[clang] [CIR] LLVMIR lowering for cir.call (PR #138873)

[Andy Kaylor via cfe-commits]

================
@@ -651,6 +651,50 @@ mlir::LogicalResult CIRToLLVMReturnOpLowering::matchAndRewrite(
   return mlir::LogicalResult::success();
 }
 
+static mlir::LogicalResult
+rewriteCallOrInvoke(mlir::Operation *op, mlir::ValueRange callOperands,
+                    mlir::ConversionPatternRewriter &rewriter,
+                    const mlir::TypeConverter *converter,
+                    mlir::FlatSymbolRefAttr calleeAttr) {
+  llvm::SmallVector<mlir::Type, 8> llvmResults;
+  auto cirResults = op->getResultTypes();
+
+  if (converter->convertTypes(cirResults, llvmResults).failed())
+    return mlir::failure();
+
+  assert(!cir::MissingFeatures::opCallCallConv());
+  assert(!cir::MissingFeatures::opCallSideEffect());
+
+  mlir::LLVM::LLVMFunctionType llvmFnTy;
+  if (calleeAttr) { // direct call
+    auto fn =
----------------
andykaylor wrote:

```suggestion
    cir::FuncOp fn =
```
I'm not sure this is the correct type. Mainly, don't use auto here.

https://github.com/llvm/llvm-project/pull/138873