Merge pull request swiftlang#40738 from eeckstein/rename-dealloc-ref-stack

Rename `dealloc_ref [stack]` and enable StackPromotion for OSSA

Author: eeckstein

SwiftCompilerSources/Sources/SIL/Instruction.swift

@@ -208,6 +208,10 @@ final public class DeallocStackInst : Instruction, UnaryInstruction {
   }
 }
 
+final public class DeallocStackRefInst : Instruction, UnaryInstruction {
+  public var allocRef: AllocRefInst { operand as! AllocRefInst }
+}
+
 final public class CondFailInst : Instruction, UnaryInstruction {
   public override var mayTrap: Bool { true }
 

SwiftCompilerSources/Sources/SIL/Registration.swift

@@ -42,6 +42,7 @@ public func registerSILClasses() {
   register(EndAccessInst.self)
   register(EndBorrowInst.self)
   register(DeallocStackInst.self)
+  register(DeallocStackRefInst.self)
   register(CondFailInst.self)
   register(FixLifetimeInst.self)
   register(DebugValueInst.self)

docs/SIL.rst

@@ -3143,8 +3143,8 @@ optional ``objc`` attribute indicates that the object should be
 allocated using Objective-C's allocation methods (``+allocWithZone:``).
 
 The optional ``stack`` attribute indicates that the object can be allocated
-on the stack instead on the heap. In this case the instruction must have
-balanced with a ``dealloc_ref [stack]`` instruction to mark the end of the
+on the stack instead on the heap. In this case the instruction must be
+balanced with a ``dealloc_stack_ref`` instruction to mark the end of the
 object's lifetime.
 Note that the ``stack`` attribute only specifies that stack allocation is
 possible. The final decision on stack allocation is done during llvm IR
@@ -3381,13 +3381,25 @@ project_box
 
 Given a ``@box T`` reference, produces the address of the value inside the box.
 
+dealloc_stack_ref
+`````````````````
+::
+
+  sil-instruction ::= 'dealloc_stack_ref' sil-operand
+
+  dealloc_stack_ref %0 : $T
+  // $T must be a class type
+  // %0 must be an 'alloc_ref [stack]' instruction
+
+Marks the deallocation of the stack space for an ``alloc_ref [stack]``.
+
 dealloc_ref
 ```````````
 ::
 
-  sil-instruction ::= 'dealloc_ref' ('[' 'stack' ']')? sil-operand
+  sil-instruction ::= 'dealloc_ref' sil-operand
 
-  dealloc_ref [stack] %0 : $T
+  dealloc_ref %0 : $T
   // $T must be a class type
 
 Deallocates an uninitialized class type instance, bypassing the reference

include/swift/SIL/SILBuilder.h

@@ -2005,10 +2005,14 @@ class SILBuilder {
     return insert(new (getModule())
                       DeallocStackInst(getSILDebugLocation(Loc), operand));
   }
-  DeallocRefInst *createDeallocRef(SILLocation Loc, SILValue operand,
-                                   bool canBeOnStack) {
+  DeallocStackRefInst *createDeallocStackRef(SILLocation Loc,
+                                                     SILValue operand) {
+    return insert(new (getModule())
+                    DeallocStackRefInst(getSILDebugLocation(Loc), operand));
+  }
+  DeallocRefInst *createDeallocRef(SILLocation Loc, SILValue operand) {
     return insert(new (getModule()) DeallocRefInst(
-        getSILDebugLocation(Loc), operand, canBeOnStack));
+        getSILDebugLocation(Loc), operand));
   }
   DeallocPartialRefInst *createDeallocPartialRef(SILLocation Loc,
                                                  SILValue operand,

include/swift/SIL/SILCloner.h

@@ -2488,8 +2488,16 @@ SILCloner<ImplClass>::visitDeallocRefInst(DeallocRefInst *Inst) {
   getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
   recordClonedInstruction(
       Inst, getBuilder().createDeallocRef(getOpLocation(Inst->getLoc()),
-                                          getOpValue(Inst->getOperand()),
-                                          Inst->canAllocOnStack()));
+                                          getOpValue(Inst->getOperand())));
+}
+
+template<typename ImplClass>
+void
+SILCloner<ImplClass>::visitDeallocStackRefInst(DeallocStackRefInst *Inst) {
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+  recordClonedInstruction(
+      Inst, getBuilder().createDeallocStackRef(getOpLocation(Inst->getLoc()),
+                                          getOpValue(Inst->getOperand())));
 }
 
 template<typename ImplClass>

include/swift/SIL/SILInstruction.h

@@ -7619,6 +7619,18 @@ class DeallocStackInst :
       : UnaryInstructionBase(DebugLoc, operand) {}
 };
 
+/// Like DeallocStackInst, but for `alloc_ref [stack]`.
+class DeallocStackRefInst
+    : public UnaryInstructionBase<SILInstructionKind::DeallocStackRefInst,
+                                  DeallocationInst> {
+  friend SILBuilder;
+
+  DeallocStackRefInst(SILDebugLocation DebugLoc, SILValue Operand)
+      : UnaryInstructionBase(DebugLoc, Operand) {}
+public:
+  AllocRefInst *getAllocRef() { return cast<AllocRefInst>(getOperand()); }
+};
+
 /// Deallocate memory for a reference type instance from a destructor or
 /// failure path of a constructor.
 ///
@@ -7632,21 +7644,8 @@ class DeallocRefInst :
                               DeallocationInst> {
   friend SILBuilder;
 
-private:
-  DeallocRefInst(SILDebugLocation DebugLoc, SILValue Operand,
-                 bool canBeOnStack = false)
-      : UnaryInstructionBase(DebugLoc, Operand) {
-    SILNode::Bits.DeallocRefInst.OnStack = canBeOnStack;
-  }
-
-public:
-  bool canAllocOnStack() const {
-    return SILNode::Bits.DeallocRefInst.OnStack;
-  }
-
-  void setStackAllocatable(bool OnStack) {
-    SILNode::Bits.DeallocRefInst.OnStack = OnStack;
-  }
+  DeallocRefInst(SILDebugLocation DebugLoc, SILValue Operand)
+      : UnaryInstructionBase(DebugLoc, Operand) { }
 };
 
 /// Deallocate memory for a reference type instance from a failure path of a

include/swift/SIL/SILNode.h

@@ -218,10 +218,6 @@ class alignas(8) SILNode :
     Length : 32
   );
 
-  SWIFT_INLINE_BITFIELD(DeallocRefInst, DeallocationInst, 1,
-    OnStack : 1
-  );
-
   // Ensure that AllocBoxInst bitfield does not overflow.
   IBWTO_BITFIELD_EMPTY(AllocBoxInst, AllocationInst);
   // Ensure that AllocExistentialBoxInst bitfield does not overflow.

include/swift/SIL/SILNodes.def

@@ -808,6 +808,8 @@ ABSTRACT_INST(TermInst, SILInstruction)
 ABSTRACT_INST(DeallocationInst, SILInstruction)
   BRIDGED_NON_VALUE_INST(DeallocStackInst, dealloc_stack,
                  DeallocationInst, MayHaveSideEffects, DoesNotRelease)
+  BRIDGED_NON_VALUE_INST(DeallocStackRefInst, dealloc_stack_ref,
+                 DeallocationInst, MayHaveSideEffects, DoesNotRelease)
   BRIDGED_NON_VALUE_INST(DeallocRefInst, dealloc_ref,
                  DeallocationInst, MayHaveSideEffects, DoesNotRelease)
   NON_VALUE_INST(DeallocPartialRefInst, dealloc_partial_ref,

include/swift/SILOptimizer/Utils/ValueLifetime.h

@@ -197,7 +197,8 @@ class ValueLifetimeAnalysis {
            (hasUsersBeforeDef || bb != getDefValueParentBlock());
   }
 
-  /// Checks if there is a dealloc_ref inside the value's live range.
+  /// Checks if there is a dealloc_ref or dealloc_stack_ref inside the
+  /// value's live range.
   bool containsDeallocRef(const FrontierImpl &frontier);
 
   /// For debug dumping.

lib/IRGen/IRGenSIL.cpp

@@ -1257,6 +1257,7 @@ class IRGenSILFunction :
   void visitEndCOWMutationInst(EndCOWMutationInst *i);
   void visitIsEscapingClosureInst(IsEscapingClosureInst *i);
   void visitDeallocStackInst(DeallocStackInst *i);
+  void visitDeallocStackRefInst(DeallocStackRefInst *i);
   void visitDeallocBoxInst(DeallocBoxInst *i);
   void visitDeallocRefInst(DeallocRefInst *i);
   void visitDeallocPartialRefInst(DeallocPartialRefInst *i);
@@ -4515,9 +4516,9 @@ void IRGenSILFunction::visitSetDeallocatingInst(SetDeallocatingInst *i) {
     //     ...
     //   set_deallocating %0 // not needed
     //     // code which does not depend on the RC_DEALLOCATING_FLAG flag.
-    //   dealloc_ref %0      // not needed (stems from the inlined deallocator)
+    //   dealloc_ref %0      // stems from the inlined deallocator
     //     ...
-    //   dealloc_ref [stack] %0
+    //   dealloc_stack_ref %0
     SILBasicBlock::iterator Iter(i);
     SILBasicBlock::iterator End = i->getParent()->end();
     for (++Iter; Iter != End; ++Iter) {
@@ -5432,32 +5433,10 @@ void IRGenSILFunction::visitDeallocStackInst(swift::DeallocStackInst *i) {
   allocatedTI.deallocateStack(*this, stackAddr, allocatedType);
 }
 
-void IRGenSILFunction::visitDeallocRefInst(swift::DeallocRefInst *i) {
-  // Lower the operand.
+void IRGenSILFunction::visitDeallocStackRefInst(DeallocStackRefInst *i) {
   Explosion self = getLoweredExplosion(i->getOperand());
   auto selfValue = self.claimNext();
-  auto *ARI = dyn_cast<AllocRefInst>(i->getOperand());
-  if (!i->canAllocOnStack()) {
-    if (ARI && StackAllocs.count(ARI)) {
-      // We can ignore dealloc_refs (without [stack]) for stack allocated
-      // objects.
-      //
-      //   %0 = alloc_ref [stack]
-      //     ...
-      //   dealloc_ref %0     // not needed (stems from the inlined deallocator)
-      //     ...
-      //   dealloc_ref [stack] %0
-      return;
-    }
-
-    auto classType = i->getOperand()->getType();
-    emitClassDeallocation(*this, classType, selfValue);
-    return;
-  }
-  // It's a dealloc_ref [stack]. Even if the alloc_ref did not allocate the
-  // object on the stack, we don't have to deallocate it, because it is
-  // deallocated in the final release.
-  assert(ARI->canAllocOnStack());
+  auto *ARI = i->getAllocRef();
   if (StackAllocs.count(ARI)) {
     if (IGM.IRGen.Opts.EmitStackPromotionChecks) {
       selfValue = Builder.CreateBitCast(selfValue, IGM.RefCountedPtrTy);
@@ -5473,6 +5452,25 @@ void IRGenSILFunction::visitDeallocRefInst(swift::DeallocRefInst *i) {
   }
 }
 
+void IRGenSILFunction::visitDeallocRefInst(swift::DeallocRefInst *i) {
+  // Lower the operand.
+  Explosion self = getLoweredExplosion(i->getOperand());
+  auto selfValue = self.claimNext();
+  auto *ARI = dyn_cast<AllocRefInst>(i->getOperand());
+  if (ARI && StackAllocs.count(ARI)) {
+    // We can ignore dealloc_refs for stack allocated objects.
+    //
+    //   %0 = alloc_ref [stack]
+    //     ...
+    //   dealloc_ref %0     // not needed (stems from the inlined deallocator)
+    //     ...
+    //   dealloc_stack_ref %0
+    return;
+  }
+  auto classType = i->getOperand()->getType();
+  emitClassDeallocation(*this, classType, selfValue);
+}
+
 void IRGenSILFunction::visitDeallocPartialRefInst(swift::DeallocPartialRefInst *i) {
   Explosion self = getLoweredExplosion(i->getInstance());
   auto selfValue = self.claimNext();