[clang] [CIR] Record target-cpu and target-features on function declarations (PR #214986)

[Erich Keane via cfe-commits]

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@@ -806,6 +806,13 @@ getFeatureDeltaFromDefault(const CIRGenModule &cgm, llvm::StringRef targetCPU,
   return delta;
 }
 
+/// The names getCPUAndFeaturesAttributes produces.  setNonAliasAttributes
+/// clears them before writing a definition's values, so the two have to agree.
+static constexpr llvm::StringLiteral targetCPUAttrName = "cir.target-cpu";
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erichkeane wrote:

Perhaps these belong in CIRDialect.td along with all our attribute names? 

https://github.com/llvm/llvm-project/pull/214986