[clang] [CIR] Implement initial LoweringPrepare support for global ctors (PR #161452)

[Andy Kaylor via cfe-commits]

================
@@ -589,6 +621,113 @@ void LoweringPreparePass::lowerUnaryOp(cir::UnaryOp op) {
   op.erase();
 }
 
+cir::FuncOp
+LoweringPreparePass::buildCXXGlobalVarDeclInitFunc(cir::GlobalOp op) {
+  // TODO(cir): Store this in the GlobalOp.
+  // This should come from the MangleContext, but for now I'm hardcoding it.
+  SmallString<256> fnName("__cxx_global_var_init");
+  // Get a unique name
+  uint32_t cnt = dynamicInitializerNames[fnName]++;
+  if (cnt)
+    fnName += "." + llvm::Twine(cnt).str();
+
+  // Create a variable initialization function.
+  CIRBaseBuilderTy builder(getContext());
+  builder.setInsertionPointAfter(op);
+  auto voidTy = cir::VoidType::get(builder.getContext());
+  auto fnType = cir::FuncType::get({}, voidTy);
+  FuncOp f = buildRuntimeFunction(builder, fnName, op.getLoc(), fnType,
+                                  cir::GlobalLinkageKind::InternalLinkage);
+
+  // Move over the initialzation code of the ctor region.
+  mlir::Block *entryBB = f.addEntryBlock();
+  if (!op.getCtorRegion().empty()) {
+    mlir::Block &block = op.getCtorRegion().front();
+    entryBB->getOperations().splice(entryBB->begin(), block.getOperations(),
+                                    block.begin(), std::prev(block.end()));
+  }
+
+  // Register the destructor call with __cxa_atexit
+  auto &dtorRegion = op.getDtorRegion();
----------------
andykaylor wrote:

This should use the type.

https://github.com/llvm/llvm-project/pull/161452