cmake: add command line options to output script profiling data

For users of CMake who want to optimize their scripts if they take a
while to run, this commit adds the ability to output profiling data.

To enable this output, it adds the two command line parameters
to select the output path and format.

This commit adds the first profiling format of type ``google-trace``,
which is the output is a JSON file containing Duration events as per the
Google Trace Format specification:

https://docs.google.com/document/d/1CvAClvFfyA5R-
PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview#

1 files changed, 57 insertions, 0 deletions

diff --git a/Source/cmake.cxx b/Source/cmake.cxx
index f4b9f16..29ed61d 100644
--- a/Source/cmake.cxx
+++ b/Source/cmake.cxx
@@ -9,6 +9,7 @@
 #include <initializer_list>
 #include <iostream>
 #include <sstream>
+#include <stdexcept>
 #include <utility>
 
 #include <cm/memory>
@@ -39,6 +40,9 @@
 #include "cmLinkLineComputer.h"
 #include "cmLocalGenerator.h"
 #include "cmMakefile.h"
+#if !defined(CMAKE_BOOTSTRAP)
+#  include "cmMakefileProfilingData.h"
+#endif
 #include "cmMessenger.h"
 #include "cmState.h"
 #include "cmStateDirectory.h"
@@ -613,6 +617,10 @@ void cmake::SetArgs(const std::vector<std::string>& args)
 {
   bool haveToolset = false;
   bool havePlatform = false;
+#if !defined(CMAKE_BOOTSTRAP)
+  std::string profilingFormat;
+  std::string profilingOutput;
+#endif
   for (unsigned int i = 1; i < args.size(); ++i) {
     std::string const& arg = args[i];
     if (arg.find("-H", 0) == 0 || arg.find("-S", 0) == 0) {
@@ -839,6 +847,20 @@ void cmake::SetArgs(const std::vector<std::string>& args)
         return;
       }
       this->SetGlobalGenerator(std::move(gen));
+#if !defined(CMAKE_BOOTSTRAP)
+    } else if (arg.find("--profiling-format", 0) == 0) {
+      profilingFormat = arg.substr(strlen("--profiling-format="));
+      if (profilingFormat.empty()) {
+        cmSystemTools::Error("No format specified for --profiling-format");
+      }
+    } else if (arg.find("--profiling-output", 0) == 0) {
+      profilingOutput = arg.substr(strlen("--profiling-output="));
+      profilingOutput = cmSystemTools::CollapseFullPath(profilingOutput);
+      cmSystemTools::ConvertToUnixSlashes(profilingOutput);
+      if (profilingOutput.empty()) {
+        cmSystemTools::Error("No path specified for --profiling-output");
+      }
+#endif
     }
     // no option assume it is the path to the source or an existing build
     else {
@@ -856,6 +878,29 @@ void cmake::SetArgs(const std::vector<std::string>& args)
     }
   }
 
+#if !defined(CMAKE_BOOTSTRAP)
+  if (!profilingOutput.empty() || !profilingFormat.empty()) {
+    if (profilingOutput.empty()) {
+      cmSystemTools::Error(
+        "--profiling-format specified but no --profiling-output!");
+      return;
+    }
+    if (profilingFormat == "google-trace") {
+      try {
+        this->ProfilingOutput =
+          cm::make_unique<cmMakefileProfilingData>(profilingOutput);
+      } catch (std::runtime_error& e) {
+        cmSystemTools::Error(
+          cmStrCat("Could not start profiling: ", e.what()));
+        return;
+      }
+    } else {
+      cmSystemTools::Error("Invalid format specified for --profiling-format");
+      return;
+    }
+  }
+#endif
+
   const bool haveSourceDir = !this->GetHomeDirectory().empty();
   const bool haveBinaryDir = !this->GetHomeOutputDirectory().empty();
 
@@ -2952,3 +2997,15 @@ void cmake::SetDeprecatedWarningsAsErrors(bool b)
                       " and functions.",
                       cmStateEnums::INTERNAL);
 }
+
+#if !defined(CMAKE_BOOTSTRAP)
+cmMakefileProfilingData& cmake::GetProfilingOutput()
+{
+  return *(this->ProfilingOutput);
+}
+
+bool cmake::IsProfilingEnabled() const
+{
+  return static_cast<bool>(this->ProfilingOutput);
+}
+#endif