Index: compiler-rt/trunk/lib/profile/InstrProfiling.h
===================================================================
--- compiler-rt/trunk/lib/profile/InstrProfiling.h
+++ compiler-rt/trunk/lib/profile/InstrProfiling.h
@@ -170,6 +170,14 @@
  */
 const char *__llvm_profile_get_path_prefix();
 
+/*!
+ * \brief Return filename (including path) of the profile data. Note that if the
+ * user calls __llvm_profile_set_filename later after invoking this interface,
+ * the actual file name may differ from what is returned here.
+ * Side-effect: this API call will invoke malloc with dynamic memory allocation.
+ */
+const char *__llvm_profile_get_filename();
+
 /*! \brief Get the magic token for the file format. */
 uint64_t __llvm_profile_get_magic(void);
 
Index: compiler-rt/trunk/lib/profile/InstrProfilingFile.c
===================================================================
--- compiler-rt/trunk/lib/profile/InstrProfilingFile.c
+++ compiler-rt/trunk/lib/profile/InstrProfilingFile.c
@@ -69,6 +69,7 @@
    * by runtime. */
   unsigned OwnsFilenamePat;
   const char *ProfilePathPrefix;
+  const char *Filename;
   char PidChars[MAX_PID_SIZE];
   char Hostname[COMPILER_RT_MAX_HOSTLEN];
   unsigned NumPids;
@@ -84,11 +85,11 @@
   ProfileNameSpecifier PNS;
 } lprofFilename;
 
-COMPILER_RT_WEAK lprofFilename lprofCurFilename = {0, 0, 0, {0}, {0},
-                                                   0, 0, 0, PNS_unknown};
+COMPILER_RT_WEAK lprofFilename lprofCurFilename = {0,   0, 0, 0, {0},
+                                                   {0}, 0, 0, 0, PNS_unknown};
 
 static int getCurFilenameLength();
-static const char *getCurFilename(char *FilenameBuf);
+static const char *getCurFilename(char *FilenameBuf, int ForceUseBuf);
 static unsigned doMerging() { return lprofCurFilename.MergePoolSize; }
 
 /* Return 1 if there is an error, otherwise return  0.  */
@@ -266,7 +267,7 @@
 
   Length = getCurFilenameLength();
   FilenameBuf = (char *)COMPILER_RT_ALLOCA(Length + 1);
-  Filename = getCurFilename(FilenameBuf);
+  Filename = getCurFilename(FilenameBuf, 0);
   if (!Filename)
     return;
 
@@ -311,9 +312,12 @@
   char *Hostname = &lprofCurFilename.Hostname[0];
   int MergingEnabled = 0;
 
-  /* Clean up cached prefix.  */
+  /* Clean up cached prefix and filename.  */
   if (lprofCurFilename.ProfilePathPrefix)
     free((void *)lprofCurFilename.ProfilePathPrefix);
+  if (lprofCurFilename.Filename)
+    free((void *)lprofCurFilename.Filename);
+
   memset(&lprofCurFilename, 0, sizeof(lprofCurFilename));
 
   if (lprofCurFilename.FilenamePat && lprofCurFilename.OwnsFilenamePat) {
@@ -428,17 +432,25 @@
 /* Return the pointer to the current profile file name (after substituting
  * PIDs and Hostnames in filename pattern. \p FilenameBuf is the buffer
  * to store the resulting filename. If no substitution is needed, the
- * current filename pattern string is directly returned. */
-static const char *getCurFilename(char *FilenameBuf) {
-  int I, J, PidLength, HostNameLength;
+ * current filename pattern string is directly returned, unless ForceUseBuf
+ * is enabled. */
+static const char *getCurFilename(char *FilenameBuf, int ForceUseBuf) {
+  int I, J, PidLength, HostNameLength, FilenamePatLength;
   const char *FilenamePat = lprofCurFilename.FilenamePat;
 
   if (!lprofCurFilename.FilenamePat || !lprofCurFilename.FilenamePat[0])
     return 0;
 
   if (!(lprofCurFilename.NumPids || lprofCurFilename.NumHosts ||
-        lprofCurFilename.MergePoolSize))
-    return lprofCurFilename.FilenamePat;
+        lprofCurFilename.MergePoolSize)) {
+    if (!ForceUseBuf)
+      return lprofCurFilename.FilenamePat;
+
+    FilenamePatLength = strlen(lprofCurFilename.FilenamePat);
+    memcpy(FilenameBuf, lprofCurFilename.FilenamePat, FilenamePatLength);
+    FilenameBuf[FilenamePatLength] = '\0';
+    return FilenameBuf;
+  }
 
   PidLength = strlen(lprofCurFilename.PidChars);
   HostNameLength = strlen(lprofCurFilename.Hostname);
@@ -492,7 +504,7 @@
 
   Length = getCurFilenameLength();
   FilenameBuf = (char *)COMPILER_RT_ALLOCA(Length + 1);
-  Filename = getCurFilename(FilenameBuf);
+  Filename = getCurFilename(FilenameBuf, 0);
   if (!Filename)
     return "\0";
 
@@ -512,6 +524,29 @@
   return Prefix;
 }
 
+COMPILER_RT_VISIBILITY
+const char *__llvm_profile_get_filename(void) {
+  int Length;
+  char *FilenameBuf;
+  const char *Filename;
+
+  if (lprofCurFilename.Filename)
+    return lprofCurFilename.Filename;
+
+  Length = getCurFilenameLength();
+  FilenameBuf = (char *)malloc(Length + 1);
+  if (!FilenameBuf) {
+    PROF_ERR("Failed to %s\n", "allocate memory.");
+    return "\0";
+  }
+  Filename = getCurFilename(FilenameBuf, 1);
+  if (!Filename)
+    return "\0";
+
+  lprofCurFilename.Filename = FilenameBuf;
+  return FilenameBuf;
+}
+
 /* This method is invoked by the runtime initialization hook
  * InstrProfilingRuntime.o if it is linked in. Both user specified
  * profile path via -fprofile-instr-generate= and LLVM_PROFILE_FILE
@@ -568,7 +603,7 @@
 
   Length = getCurFilenameLength();
   FilenameBuf = (char *)COMPILER_RT_ALLOCA(Length + 1);
-  Filename = getCurFilename(FilenameBuf);
+  Filename = getCurFilename(FilenameBuf, 0);
 
   /* Check the filename. */
   if (!Filename) {
Index: compiler-rt/trunk/test/profile/instrprof-get-filename.c
===================================================================
--- compiler-rt/trunk/test/profile/instrprof-get-filename.c
+++ compiler-rt/trunk/test/profile/instrprof-get-filename.c
@@ -0,0 +1,39 @@
+// Test __llvm_profile_get_filename.
+// RUN: %clang_pgogen -O2 -o %t %s
+// RUN: %run %t
+
+#include <stdio.h>
+#include <string.h>
+
+const char *__llvm_profile_get_filename();
+void __llvm_profile_set_filename(const char *);
+
+int main(int argc, const char *argv[]) {
+  int i;
+  const char *filename;
+  const char *new_filename = "/path/to/test.profraw";
+
+  filename = __llvm_profile_get_filename();
+  if (strncmp(filename, "default_", 8)) {
+    fprintf(stderr,
+            "Error: got filename %s, expected it to start with 'default_'\n",
+            filename);
+    return 1;
+  }
+  if (strcmp(filename + strlen(filename) - strlen(".profraw"), ".profraw")) {
+    fprintf(stderr,
+            "Error: got filename %s, expected it to end with '.profraw'\n",
+            filename);
+    return 1;
+  }
+
+  __llvm_profile_set_filename(new_filename);
+  filename = __llvm_profile_get_filename();
+  if (strcmp(filename, new_filename)) {
+    fprintf(stderr, "Error: got filename %s, expected '%s'\n", filename,
+            new_filename);
+    return 1;
+  }
+
+  return 0;
+}