InstrProf: Support profiling dlopen'd shared libraries

Shared objects are hard.  After this commit, we do the right thing when
profiling two separate shared objects that have been dlopen'd with
`RTLD_LOCAL`, when the main executable is *not* being profiled.

This mainly simplifies the writer logic.

  - At initialization, determine the output filename and truncate the
    file.  Depending on whether shared objects can see each other, this
    may happen multiple times.

  - At exit, each executable writes its own profile in append mode.

<rdar://problem/16918688>

llvm-svn: 209053

1 files changed, 91 insertions, 75 deletions

diff --git a/compiler-rt/lib/profile/InstrProfilingFile.c b/compiler-rt/lib/profile/InstrProfilingFile.c
index 5ed32d56267..779a68225c3 100644
--- a/compiler-rt/lib/profile/InstrProfilingFile.c
+++ b/compiler-rt/lib/profile/InstrProfilingFile.c
@@ -53,75 +53,60 @@ static int writeFile(FILE *File) {
   return 0;
 }
 
-typedef struct __llvm_profile_writer {
-  struct __llvm_profile_writer *Next;
-  int (*Data)(FILE *);
-} __llvm_profile_writer;
-
-__attribute__((weak)) __llvm_profile_writer *__llvm_profile_HeadWriter = NULL;
-static __llvm_profile_writer Writer = {NULL, writeFile};
-
-__attribute__((visibility("hidden")))
-void __llvm_profile_register_write_file(void) {
-  static int HasBeenRegistered = 0;
-
-  if (HasBeenRegistered)
-    return;
-
-  HasBeenRegistered = 1;
-  Writer.Next = __llvm_profile_HeadWriter;
-  __llvm_profile_HeadWriter = &Writer;
-}
-
 static int writeFileWithName(const char *OutputName) {
   int RetVal;
   FILE *OutputFile;
   if (!OutputName || !OutputName[0])
     return -1;
-  OutputFile = fopen(OutputName, "w");
+
+  /* Append to the file to support profiling multiple shared objects. */
+  OutputFile = fopen(OutputName, "a");
   if (!OutputFile)
     return -1;
 
-  __llvm_profile_writer *Writer = __llvm_profile_HeadWriter;
-  if (Writer)
-    for (; Writer; Writer = Writer->Next) {
-      RetVal = Writer->Data(OutputFile);
-      if (RetVal != 0)
-        break;
-    }
-  else
-    // Default to calling this executable's writeFile.
-    RetVal = writeFile(OutputFile);
+  RetVal = writeFile(OutputFile);
 
   fclose(OutputFile);
   return RetVal;
 }
 
+__attribute__((weak)) int __llvm_profile_OwnsFilename = 0;
 __attribute__((weak)) const char *__llvm_profile_CurrentFilename = NULL;
-__attribute__((weak)) void __llvm_profile_set_filename(const char *Filename) {
+
+static void setFilename(const char *Filename, int OwnsFilename) {
+  if (__llvm_profile_OwnsFilename)
+    free((char *)__llvm_profile_CurrentFilename);
+
   __llvm_profile_CurrentFilename = Filename;
+  __llvm_profile_OwnsFilename = OwnsFilename;
 }
 
-int getpid(void);
-__attribute__((weak)) int __llvm_profile_write_file(void) {
-  char *AllocatedFilename = NULL;
-  int I, J;
-  int RetVal;
+static void truncateCurrentFile(void) {
+  const char *Filename = __llvm_profile_CurrentFilename;
+  if (!Filename || !Filename[0])
+    return;
 
-#define MAX_PID_SIZE 16
-  char PidChars[MAX_PID_SIZE] = { 0 };
-  int PidLength = 0;
-  int NumPids = 0;
+  /* Truncate the file.  Later we'll reopen and append. */
+  FILE *File = fopen(Filename, "w");
+  if (!File)
+    return;
+  fclose(File);
+}
 
-  /* Get the filename. */
-  const char *Filename = __llvm_profile_CurrentFilename;
-#define UPDATE_FILENAME(NextFilename) \
-  if (!Filename || !Filename[0]) Filename = NextFilename
-  UPDATE_FILENAME(getenv("LLVM_PROFILE_FILE"));
-  UPDATE_FILENAME("default.profraw");
-#undef UPDATE_FILENAME
+static void setDefaultFilename(void) { setFilename("default.profraw", 0); }
+
+int getpid(void);
+static int setFilenameFromEnvironment(void) {
+  const char *Filename = getenv("LLVM_PROFILE_FILE");
+  if (!Filename || !Filename[0])
+    return -1;
 
   /* Check the filename for "%p", which indicates a pid-substitution. */
+#define MAX_PID_SIZE 16
+  char PidChars[MAX_PID_SIZE] = {0};
+  int NumPids = 0;
+  int PidLength = 0;
+  int I;
   for (I = 0; Filename[I]; ++I)
     if (Filename[I] == '%' && Filename[++I] == 'p')
       if (!NumPids++) {
@@ -129,43 +114,74 @@ __attribute__((weak)) int __llvm_profile_write_file(void) {
         if (PidLength <= 0)
           return -1;
       }
-  if (NumPids) {
-    /* Allocate enough space for the substituted filename. */
-    AllocatedFilename = (char*)malloc(I + NumPids*(PidLength - 2) + 1);
-    if (!AllocatedFilename)
-      return -1;
-
-    /* Construct the new filename. */
-    for (I = 0, J = 0; Filename[I]; ++I)
-      if (Filename[I] == '%') {
-        if (Filename[++I] == 'p') {
-          memcpy(AllocatedFilename + J, PidChars, PidLength);
-          J += PidLength;
-        }
-        /* Drop any unknown substitutions. */
-      } else
-        AllocatedFilename[J++] = Filename[I];
-    AllocatedFilename[J] = 0;
-
-    /* Actually use the computed name. */
-    Filename = AllocatedFilename;
+  if (!NumPids) {
+    setFilename(Filename, 0);
+    return 0;
   }
 
-  /* Write the file. */
-  RetVal = writeFileWithName(Filename);
+  /* Allocate enough space for the substituted filename. */
+  char *Allocated = (char*)malloc(I + NumPids*(PidLength - 2) + 1);
+  if (!Allocated)
+    return -1;
 
-  /* Free the filename. */
-  if (AllocatedFilename)
-    free(AllocatedFilename);
+  /* Construct the new filename. */
+  int J;
+  for (I = 0, J = 0; Filename[I]; ++I)
+    if (Filename[I] == '%') {
+      if (Filename[++I] == 'p') {
+        memcpy(Allocated + J, PidChars, PidLength);
+        J += PidLength;
+      }
+      /* Drop any unknown substitutions. */
+    } else
+      Allocated[J++] = Filename[I];
+  Allocated[J] = 0;
 
-  return RetVal;
+  /* Use the computed name. */
+  setFilename(Allocated, 1);
+  return 0;
+}
+
+static void setFilenameAutomatically(void) {
+  if (!setFilenameFromEnvironment())
+    return;
+
+  setDefaultFilename();
+}
+
+__attribute__((visibility("hidden")))
+void __llvm_profile_initialize_file(void) {
+  /* Check if the filename has been initialized. */
+  if (__llvm_profile_CurrentFilename)
+    return;
+
+  /* Detect the filename and truncate. */
+  setFilenameAutomatically();
+  truncateCurrentFile();
+}
+
+__attribute__((visibility("hidden")))
+void __llvm_profile_set_filename(const char *Filename) {
+  setFilename(Filename, 0);
+  truncateCurrentFile();
+}
+
+__attribute__((visibility("hidden")))
+int __llvm_profile_write_file(void) {
+  /* Check the filename. */
+  if (!__llvm_profile_CurrentFilename)
+    return -1;
+
+  /* Write the file. */
+  return writeFileWithName(__llvm_profile_CurrentFilename);
 }
 
 static void writeFileWithoutReturn(void) {
   __llvm_profile_write_file();
 }
 
-__attribute__((weak)) int __llvm_profile_register_write_file_atexit(void) {
+__attribute__((visibility("hidden")))
+int __llvm_profile_register_write_file_atexit(void) {
   static int HasBeenRegistered = 0;
 
   if (HasBeenRegistered)