Add a poison flag to SIL destroy_value.

When the IRGen side is implemented, this will overwrite shadow debug
variables with a poison sentinel for all references within the value.

Author: atrick

docs/SIL.rst

@@ -5178,7 +5178,7 @@ destroy_value
 
 ::
 
-  sil-instruction ::= 'destroy_value' sil-operand
+  sil-instruction ::= 'destroy_value' '[poison]'? sil-operand
 
   destroy_value %0 : $A
 

include/swift/SIL/SILBuilder.h

@@ -1245,13 +1245,14 @@ class SILBuilder {
                       CopyValueInst(getSILDebugLocation(Loc), operand));
   }
 
-  DestroyValueInst *createDestroyValue(SILLocation Loc, SILValue operand) {
+  DestroyValueInst *createDestroyValue(SILLocation Loc, SILValue operand,
+                                       bool poisonRefs = false) {
     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));
+    return insert(new (getModule()) DestroyValueInst(getSILDebugLocation(Loc),
+                                                     operand, poisonRefs));
   }
 
   UnconditionalCheckedCastInst *

include/swift/SIL/SILCloner.h

@@ -1807,7 +1807,8 @@ void SILCloner<ImplClass>::visitDestroyValueInst(DestroyValueInst *Inst) {
 
   recordClonedInstruction(
       Inst, getBuilder().createDestroyValue(getOpLocation(Inst->getLoc()),
-                                            getOpValue(Inst->getOperand())));
+                                            getOpValue(Inst->getOperand()),
+                                            Inst->poisonRefs()));
 }
 
 template <typename ImplClass>

include/swift/SIL/SILInstruction.h

@@ -7141,8 +7141,17 @@ class DestroyValueInst
                                   NonValueInstruction> {
   friend class SILBuilder;
 
-  DestroyValueInst(SILDebugLocation DebugLoc, SILValue operand)
-      : UnaryInstructionBase(DebugLoc, operand) {}
+  DestroyValueInst(SILDebugLocation DebugLoc, SILValue operand, bool poisonRefs)
+      : UnaryInstructionBase(DebugLoc, operand) {
+    setPoisonRefs(poisonRefs);
+  }
+
+public:
+  bool poisonRefs() const { return SILNode::Bits.DestroyValueInst.PoisonRefs; }
+
+  void setPoisonRefs(bool poisonRefs = true) {
+    SILNode::Bits.DestroyValueInst.PoisonRefs = poisonRefs;
+  }
 };
 
 /// Given an object reference, return true iff it is non-nil and refers

include/swift/SIL/SILNode.h

@@ -337,6 +337,9 @@ class alignas(8) SILNode {
     Immutable : 1
   );
 
+  SWIFT_INLINE_BITFIELD(DestroyValueInst, NonValueInstruction, 1,
+                        PoisonRefs : 1);
+
   SWIFT_INLINE_BITFIELD(EndCOWMutationInst, NonValueInstruction, 1,
     KeepUnique : 1
   );

lib/SIL/IR/SILInstruction.cpp

@@ -384,6 +384,11 @@ namespace {
       return true;
     }
 
+    bool visitDestroyValueInst(const DestroyValueInst *RHS) {
+      auto *left = cast<DestroyValueInst>(LHS);
+      return left->poisonRefs() == RHS->poisonRefs();
+    }
+
     bool visitBeginCOWMutationInst(const BeginCOWMutationInst *RHS) {
       auto *left = cast<BeginCOWMutationInst>(LHS);
       return left->isNative() == RHS->isNative();

lib/SIL/IR/SILPrinter.cpp

@@ -1703,6 +1703,8 @@ class SILPrinter : public SILInstructionVisitor<SILPrinter> {
 #include "swift/AST/ReferenceStorage.def"
 
   void visitDestroyValueInst(DestroyValueInst *I) {
+    if (I->poisonRefs())
+      *this << "[poison] ";
     *this << getIDAndType(I->getOperand());
   }
 

lib/SIL/Parser/ParseSIL.cpp

@@ -2974,7 +2974,6 @@ bool SILParser::parseSpecificSILInstruction(SILBuilder &B,
     UNARY_INSTRUCTION(IsUnique)
     UNARY_INSTRUCTION(DestroyAddr)
     UNARY_INSTRUCTION(CopyValue)
-    UNARY_INSTRUCTION(DestroyValue)
     UNARY_INSTRUCTION(EndBorrow)
     UNARY_INSTRUCTION(DestructureStruct)
     UNARY_INSTRUCTION(DestructureTuple)
@@ -3001,6 +3000,14 @@ bool SILParser::parseSpecificSILInstruction(SILBuilder &B,
 #undef UNARY_INSTRUCTION
 #undef REFCOUNTING_INSTRUCTION
 
+  case SILInstructionKind::DestroyValueInst: {
+    bool poisonRefs = false;
+    if (parseSILOptional(poisonRefs, *this, "poison")
+        || parseTypedValueRef(Val, B) || parseSILDebugLocation(InstLoc, B))
+      return true;
+    ResultVal = B.createDestroyValue(InstLoc, Val, poisonRefs);
+    break;
+  }
   case SILInstructionKind::BeginCOWMutationInst: {
     bool native = false;
     if (parseSILOptional(native, *this, "native") ||

lib/SIL/Verifier/SILVerifier.cpp

@@ -2482,7 +2482,8 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
             "Source value should be an object value");
     require(!I->getOperand()->getType().isTrivial(*I->getFunction()),
             "Source value should be non-trivial");
-    require(!fnConv.useLoweredAddresses() || F.hasOwnership(),
+    require(I->poisonRefs() || !fnConv.useLoweredAddresses()
+            || F.hasOwnership(),
             "destroy_value is only valid in functions with qualified "
             "ownership");
   }

lib/Serialization/DeserializeSIL.cpp

@@ -1858,7 +1858,6 @@ bool SILDeserializer::readSILInstruction(SILFunction *Fn,
   REFCOUNTING_INSTRUCTION(RetainValueAddr)
   REFCOUNTING_INSTRUCTION(UnmanagedRetainValue)
   UNARY_INSTRUCTION(CopyValue)
-  UNARY_INSTRUCTION(DestroyValue)
   REFCOUNTING_INSTRUCTION(ReleaseValue)
   REFCOUNTING_INSTRUCTION(ReleaseValueAddr)
   REFCOUNTING_INSTRUCTION(UnmanagedReleaseValue)
@@ -1898,6 +1897,17 @@ bool SILDeserializer::readSILInstruction(SILFunction *Fn,
     break;
   }
 
+  case SILInstructionKind::DestroyValueInst: {
+    assert(RecordKind == SIL_ONE_OPERAND && "Layout should be OneOperand.");
+    unsigned poisonRefs = Attr;
+    ResultInst = Builder.createDestroyValue(
+        Loc,
+        getLocalValue(ValID, getSILType(MF->getType(TyID),
+                                        (SILValueCategory)TyCategory, Fn)),
+        poisonRefs != 0);
+    break;
+  }
+
   case SILInstructionKind::BeginCOWMutationInst: {
     assert(RecordKind == SIL_ONE_OPERAND && "Layout should be OneOperand.");
     unsigned isNative = Attr;