Update FIR registration to not rely on the global MLIR dialect registry (NFC)

MLIR is removing "soon" the global dialect registry, this patch is
transitionning FIR to not rely on it anymore.

Author: joker-eph

flang/include/flang/Optimizer/Dialect/FIRDialect.h

@@ -32,19 +32,17 @@ class FIROpsDialect final : public mlir::Dialect {
                       mlir::DialectAsmPrinter &p) const override;
 };
 
-/// Register the dialect with MLIR
-inline void registerFIR() {
-  // we want to register exactly once
-  [[maybe_unused]] static bool init_once = [] {
-    mlir::registerDialect<mlir::AffineDialect>();
-    mlir::registerDialect<mlir::LLVM::LLVMDialect>();
-    mlir::registerDialect<mlir::omp::OpenMPDialect>();
-    mlir::registerDialect<mlir::scf::SCFDialect>();
-    mlir::registerDialect<mlir::StandardOpsDialect>();
-    mlir::registerDialect<mlir::vector::VectorDialect>();
-    mlir::registerDialect<FIROpsDialect>();
-    return true;
-  }();
+/// Register the dialect with the provided registry.
+inline void registerFIRDialects(mlir::DialectRegistry &registry) {
+  // clang-format off
+  registry.insert<mlir::AffineDialect,
+                  mlir::LLVM::LLVMDialect,
+                  mlir::omp::OpenMPDialect,
+                  mlir::scf::SCFDialect,
+                  mlir::StandardOpsDialect,
+                  mlir::vector::VectorDialect,
+                  FIROpsDialect>();
+  // clang-format on
 }
 
 /// Register the standard passes we use. This comes from registerAllPasses(),

flang/tools/tco/tco.cpp

@@ -60,8 +60,9 @@ static int compileFIR() {
   // load the file into a module
   SourceMgr sourceMgr;
   sourceMgr.AddNewSourceBuffer(std::move(*fileOrErr), SMLoc());
-  auto context = std::make_unique<mlir::MLIRContext>();
-  auto owningRef = mlir::parseSourceFile(sourceMgr, context.get());
+  mlir::MLIRContext context;
+  fir::registerFIRDialects(context.getDialectRegistry());
+  auto owningRef = mlir::parseSourceFile(sourceMgr, &context);
 
   if (!owningRef) {
     errs() << "Error can't load file " << inputFilename << '\n';
@@ -76,7 +77,7 @@ static int compileFIR() {
   ToolOutputFile out(outputFilename, ec, sys::fs::OF_None);
 
   // run passes
-  mlir::PassManager pm{context.get()};
+  mlir::PassManager pm{&context};
   mlir::applyPassManagerCLOptions(pm);
   if (emitFir) {
     // parse the input and pretty-print it back out
@@ -103,7 +104,6 @@ static int compileFIR() {
 }
 
 int main(int argc, char **argv) {
-  fir::registerFIR();
   fir::registerFIRPasses();
   [[maybe_unused]] InitLLVM y(argc, argv);
   mlir::registerPassManagerCLOptions();