[ownership] Add a frontend option -disable-ossa-opts to disable ossa based opts for benchmarking purposes.

include/swift/AST/SILOptions.h

@@ -53,6 +53,10 @@ public:
   /// Controls whether the SIL ARC optimizations are run.
   bool EnableARCOptimizations = true;
 
+  /// Controls whether specific OSSA optimizations are run. For benchmarking
+  /// purposes.
+  bool EnableOSSAOptimizations = true;
+
   /// Should we run any SIL performance optimizations
   ///
   /// Useful when you want to enable -O LLVM opts but not -O SIL opts.

include/swift/Option/FrontendOptions.td

@@ -254,6 +254,8 @@ def debugger_support : Flag<["-"], "debugger-support">,
 
 def disable_arc_opts : Flag<["-"], "disable-arc-opts">,
   HelpText<"Don't run SIL ARC optimization passes.">;
+def disable_ossa_opts : Flag<["-"], "disable-ossa-opts">,
+  HelpText<"Don't run SIL OSSA optimization passes.">;
 
 def disable_sil_partial_apply : Flag<["-"], "disable-sil-partial-apply">,
   HelpText<"Disable use of partial_apply in SIL generation">;

lib/Frontend/CompilerInvocation.cpp

@@ -844,6 +844,7 @@ static bool ParseSILArgs(SILOptions &Opts, ArgList &Args,
   Opts.RemoveRuntimeAsserts |= Args.hasArg(OPT_RemoveRuntimeAsserts);
 
   Opts.EnableARCOptimizations |= !Args.hasArg(OPT_disable_arc_opts);
+  Opts.EnableOSSAOptimizations &= !Args.hasArg(OPT_disable_ossa_opts);
   Opts.DisableSILPerfOptimizations |= Args.hasArg(OPT_disable_sil_perf_optzns);
   Opts.VerifyAll |= Args.hasArg(OPT_sil_verify_all);
   Opts.DebugSerialization |= Args.hasArg(OPT_sil_debug_serialization);

lib/SILOptimizer/Mandatory/SemanticARCOpts.cpp

@@ -772,6 +772,10 @@ struct SemanticARCOpts : SILFunctionTransform {
   void run() override {
     SILFunction &f = *getFunction();
 
+    // Return early if we are not performing OSSA optimizations.
+    if (!f.getModule().getOptions().EnableOSSAOptimizations)
+      return;
+
     // Make sure we are running with ownership verification enabled.
     assert(f.getModule().getOptions().VerifySILOwnership &&
            "Can not perform semantic arc optimization unless ownership "

lib/SILOptimizer/Transforms/DestroyHoisting.cpp

@@ -716,6 +716,10 @@ public:
     if (!F->hasOwnership())
       return;
 
+    // If we are not supposed to perform ossa optimizations, bail.
+    if (!F->getModule().getOptions().EnableOSSAOptimizations)
+      return;
+
     LLVM_DEBUG(llvm::dbgs() << "*** DestroyHoisting on function: "
                             << F->getName() << " ***\n");