SIL: remove instruction leaks checking

It's not thread safe and can cause false alarms in case multiple modules exist in different threads. E.g. when building swiftmodules from interfaces.
The leaking check is not important anymore because the builder APIs enforce that instructions are not leaking.
I.e. it's not possible to create an instruction without inserting it into a basic block. Also, it's not possible to remove an instruction from a block without deleting it.

rdar://122169263

Author: eeckstein

include/swift/AST/SILOptions.h

@@ -270,12 +270,6 @@ class SILOptions {
   /// Are we parsing the stdlib, i.e. -parse-stdlib?
   bool ParseStdlib = false;
 
-  /// If true, check for leaking instructions when the SILModule is destructed.
-  ///
-  /// Warning: this is not thread safe. It can only be enabled in case there
-  /// is a single SILModule in a single thread.
-  bool checkSILModuleLeaks = false;
-
   /// Are we building in embedded Swift mode?
   bool EmbeddedSwift = false;
 

include/swift/SIL/SILInstruction.h

@@ -900,11 +900,6 @@ class SILInstruction : public llvm::ilist_node<SILInstruction> {
     return NumDeletedInstructions;
   }
 
-  static void resetInstructionCounts() {
-    NumCreatedInstructions = 0;
-    NumDeletedInstructions = 0;
-  }
-
   /// Pretty-print the value.
   void dump() const;
   void print(raw_ostream &OS) const;

include/swift/SIL/SILModule.h

@@ -939,19 +939,6 @@ class SILModule {
   /// Check linear OSSA lifetimes, assuming complete OSSA.
   void verifyOwnership() const;
 
-  /// Check if there are any leaking instructions.
-  ///
-  /// Aborts with an error if more instructions are allocated than contained in
-  /// the module.
-  void checkForLeaks() const;
-
-  /// Check if there are any leaking instructions after the SILModule is
-  /// destructed.
-  ///
-  /// The SILModule destructor already calls checkForLeaks(). This function is
-  /// useful to check if the destructor itself destroys all data structures.
-  static void checkForLeaksAfterDestruction();
-
   /// Pretty-print the module.
   void dump(bool Verbose = false) const;
 

lib/DriverTool/sil_opt_main.cpp

@@ -708,7 +708,6 @@ int sil_opt_main(ArrayRef<const char *> argv, void *MainAddr) {
   SILOpts.VerifySILOwnership = !options.DisableSILOwnershipVerifier;
   SILOpts.OptRecordFile = options.RemarksFilename;
   SILOpts.OptRecordPasses = options.RemarksPasses;
-  SILOpts.checkSILModuleLeaks = true;
   SILOpts.EnableStackProtection = true;
   SILOpts.EnableMoveInoutStackProtection = options.EnableMoveInoutStackProtection;
 

lib/FrontendTool/FrontendTool.cpp

@@ -2235,10 +2235,6 @@ int swift::performFrontend(ArrayRef<const char *> Args,
     llvm::setBugReportMsg(nullptr);
   }
 
-  /// Enable leaks checking because this SILModule is the only one in the process
-  /// (leaks checking is not thread safe).
-  Invocation.getSILOptions().checkSILModuleLeaks = true;
-
   PrettyStackTraceFrontend frontendTrace(Invocation);
 
   // Make an array of PrettyStackTrace objects to dump the configuration files

lib/IRGen/IRGen.cpp

@@ -1231,10 +1231,7 @@ GeneratedModule IRGenRequest::evaluate(Evaluator &evaluator,
   // Free the memory occupied by the SILModule.
   // Execute this task in parallel to the embedding of bitcode.
   auto SILModuleRelease = [&SILMod]() {
-    bool checkForLeaks = SILMod->getOptions().checkSILModuleLeaks;
     SILMod.reset(nullptr);
-    if (checkForLeaks)
-      SILModule::checkForLeaksAfterDestruction();
   };
   auto Thread = std::thread(SILModuleRelease);
   // Wait for the thread to terminate.
@@ -1546,10 +1543,7 @@ static void performParallelIRGeneration(IRGenDescriptor desc) {
   // Free the memory occupied by the SILModule.
   // Execute this task in parallel to the LLVM compilation.
   auto SILModuleRelease = [&SILMod]() {
-    bool checkForLeaks = SILMod->getOptions().checkSILModuleLeaks;
     SILMod.reset(nullptr);
-    if (checkForLeaks)
-      SILModule::checkForLeaksAfterDestruction();
   };
   auto releaseModuleThread = std::thread(SILModuleRelease);
 

lib/SIL/IR/SILModule.cpp

@@ -126,8 +126,6 @@ SILModule::SILModule(llvm::PointerUnion<FileUnit *, ModuleDecl *> context,
 
 SILModule::~SILModule() {
 #ifndef NDEBUG
-  checkForLeaks();
-
   NumSlabsAllocated += numAllocatedSlabs;
   assert(numAllocatedSlabs == freeSlabs.size() && "leaking slabs in SILModule");
 #endif
@@ -163,65 +161,6 @@ SILModule::~SILModule() {
   flushDeletedInsts();
 }
 
-void SILModule::checkForLeaks() const {
-
-  /// Leak checking is not thread safe, because the instruction counters are
-  /// global non-atomic variables. Leak checking can only be done in case there
-  /// is a single SILModule in a single thread.
-  if (!getOptions().checkSILModuleLeaks)
-    return;
-
-  int instsInModule = scheduledForDeletion.size();
-
-  for (const SILFunction &F : *this) {
-    const SILFunction *sn = &F;
-    do {
-      for (const SILBasicBlock &block : *sn) {
-        instsInModule += std::distance(block.begin(), block.end());
-      }
-    } while ((sn = sn->snapshots) != nullptr);
-  }
-  for (const SILFunction &F : zombieFunctions) {
-    const SILFunction *sn = &F;
-    do {
-      for (const SILBasicBlock &block : F) {
-        instsInModule += std::distance(block.begin(), block.end());
-      }
-    } while ((sn = sn->snapshots) != nullptr);
-  }
-  for (const SILGlobalVariable &global : getSILGlobals()) {
-      instsInModule += std::distance(global.StaticInitializerBlock.begin(),
-                                     global.StaticInitializerBlock.end());
-  }
-  
-  int numAllocated = SILInstruction::getNumCreatedInstructions() -
-                       SILInstruction::getNumDeletedInstructions();
-                       
-  if (numAllocated != instsInModule) {
-    llvm::errs() << "Leaking instructions!\n";
-    llvm::errs() << "Allocated instructions: " << numAllocated << '\n';
-    llvm::errs() << "Instructions in module: " << instsInModule << '\n';
-    llvm_unreachable("leaking instructions");
-  }
-  
-  assert(PlaceholderValue::getNumPlaceholderValuesAlive() == 0 &&
-         "leaking placeholders");
-}
-
-void SILModule::checkForLeaksAfterDestruction() {
-// Disabled in release (non-assert) builds because this check fails in rare
-// cases in lldb, causing crashes. rdar://70826934
-#ifndef NDEBUG
-  int numAllocated = SILInstruction::getNumCreatedInstructions() -
-                     SILInstruction::getNumDeletedInstructions();
-
-  if (numAllocated != 0) {
-    llvm::errs() << "Leaking " << numAllocated << " instructions!\n";
-    llvm_unreachable("leaking instructions");
-  }
-#endif
-}
-
 std::unique_ptr<SILModule> SILModule::createEmptyModule(
     llvm::PointerUnion<FileUnit *, ModuleDecl *> context,
     Lowering::TypeConverter &TC, const SILOptions &Options,

lib/SIL/Parser/ParseSIL.cpp

@@ -101,9 +101,6 @@ ParseSILModuleRequest::evaluate(Evaluator &evaluator,
   auto bufferID = SF->getBufferID();
   assert(bufferID);
 
-  // For leak detection.
-  SILInstruction::resetInstructionCounts();
-
   auto silMod = SILModule::createEmptyModule(desc.context, desc.conv,
                                              desc.opts);
   SILParserState parserState(*silMod.get());

lib/SIL/Verifier/SILVerifier.cpp

@@ -7255,8 +7255,6 @@ void SILModule::verify(CalleeCache *calleeCache,
   if (!verificationEnabled(*this))
     return;
 
-  checkForLeaks();
-
   // Uniquing set to catch symbol name collisions.
   llvm::DenseSet<StringRef> symbolNames;
 

lib/SILGen/SILGen.cpp

@@ -2115,9 +2115,6 @@ ASTLoweringRequest::evaluate(Evaluator &evaluator,
     return evaluateOrFatal(evaluator, ParseSILModuleRequest{desc});
   }
 
-  // For leak detection.
-  SILInstruction::resetInstructionCounts();
-
   auto silMod = SILModule::createEmptyModule(desc.context, desc.conv,
                                              desc.opts, desc.irgenOptions);