SILGen: Add PrettyStackTraces for witness table emission

Author: slavapestov

lib/SILGen/SILGenType.cpp

@@ -24,6 +24,7 @@
 #include "swift/AST/ASTMangler.h"
 #include "swift/AST/GenericEnvironment.h"
 #include "swift/AST/ProtocolConformance.h"
+#include "swift/AST/PrettyStackTrace.h"
 #include "swift/AST/SubstitutionMap.h"
 #include "swift/AST/TypeMemberVisitor.h"
 #include "swift/SIL/FormalLinkage.h"
@@ -410,6 +411,10 @@ class SILGenConformance : public SILGenWitnessTable<SILGenConformance> {
     if (!Conformance)
       return nullptr;
 
+    PrettyStackTraceConformance trace(SGM.getASTContext(),
+                                      "generating SIL witness table",
+                                      Conformance);
+
     auto *proto = Conformance->getProtocol();
     visitProtocolDecl(proto);
 
@@ -773,6 +778,10 @@ class SILGenSelfConformanceWitnessTable
   }
 
   void emit() {
+    PrettyStackTraceConformance trace(SGM.getASTContext(),
+                                      "generating SIL witness table",
+                                      conformance);
+
     // Add entries for all the requirements.
     visitProtocolDecl(conformance->getProtocol());