PGO: Add explicit static initialization

Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable.  After this commit (and its pair in clang),
the driver will create a use of this variable.  Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.

The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit.  Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.

<rdar://problem/15943240>

llvm-svn: 204380

1 files changed, 0 insertions, 5 deletions

diff --git a/compiler-rt/lib/profile/InstrProfilingExtras.c b/compiler-rt/lib/profile/InstrProfilingExtras.c
index 03399a3477f..45a7f8ce52c 100644
--- a/compiler-rt/lib/profile/InstrProfilingExtras.c
+++ b/compiler-rt/lib/profile/InstrProfilingExtras.c
@@ -9,7 +9,6 @@
 
 #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;
@@ -26,7 +25,6 @@ void __llvm_pgo_write_file(const char *OutputName) {
   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");
@@ -35,9 +33,6 @@ void __llvm_pgo_write_default_file() {
   __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;