[arc] Change guaranteed arc opts to be based on SemanticARCOpts and move from Diagnostic pipeline -> Onone pipeline.

The pass is already not being run during normal compilation scenarios today
since it bails on OSSA except in certain bit-rot situations where a test wasn't
updated and so was inadvertently invoking the pass. I discovered these while
originally just trying to eliminate the pass from the diagnostic pipeline. The
reason why I am doing this in one larger change is that I found there were a
bunch of sil tests inadvertently relying on guaranteed arc opts to eliminate
copy traffic. So, if I just removed this and did this in two steps, I would
basically be unoptimizing then re-optimizing the tests.

Some notes:

1. The new guaranteed arc opts is based off of SemanticARCOpts and runs only on
   ossa. Specifically, in this new pass, we just perform simple
   canonicalizations that do not involve any significant analysis. Some
   examples: a copy_value all of whose uses are destroys. This will do what the
   original pass did and more without more compile time. I did a conservative
   first approximation, but we can probably tune this a bit.

2. the reason why I am doing this now is that I was trying to eliminate the
   enable-ownership-stripping-after-serialization flag and discovered that the
   test opaque_value_mandatory implicitly depends on this since sil-opt by
   default was the only place left in the compiler with that option set to false
   by default. So I am eliminating that dependency before I land the larger
   change.

Author: gottesmm

lib/SILOptimizer/Mandatory/CMakeLists.txt

@@ -12,7 +12,6 @@ target_sources(swiftSILOptimizer PRIVATE
   DiagnoseStaticExclusivity.cpp
   DiagnoseUnreachable.cpp
   Differentiation.cpp
-  GuaranteedARCOpts.cpp
   IRGenPrepare.cpp
   MandatoryInlining.cpp
   PredictableMemOpt.cpp

lib/SILOptimizer/Mandatory/GuaranteedARCOpts.cpp

@@ -78,8 +78,15 @@ static void addDefiniteInitialization(SILPassPipelinePlan &P) {
   P.addRawSILInstLowering();
 }
 
-static void addMandatoryOptPipeline(SILPassPipelinePlan &P) {
-  P.startPipeline("Guaranteed Passes");
+// This pipeline defines a set of mandatory diagnostic passes and a set of
+// supporting optimization passes that enable those diagnostics. These are run
+// before any performance optimizations and in contrast to those optimizations
+// _IS_ run when SourceKit emits diagnostics.
+//
+// Any passes not needed for diagnostic emission that need to run at -Onone
+// should be in the -Onone pass pipeline and the prepare optimizations pipeline.
+static void addMandatoryDiagnosticOptPipeline(SILPassPipelinePlan &P) {
+  P.startPipeline("Mandatory Diagnostic Passes + Enabling Optimization Passes");
   P.addSILGenCleanup();
   P.addDiagnoseInvalidEscapingCaptures();
   P.addDiagnoseStaticExclusivity();
@@ -142,7 +149,6 @@ static void addMandatoryOptPipeline(SILPassPipelinePlan &P) {
   // dead allocations.
   P.addPredictableDeadAllocationElimination();
 
-  P.addGuaranteedARCOpts();
   P.addDiagnoseUnreachable();
   P.addDiagnoseInfiniteRecursion();
   P.addYieldOnceCheck();
@@ -169,7 +175,7 @@ SILPassPipelinePlan::getDiagnosticPassPipeline(const SILOptions &Options) {
   }
 
   // Otherwise run the rest of diagnostics.
-  addMandatoryOptPipeline(P);
+  addMandatoryDiagnosticOptPipeline(P);
 
   if (SILViewGuaranteedCFG) {
     addCFGPrinterPipeline(P, "SIL View Guaranteed CFG");
@@ -738,9 +744,14 @@ SILPassPipelinePlan
 SILPassPipelinePlan::getOnonePassPipeline(const SILOptions &Options) {
   SILPassPipelinePlan P(Options);
 
-  P.startPipeline("Mandatory Combines");
+  // These are optimizations that we do not need to enable diagnostics (or
+  // depend on other passes needed for diagnostics). Thus we can run them later
+  // and avoid having SourceKit run these passes when just emitting diagnostics
+  // in the editor.
+  P.startPipeline("non-Diagnostic Enabling Mandatory Optimizations");
   P.addForEachLoopUnroll();
   P.addMandatoryCombine();
+  P.addGuaranteedARCOpts();
 
   // First serialize the SIL if we are asked to.
   P.startPipeline("Serialization");