Merge pull request swiftlang#24674 from linux-on-ibm-z/payload-schema-deadcode

[IRGen]: Remove unused explosion schema from enum payload schema

Author: slavapestov

lib/IRGen/EnumPayload.h

@@ -26,54 +26,38 @@ namespace swift {
 namespace irgen {
 
 /// A description of how to represent an enum payload as a value.
-/// A payload can either use a generic word-chunked representation, or attempt
-/// to follow the explosion schema of one of its payload types.
+/// A payload can either use a generic word-chunked representation,
+/// or attempt to follow the explosion schema of one of its payload
+/// types.
+/// TODO: the current code only ever uses the generic word-chunked
+/// representation, it might be better if it used an appropriate
+/// explosion schema instead.
 class EnumPayloadSchema {
-  using BitSizeTy = llvm::PointerEmbeddedInt<unsigned, 31>;
-
-  const llvm::PointerUnion<ExplosionSchema *, BitSizeTy> Value;
-
+  // A size in bits less than 0 indicates that the payload size is
+  // dynamic.
+  const int64_t BitSize;
 public:
-  EnumPayloadSchema() : Value((ExplosionSchema *)nullptr) {}
-
-  explicit operator bool() {
-    return Value.getOpaqueValue() != nullptr;
-  }
+  /// Create a new schema with a dynamic size.
+  EnumPayloadSchema() : BitSize(-1) {}
 
+  /// Create a new schema with the given fixed size in bits.
   explicit EnumPayloadSchema(unsigned bits)
-    : Value(BitSizeTy(bits)) {}
-
-  EnumPayloadSchema(ExplosionSchema &s)
-    : Value(&s) {}
+    : BitSize(static_cast<int64_t>(bits)) {}
 
-  static EnumPayloadSchema withBitSize(unsigned bits) {
-    return EnumPayloadSchema(bits);
-  }
-  
-  ExplosionSchema *getSchema() const {
-    return Value.dyn_cast<ExplosionSchema*>();
+  /// Report whether the schema has a fixed size.
+  explicit operator bool() const {
+    return BitSize >= 0;
   }
-  
+
   /// Invoke a functor for each element type in the schema.
   template<typename TypeFn /* void(llvm::Type *schemaType) */>
   void forEachType(IRGenModule &IGM, TypeFn &&fn) const {
-    // Follow an explosion schema if we have one.
-    if (auto *explosion = Value.dyn_cast<ExplosionSchema *>()) {
-      for (auto &element : *explosion) {
-        auto type = element.getScalarType();
-        assert(IGM.DataLayout.getTypeSizeInBits(type)
-                 == IGM.DataLayout.getTypeAllocSizeInBits(type)
-               && "enum payload schema elements should use full alloc size");
-        (void) type;
-        fn(element.getScalarType());
-      }
-      return;
-    }
-    
-    // Otherwise, chunk into pointer-sized integer values by default.
-    unsigned bitSize = Value.get<BitSizeTy>();
-    unsigned pointerSize = IGM.getPointerSize().getValueInBits();
-    
+    assert(BitSize >= 0 && "payload size must not be dynamic");
+
+    // Chunk into pointer-sized integer values.
+    int64_t bitSize = BitSize;
+    int64_t pointerSize = IGM.getPointerSize().getValueInBits();
+
     while (bitSize >= pointerSize) {
       fn(IGM.SizeTy);
       bitSize -= pointerSize;

lib/IRGen/GenEnum.cpp

@@ -1334,11 +1334,6 @@ namespace {
         PayloadBitCount = ~0u;
       }
     }
-    
-    ~PayloadEnumImplStrategyBase() override {
-      if (auto schema = PayloadSchema.getSchema())
-        delete schema;
-    }
 
     void getSchema(ExplosionSchema &schema) const override {
       if (TIK < Loadable) {

lib/IRGen/TypeLayoutVerifier.cpp

@@ -115,7 +115,7 @@ IRGenTypeVerifierFunction::emit(ArrayRef<CanType> formalTypes) {
         auto fixedXIOpaque = Builder.CreateBitCast(fixedXIBuf,
                                                        IGM.OpaquePtrTy);
         auto xiMask = fixedTI->getFixedExtraInhabitantMask(IGM);
-        auto xiSchema = EnumPayloadSchema::withBitSize(xiMask.getBitWidth());
+        auto xiSchema = EnumPayloadSchema(xiMask.getBitWidth());
 
         auto maxXiCount = std::min(xiCount, 256u);
         auto numCases = llvm::ConstantInt::get(IGM.Int32Ty, maxXiCount);