[SIL] Add dead_end flag to destroy_value.

docs/SIL.rst

@@ -6664,7 +6664,7 @@ destroy_value
 
 ::
 
-  sil-instruction ::= 'destroy_value' '[poison]'? sil-operand
+  sil-instruction ::= 'destroy_value' '[dead_end]'? '[poison]'? sil-operand
 
   destroy_value %0 : $A
 
@@ -6682,6 +6682,9 @@ For aggregate types, especially enums, it is typically both easier
 and more efficient to reason about aggregate destroys than it is to
 reason about destroys of the subobjects.
 
+The optional ``dead_end`` attribute specifies that this instruction was created
+during lifetime completion and is eligible for deletion during OSSA lowering.
+
 autorelease_value
 `````````````````
 

include/swift/SIL/SILBuilder.h

@@ -1442,16 +1442,16 @@ class SILBuilder {
                       ExplicitCopyValueInst(getSILDebugLocation(Loc), operand));
   }
 
-  DestroyValueInst *
-  createDestroyValue(SILLocation Loc, SILValue operand,
-                     PoisonRefs_t poisonRefs = DontPoisonRefs) {
+  DestroyValueInst *createDestroyValue(SILLocation Loc, SILValue operand,
+                                       PoisonRefs_t poisonRefs = DontPoisonRefs,
+                                       IsDeadEnd_t isDeadEnd = IsntDeadEnd) {
     assert(getFunction().hasOwnership());
     assert(isLoadableOrOpaque(operand->getType()));
     assert(!operand->getType().isTrivial(getFunction()) &&
            "Should not be passing trivial values to this api. Use instead "
            "emitDestroyValueOperation");
-    return insert(new (getModule()) DestroyValueInst(getSILDebugLocation(Loc),
-                                                     operand, poisonRefs));
+    return insert(new (getModule()) DestroyValueInst(
+        getSILDebugLocation(Loc), operand, poisonRefs, isDeadEnd));
   }
 
   MoveValueInst *createMoveValue(

include/swift/SIL/SILCloner.h

@@ -2208,10 +2208,10 @@ void SILCloner<ImplClass>::visitDestroyValueInst(DestroyValueInst *Inst) {
                   RefCountingInst::Atomicity::Atomic));
   }
 
-  recordClonedInstruction(
-      Inst, getBuilder().createDestroyValue(getOpLocation(Inst->getLoc()),
-                                            getOpValue(Inst->getOperand()),
-                                            Inst->poisonRefs()));
+  recordClonedInstruction(Inst, getBuilder().createDestroyValue(
+                                    getOpLocation(Inst->getLoc()),
+                                    getOpValue(Inst->getOperand()),
+                                    Inst->poisonRefs(), Inst->isDeadEnd()));
 }
 
 template <typename ImplClass>

include/swift/SIL/SILInstruction.h

@@ -8806,16 +8806,22 @@ class UnownedCopyValueInst
   };
 #include "swift/AST/ReferenceStorage.def"
 
+enum IsDeadEnd_t : bool {
+  IsntDeadEnd = false,
+  IsDeadEnd = true,
+};
+
 class DestroyValueInst
     : public UnaryInstructionBase<SILInstructionKind::DestroyValueInst,
                                   NonValueInstruction> {
   friend class SILBuilder;
   USE_SHARED_UINT8;
 
   DestroyValueInst(SILDebugLocation DebugLoc, SILValue operand,
-                   PoisonRefs_t poisonRefs)
+                   PoisonRefs_t poisonRefs, IsDeadEnd_t isDeadEnd)
       : UnaryInstructionBase(DebugLoc, operand) {
-    setPoisonRefs(poisonRefs);
+    sharedUInt8().DestroyValueInst.poisonRefs = poisonRefs;
+    sharedUInt8().DestroyValueInst.deadEnd = isDeadEnd;
   }
 
 public:
@@ -8843,6 +8849,10 @@ class DestroyValueInst
   /// If the value being destroyed is a stack allocation of a nonescaping
   /// closure, then return the PartialApplyInst that allocated the closure.
   PartialApplyInst *getNonescapingClosureAllocation() const;
+
+  IsDeadEnd_t isDeadEnd() const {
+    return IsDeadEnd_t(sharedUInt8().DestroyValueInst.deadEnd);
+  }
 };
 
 class MoveValueInst

include/swift/SIL/SILNode.h

@@ -205,7 +205,9 @@ class alignas(8) SILNode :
     SHARED_FIELD(AddressToPointerInst, bool needsStackProtection);
     SHARED_FIELD(IndexAddrInst, bool needsStackProtection);
     SHARED_FIELD(HopToExecutorInst, bool mandatory);
-    SHARED_FIELD(DestroyValueInst, bool poisonRefs);
+    SHARED_FIELD(DestroyValueInst, uint8_t
+        poisonRefs : 1,
+        deadEnd : 1);
     SHARED_FIELD(EndCOWMutationInst, bool keepUnique);
     SHARED_FIELD(ConvertFunctionInst, bool withoutActuallyEscaping);
     SHARED_FIELD(BeginCOWMutationInst, bool native);

lib/SIL/IR/SILPrinter.cpp

@@ -2231,6 +2231,8 @@ class SILPrinter : public SILInstructionVisitor<SILPrinter> {
   void visitDestroyValueInst(DestroyValueInst *I) {
     if (I->poisonRefs())
       *this << "[poison] ";
+    if (I->isDeadEnd())
+      *this << "[dead_end] ";
     *this << getIDAndType(I->getOperand());
   }
 

lib/SIL/Parser/ParseSIL.cpp

@@ -3352,11 +3352,24 @@ bool SILParser::parseSpecificSILInstruction(SILBuilder &B,
     break;
   }
   case SILInstructionKind::DestroyValueInst: {
-    bool poisonRefs = false;
-    if (parseSILOptional(poisonRefs, *this, "poison")
-        || parseTypedValueRef(Val, B) || parseSILDebugLocation(InstLoc, B))
+    PoisonRefs_t poisonRefs = DontPoisonRefs;
+    IsDeadEnd_t isDeadEnd = IsntDeadEnd;
+    StringRef attributeName;
+    SourceLoc attributeLoc;
+    while (parseSILOptional(attributeName, attributeLoc, *this)) {
+      if (attributeName == "poison")
+        poisonRefs = PoisonRefs;
+      else if (attributeName == "dead_end")
+        isDeadEnd = IsDeadEnd;
+      else {
+        P.diagnose(attributeLoc, diag::sil_invalid_attribute_for_instruction,
+                   attributeName, "destroy_value");
+        return true;
+      }
+    }
+    if (parseTypedValueRef(Val, B) || parseSILDebugLocation(InstLoc, B))
       return true;
-    ResultVal = B.createDestroyValue(InstLoc, Val, PoisonRefs_t(poisonRefs));
+    ResultVal = B.createDestroyValue(InstLoc, Val, poisonRefs, isDeadEnd);
     break;
   }
   case SILInstructionKind::BeginCOWMutationInst: {

lib/SIL/Verifier/SILVerifier.cpp

@@ -3405,6 +3405,10 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     require(!fnConv.useLoweredAddresses() || F.hasOwnership(),
             "destroy_value is only valid in functions with qualified "
             "ownership");
+    if (I->isDeadEnd()) {
+      require(getDeadEndBlocks().isDeadEnd(I->getParentBlock()),
+              "a dead_end destroy_value must be in a dead-end block");
+    }
   }
 
   void checkReleaseValueInst(ReleaseValueInst *I) {

lib/Serialization/DeserializeSIL.cpp

@@ -2323,12 +2323,13 @@ bool SILDeserializer::readSILInstruction(SILFunction *Fn,
   case SILInstructionKind::DestroyValueInst: {
     assert(RecordKind == SIL_ONE_OPERAND && "Layout should be OneOperand.");
     PoisonRefs_t poisonRefs = PoisonRefs_t(Attr & 0x1);
+    IsDeadEnd_t isDeadEnd = IsDeadEnd_t((Attr >> 1) & 0x1);
     ResultInst = Builder.createDestroyValue(
         Loc,
         getLocalValue(
             Builder.maybeGetFunction(), ValID,
             getSILType(MF->getType(TyID), (SILValueCategory)TyCategory, Fn)),
-        poisonRefs);
+        poisonRefs, isDeadEnd);
     break;
   }
 

lib/Serialization/ModuleFormat.h

@@ -58,8 +58,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR =
-    878; // immortal bit in LifetimeDependence
+const uint16_t SWIFTMODULE_VERSION_MINOR = 879; // dead_end flag on destroy_value
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///

lib/Serialization/SerializeSIL.cpp

@@ -1575,7 +1575,7 @@ void SILSerializer::writeSILInstruction(const SILInstruction &SI) {
     } else if (auto *HTE = dyn_cast<HopToExecutorInst>(&SI)) {
       Attr = HTE->isMandatory();
     } else if (auto *DVI = dyn_cast<DestroyValueInst>(&SI)) {
-      Attr = DVI->poisonRefs();
+      Attr = unsigned(DVI->poisonRefs()) | (unsigned(DVI->isDeadEnd()) << 1);
     } else if (auto *BCMI = dyn_cast<BeginCOWMutationInst>(&SI)) {
       Attr = BCMI->isNative();
     } else if (auto *ECMI = dyn_cast<EndCOWMutationInst>(&SI)) {

test/SIL/Parser/basic2.sil

@@ -8,6 +8,8 @@ class Klass {}
   var rhs: Klass
 }
 
+sil @getKlass : $@convention(thin) () -> (@owned Klass)
+
 // CHECK-LABEL: sil [ossa] @test_copy_release_value
 // CHECK: bb0([[T0:%[0-9]+]] : @owned $Builtin.NativeObject):
 // CHECK-NEXT: [[COPY_RESULT:%.*]] = copy_value [[T0]] : $Builtin.NativeObject
@@ -347,3 +349,39 @@ bb1:
   extend_lifetime %k : $Klass
   br bb1
 }
+
+// CHECK-LABEL: sil [ossa] @test_destroy_value : {{.*}} {
+// CHECK:         destroy_value
+// CHECK:         destroy_value [poison]
+// CHECK:         destroy_value [dead_end]
+// CHECK:         destroy_value [poison] [dead_end]
+// CHECK-LABEL: } // end sil function 'test_destroy_value'
+sil [ossa] @test_destroy_value : $@convention(thin) () -> () {
+entry:
+  %getKlass = function_ref @getKlass : $@convention(thin) () -> (@owned Klass)
+  cond_br undef, good, bad
+
+good:
+  cond_br undef, gleft, gright
+gleft:
+  %k1 = apply %getKlass() : $@convention(thin) () -> (@owned Klass)
+  destroy_value %k1 : $Klass
+  br exit
+gright:
+  %k2 = apply %getKlass() : $@convention(thin) () -> (@owned Klass)
+  destroy_value [poison] %k2 : $Klass
+  br exit
+exit:
+  %retval = tuple()
+  return %retval : $()
+bad:
+  cond_br undef, bleft, bright
+bleft:
+  %k3 = apply %getKlass() : $@convention(thin) () -> (@owned Klass)
+  destroy_value [dead_end] %k3 : $Klass
+  unreachable
+bright:
+  %k4 = apply %getKlass() : $@convention(thin) () -> (@owned Klass)
+  destroy_value [poison] [dead_end] %k4 : $Klass
+  unreachable
+}

test/SIL/Serialization/basic2.sil

@@ -6,6 +6,9 @@
 
 import Builtin
 
+class C {}
+sil @getC : $@convention(thin) () -> (@owned C)
+
 // CHECK-LABEL: sil [ossa] @test_allocbox_moveable_value_debuginfo_flag : $@convention(thin) () -> () {
 // CHECK: alloc_box [moveable_value_debuginfo] ${ var Builtin.NativeObject }
 // CHECK: } // end sil function 'test_allocbox_moveable_value_debuginfo_flag'
@@ -59,6 +62,60 @@ bb0(%0 : @owned $Builtin.NativeObject):
   return %9999 : $()
 }
 
+// CHECK-LABEL: sil [ossa] @test_destroy_value : {{.*}} {
+// CHECK:         cond_br undef, [[GOOD:bb[0-9]+]], [[BAD:bb[0-9]+]]
+// CHECK:       [[BAD]]:
+// CHECK:         cond_br undef, [[BLEFT:bb[0-9]+]], [[BRIGHT:bb[0-9]+]]
+// CHECK:       [[BRIGHT]]:
+// CHECK:         %3 = apply %0()
+// CHECK:         destroy_value [poison] [dead_end] %3
+// CHECK:         unreachable
+// CHECK:       [[BLEFT]]:
+// CHECK:         %6 = apply %0()
+// CHECK:         destroy_value [dead_end] %6
+// CHECK:         unreachable
+// CHECK:       [[GOOD]]:
+// CHECK:         cond_br undef, [[GLEFT:bb[0-9]+]], [[GRIGHT:bb[0-9]+]]
+// CHECK:       [[GRIGHT]]:
+// CHECK:         %10 = apply %0()
+// CHECK:         destroy_value [poison] %10
+// CHECK:         br [[EXIT:bb[0-9]+]]
+// CHECK:       [[GLEFT]]:
+// CHECK:         %13 = apply %0()
+// CHECK:         destroy_value %13
+// CHECK:         br [[EXIT]]
+// CHECK:       [[EXIT]]:
+// CHECK-LABEL: } // end sil function 'test_destroy_value'
+sil [ossa] @test_destroy_value : $@convention(thin) () -> () {
+entry:
+  %getC = function_ref @getC : $@convention(thin) () -> (@owned C)
+  cond_br undef, good, bad
+
+good:
+  cond_br undef, gleft, gright
+gleft:
+  %k1 = apply %getC() : $@convention(thin) () -> (@owned C)
+  destroy_value %k1 : $C
+  br exit
+gright:
+  %k2 = apply %getC() : $@convention(thin) () -> (@owned C)
+  destroy_value [poison] %k2 : $C
+  br exit
+exit:
+  %retval = tuple()
+  return %retval : $()
+bad:
+  cond_br undef, bleft, bright
+bleft:
+  %k3 = apply %getC() : $@convention(thin) () -> (@owned C)
+  destroy_value [dead_end] %k3 : $C
+  unreachable
+bright:
+  %k4 = apply %getC() : $@convention(thin) () -> (@owned C)
+  destroy_value [poison] [dead_end] %k4 : $C
+  unreachable
+}
+
 // CHECK-LABEL: sil [ossa] @test_explicit_copy_addr : $@convention(thin) (@owned Builtin.NativeObject) -> () {
 // CHECK: explicit_copy_addr %{{[0-9]+}} to [init] %{{[0-9]+}} :
 // CHECK: explicit_copy_addr [take] %{{[0-9]+}} to [init] %{{[0-9]+}} :

test/SIL/cloning.sil

@@ -226,3 +226,40 @@ entry(%o : @owned $Builtin.NativeObject):
   %retval = apply %callee(%o) : $@convention(thin) (@owned Builtin.NativeObject) -> ()
   return %retval : $()
 }
+
+sil [ossa] [always_inline] @callee_destroy_value : $@convention(thin) (@owned X) -> () {
+entry(%x : @owned $X):
+  cond_br undef, good, bad
+good:
+  cond_br undef, gleft, gright
+gleft:
+  destroy_value %x : $X
+  br exit
+gright:
+  destroy_value [poison] %x : $X
+  br exit
+exit:
+  %retval = tuple()
+  return %retval : $()
+bad:
+  cond_br undef, bleft, bright
+bleft:
+  destroy_value [dead_end] %x : $X
+  unreachable
+bright:
+  destroy_value [poison] [dead_end] %x : $X
+  unreachable
+}
+
+// CHECK-LABEL: sil [ossa] @caller_destroy_value : {{.*}} {
+// CHECK:         destroy_value
+// CHECK:         destroy_value [poison]
+// CHECK:         destroy_value [dead_end]
+// CHECK:         destroy_value [poison] [dead_end]
+// CHECK-LABEL: } // end sil function 'caller_destroy_value'
+sil [ossa] @caller_destroy_value : $@convention(thin) (@owned X) -> () {
+entry(%x : @owned $X):
+  %callee = function_ref @callee_destroy_value : $@convention(thin) (@owned X) -> ()
+  %res = apply %callee(%x) : $@convention(thin) (@owned X) -> ()
+  return %res : $()
+}

test/SIL/verifier_failures.sil

@@ -18,3 +18,16 @@ sil [ossa] @end_borrow_1_addr_alloc_stack : $@convention(thin) () -> () {
   %retval = tuple ()
   return %retval : $()
 }
+
+// CHECK-LABEL: Begin Error in function destroy_value_dead_end
+// CHECK:       SIL verification failed: a dead_end destroy_value must be in a dead-end block
+// CHECK:       Verifying instruction:
+// CHECK:            [[ARGUMENT:%[^,]+]] = argument
+// CHECK:       ->   destroy_value [dead_end] [[ARGUMENT]]
+// CHECK-LABEL: End Error in function destroy_value_dead_end
+sil [ossa] @destroy_value_dead_end : $@convention(thin) (@owned C) -> () {
+entry(%c : @owned $C):
+  destroy_value [dead_end] %c : $C
+  %retval = tuple()
+  return %retval : $()
+}