[llvm] [NVPTX] Add Custom ABI (abi_preserve) support via function attributes (PR #227499)

[Akshay Deodhar via llvm-commits]

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@@ -59,6 +61,16 @@ bool hasBlocksAreClusters(const Function &);
 
 bool isParamGridConstant(const Argument &);
 
+/// Maps the name of each nvvm.abi_preserve* attribute that is present to its
+/// register count, in PTX emission order. An absent attribute has no entry.
+using ABIPreserve = SmallMapVector<StringRef, unsigned, 2>;
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akshayrdeodhar wrote:

We are likely to add more of these attributes in the future. This structure will allow us to simply modify the lists, and change nothing else.

https://github.com/llvm/llvm-project/pull/227499