[clang] [CIR] Add support for the IdiomRecognizer pass (PR #208854)

[Erich Keane via cfe-commits]

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@@ -3537,6 +3540,23 @@ void CIRGenModule::setCXXSpecialMemberAttr(
   }
 }
 
+void CIRGenModule::setFuncIdentityAttr(cir::FuncOp funcOp,
+                                       const clang::FunctionDecl *funcDecl) {
+  // Only a free std function with a plain identifier can match a known
+  // entity, so members, static members, and operators never take a tag.
+  // Inline namespaces, like the versioning namespace of libc++, count as
+  // part of std.
+  if (!funcDecl || !funcDecl->getIdentifier() || isa<CXXMethodDecl>(funcDecl) ||
+      !funcDecl->isInStdNamespace())
+    return;
+
+  // The names and the tags come from CIRStdOps.td, and the recognizer
+  // checks the shape of each call.
+  if (funcDecl->getName() == cir::StdFindOp::getFunctionName())
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erichkeane wrote:

This seems like we really need to set up a `llvm::StringSwitch` on the name for a name->enum conversion function.

https://github.com/llvm/llvm-project/pull/208854