[llvm] [NVPTX] Add family-specific architectures support (PR #141899)

[Artem Belevich via llvm-commits]

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@@ -33,20 +33,61 @@ class FeaturePTX<int version>:
    SubtargetFeature<"ptx"# version, "PTXVersion",
                     "" # version,
                     "Use PTX version " # version>;
-
+//
+// NVPTX Architecture Hierarchy and Ordering:
+// 
+// Family: 2/3/5/6/7/8/9/10/12 (Follows Onion model, older family is compatible with newer family)
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Artem-B wrote:

Sorry, this is confusing on multiple levels. 
- where do the numbers come from?
- the term 'family' appears to carry a different meaning here vs the 'family' used further down for architectures with the `f` suffix. CUDA documentation uses "Major revision number" or "Major architecture" here.
- "Onion model", while somewhat descriptive, is somewhat informal. I'd stick with specific ordering properties. Major revision numbers are strictly ordered.




https://github.com/llvm/llvm-project/pull/141899