PruneVTables: Add DEBUG logging of the pass decisions

Author: jckarter

lib/SILOptimizer/Transforms/PruneVTables.cpp

@@ -29,43 +29,71 @@ namespace {
 class PruneVTables : public SILModuleTransform {
   void runOnVTable(SILModule *M,
                    SILVTable *vtable) {
+    LLVM_DEBUG(llvm::dbgs() << "PruneVTables inspecting table:\n";
+               vtable->print(llvm::dbgs()));
     for (auto &entry : vtable->getMutableEntries()) {
 
       // We don't need to worry about entries that are overridden,
       // or have already been found to have no overrides.
-      if (entry.isNonOverridden())
+      if (entry.isNonOverridden()) {
+        LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
+                   entry.getMethod().print(llvm::dbgs());
+                   llvm::dbgs() << " is already nonoverridden\n");
         continue;
+      }
 
       switch (entry.getKind()) {
       case SILVTable::Entry::Normal:
       case SILVTable::Entry::Inherited:
         break;
 
       case SILVTable::Entry::Override:
+        LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
+                   entry.getMethod().print(llvm::dbgs());
+                   llvm::dbgs() << " is an override\n");
         continue;
       }
 
       // The destructor entry must remain.
       if (entry.getMethod().kind == SILDeclRef::Kind::Deallocator) {
+        LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
+                   entry.getMethod().print(llvm::dbgs());
+                   llvm::dbgs() << " is a destructor\n");
         continue;
       }
 
       auto methodDecl = entry.getMethod().getAbstractFunctionDecl();
-      if (!methodDecl)
+      if (!methodDecl) {
+        LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
+                   entry.getMethod().print(llvm::dbgs());
+                   llvm::dbgs() << " is not a function decl\n");
         continue;
+      }
 
       // Is the method declared final?
       if (!methodDecl->isFinal()) {
         // Are callees of this entry statically knowable?
-        if (!calleesAreStaticallyKnowable(*M, entry.getMethod()))
+        if (!calleesAreStaticallyKnowable(*M, entry.getMethod())) {
+          LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
+                     entry.getMethod().print(llvm::dbgs());
+                     llvm::dbgs() << " does not have statically-knowable callees\n");
           continue;
+        }
 
         // Does the method have any overrides in this module?
-        if (methodDecl->isOverridden())
+        if (methodDecl->isOverridden()) {
+          LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
+                     entry.getMethod().print(llvm::dbgs());
+                     llvm::dbgs() << " has overrides\n");
           continue;
+        }
       }
+      LLVM_DEBUG(llvm::dbgs() << "++ entry for ";
+                 entry.getMethod().print(llvm::dbgs());
+                 llvm::dbgs() << " can be marked non-overridden!\n");
       ++NumNonoverriddenVTableEntries;
       entry.setNonOverridden(true);
+      vtable->updateVTableCache(entry);
     }
   }