Refactor TimeProfiler write methods (NFC)

Added a write method for TimeTrace that takes two strings representing
file names. The first is any file name that may have been provided by the
user via `time-trace-file` flag, and the second is a fallback that should
be configured by the caller. This method makes it cleaner to write the
trace output because there is no longer a need to check file names at the
caller and simplifies future TimeTrace usages.

Reviewed By: modocache

Differential Revision: https://reviews.llvm.org/D74514

lld/ELF/Driver.cpp

@@ -530,17 +530,14 @@ void LinkerDriver::main(ArrayRef<const char *> argsArr) {
   }
 
   if (config->timeTraceEnabled) {
-    // Write the result of the time trace profiler.
-    std::string path = args.getLastArgValue(OPT_time_trace_file_eq).str();
-    if (path.empty())
-      path = (config->outputFile + ".time-trace").str();
-    std::error_code ec;
-    raw_fd_ostream os(path, ec, sys::fs::OF_Text);
-    if (ec) {
-      error("cannot open " + path + ": " + ec.message());
+    if (auto E = timeTraceProfilerWrite(args.getLastArgValue(OPT_time_trace_file_eq).str(),
+                                        config->outputFile)) {
+      handleAllErrors(std::move(E), [&](const StringError &SE) {
+        error(SE.getMessage());
+      });
       return;
     }
-    timeTraceProfilerWrite(os);
+
     timeTraceProfilerCleanup();
   }
 }

llvm/include/llvm/Support/TimeProfiler.h

@@ -9,6 +9,7 @@
 #ifndef LLVM_SUPPORT_TIME_PROFILER_H
 #define LLVM_SUPPORT_TIME_PROFILER_H
 
+#include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace llvm {
@@ -33,11 +34,19 @@ inline bool timeTraceProfilerEnabled() {
   return getTimeTraceProfilerInstance() != nullptr;
 }
 
-/// Write profiling data to output file.
+/// Write profiling data to output stream.
 /// Data produced is JSON, in Chrome "Trace Event" format, see
 /// https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview
 void timeTraceProfilerWrite(raw_pwrite_stream &OS);
 
+/// Write profiling data to a file.
+/// The function will write to \p PreferredFileName if provided, if not
+/// then will write to \p FallbackFileName appending .time-trace.
+/// Returns a StringError indicating a failure if the function is
+/// unable to open the file for writing.
+Error timeTraceProfilerWrite(StringRef PreferredFileName,
+                             StringRef FallbackFileName);
+
 /// Manually begin a time section, with the given \p Name and \p Detail.
 /// Profiler copies the string data, so the pointers can be given into
 /// temporaries. Time sections can be hierarchical; every Begin must have a

llvm/lib/Support/TimeProfiler.cpp

@@ -279,6 +279,26 @@ void timeTraceProfilerWrite(raw_pwrite_stream &OS) {
   TimeTraceProfilerInstance->Write(OS);
 }
 
+Error timeTraceProfilerWrite(StringRef PreferredFileName,
+                             StringRef FallbackFileName) {
+  assert(TimeTraceProfilerInstance != nullptr &&
+         "Profiler object can't be null");
+
+  std::string Path = PreferredFileName.str();
+  if (Path.empty()) {
+    Path = FallbackFileName == "-" ? "out" : FallbackFileName.str();
+    Path += ".time-trace";
+  }
+
+  std::error_code EC;
+  raw_fd_ostream OS(Path, EC, sys::fs::OF_Text);
+  if (EC)
+    return createStringError(EC, "Could not open " + Path);
+
+  timeTraceProfilerWrite(OS);
+  return Error::success();
+}
+
 void timeTraceProfilerBegin(StringRef Name, StringRef Detail) {
   if (TimeTraceProfilerInstance != nullptr)
     TimeTraceProfilerInstance->begin(std::string(Name),