Encapsulate PassManager debug flags to avoid static init and cxa_exit.

This puts all the global PassManager debugging flags, like
-print-after-all and -time-passes, behind a managed static. This
eliminates their static initializers and, more importantly, exit-time
destructors.

The only behavioral change I anticipate is that tools need to
initialize the PassManager before parsing the command line in order to
export these options, which makes sense. Tools that already initialize
the standard passes (opt/llc) don't need to do anything new.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190974 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-diff/llvm-diff.cpp

@@ -20,6 +20,7 @@
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IRReader/IRReader.h"
+#include "llvm/PassManager.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SourceMgr.h"
@@ -67,6 +68,9 @@ static cl::list<std::string> GlobalsToCompare(cl::Positional,
                                               cl::desc("<globals to compare>"));
 
 int main(int argc, char **argv) {
+  // Initialize PassManager for -time-passes support.
+  initializePassManager();
+
   cl::ParseCommandLineOptions(argc, argv);
 
   LLVMContext Context;