Runtime: Expose assignExistentialWithCopy entry points.

The assign-with-copy operation on existentials is complex enough to be emitted as a function call, which is currently generated on-demand by IRGen for every existential layout. We can instead use the implementation out of the runtime. Provide entry points for zero, one, and any number of witness tables.

Swift SVN r9815

stdlib/runtime/Metadata.cpp

@@ -1136,6 +1136,10 @@ struct OpaqueExistentialValueWitnesses {
                      
     // Metadata pointer.
     const Metadata *metadata;
+                     
+    // Get the number of witness tables.
+    static unsigned getNumWitnesses(const Metadata *self);
+
     // Get a reference to the nth witness table.
     const void *&getWitness(unsigned i);
     const void *getWitness(unsigned i) const;
@@ -1192,7 +1196,7 @@ struct OpaqueExistentialValueWitnesses {
                                        Container *src,
                                        const Metadata *self) {
     dest->metadata = src->metadata;
-    for (unsigned i = 0; i != NUM_WITNESS_TABLES; ++i)
+    for (unsigned i = 0, e = Container::getNumWitnesses(self); i < e; ++i)
       dest->getWitness(i) = src->getWitness(i);
     src->metadata->vw_initializeBufferWithCopyOfBuffer(
                                          dest->getValueBuffer(self),
@@ -1242,7 +1246,7 @@ struct OpaqueExistentialValueWitnesses {
                                        Container *src,
                                        const Metadata *self) {
     dest->metadata = src->metadata;
-    for (unsigned i = 0; i != NUM_WITNESS_TABLES; ++i)
+    for (unsigned i = 0, e = Container::getNumWitnesses(self); i < e; ++i)
       dest->getWitness(i) = src->getWitness(i);
     auto srcValue = src->metadata->vw_projectBuffer(src->getValueBuffer(self));
     
@@ -1284,6 +1288,10 @@ struct OpaqueExistentialValueWitnesses<NUM_VALUE_WITNESSES>::Container {
   // Fixed-size buffer.
   ValueBuffer valueBuffer;
   
+  static unsigned getNumWitnesses(const Metadata *self) {
+    return NUM_VALUE_WITNESSES;
+  }
+  
   // Get a reference to the nth witness table.
   const void *&getWitness(unsigned i) { return _witnesses[i]; }
   const void *getWitness(unsigned i) const { return _witnesses[i]; }
@@ -1313,6 +1321,10 @@ struct OpaqueExistentialValueWitnesses<0>::Container {
   // Fixed-size buffer.
   ValueBuffer valueBuffer;
 
+  static unsigned getNumWitnesses(const Metadata *self) {
+    return 0;
+  }
+
   // Get a reference to the nth witness table. This shouldn't happen.
   const void *&getWitness(unsigned i) { abort(); }
   const void *getWitness(unsigned i) const { abort(); }
@@ -1340,6 +1352,11 @@ struct OpaqueExistentialValueWitnesses<VariableValueWitnesses>::Container {
   // Metadata pointer.
   const Metadata *metadata;
 
+  static unsigned getNumWitnesses(const Metadata *self) {
+    auto existSelf = static_cast<const ExistentialTypeMetadata*>(self);
+    return existSelf->Flags.getNumWitnessTables();
+  }
+
   const void **_getWitnesses() {
     return reinterpret_cast<const void**>(this + 1);
   }
@@ -1528,3 +1545,65 @@ swift::swift_getExistentialMetadata(size_t numProtocols,
   
   return ExistentialTypes.add(entry)->getData();
 }
+
+/// \brief Perform a copy-assignment from one existential container to another.
+/// Both containers must be of the same existential type representable with no
+/// witness tables.
+OpaqueValue *swift::swift_assignExistentialWithCopy0(OpaqueValue *dest,
+                                                     const OpaqueValue *src,
+                                                     const Metadata *type) {
+  auto destVal =
+    reinterpret_cast<OpaqueExistentialValueWitnesses<0>::Container*>(dest);
+  auto srcCVal =
+    reinterpret_cast<const OpaqueExistentialValueWitnesses<0>::Container*>(src);
+  auto srcVal =
+    const_cast<OpaqueExistentialValueWitnesses<0>::Container*>(srcCVal);
+  
+  auto result =
+    OpaqueExistentialValueWitnesses<0>::assignWithCopy(destVal, srcVal, type);
+  
+  return reinterpret_cast<OpaqueValue*>(result);
+}
+
+/// \brief Perform a copy-assignment from one existential container to another.
+/// Both containers must be of the same existential type representable with one
+/// witness table.
+OpaqueValue *swift::swift_assignExistentialWithCopy1(OpaqueValue *dest,
+                                                     const OpaqueValue *src,
+                                                     const Metadata *type) {
+  auto destVal =
+    reinterpret_cast<OpaqueExistentialValueWitnesses<1>::Container*>(dest);
+  auto srcCVal =
+    reinterpret_cast<const OpaqueExistentialValueWitnesses<1>::Container*>(src);
+  auto srcVal =
+    const_cast<OpaqueExistentialValueWitnesses<1>::Container*>(srcCVal);
+  
+  auto result =
+    OpaqueExistentialValueWitnesses<1>::assignWithCopy(destVal, srcVal, type);
+
+  return reinterpret_cast<OpaqueValue*>(result);
+}
+
+/// \brief Perform a copy-assignment from one existential container to another.
+/// Both containers must be of the same existential type representable with the
+/// same number of witness tables.
+OpaqueValue *swift::swift_assignExistentialWithCopy(OpaqueValue *dest,
+                                                    const OpaqueValue *src,
+                                                    const Metadata *type) {
+  auto destVal =
+    reinterpret_cast<OpaqueExistentialValueWitnesses<VariableValueWitnesses>
+                     ::Container*>(dest);
+  auto srcCVal =
+    reinterpret_cast<const OpaqueExistentialValueWitnesses
+                           <VariableValueWitnesses>::Container*>(src);
+  auto srcVal =
+    const_cast<OpaqueExistentialValueWitnesses<VariableValueWitnesses>
+               ::Container*>(srcCVal);
+  
+  auto result =
+    OpaqueExistentialValueWitnesses<VariableValueWitnesses>
+      ::assignWithCopy(destVal, srcVal, type);
+
+  return reinterpret_cast<OpaqueValue*>(result);
+}
+