[clang] [CIR] Realign CIR-to-LLVM IR lowering code with incubator (PR #129293)

[Erich Keane via cfe-commits]

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@@ -218,12 +221,31 @@ mlir::LogicalResult CIRToLLVMGlobalOpLowering::matchAndRewrite(
   SmallVector<mlir::NamedAttribute> attributes;
 
   if (init.has_value()) {
-    GlobalInitAttrRewriter initRewriter(llvmType, rewriter);
-    init = initRewriter.rewriteInitAttr(init.value());
-    // If initRewriter returned a null attribute, init will have a value but
-    // the value will be null. If that happens, initRewriter didn't handle the
-    // attribute type. It probably needs to be added to GlobalInitAttrRewriter.
-    if (!init.value()) {
+    if (mlir::isa<cir::FPAttr, cir::IntAttr>(init.value())) {
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erichkeane wrote:

This section is a bit worse unfortunately.  We might consider extracting this type at one point.  

Why did we remove the use of `GlobalInitAttrRewriter` (or am I missing a use elsewhere?), and do we intend to bring it back?    Could it be used here instead like it was before?

https://github.com/llvm/llvm-project/pull/129293