[ownership] Add new OwnershipEliminatorPass that does not run when the current module is the stdlib.

As part of bringing up ossa on the rest of the optimizer, I am going to be first
moving ossa back for the stdlib module since the stdlib module does not have any
sil based dependencies. To do so, I am adding this pass that I can place at the
beginning of the pipeline (where NonTransparentFunctionOwnershipModelEliminator
runs today) and then move NonTransparentFunctionOwnershipModelEliminator down as
I update passes. If we are processing the stdlib, the ome doesn't run early and
instead runs late. If we are not processing the stdlib, we perform first an OME
run early and then perform an additional OME run that does nothing since
lowering ownership is an idempotent operation.

Author: gottesmm

include/swift/SILOptimizer/PassManager/Passes.def

@@ -248,6 +248,9 @@ PASS(OwnershipModelEliminator, "ownership-model-eliminator",
 PASS(NonTransparentFunctionOwnershipModelEliminator,
      "non-transparent-func-ownership-model-eliminator",
      "Eliminate Ownership Annotations from non-transparent SIL Functions")
+PASS(NonStdlibNonTransparentFunctionOwnershipModelEliminator,
+     "non-stdlib-non-transparent-func-ownership-model-eliminator",
+     "Eliminate Ownership Annotations from non-transparent SIL Functions only when not processing the stdlib.")
 PASS(RCIdentityDumper, "rc-id-dumper",
      "Print Reference Count Identities")
 PASS(AlwaysInlineInliner, "always-inline",

lib/SILOptimizer/Mandatory/OwnershipModelEliminator.cpp

@@ -362,16 +362,24 @@ namespace {
 
 struct OwnershipModelEliminator : SILModuleTransform {
   bool SkipTransparent;
+  bool SkipStdlibModule;
 
-  OwnershipModelEliminator(bool SkipTransparent)
-      : SkipTransparent(SkipTransparent) {}
+  OwnershipModelEliminator(bool SkipTransparent, bool SkipStdlibModule)
+      : SkipTransparent(SkipTransparent), SkipStdlibModule(SkipStdlibModule) {}
 
   void run() override {
     if (DumpBefore.size()) {
       getModule()->dump(DumpBefore.c_str());
     }
 
     auto &Mod = *getModule();
+
+    // If we are supposed to skip the stdlib module and we are in the stdlib
+    // module bail.
+    if (SkipStdlibModule && Mod.isStdlibModule()) {
+      return;
+    }
+
     for (auto &F : Mod) {
       // If F does not have ownership, skip it. We have no further work to do.
       if (!F.hasOwnership())
@@ -429,9 +437,17 @@ struct OwnershipModelEliminator : SILModuleTransform {
 } // end anonymous namespace
 
 SILTransform *swift::createOwnershipModelEliminator() {
-  return new OwnershipModelEliminator(false /*skip transparent*/);
+  return new OwnershipModelEliminator(false /*skip transparent*/,
+                                      false /*ignore stdlib*/);
 }
 
 SILTransform *swift::createNonTransparentFunctionOwnershipModelEliminator() {
-  return new OwnershipModelEliminator(true /*skip transparent*/);
+  return new OwnershipModelEliminator(true /*skip transparent*/,
+                                      false /*ignore stdlib*/);
+}
+
+SILTransform *
+swift::createNonStdlibNonTransparentFunctionOwnershipModelEliminator() {
+  return new OwnershipModelEliminator(true /*skip transparent*/,
+                                      true /*ignore stdlib*/);
 }

test/SILOptimizer/ome_ignore_stdlib.sil

@@ -0,0 +1,13 @@
+// RUN: %target-sil-opt -non-stdlib-non-transparent-func-ownership-model-eliminator %s | %FileCheck %s
+// RUN: %target-sil-opt -non-stdlib-non-transparent-func-ownership-model-eliminator %s -module-name Swift | %FileCheck -check-prefix=STDLIB-CHECK %s
+
+// CHECK-NOT: [ossa]
+// STDLIB-CHECK: [ossa]
+
+sil_stage canonical
+
+sil [ossa] @my_ossa : $@convention(thin) () -> () {
+bb0:
+  %9999 = tuple()
+  return %9999 : $()
+}