Dump instruction set features in .cfg

This commit adds a compilation block at the beginning of the .cfg
dumped by the optimizing compiler when --dump-cfg is enabled.

The compilation block appears in the following form:

begin_compilation
  name "isa_features:feature1,-feature2"
  method "isa_features:feature1,-feature2"
  date 1580721972
end_compilation

This compilation block dump is passed to checker script (see
https://android-review.googlesource.com/c/platform/art/+/1290997)
for checking if a certain instruction set feature was used at compile
time.

Author:    Fabio Rinaldi
Committer: Artem Serov

Bug: 147876827
Test: ./art/tools/checker/run_unit_tests.py
Test: test.py --target --optimizing
Change-Id: If4309af4bab892f715aad1d3bd338f8ee11e497c
diff --git a/compiler/optimizing/graph_visualizer.cc b/compiler/optimizing/graph_visualizer.cc
index 23b93fc..922a6f6 100644
--- a/compiler/optimizing/graph_visualizer.cc
+++ b/compiler/optimizing/graph_visualizer.cc
@@ -21,6 +21,7 @@
 #include <cctype>
 #include <sstream>
 
+#include "android-base/stringprintf.h"
 #include "art_method.h"
 #include "base/intrusive_forward_list.h"
 #include "bounds_check_elimination.h"
@@ -42,6 +43,8 @@
 
 namespace art {
 
+using android::base::StringPrintf;
+
 static bool HasWhitespace(const char* str) {
   DCHECK(str != nullptr);
   while (str[0] != 0) {
@@ -903,6 +906,19 @@
   printer.Flush();
 }
 
+std::string HGraphVisualizer::InsertMetaDataAsCompilationBlock(const std::string& meta_data) {
+  std::string time_str = std::to_string(time(nullptr));
+  std::string quoted_meta_data = "\"" + meta_data + "\"";
+  return StringPrintf("begin_compilation\n"
+                      "  name %s\n"
+                      "  method %s\n"
+                      "  date %s\n"
+                      "end_compilation\n",
+                      quoted_meta_data.c_str(),
+                      quoted_meta_data.c_str(),
+                      time_str.c_str());
+}
+
 void HGraphVisualizer::DumpGraph(const char* pass_name,
                                  bool is_after_pass,
                                  bool graph_in_bad_state) const {