[firtool] Refactor firtool.cpp, emit more specific --mlir-timing output.

Just pass down the output filename instead of a lambda, there is no
need for the extra abstraction here.  While here, change the timer
in the various flavors of output to be more specific than "Output".

tools/firtool/firtool.cpp

@@ -201,7 +201,7 @@ static std::unique_ptr<Pass> createSimpleCanonicalizerPass() {
 /// Process a single buffer of the input.
 static LogicalResult
 processBuffer(MLIRContext &context, TimingScope &ts, llvm::SourceMgr &sourceMgr,
-              llvm::function_ref<LogicalResult(ModuleOp)> callback) {
+              Optional<std::unique_ptr<llvm::ToolOutputFile>> &outputFile) {
   // Add the annotation file if one was explicitly specified.
   std::string annotationFilenameDetermined;
   if (!inputAnnotationFilename.empty()) {
@@ -231,8 +231,21 @@ processBuffer(MLIRContext &context, TimingScope &ts, llvm::SourceMgr &sourceMgr,
 
   // If the user asked for just a parse, stop here.
   if (parseOnly) {
-    auto outputTimer = ts.nest("Output");
-    return callback(module.release());
+    mlir::ModuleOp theModule = module.release();
+    switch (outputFormat) {
+    case OutputMLIR: {
+      auto outputTimer = ts.nest("Print .mlir output");
+      theModule->print(outputFile.getValue()->os());
+      return success();
+    }
+    case OutputDisabled:
+      return success();
+    case OutputVerilog:
+    case OutputSplitVerilog:
+      llvm::errs()
+          << "verilog emission is not supported in -parse-only mode.\n";
+      return failure();
+    }
   }
 
   // Apply any pass manager command line options.
@@ -347,12 +360,30 @@ processBuffer(MLIRContext &context, TimingScope &ts, llvm::SourceMgr &sourceMgr,
   if (failed(pm.run(module.get())))
     return failure();
 
-  auto outputTimer = ts.nest("Output");
-
   // Note that we intentionally "leak" the Module into the MLIRContext instead
   // of deallocating it.  There is no need to deallocate it right before
   // process exit.
-  return callback(module.release());
+  mlir::ModuleOp theModule = module.release();
+
+  // Emit a single file or multiple files depending on the output format.
+  switch (outputFormat) {
+  case OutputMLIR: {
+    auto outputTimer = ts.nest("Print .mlir output");
+    theModule->print(outputFile.getValue()->os());
+    return success();
+  }
+  case OutputDisabled:
+    return success();
+  case OutputVerilog: {
+    auto outputTimer = ts.nest("ExportVerilog emission");
+    return exportVerilog(theModule, outputFile.getValue()->os());
+  }
+  case OutputSplitVerilog: {
+    auto outputTimer = ts.nest("Split ExportVerilog emission");
+    return exportSplitVerilog(theModule, outputFilename);
+  }
+  }
+  return failure();
 }
 
 /// Process a single split of the input. This allocates a source manager and
@@ -361,17 +392,17 @@ processBuffer(MLIRContext &context, TimingScope &ts, llvm::SourceMgr &sourceMgr,
 static LogicalResult
 processInputSplit(MLIRContext &context, TimingScope &ts,
                   std::unique_ptr<llvm::MemoryBuffer> buffer,
-                  llvm::function_ref<LogicalResult(ModuleOp)> emitCallback) {
+                  Optional<std::unique_ptr<llvm::ToolOutputFile>> &outputFile) {
   llvm::SourceMgr sourceMgr;
   sourceMgr.AddNewSourceBuffer(std::move(buffer), llvm::SMLoc());
   if (verifyDiagnostics) {
     SourceMgrDiagnosticVerifierHandler sourceMgrHandler(sourceMgr, &context);
     context.printOpOnDiagnostic(false);
-    (void)processBuffer(context, ts, sourceMgr, emitCallback);
+    (void)processBuffer(context, ts, sourceMgr, outputFile);
     return sourceMgrHandler.verify();
   } else {
     SourceMgrDiagnosticHandler sourceMgrHandler(sourceMgr, &context);
-    return processBuffer(context, ts, sourceMgr, emitCallback);
+    return processBuffer(context, ts, sourceMgr, outputFile);
   }
 }
 
@@ -380,7 +411,7 @@ processInputSplit(MLIRContext &context, TimingScope &ts,
 static LogicalResult
 processInput(MLIRContext &context, TimingScope &ts,
              std::unique_ptr<llvm::MemoryBuffer> input,
-             llvm::function_ref<LogicalResult(ModuleOp)> emitCallback) {
+             Optional<std::unique_ptr<llvm::ToolOutputFile>> &outputFile) {
   if (splitInputFile) {
     // Emit an error if the user provides a separate annotation file alongside
     // split input. This is technically not a problem, but the user likely
@@ -398,12 +429,11 @@ processInput(MLIRContext &context, TimingScope &ts,
     return splitAndProcessBuffer(
         std::move(input),
         [&](std::unique_ptr<MemoryBuffer> buffer, raw_ostream &) {
-          return processInputSplit(context, ts, std::move(buffer),
-                                   emitCallback);
+          return processInputSplit(context, ts, std::move(buffer), outputFile);
         },
         llvm::outs());
   } else {
-    return processInputSplit(context, ts, std::move(input), emitCallback);
+    return processInputSplit(context, ts, std::move(input), outputFile);
   }
 }
 
@@ -460,28 +490,12 @@ static LogicalResult executeFirtool(MLIRContext &context) {
     }
   }
 
-  // Emit a single file or multiple files depending on the output format.
-  auto emitCallback = [&](ModuleOp module) -> LogicalResult {
-    switch (outputFormat) {
-    case OutputMLIR:
-      module->print(outputFile.getValue()->os());
-      return success();
-    case OutputDisabled:
-      return success();
-    case OutputVerilog:
-      return exportVerilog(module, outputFile.getValue()->os());
-    case OutputSplitVerilog:
-      return exportSplitVerilog(module, outputFilename);
-    }
-    return failure();
-  };
-
   // Register our dialects.
   context.loadDialect<firrtl::FIRRTLDialect, hw::HWDialect, comb::CombDialect,
                       sv::SVDialect>();
 
   // Process the input.
-  if (failed(processInput(context, ts, std::move(input), emitCallback)))
+  if (failed(processInput(context, ts, std::move(input), outputFile)))
     return failure();
 
   // If the result succeeded and we're emitting a file, close it.