Add a helper function to convert LogicalResult to int for return from main

[tkoeppe]

Summary

At present, a lot of code contains main function bodies like "return failed(mlir::MlirOptMain(...);". This is unfortunate for two reasons: a) it uses ADL, which is maybe not what the free "failed" function was designed for; and b) it is a bit awkward to read, requring the reader to both understand the boolean nature of the value and the semantics of main's return value. (And it's also not portable, since 1 is not a portable success value.)

The replacement code, return mlir::AsMainReturnCode(mlir::MlirOptMain(...)) is a bit more self-explanatory.

The change applies the new function to a few internal uses of MlirOptMain, too.

[mehdi_amini]

Can you also introduce uses for this in the in-tree tools?

mlir/include/mlir/Support/MlirOptMain.h

75

Please fix :)

[tkoeppe]

Addressed both comments; function renamed to lowerSnakeCase.

mlir/examples/standalone/standalone-opt/standalone-opt.cpp

int main(int argc, char **argv) {
   mlir::DialectRegistry registry;
   registry.insert<mlir::standalone::StandaloneDialect>();
   registry.insert<mlir::StandardOpsDialect>();
   // Add the following to include *all* MLIR Core dialects, or selectively
   // include what you need like above. You only need to register dialects that
   // will be *parsed* by the tool, not the one generated
   // registerAllDialects(registry);
 
-  return failed(
+  return mlir::asMainReturnCode(
       mlir::MlirOptMain(argc, argv, "Standalone optimizer driver\n", registry));
 }

mlir/include/mlir/Support/MlirOptMain.h

 //===----------------------------------------------------------------------===//
 
 #ifndef MLIR_SUPPORT_MLIROPTMAIN_H
 #define MLIR_SUPPORT_MLIROPTMAIN_H
 
 #include "mlir/Support/LogicalResult.h"
 #include "llvm/ADT/StringRef.h"
 
+#include <cstdlib>
 #include <memory>
 
 namespace llvm {
 class raw_ostream;
 class MemoryBuffer;
 } // end namespace llvm
 
 namespace mlir {

 /// - registry should contain all the dialects that can be parsed in the source.
 /// - preloadDialectsInContext will trigger the upfront loading of all
 ///   dialects from the global registry in the MLIRContext. This option is
 ///   deprecated and will be removed soon.
 LogicalResult MlirOptMain(int argc, char **argv, llvm::StringRef toolName,
                           DialectRegistry &registry,
                           bool preloadDialectsInContext = false);
 
+/// Helper wrapper to return the result of MlirOptMain directly from main.
+///
+/// Example:
+///
+///     int main(int argc, char **argv) {
+///       // ...
+///       return mlir::asMainReturnCode(mlir::MlirOptMain(
+///           argc, argv, /* ... */);
+///     }
+///
+inline int asMainReturnCode(LogicalResult r) {
+  return r.succeeded() ? EXIT_SUCCESS : EXIT_FAILURE;
+}
+
 } // end namespace mlir
 
 #endif // MLIR_SUPPORT_MLIROPTMAIN_H

mlir/tools/mlir-opt/mlir-opt.cpp

 #ifdef MLIR_INCLUDE_TESTS
   registerTestPasses();
 #endif
   DialectRegistry registry;
   registerAllDialects(registry);
 #ifdef MLIR_INCLUDE_TESTS
   test::registerTestDialect(registry);
 #endif
-  return failed(MlirOptMain(argc, argv, "MLIR modular optimizer driver\n",
-                            registry,
-                            /*preloadDialectsInContext=*/false));
+  return mlir::asMainReturnCode(
+      mlir::MlirOptMain(argc, argv, "MLIR modular optimizer driver\n", registry,
 }