Enable late OME via an experimental flag (swiftlang#39363)

Author: meg-gupta

lib/SILOptimizer/PassManager/PassPipeline.cpp

@@ -51,6 +51,10 @@ static llvm::cl::opt<bool> SILViewSILGenCFG(
     "sil-view-silgen-cfg", llvm::cl::init(false),
     llvm::cl::desc("Enable the sil cfg viewer pass before diagnostics"));
 
+static llvm::cl::opt<bool>
+    SILEnableLateOME("sil-enable-late-ome", llvm::cl::init(false),
+                     llvm::cl::desc("Enable late OwnershipModel elimination"));
+
 //===----------------------------------------------------------------------===//
 //                          Diagnostic Pass Pipeline
 //===----------------------------------------------------------------------===//
@@ -365,7 +369,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
   P.addDevirtualizer();
   P.addARCSequenceOpts();
 
-  if (P.getOptions().EnableOSSAModules) {
+  if (P.getOptions().EnableOSSAModules || SILEnableLateOME) {
     // We earlier eliminated ownership if we are not compiling the stdlib. Now
     // handle the stdlib functions, re-simplifying, eliminating ARC as we do.
     if (!P.getOptions().DisableCopyPropagation) {
@@ -391,7 +395,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
   }
 
   // Clean up Semantic ARC before we perform additional post-inliner opts.
-  if (P.getOptions().EnableOSSAModules) {
+  if (P.getOptions().EnableOSSAModules || SILEnableLateOME) {
     if (!P.getOptions().DisableCopyPropagation) {
       P.addCopyPropagation();
     }
@@ -458,7 +462,7 @@ void addFunctionPasses(SILPassPipelinePlan &P,
   P.addARCSequenceOpts();
 
   // Run a final round of ARC opts when ownership is enabled.
-  if (P.getOptions().EnableOSSAModules) {
+  if (P.getOptions().EnableOSSAModules || SILEnableLateOME) {
     if (!P.getOptions().DisableCopyPropagation) {
       P.addCopyPropagation();
     }
@@ -515,7 +519,7 @@ static void addPerfEarlyModulePassPipeline(SILPassPipelinePlan &P) {
   if (P.getOptions().StopOptimizationBeforeLoweringOwnership)
     return;
 
-  if (!P.getOptions().EnableOSSAModules)
+  if (!P.getOptions().EnableOSSAModules && !SILEnableLateOME)
     P.addNonTransparentFunctionOwnershipModelEliminator();
 
   // Start by linking in referenced functions from other modules.
@@ -811,7 +815,7 @@ SILPassPipelinePlan::getPerformancePassPipeline(const SILOptions &Options) {
 
   // Run one last copy propagation/semantic arc opts run before serialization/us
   // lowering ownership.
-  if (P.getOptions().EnableOSSAModules) {
+  if (P.getOptions().EnableOSSAModules || SILEnableLateOME) {
     if (!P.getOptions().DisableCopyPropagation) {
       P.addCopyPropagation();
     }