[embedded] Re-enable ReleaseDevirtualizer and teach it to look for specialized destructors

Author: kubamracek

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/ReleaseDevirtualizer.swift

@@ -107,7 +107,14 @@ private func tryDevirtualizeRelease(
   // argument.
   let functionRef = builder.createFunctionRef(dealloc)
 
-  let substitutionMap = context.getContextSubstitutionMap(for: type)
+  let substitutionMap: SubstitutionMap
+  if dealloc.isGenericFunction {
+    substitutionMap = context.getContextSubstitutionMap(for: type)
+  } else {
+    // In embedded Swift, dealloc might be a specialized deinit, so the substitution map on the old apply isn't valid for the new apply
+    substitutionMap = SubstitutionMap()
+  }
+
   builder.createApply(function: functionRef, substitutionMap, arguments: [beginDealloc])
   context.erase(instruction: lastRelease)
 }

lib/SILOptimizer/Analysis/BasicCalleeAnalysis.cpp

@@ -306,6 +306,15 @@ CalleeList CalleeCache::getDestructors(SILType type, bool isExactType) const {
   if (isExactType || classDecl->isFinal()) {
     // In case of a final class, just pick the deinit of the class.
     SILDeclRef destructor = SILDeclRef(classDecl->getDestructor());
+    
+    // In embedded Swift, we need the specialized destructor, not the generic
+    // one.
+    if (auto *vtable = M.lookUpSpecializedVTable(type)) {
+      if (auto entry = vtable->getEntry(M, destructor))
+        return CalleeList(entry->getImplementation());
+      return CalleeList();
+    }
+
     if (SILFunction *destrImpl = M.lookUpFunction(destructor))
       return CalleeList(destrImpl);
     return CalleeList();

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -760,14 +760,8 @@ static void addMidLevelFunctionPipeline(SILPassPipelinePlan &P) {
 static void addLowLevelPassPipeline(SILPassPipelinePlan &P) {
   P.startPipeline("LowLevel,Function", true /*isFunctionPassPipeline*/);
 
-  // MandatoryPerformanceOptimizations already took care of all specializations
-  // in embedded Swift mode, running the release devirtualizer might introduce
-  // more generic calls from non-generic functions, which breaks the assumptions
-  // of embedded Swift.
-  if (!P.getOptions().EmbeddedSwift) {
-    // Should be after FunctionSignatureOpts and before the last inliner.
-    P.addReleaseDevirtualizer();
-  }
+  // Should be after FunctionSignatureOpts and before the last inliner.
+  P.addReleaseDevirtualizer();
 
   addFunctionPasses(P, OptimizationLevelKind::LowLevel);
 

test/embedded/classes-stack-promotion.swift

@@ -86,7 +86,9 @@ struct Main {
 // CHECK-IR-NEXT:   call {{.*}}@"$s4main5print_10terminatorys12StaticStringV_AEtF"
 // CHECK-IR-NEXT:   call {{.*}}@"$s4main5print_10terminatorys12StaticStringV_AEtF"
 // CHECK-IR-NEXT:   call {{.*}}@"$s4main3bar1oyAA7MyClassC_tF"
-// CHECK-IR-NEXT:   call {{.*}}@swift_release
+// CHECK-IR-NEXT:   call {{.*}}@swift_setDeallocating
+// CHECK-IR-NEXT:   call {{.*}}@"$s4main5print_10terminatorys12StaticStringV_AEtF"
+// CHECK-IR-NEXT:   call {{.*}}@"$s4main5print_10terminatorys12StaticStringV_AEtF"
 // CHECK-IR-NEXT:   call {{.*}}@llvm.lifetime.end.p0
 // CHECK-IR-NEXT:   call {{.*}}@"$s4main5print_10terminatorys12StaticStringV_AEtF"
 // CHECK-IR-NEXT:   call {{.*}}@swift_initStackObject