[flang] Adapt mlir based error status handling in `tco` tool

[SouraVX]

Summary

Earlier scheme was using negative integers for communicating error status,
switch to canonical MLIR style.

f18 commit authored by @schweitz:
https://github.com/flang-compiler/f18-llvm-project/commit/c1af08d6e70b66c08ee2fbf2e63c764ec2e006e5

[clementval]

LGTM

[svedanayagam]

Looks good.

[SouraVX]

@mehdi_amini are you Okay with this patch ?

[mehdi_amini]

Beyond this, is tco supposed to be the opt tool or do we need another one? If it is supposed to be the opt tool, can it be renamed fir-opt for consistency?

[clementval]

In D96068#2544145, @mehdi_amini wrote:

Beyond this, is tco supposed to be the opt tool or do we need another one? If it is supposed to be the opt tool, can it be renamed fir-opt for consistency?

We have a fir-opt tool that should be upstream soon. Once we have it tco will be more like mlir-translate in the end when we remove the emit-fir option.

[schweitz]

In D96068#2545163, @clementval wrote:

In D96068#2544145, @mehdi_amini wrote:

Beyond this, is tco supposed to be the opt tool or do we need another one? If it is supposed to be the opt tool, can it be renamed fir-opt for consistency?

We have a fir-opt tool that should be upstream soon. Once we have it tco will be more like mlir-translate in the end when we remove the emit-fir option.

Yes, tco is the tool for testing LLVM code generation. fir-opt hasn't been merged yet.

flang/tools/tco/tco.cpp

static cl::opt<bool> emitFir("emit-fir",
                              cl::init(false));
 
 static void printModuleBody(mlir::ModuleOp mod, raw_ostream &output) {
   for (auto &op : mod.getBody()->without_terminator())
     output << op << '\n';
 }
 
 // compile a .fir file
-static int compileFIR() {
+static mlir::LogicalResult
+compileFIR(const mlir::PassPipelineCLParser &passPipeline) {
   // check that there is a file to load
   ErrorOr<std::unique_ptr<MemoryBuffer>> fileOrErr =
       MemoryBuffer::getFileOrSTDIN(inputFilename);
 
   if (std::error_code EC = fileOrErr.getError()) {
     errs() << "Could not open file: " << EC.message() << '\n';
-    return 1;
+    return mlir::failure();
   }
 
   // load the file into a module
   SourceMgr sourceMgr;
   sourceMgr.AddNewSourceBuffer(std::move(*fileOrErr), SMLoc());
   mlir::MLIRContext context;
   fir::registerFIRDialects(context.getDialectRegistry());
   auto owningRef = mlir::parseSourceFile(sourceMgr, &context);
 
   if (!owningRef) {
     errs() << "Error can't load file " << inputFilename << '\n';
-    return 2;
+    return mlir::failure();
   }
   if (mlir::failed(owningRef->verify())) {
     errs() << "Error verifying FIR module\n";
-    return 4;
+    return mlir::failure();
   }
 
   std::error_code ec;
   ToolOutputFile out(outputFilename, ec, sys::fs::OF_None);
 
   // run passes
   mlir::PassManager pm{&context};
   mlir::applyPassManagerCLOptions(pm);
   if (emitFir) {
     // parse the input and pretty-print it back out
     // -emit-fir intentionally disables all the passes
   } else {
     // TODO: Actually add passes when added to FIR code base
     // add all the passes
     // the user can disable them individually
   }
 
   // run the pass manager
   if (mlir::succeeded(pm.run(*owningRef))) {
     // passes ran successfully, so keep the output
     if (emitFir)
       printModuleBody(*owningRef, out.os());
     out.keep();
-    return 0;
+    return mlir::success();
   }
 
   // pass manager failed
   printModuleBody(*owningRef, errs());
   errs() << "\n\nFAILED: " << inputFilename << '\n';
-  return 8;
+  return mlir::failure();
 }
 
 int main(int argc, char **argv) {
   fir::registerFIRPasses();
   [[maybe_unused]] InitLLVM y(argc, argv);
   mlir::registerPassManagerCLOptions();
   mlir::PassPipelineCLParser passPipe("", "Compiler passes to run");
   cl::ParseCommandLineOptions(argc, argv, "Tilikum Crossing Optimizer\n");
-  return compileFIR();
+  return mlir::failed(compileFIR(passPipe));
 }