIfUnsupported" rather than either having the compression scheme (I 
> > > > think it could be the CompressionAlgorithm itself, rather than having 
> > > > the separate OptionalCompressionKind abstraction) either be null 
> > > > itself, or expose an "isAvailable" operation directly on the 
> > > > CompressionAlgorithm?
> > > > 
> > > > Even if the 
> > > > CompressionKind/OptionalCompressionKind/CompressionAlgorithm 
> > > > abstractions are kept, I'm not sure why the above code is preferred 
> > > > over, say:
> > > > 
> > > > ```
> > > > if (Compress && DoInstrProfNameCompression && OptionalCompressionScheme 
> > > > /* .isAvailable(), if we want to be more explicit */) {
> > > >   ...
> > > > }
> > > > ```
> > > > 
> > > > What's the benefit that `noneIfUnsupported` is providing? (& generally 
> > > > I'd expect the `Compress && DoInstrProfNameCompression` to be 
> > > > tested/exit early before even naming/constructing/querying/doing 
> > > > anything with the compression scheme/algorithm/etc - so there'd be no 
> > > > need to combine the tests for availability and the tests for whether 
> > > > compression was requested)
> > > > 
> > > > Perhaps this API is motivated by a desire to implement something much 
> > > > closer to the original code than is necessary/suitable? Or some other 
> > > > use case/benefit I'm not quite understanding yet?
> > > I shall remove `noneIfUnsupported`. You express good points, we can 
> > > simply check `if(OptionalCompressionScheme && 
> > > *OptionalCompressionScheme)` where necessary.
> > though it will make a lot of existing code patterns less clear, and more 
> > verbose
> and sometimes you really do need to re code the exact thing 
> `noneIfUnsupported` encapsulates...
Are there examples within LLVM that you can show compare/contrast 
`noneIfUnsupported` helps?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130516/new/

https://reviews.llvm.org/D130516

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