WIP: [profile] Playing with multi-process profiling and coverage generation.

[Dor1s]

Trying to fix issue with coverage stats being duplicated if fork() is used

[Dor1s]

Another set of local changes, not for review yet.

lib/profile/InstrProfilingFile.c

static void truncateCurrentFile(void) {
 
   /* Truncate the file.  Later we'll reopen and append. */
   File = fopen(Filename, "w");
   if (!File)
     return;
   fclose(File);
 }
 
-static const char *DefaultProfileName = "default.profraw";
+const char *getFilenamePatDefault(void) {
+  const char* procname = getprogname();
+  const pid_t pid = getpid();
+  char* name;
+  asprintf(&name, "%s.%d.profraw", procname, pid);
+  return name;
+}
+
+
+static const char *DefaultProfileName; // = getFilenamePatDefault(); //"default.profraw";
 static void resetFilenameToDefault(void) {
   if (lprofCurFilename.FilenamePat && lprofCurFilename.OwnsFilenamePat) {
     free((void *)lprofCurFilename.FilenamePat);
   }
   memset(&lprofCurFilename, 0, sizeof(lprofCurFilename));
   lprofCurFilename.FilenamePat = DefaultProfileName;
   lprofCurFilename.PNS = PNS_default;
 }

  * InstrProfilingRuntime.o if it is linked in. Both user specified
  * profile path via -fprofile-instr-generate= and LLVM_PROFILE_FILE
  * environment variable can override this default value. */
 COMPILER_RT_VISIBILITY
 void __llvm_profile_initialize_file(void) {
   const char *EnvFilenamePat;
   const char *SelectedPat = NULL;
   ProfileNameSpecifier PNS = PNS_unknown;
+  if (!DefaultProfileName)
+    DefaultProfileName = getFilenamePatDefault();
   int hasCommandLineOverrider = (INSTR_PROF_PROFILE_NAME_VAR[0] != 0);
 
   EnvFilenamePat = getFilenamePatFromEnv();
   if (EnvFilenamePat) {
     /* Pass CopyFilenamePat = 1, to ensure that the filename would be valid 
        at the  moment when __llvm_profile_write_file() gets executed. */
     parseAndSetFilename(EnvFilenamePat, PNS_environment, 1);
     return;

test/profile/Inputs/instrprof-multi-process-child.c

+int main() {
+  return 0;
+}

test/profile/Inputs/instrprof-multi-process-parent.c

+#include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int main(int argc, char* argv[]) {
+  char *cmd;
+  asprintf(&cmd, "%s/child", dirname(argv[0]));
+  if (fork() == 0) {
+    system(cmd);
+  }
+
+  return 0;
+}

test/profile/instrprof-multi-process.test

+# Test that profiler works with applications running multiple processes.
+RUN: rm -rf %t.d
+RUN: mkdir -p %t.d
+RUN: %clang_profgen -O0 %S/Inputs/instrprof-multi-process-parent.c -o %t.d/parent
+RUN: %clang_profgen -O0 %S/Inputs/instrprof-multi-process-child.c -o %t.d/child
+RUN: %t.d/parent
+
+RUN: llvm-profdata merge -o %t.profdata parent.*.profraw child.*.profraw