Add a Function::isExternal utility to simplify checks for external functions.

PiperOrigin-RevId: 235746553

mlir/include/mlir/IR/Function.h

@@ -80,6 +80,9 @@ public:
   /// Unlink this function from its module and delete it.
   void erase();
 
+  /// Returns true if this function is external, i.e. it has no body.
+  bool isExternal() const { return empty(); }
+
   //===--------------------------------------------------------------------===//
   // Body Handling
   //===--------------------------------------------------------------------===//

mlir/lib/Analysis/Verifier.cpp

@@ -90,7 +90,7 @@ bool FuncVerifier::verify() {
                                    fn.getName().c_str());
 
   // External functions have nothing more to check.
-  if (fn.empty())
+  if (fn.isExternal())
     return false;
 
   // Verify the first block has no predecessors.

mlir/lib/IR/AsmPrinter.cpp

@@ -1301,7 +1301,7 @@ void FunctionPrinter::printFunctionSignature() {
   auto fnType = function->getType();
 
   // If this is an external function, don't print argument labels.
-  if (function->empty()) {
+  if (function->isExternal()) {
     interleaveComma(fnType.getInputs(),
                     [&](Type eltType) { printType(eltType); });
   } else {

mlir/lib/Pass/Pass.cpp

@@ -37,7 +37,7 @@ void ModulePass::anchor() {}
 PassResult FunctionPass::runOnModule(Module *m) {
   for (auto &fn : *m) {
     // All function passes ignore external functions.
-    if (fn.empty())
+    if (fn.isExternal())
       continue;
 
     if (runOnFunction(&fn))

mlir/lib/Target/LLVMIR/ConvertToLLVMIR.cpp

@@ -513,7 +513,7 @@ bool ModuleTranslation::convertFunctions() {
   // Convert functions.
   for (const Function &function : mlirModule) {
     // Ignore external functions.
-    if (function.empty())
+    if (function.isExternal())
       continue;
 
     if (convertOneFunction(function))