[clang][deps] Print timing information

This patch adds new `-print-timing` option to `clang-scan-deps`. It measures the wall and process time taken to scan dependencies for the compilation database. This provides more representative data compared to measuring the timing for the whole tool invocation, since that includes parsing and generating JSON files, which can be significant for larger inputs.

Reviewed By: akyrtzi

Differential Revision: https://reviews.llvm.org/D147815

clang/test/ClangScanDeps/print-timing.c

@@ -0,0 +1,9 @@
+// RUN: rm -rf %t && mkdir %t
+// RUN: split-file %s %t
+
+// RUN: clang-scan-deps -compilation-database %t/cdb.json -print-timing > %t/result.json 2>%t/errs
+// RUN: cat %t/errs | FileCheck %s
+// CHECK: clang-scan-deps timing: {{[0-9]+}}.{{[0-9][0-9]}}s wall, {{[0-9]+}}.{{[0-9][0-9]}}s process
+
+//--- cdb.json
+[]

clang/tools/clang-scan-deps/ClangScanDeps.cpp

@@ -19,13 +19,15 @@
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileUtilities.h"
+#include "llvm/Support/Format.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/JSON.h"
 #include "llvm/Support/LLVMDriver.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/ThreadPool.h"
 #include "llvm/Support/Threading.h"
+#include "llvm/Support/Timer.h"
 #include "llvm/TargetParser/Host.h"
 #include <mutex>
 #include <optional>
@@ -90,6 +92,7 @@ static std::vector<std::string> ModuleDepTargets;
 static bool DeprecatedDriverCommand;
 static ResourceDirRecipeKind ResourceDirRecipe;
 static bool Verbose;
+static bool PrintTiming;
 static std::vector<const char *> CommandLine;
 
 #ifndef NDEBUG
@@ -200,6 +203,8 @@ static void ParseArgs(int argc, char **argv) {
     ResourceDirRecipe = *Kind;
   }
 
+  PrintTiming = Args.hasArg(OPT_print_timing);
+
   Verbose = Args.hasArg(OPT_verbose);
 
   RoundTripArgs = Args.hasArg(OPT_round_trip_args);
@@ -857,6 +862,10 @@ int clang_scan_deps_main(int argc, char **argv, const llvm::ToolContext &) {
     llvm::outs() << "Running clang-scan-deps on " << Inputs.size()
                  << " files using " << Pool.getThreadCount() << " workers\n";
   }
+
+  llvm::Timer T;
+  T.startTimer();
+
   for (unsigned I = 0; I < Pool.getThreadCount(); ++I) {
     Pool.async([&, I]() {
       llvm::StringSet<> AlreadySeenModules;
@@ -946,6 +955,12 @@ int clang_scan_deps_main(int argc, char **argv, const llvm::ToolContext &) {
   }
   Pool.wait();
 
+  T.stopTimer();
+  if (PrintTiming)
+    llvm::errs() << llvm::format(
+        "clang-scan-deps timing: %0.2fs wall, %0.2fs process\n",
+        T.getTotalTime().getWallTime(), T.getTotalTime().getProcessTime());
+
   if (RoundTripArgs)
     if (FD && FD->roundTripCommands(llvm::errs()))
       HadErrors = true;

clang/tools/clang-scan-deps/Opts.td

@@ -31,6 +31,8 @@ def deprecated_driver_command : F<"deprecated-driver-command", "use a single dri
 
 defm resource_dir_recipe : Eq<"resource-dir-recipe", "How to produce missing '-resource-dir' argument">;
 
+def print_timing : F<"print-timing", "Print timing information">;
+
 def verbose : F<"v", "Use verbose output">;
 
 def round_trip_args : F<"round-trip-args", "verify that command-line arguments are canonical by parsing and re-serializing">;