[PM] Add pass run listeners to the pass manager.

This commit provides the necessary C/C++ APIs and infastructure to enable fine-
grain progress report and safe suspension points after each pass in the pass
manager.

Clients can provide a callback function to the pass manager to call after each
pass. This can be used in a variety of ways (progress report, dumping of IR
between passes, safe suspension of threads, etc).

The run listener list is maintained in the LLVMContext, which allows a multi-
threaded client to be only informed for it's own thread. This of course assumes
that the client created a LLVMContext for each thread.

This fixes <rdar://problem/16728690>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207430 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/LLVMContextImpl.cpp

@@ -15,11 +15,32 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/Module.h"
+#include "llvm/PassSupport.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Regex.h"
 #include <algorithm>
 using namespace llvm;
 
+/// Notify that we finished running a pass.
+void LLVMContextImpl::notifyPassRun(LLVMContext *C, Pass *P, Module *M,
+                                    Function *F, BasicBlock *BB) {
+  for (auto const &L : RunListeners)
+    L->passRun(C, P, M, F, BB);
+}
+/// Register the given PassRunListener to receive notifyPassRun()
+/// callbacks whenever a pass ran.
+void LLVMContextImpl::addRunListener(PassRunListener *L) {
+  RunListeners.push_back(L);
+}
+/// Unregister a PassRunListener so that it no longer receives
+/// notifyPassRun() callbacks.
+void LLVMContextImpl::removeRunListener(PassRunListener *L) {
+  auto I = std::find(RunListeners.begin(), RunListeners.end(), L);
+  assert(I != RunListeners.end() && "RunListener not registered!");
+  delete *I;
+  RunListeners.erase(I);
+}
+
 LLVMContextImpl::LLVMContextImpl(LLVMContext &C)
   : TheTrueVal(nullptr), TheFalseVal(nullptr),
     VoidTy(C, Type::VoidTyID),
@@ -188,6 +209,11 @@ LLVMContextImpl::~LLVMContextImpl() {
 
   // Destroy MDStrings.
   DeleteContainerSeconds(MDStringCache);
+
+  // Destroy all run listeners.
+  for (auto &L : RunListeners)
+    delete L;
+  RunListeners.clear();
 }
 
 // ConstantsContext anchors