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

[Durgadoss R via llvm-commits]

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@@ -41,12 +41,14 @@ foreach sm = [20, 21, 30, 32, 35, 37, 50, 52, 53,
 
 // Arch-specific targets. PTX for these is not compatible with any other
 // architectures.
-def SM90a : FeatureSM<"90a", 901>;
-def SM100a: FeatureSM<"100a", 1001>;
-def SM101a: FeatureSM<"101a", 1011>;
-def SM103a: FeatureSM<"103a", 1031>;
-def SM120a: FeatureSM<"120a", 1201>;
-def SM121a: FeatureSM<"121a", 1211>;
+foreach sm = [90, 100, 101, 103, 120, 121] in {
+  def SM#sm#a : FeatureSM<""#sm#"a", !add(!mul(sm, 10), 1)>;
+}
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durga4github wrote:

The full-sm-version was more explicit in the above definitions.

Can we have a comment providing one example?
```
// The fullSMVersion of sm90a corresponds to 901.
```

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