PGO: Splitting implementation files; no functionality change

Split implementation files along a uses-libc/shouldn't-use-libc
boundary.

  - InstrProfiling.h is a shared header.

  - InstrProfiling.c provides an API to extract profiling data from the
    runtime, but avoids the use of libc.  Currently this is a lie:
    __llvm_pgo_write_buffer() uses `FILE*` and related functions.  It
    will be updated soon to write to a `char*` buffer instead.

  - InstrProfilingExtras.c provides a more convenient API for
    interfacing with the profiling runtime, but has logic that does (and
    will continue to) use libc.

<rdar://problem/15943240>

llvm-svn: 204268
diff --git a/compiler-rt/lib/profile/InstrProfilingExtras.c b/compiler-rt/lib/profile/InstrProfilingExtras.c
new file mode 100644
index 0000000..03399a3
--- /dev/null
+++ b/compiler-rt/lib/profile/InstrProfilingExtras.c
@@ -0,0 +1,49 @@
+/*===- InstrProfilingExtras.c - Support library for PGO instrumentation ---===*\
+|*
+|*                     The LLVM Compiler Infrastructure
+|*
+|* This file is distributed under the University of Illinois Open Source
+|* License. See LICENSE.TXT for details.
+|*
+\*===----------------------------------------------------------------------===*/
+
+#include "InstrProfiling.h"
+
+/*! \brief Write instrumentation data to the given file. */
+void __llvm_pgo_write_file(const char *OutputName) {
+  /* TODO: Requires libc: move to separate translation unit. */
+  FILE *OutputFile;
+  if (!OutputName || !OutputName[0])
+    return;
+  OutputFile = fopen(OutputName, "w");
+  if (!OutputFile) return;
+
+  /* TODO: mmap file to buffer of size __llvm_pgo_get_size_for_buffer() and
+   * pass the buffer in, instead of the file.
+   */
+  __llvm_pgo_write_buffer(OutputFile);
+
+  fclose(OutputFile);
+}
+
+/*! \brief Write instrumentation data to the default file. */
+void __llvm_pgo_write_default_file() {
+  /* TODO: Requires libc: move to separate translation unit. */
+  const char *OutputName = getenv("LLVM_PROFILE_FILE");
+  if (OutputName == NULL || OutputName[0] == '\0')
+    OutputName = "default.profdata";
+  __llvm_pgo_write_file(OutputName);
+}
+
+/*!
+ * \brief Register to write instrumentation data to the default file at exit.
+ */
+void __llvm_pgo_register_write_atexit() {
+  /* TODO: Requires libc: move to separate translation unit. */
+  static int HasBeenRegistered = 0;
+
+  if (!HasBeenRegistered) {
+    HasBeenRegistered = 1;
+    atexit(__llvm_pgo_write_default_file);
+  }
+}