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

[Rajat Bajpai via llvm-commits]

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@@ -33,20 +33,66 @@ class FeaturePTX<int version>:
    SubtargetFeature<"ptx"# version, "PTXVersion",
                     "" # version,
                     "Use PTX version " # version>;
-
+// NVPTX Architecture Hierarchy and Ordering:
+//
+// GPU architectures: sm_2Y/sm_3Y/sm_5Y/sm_6Y/sm_7Y/sm_8Y/sm_9Y/sm_10Y/sm_12Y
+// ('Y' represents version within the architecture)
+// The architectures have name of form sm_XYz where 'X' represent the generation
+// number, 'Y' represents the version within the architecture, and 'z' represents
+// the optional feature suffix.
+// If X1Y1 <= X2Y2, then GPU capabilities of sm_X1Y1 are included in sm_X2Y2.
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rajatbajpai wrote:

I tried cover to Archs in this order: no-feature suffix -> family-specific -> arch-specific. So, I'll prefer to not discuss feature suffix in this para.

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