[CanonicalizeOSSALifetime] Extend Onone lifetimes.

To improve the debugging experience of values whose lifetimes are
canonicalized without compromising the semantics expressed in the source
language, when canonicalizing OSSA lifetimes at Onone, lengthen
lifetimes as much as possible without incurring copies that would be
eliminated at O.

rdar://99618502

Author: nate-chandler

include/swift/SILOptimizer/Utils/CanonicalizeOSSALifetime.h

@@ -130,7 +130,7 @@ void diagnoseRequiredCopyOfMoveOnly(Operand *use,
 ///
 /// This result remains valid during copy rewriting. The only instructions
 /// referenced it contains are consumes that cannot be deleted.
-class CanonicalOSSAConsumeInfo {
+class CanonicalOSSAConsumeInfo final {
   /// Map blocks on the lifetime boundary to the last consuming instruction.
   llvm::SmallDenseMap<SILBasicBlock *, SILInstruction *, 4> finalBlockConsumes;
 
@@ -159,6 +159,10 @@ class CanonicalOSSAConsumeInfo {
     return false;
   }
 
+  CanonicalOSSAConsumeInfo() {}
+  CanonicalOSSAConsumeInfo(CanonicalOSSAConsumeInfo const &) = delete;
+  CanonicalOSSAConsumeInfo &
+  operator=(CanonicalOSSAConsumeInfo const &) = delete;
   SWIFT_ASSERT_ONLY_DECL(void dump() const LLVM_ATTRIBUTE_USED);
 };
 
@@ -169,7 +173,7 @@ class CanonicalOSSAConsumeInfo {
 ///
 /// TODO: Move all the private per-definition members into an implementation
 /// class in the .cpp file.
-class CanonicalizeOSSALifetime {
+class CanonicalizeOSSALifetime final {
 public:
   /// Find the original definition of a potentially copied value. \p copiedValue
   /// must be an owned value. It is usually a copy but may also be a destroy.
@@ -205,6 +209,10 @@ class CanonicalizeOSSALifetime {
   /// liveness may be pruned during canonicalization.
   bool pruneDebugMode;
 
+  /// If true, lifetimes will not be shortened except when necessary to avoid
+  /// copies.
+  bool maximizeLifetime;
+
   /// If true and we are processing a value of move_only type, emit a diagnostic
   /// when-ever we need to insert a copy_value.
   std::function<void(Operand *)> moveOnlyCopyValueNotification;
@@ -240,6 +248,9 @@ class CanonicalizeOSSALifetime {
   /// Visited set for general def-use traversal that prevents revisiting values.
   GraphNodeWorklist<SILValue, 8> defUseWorklist;
 
+  /// The blocks that were discovered by PrunedLiveness.
+  SmallVector<SILBasicBlock *, 32> discoveredBlocks;
+
   /// Pruned liveness for the extended live range including copies. For this
   /// purpose, only consuming instructions are considered "lifetime
   /// ending". end_borrows do not end a liverange that may include owned copies.
@@ -248,7 +259,7 @@ class CanonicalizeOSSALifetime {
   /// The destroys of the value.  These are not uses, but need to be recorded so
   /// that we know when the last use in a consuming block is (without having to
   /// repeatedly do use-def walks from destroys).
-  SmallPtrSet<SILInstruction *, 8> destroys;
+  SmallPtrSetVector<SILInstruction *, 8> destroys;
 
   /// Information about consuming instructions discovered in this canonical OSSA
   /// lifetime.
@@ -286,15 +297,17 @@ class CanonicalizeOSSALifetime {
   }
 
   CanonicalizeOSSALifetime(
-      bool pruneDebugMode, NonLocalAccessBlockAnalysis *accessBlockAnalysis,
-      DominanceInfo *domTree, InstructionDeleter &deleter,
+      bool pruneDebugMode, bool maximizeLifetime,
+      NonLocalAccessBlockAnalysis *accessBlockAnalysis, DominanceInfo *domTree,
+      InstructionDeleter &deleter,
       std::function<void(Operand *)> moveOnlyCopyValueNotification = nullptr,
       std::function<void(Operand *)> moveOnlyFinalConsumingUse = nullptr)
-      : pruneDebugMode(pruneDebugMode),
+      : pruneDebugMode(pruneDebugMode), maximizeLifetime(maximizeLifetime),
         moveOnlyCopyValueNotification(moveOnlyCopyValueNotification),
         moveOnlyFinalConsumingUse(moveOnlyFinalConsumingUse),
         accessBlockAnalysis(accessBlockAnalysis), domTree(domTree),
-        deleter(deleter) {}
+        deleter(deleter),
+        liveness(maximizeLifetime ? &discoveredBlocks : nullptr) {}
 
   SILValue getCurrentDef() const { return liveness.getDef(); }
 
@@ -313,6 +326,7 @@ class CanonicalizeOSSALifetime {
     consumingBlocks.clear();
     debugValues.clear();
     liveness.clear();
+    discoveredBlocks.clear();
   }
 
   /// Top-Level API: rewrites copies and destroys within \p def's extended
@@ -331,7 +345,7 @@ class CanonicalizeOSSALifetime {
 
   InstModCallbacks &getCallbacks() { return deleter.getCallbacks(); }
 
-protected:
+private:
   void recordDebugValue(DebugValueInst *dvi) { debugValues.insert(dvi); }
 
   void recordConsumingUse(Operand *use) {
@@ -343,9 +357,14 @@ class CanonicalizeOSSALifetime {
 
   void extendLivenessThroughOverlappingAccess();
 
-  void findExtendedBoundary(PrunedLivenessBoundary &boundary);
+  void findOriginalBoundary(PrunedLivenessBoundary &boundary);
+
+  void findExtendedBoundary(PrunedLivenessBoundary const &originalBoundary,
+                            PrunedLivenessBoundary &boundary);
+
+  void extendUnconsumedLiveness(PrunedLivenessBoundary const &boundary);
 
-  void insertDestroysOnBoundary(PrunedLivenessBoundary &boundary);
+  void insertDestroysOnBoundary(PrunedLivenessBoundary const &boundary);
 
   void rewriteCopies();
 };

lib/SILOptimizer/Mandatory/MoveOnlyAddressChecker.cpp

@@ -746,7 +746,9 @@ struct MoveOnlyChecker {
           instToDelete->eraseFromParent();
         })),
         canonicalizer(
-            false /*pruneDebugMode*/, accessBlockAnalysis, domTree, deleter,
+            false /*pruneDebugMode*/,
+            !fn->shouldOptimize() /*maximizeLifetime*/, accessBlockAnalysis,
+            domTree, deleter,
             [&](Operand *use) { consumingUsesNeedingCopy.push_back(use); },
             [&](Operand *use) { finalConsumingUses.push_back(use); }) {}
 

lib/SILOptimizer/Mandatory/MoveOnlyObjectChecker.cpp

@@ -401,8 +401,9 @@ bool MoveOnlyChecker::check(NonLocalAccessBlockAnalysis *accessBlockAnalysis,
   };
 
   CanonicalizeOSSALifetime canonicalizer(
-      false /*pruneDebugMode*/, accessBlockAnalysis, domTree, deleter,
-      foundConsumingUseNeedingCopy, foundConsumingUseNotNeedingCopy);
+      false /*pruneDebugMode*/, !fn->shouldOptimize() /*maximizeLifetime*/,
+      accessBlockAnalysis, domTree, deleter, foundConsumingUseNeedingCopy,
+      foundConsumingUseNotNeedingCopy);
   auto moveIntroducers = llvm::makeArrayRef(moveIntroducersToProcess.begin(),
                                             moveIntroducersToProcess.end());
   SmallPtrSet<MarkMustCheckInst *, 4> valuesWithDiagnostics;

lib/SILOptimizer/SILCombiner/SILCombine.cpp

@@ -350,8 +350,10 @@ void SILCombiner::canonicalizeOSSALifetimes(SILInstruction *currentInst) {
   InstructionDeleter deleter(std::move(canonicalizeCallbacks));
 
   DominanceInfo *domTree = DA->get(&Builder.getFunction());
-  CanonicalizeOSSALifetime canonicalizer(false /*prune debug*/, NLABA, domTree,
-                                         deleter);
+  CanonicalizeOSSALifetime canonicalizer(
+      false /*prune debug*/,
+      !parentTransform->getFunction()->shouldOptimize() /*maximizeLifetime*/,
+      NLABA, domTree, deleter);
   CanonicalizeBorrowScope borrowCanonicalizer(deleter);
 
   while (!defsToCanonicalize.empty()) {

lib/SILOptimizer/Transforms/CopyPropagation.cpp

@@ -373,7 +373,7 @@ static bool sinkOwnedForward(SILInstruction *ownedForward,
 namespace {
 
 class CopyPropagation : public SILFunctionTransform {
-  /// True if debug_value instructions should be pruned.
+  /// If true, debug_value instructions should be pruned.
   bool pruneDebug;
   /// True if all values should be canonicalized.
   bool canonicalizeAll;
@@ -437,8 +437,9 @@ void CopyPropagation::run() {
 
   // canonicalizer performs all modifications through deleter's callbacks, so we
   // don't need to explicitly check for changes.
-  CanonicalizeOSSALifetime canonicalizer(pruneDebug, accessBlockAnalysis,
-                                         domTree, deleter);
+  CanonicalizeOSSALifetime canonicalizer(
+      pruneDebug, /*maximizeLifetime=*/!getFunction()->shouldOptimize(),
+      accessBlockAnalysis, domTree, deleter);
 
   // NOTE: We assume that the function is in reverse post order so visiting the
   //       blocks and pushing begin_borrows as we see them and then popping them