[arc] Sink the re-running of ARC opts with frozen epilogue releases further into ARCSequenceOpts so that the loop visitor does not need to have any special handling for ARCSequenceOpts.

Previously, we would outside of ARCSequenceOpts, run ARCSequenceOpts twice with
a flag set in one case and a flag unset in the other case. Now ARCSequenceOpts
internally performs these two runs of the optimization.

Author: gottesmm

include/swift/SILAnalysis/ARCAnalysis.h

@@ -148,6 +148,13 @@ class ConsumedArgToEpilogueReleaseMatcher {
     return I->second;
   }
 
+  SILInstruction *releaseForArgument(SILValue V) const {
+    auto *Arg = dyn_cast<SILArgument>(V);
+    if (!Arg)
+      return nullptr;
+    return releaseForArgument(Arg);
+  }
+
   /// Recompute the mapping from argument to consumed arg.
   void recompute();
 

lib/SILAnalysis/ARCAnalysis.cpp

@@ -515,6 +515,8 @@ ConsumedArgToEpilogueReleaseMatcher::ConsumedArgToEpilogueReleaseMatcher(
 }
 
 void ConsumedArgToEpilogueReleaseMatcher::recompute() {
+  ArgInstMap.clear();
+
   // Find the return BB of F. If we fail, then bail.
   SILFunction::iterator BB;
   switch (Kind) {

lib/SILPasses/ARC/ARCSequenceOpts.cpp

@@ -192,9 +192,9 @@ processFunctionWithoutLoopSupport(SILFunction &F, bool FreezePostDomReleases,
 //===----------------------------------------------------------------------===//
 
 static bool processFunctionWithLoopSupport(
-    SILFunction &F, bool FreezePostDomReleases, AliasAnalysis *AA,
-    PostOrderAnalysis *POTA, LoopRegionFunctionInfo *LRFI, SILLoopInfo *LI,
-    RCIdentityFunctionInfo *RCFI, ProgramTerminationFunctionInfo *PTFI) {
+    SILFunction &F, AliasAnalysis *AA, PostOrderAnalysis *POTA,
+    LoopRegionFunctionInfo *LRFI, SILLoopInfo *LI, RCIdentityFunctionInfo *RCFI,
+    ProgramTerminationFunctionInfo *PTFI) {
   // GlobalARCOpts seems to be taking up a lot of compile time when running on
   // globalinit_func. Since that is not *that* interesting from an ARC
   // perspective (i.e. no ref count operations in a loop), disable it on such
@@ -205,7 +205,7 @@ static bool processFunctionWithLoopSupport(
   DEBUG(llvm::dbgs() << "***** Processing " << F.getName() << " *****\n");
 
   LoopARCPairingContext Context(F, AA, LRFI, LI, RCFI, PTFI);
-  return Context.process(FreezePostDomReleases);
+  return Context.process();
 }
 
 //===----------------------------------------------------------------------===//
@@ -256,9 +256,7 @@ class ARCSequenceOpts : public SILFunctionTransform {
     auto *LRFI = getAnalysis<LoopRegionAnalysis>()->get(F);
     auto *PTFI = getAnalysis<ProgramTerminationAnalysis>()->get(F);
 
-    if (processFunctionWithLoopSupport(*F, false, AA, POTA, LRFI, LI, RCFI,
-                                       PTFI)) {
-      processFunctionWithLoopSupport(*F, true, AA, POTA, LRFI, LI, RCFI, PTFI);
+    if (processFunctionWithLoopSupport(*F, AA, POTA, LRFI, LI, RCFI, PTFI)) {
       invalidateAnalysis(SILAnalysis::InvalidationKind::CallsAndInstructions);
     }
   }

lib/SILPasses/ARC/GlobalARCPairingAnalysis.cpp

@@ -405,26 +405,45 @@ bool ARCPairingContext::performMatching(CodeMotionOrDeleteCallback &Callback) {
 //===----------------------------------------------------------------------===//
 
 void LoopARCPairingContext::runOnLoop(SILLoop *L) {
-  processRegion(LRFI->getRegion(L));
+  auto *Region = LRFI->getRegion(L);
+  if (processRegion(Region, false, false)) {
+    // We do not recompute for now since we only look at the top function level
+    // for post dominating releases.
+    processRegion(Region, true, false);
+  }
+
+  // Now that we have finished processing the loop, summarize the loop.
+  Evaluator.summarizeLoop(Region);
 }
 
 void LoopARCPairingContext::runOnFunction(SILFunction *F) {
-  processRegion(LRFI->getTopLevelRegion());
+  if (processRegion(LRFI->getTopLevelRegion(), false, false)) {
+    // We recompute the final post dom release since we may have moved the final
+    // post dominated releases.
+    processRegion(LRFI->getTopLevelRegion(), true, true);
+  }
 }
 
-void LoopARCPairingContext::processRegion(const LoopRegion *Region) {
-  bool NestingDetected = Evaluator.runOnLoop(Region, FreezePostDomReleases);
+bool LoopARCPairingContext::processRegion(const LoopRegion *Region,
+                                          bool FreezePostDomReleases,
+                                          bool RecomputePostDomReleases) {
+  bool MadeChange = false;
+  bool NestingDetected = Evaluator.runOnLoop(Region, FreezePostDomReleases,
+                                             RecomputePostDomReleases);
   bool MatchedPair = Context.performMatching(Callback);
+  MadeChange |= MatchedPair;
+  Evaluator.clearLoopState(Region);
   Context.DecToIncStateMap.clear();
   Context.IncToDecStateMap.clear();
 
   while (NestingDetected && MatchedPair) {
-    Evaluator.clearLoopState(Region);
-    NestingDetected = Evaluator.runOnLoop(Region, FreezePostDomReleases);
+    NestingDetected = Evaluator.runOnLoop(Region, FreezePostDomReleases, false);
     MatchedPair = Context.performMatching(Callback);
+    MadeChange |= MatchedPair;
+    Evaluator.clearLoopState(Region);
     Context.DecToIncStateMap.clear();
     Context.IncToDecStateMap.clear();
   }
 
-  Evaluator.summarizeLoop(Region);
+  return MadeChange;
 }

lib/SILPasses/ARC/GlobalARCPairingAnalysis.h

@@ -143,7 +143,6 @@ struct LoopARCPairingContext : SILLoopVisitor {
   LoopRegionFunctionInfo *LRFI;
   SILLoopInfo *SLI;
   CodeMotionOrDeleteCallback Callback;
-  bool FreezePostDomReleases = false;
 
   LoopARCPairingContext(SILFunction &F, AliasAnalysis *AA,
                         LoopRegionFunctionInfo *LRFI, SILLoopInfo *SLI,
@@ -154,16 +153,19 @@ struct LoopARCPairingContext : SILLoopVisitor {
                   Context.IncToDecStateMap),
         LRFI(LRFI), SLI(SLI), Callback() {}
 
-  bool process(bool FreezePDReleases) {
-    FreezePostDomReleases = FreezePDReleases;
+  bool process() {
     run();
-    return Callback.madeChange();
+    if (!Callback.madeChange())
+      return false;
+    run();
+    return true;
   }
 
   void runOnLoop(SILLoop *L) override;
   void runOnFunction(SILFunction *F) override;
 
-  void processRegion(const LoopRegion *R);
+  bool processRegion(const LoopRegion *R, bool FreezePostDomReleases,
+                     bool RecomputePostDomReleases);
 };
 
 } // end swift namespace

lib/SILPasses/ARC/GlobalLoopARCSequenceDataflow.cpp

@@ -271,7 +271,10 @@ LoopARCSequenceDataflowEvaluator::~LoopARCSequenceDataflowEvaluator() {
 }
 
 bool LoopARCSequenceDataflowEvaluator::runOnLoop(
-    const LoopRegion *R, bool FreezeOwnedArgEpilogueReleases) {
+    const LoopRegion *R, bool FreezeOwnedArgEpilogueReleases,
+    bool RecomputePostDomReleases) {
+  if (RecomputePostDomReleases)
+    ConsumedArgToReleaseMap.recompute();
   bool NestingDetected = processLoopBottomUp(R, FreezeOwnedArgEpilogueReleases);
   NestingDetected |= processLoopTopDown(R);
   return NestingDetected;

lib/SILPasses/ARC/GlobalLoopARCSequenceDataflow.h

@@ -87,7 +87,8 @@ class LoopARCSequenceDataflowEvaluator {
 
   /// Perform the sequence dataflow, bottom up and top down on the loop region
   /// \p R.
-  bool runOnLoop(const LoopRegion *R, bool FreezeOwnedArgEpilogueReleases);
+  bool runOnLoop(const LoopRegion *R, bool FreezeOwnedArgEpilogueReleases,
+                 bool RecomputePostDomReleases);
 
   /// Summarize the contents of the loop so that loops further up the loop tree
   /// can reason about the loop.

lib/SILPasses/ARC/RCStateTransitionVisitors.cpp

@@ -71,7 +71,11 @@ BottomUpDataflowRCStateVisitor<ARCState>::visitStrongDecrement(ValueBase *V) {
   // If we are running with 'frozen' owned arg releases, check if we have a
   // frozen use in the side table. If so, this release must be known safe.
   if (FreezeOwnedArgEpilogueReleases) {
-    State.updateKnownSafe(EpilogueReleaseMatcher.argumentHasRelease(Op));
+    if (auto *OwnedRelease = EpilogueReleaseMatcher.releaseForArgument(Op)) {
+      if (I != OwnedRelease) {
+        State.updateKnownSafe(true);
+      }
+    }
   }
 
   DEBUG(llvm::dbgs() << "    REF COUNT DECREMENT! Known Safe: "

test/SILPasses/globalarcopts.sil

@@ -1934,3 +1934,4 @@ bb2(%3 : $ErrorType):
   strong_release %0 : $Builtin.NativeObject
   throw %3 : $ErrorType
 }
+