[loop-arc] Teach ARC how to summarize subregions but do not wire it u…

…p to the analysis yet.

rdar://22238729

lib/SILAnalysis/ARC/ARCRegionState.cpp

@@ -30,10 +30,6 @@ ARCRegionState::ARCRegionState(LoopRegion *R)
     AllowsLeaks = isARCInertTrapBB(R->getBlock());
 }
 
-//===---
-// Utility
-//
-
 //===---
 // Bottom Up Merge
 //
@@ -160,7 +156,7 @@ void ARCRegionState::mergePredTopDown(ARCRegionState &PredRegionState) {
 }
 
 //===---
-// Bottom Up Block Visitor
+// Bottom Up Dataflow
 //
 
 bool ARCRegionState::processBlockBottomUp(
@@ -243,7 +239,7 @@ bool ARCRegionState::processBottomUp(
 }
 
 //===---
-// Top Down Block Visitor
+// Top Down Dataflow
 //
 
 bool ARCRegionState::processBlockTopDown(
@@ -327,3 +323,51 @@ bool ARCRegionState::processTopDown(
 
   return processBlockTopDown(*R->getBlock(), AA, RCIA, DecToIncStateMap);
 }
+
+//===---
+// Summary
+//
+
+void ARCRegionState::summarizeBlock(SILBasicBlock *BB) {
+  SummarizedInterestingInsts.clear();
+
+  for (auto &I : *BB)
+    if (!canNeverUseValues(&I) || !canNeverDecrementRefCounts(&I))
+      SummarizedInterestingInsts.push_back(&I);
+}
+
+void ARCRegionState::summarizeLoop(
+    const LoopRegion *R, LoopRegionFunctionInfo *LRFI,
+    llvm::DenseMap<const LoopRegion *, ARCRegionState *> &RegionStateInfo) {
+  SummarizedInterestingInsts.clear();
+  for (unsigned SubregionID : R->getSubregions()) {
+    LoopRegion *Subregion = LRFI->getRegion(SubregionID);
+    ARCRegionState *SubregionState = RegionStateInfo[Subregion];
+    std::copy(SubregionState->summarizedinterestinginsts_begin(),
+              SubregionState->summarizedinterestinginsts_end(),
+              std::back_inserter(SummarizedInterestingInsts));
+  }
+}
+
+void ARCRegionState::summarize(
+    LoopRegionFunctionInfo *LRFI,
+    llvm::DenseMap<const LoopRegion *, ARCRegionState *> &RegionStateInfo) {
+  const LoopRegion *R = getRegion();
+
+  // We do not need to summarize a function since it is the outermost loop.
+  if (R->isFunction())
+    return;
+
+  assert(R->isLoop() && "Expected to be called on a loop");
+  // Make sure that all subregions that are blocked are summarized. We know that
+  // all subloops have already been summarized.
+  for (unsigned SubregionID : R->getSubregions()) {
+    auto *Subregion = LRFI->getRegion(SubregionID);
+    if (!Subregion->isBlock())
+      continue;
+    auto *SubregionState = RegionStateInfo[Subregion];
+    SubregionState->summarizeBlock(Subregion->getBlock());
+  }
+
+  summarizeLoop(R, LRFI, RegionStateInfo);
+}

lib/SILAnalysis/ARC/ARCRegionState.h

@@ -54,6 +54,16 @@ class ARCRegionState {
   /// advantage of this to ignore control flow.
   bool AllowsLeaks;
 
+  /// A list of instructions contained in this region that can either use or
+  /// decrement reference counts.
+  ///
+  /// This is flow insensitive since we just add all of the potential
+  /// users/decrements in subregions without caring if there is only one along a
+  /// path. This is for simplicity in the first iteration.
+  ///
+  /// TODO: This needs a better name.
+  llvm::SmallVector<SILInstruction *, 4> SummarizedInterestingInsts;
+
 public:
   ARCRegionState(LoopRegion *R);
 
@@ -119,6 +129,22 @@ class ARCRegionState {
     clearBottomUpState();
   }
 
+  using const_summarizedinterestinginsts_iterator =
+      decltype(SummarizedInterestingInsts)::const_iterator;
+  const_summarizedinterestinginsts_iterator
+  summarizedinterestinginsts_begin() const {
+    return SummarizedInterestingInsts.begin();
+  }
+  const_summarizedinterestinginsts_iterator
+  summarizedinterestinginsts_end() const {
+    return SummarizedInterestingInsts.end();
+  }
+  iterator_range<const_summarizedinterestinginsts_iterator>
+  getSummarizedDecrements() const {
+    return {summarizedinterestinginsts_begin(),
+            summarizedinterestinginsts_end()};
+  }
+
   /// Returns a reference to the basic block that we are tracking.
   const LoopRegion *getRegion() const { return Region.get(); }
 
@@ -158,6 +184,10 @@ class ARCRegionState {
       ConsumedArgToEpilogueReleaseMatcher &ConsumedArgToReleaseMap,
       BlotMapVector<SILInstruction *, BottomUpRefCountState> &IncToDecStateMap);
 
+  void summarize(
+      LoopRegionFunctionInfo *LRFI,
+      llvm::DenseMap<const LoopRegion *, ARCRegionState *> &RegionStateInfo);
+
 private:
   bool processBlockBottomUp(
     SILBasicBlock &BB, AliasAnalysis *AA, RCIdentityFunctionInfo *RCIA,
@@ -172,6 +202,10 @@ class ARCRegionState {
       BlotMapVector<SILInstruction *, TopDownRefCountState> &DecToIncStateMap);
   bool processLoopTopDown();
 
+  void summarizeBlock(SILBasicBlock *BB);
+  void summarizeLoop(
+      const LoopRegion *R, LoopRegionFunctionInfo *LRFI,
+      llvm::DenseMap<const LoopRegion *, ARCRegionState *> &RegionStateInfo);
 };
 
 } // end swift namespace

lib/SILAnalysis/ARC/GlobalLoopARCSequenceDataflow.cpp

@@ -264,6 +264,7 @@ bool LoopARCSequenceDataflowEvaluator::runOnLoop(
     const LoopRegion *R, bool FreezeOwnedArgEpilogueReleases) {
   bool NestingDetected = processLoopBottomUp(R, FreezeOwnedArgEpilogueReleases);
   NestingDetected |= processLoopTopDown(R);
+  RegionStateInfo[R]->summarize(LRFI, RegionStateInfo);
   return NestingDetected;
 }