[clang] [llvm] [RFC][CodeGen] Add generic target feature checks for intrinsics (PR #201470)

[Jay Foad via cfe-commits]

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@@ -800,6 +809,14 @@ class MSBuiltin<string name> {
   string MSBuiltinName = name;
 }
 
+/// RequiresTargetFeatures - If this intrinsic requires target features,
+/// this specifies the required feature expression using feature names from the
+/// target's subtarget feature table. The expression grammar matches Clang
+/// builtins: comma means AND, | means OR, and parentheses group expressions.
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jayfoad wrote:

Should state the relative precedence of `,` and `|`.

https://github.com/llvm/llvm-project/pull/201470