[analysis] Add a new form of verification SILAnalysis::verifyFull().

This is a verification routine that is only invoked in PassManager
destructors. I am going to use this to ensure that the
PassManagerVerifierAnalysis only runs at such points (even when sil-verify-all
is enabled) since it is too expensive to run otherwise.

NOTE: The default implementation of verifyFull in this commit is a no-op. I
wanted to have verify() be the default implementation of verifyFull(), but I do
not have more time to invest in this and it seems to catch /real/ bugs, albeit
bugs unrelated to pass manager notification verification. Instead I am going to
file an SR for someone to look at it since I need to move on from this work back
to semantic SIL. At least we will not have notification failure issues anymore
and thus a large correctness issue in the compiler has been fixed. Forward
progress!

rdar://42301529

Author: gottesmm

include/swift/SILOptimizer/Analysis/Analysis.h

@@ -137,6 +137,18 @@ class SILAnalysis : public DeleteNotificationHandler {
   /// specific verification will do so.
   virtual void verify(SILFunction *F) const { verify(); }
 
+  /// Perform a potentially more expensive verification of the state of this
+  /// analysis.
+  ///
+  /// The purpose of this is to allow for more expensive verification that is
+  /// fast enough to run at the end of a pass manager once vs in between all
+  /// passes when -sil-verify-all is enabled.
+  ///
+  /// TODO: By default this is a no-op, but really it should call
+  /// verify(). Today doing a full verification seems to catch verification
+  /// errors when compiling the stdlib/overlays.
+  virtual void verifyFull() const {}
+
   /// Verify that the function \p F can be used by the analysis.
   static void verifyFunction(SILFunction *F);
 };

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -568,6 +568,22 @@ void SILPassManager::execute() {
 SILPassManager::~SILPassManager() {
   assert(IRGenPasses.empty() && "Must add IRGen SIL passes that were "
                                 "registered to the list of transformations");
+  // Before we do anything further, verify the module and our analyses. These
+  // are natural points with which to verify.
+  //
+  // TODO: We currently do not verify the module here since the verifier asserts
+  // in the normal build. This should be enabled and those problems resolved
+  // either by changing the verifier or treating those asserts as signs of a
+  // bug.
+  for (auto *A : Analyses) {
+    // We use verify full instead of just verify to ensure that passes that want
+    // to run more expensive verification after a pass manager is destroyed
+    // properly trigger.
+    //
+    // NOTE: verifyFull() has a default implementation that just calls
+    // verify(). So functionally, there is no difference here.
+    A->verifyFull();
+  }
 
   // Remove our deserialization notification handler.
   Mod->removeDeserializationNotificationHandler(