Add SIL instructions for pack indexing

docs/ABI/Mangling.rst

@@ -570,6 +570,7 @@ Types
   #if SWIFT_RUNTIME_VERSION >= 5.5
     type ::= 'Bj'                              // Builtin.Job
   #endif
+  type ::= 'BP'                              // Builtin.PackIndex
   type ::= 'BO'                              // Builtin.UnknownObject (no longer a distinct type, but still used for AnyObject)
   type ::= 'Bo'                              // Builtin.NativeObject
   type ::= 'Bp'                              // Builtin.RawPointer

include/swift/AST/TypeNodes.def

@@ -106,6 +106,7 @@ ABSTRACT_TYPE(Builtin, Type)
   BUILTIN_TYPE(BuiltinExecutor, BuiltinType)
   BUILTIN_TYPE(BuiltinFloat, BuiltinType)
   BUILTIN_TYPE(BuiltinJob, BuiltinType)
+  BUILTIN_TYPE(BuiltinPackIndex, BuiltinType)
   BUILTIN_TYPE(BuiltinRawPointer, BuiltinType)
   BUILTIN_TYPE(BuiltinRawUnsafeContinuation, BuiltinType)
   BUILTIN_TYPE(BuiltinNativeObject, BuiltinType)
@@ -193,6 +194,7 @@ LAST_TYPE(Dictionary) // Sugared types are last to make isa<SugarType>() fast.
 SINGLETON_TYPE(IntegerLiteral, BuiltinIntegerLiteral)
 SINGLETON_TYPE(Job, BuiltinJob)
 SINGLETON_TYPE(Executor, BuiltinExecutor)
+SINGLETON_TYPE(PackIndex, BuiltinPackIndex)
 SINGLETON_TYPE(RawPointer, BuiltinRawPointer)
 SINGLETON_TYPE(RawUnsafeContinuation, BuiltinRawUnsafeContinuation)
 SINGLETON_TYPE(NativeObject, BuiltinNativeObject)

include/swift/AST/Types.h

@@ -1598,6 +1598,21 @@ class BuiltinDefaultActorStorageType : public BuiltinType {
 };
 DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinDefaultActorStorageType, BuiltinType)
 
+/// BuiltinPackIndexType - The type of an (untyped) index into a pack
+/// in SIL.  Essentially a UInt32 with some structural restrictions
+/// about how it can be produced that ensures SIL maintains well-typed
+/// use-def relationships around packs.
+class BuiltinPackIndexType : public BuiltinType {
+  friend class ASTContext;
+  BuiltinPackIndexType(const ASTContext &C)
+    : BuiltinType(TypeKind::BuiltinPackIndex, C) {}
+public:
+  static bool classof(const TypeBase *T) {
+    return T->getKind() == TypeKind::BuiltinPackIndex;
+  }
+};
+DEFINE_EMPTY_CAN_TYPE_WRAPPER(BuiltinPackIndexType, BuiltinType)
+
 /// BuiltinNativeObjectType - The builtin opaque object-pointer type.
 /// Useful for keeping an object alive when it is otherwise being
 /// manipulated via an unsafe pointer type.

include/swift/SIL/SILBuilder.h

@@ -1936,6 +1936,32 @@ class SILBuilder {
         getSILDebugLocation(Loc), Existential));
   }
 
+  DynamicPackIndexInst *
+  createDynamicPackIndex(SILLocation loc, SILValue indexValue,
+                         CanPackType indexedPackType) {
+    return insert(DynamicPackIndexInst::create(getFunction(),
+                              getSILDebugLocation(loc),
+                              indexValue, indexedPackType));
+  }
+
+  PackPackIndexInst *
+  createPackPackIndex(SILLocation loc, unsigned sliceStartIndex,
+                      SILValue indexWithinSlice,
+                      CanPackType indexedPackType) {
+    return insert(PackPackIndexInst::create(getFunction(),
+                              getSILDebugLocation(loc),
+                              sliceStartIndex, indexWithinSlice,
+                              indexedPackType));
+  }
+
+  ScalarPackIndexInst *
+  createScalarPackIndex(SILLocation loc, unsigned componentIndex,
+                        CanPackType indexedPackType) {
+    return insert(ScalarPackIndexInst::create(getFunction(),
+                              getSILDebugLocation(loc),
+                              componentIndex, indexedPackType));
+  }
+
   OpenPackElementInst *
   createOpenPackElement(SILLocation loc, SILValue packIndex,
                         GenericEnvironment *openedElementEnvironment) {

include/swift/SIL/SILCloner.h

@@ -250,6 +250,25 @@ class SILCloner : protected SILInstructionVisitor<ImplClass> {
     return asImpl().remapASTType(ty);
   }
 
+  /// Remap a structural index into a pack so that it will point to the
+  /// corresponding structural index in the remapped pack type.
+  unsigned getOpStructuralPackIndex(CanPackType origPackType,
+                                    unsigned origIndex) {
+    assert(origIndex < origPackType->getNumElements());
+    unsigned newIndex = 0;
+    for (unsigned i = 0; i != origIndex; ++i) {
+      auto origComponentType = origPackType.getElementType(i);
+      if (auto origExpansionType =
+            dyn_cast<PackExpansionType>(origComponentType)) {
+        auto newShapeClass = getOpASTType(origExpansionType.getCountType());
+        newIndex += cast<PackType>(newShapeClass)->getNumElements();
+      } else {
+        newIndex++;
+      }
+    }
+    return newIndex;
+  }
+
   void remapRootOpenedType(CanOpenedArchetypeType archetypeTy) {
     assert(archetypeTy->isRoot());
 
@@ -2392,6 +2411,54 @@ void SILCloner<ImplClass>::visitDeinitExistentialValueInst(
                 getOpLocation(Inst->getLoc()), getOpValue(Inst->getOperand())));
 }
 
+template <typename ImplClass>
+void SILCloner<ImplClass>::visitDynamicPackIndexInst(
+    DynamicPackIndexInst *Inst) {
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+
+  auto newIndexValue = getOpValue(Inst->getOperand());
+  auto loc = getOpLocation(Inst->getLoc());
+  auto newPackType = cast<PackType>(getOpASTType(Inst->getIndexedPackType()));
+
+  recordClonedInstruction(
+      Inst, getBuilder().createDynamicPackIndex(loc, newIndexValue,
+                                                newPackType));
+}
+
+template <typename ImplClass>
+void SILCloner<ImplClass>::visitPackPackIndexInst(PackPackIndexInst *Inst) {
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+
+  auto newIndexValue = getOpValue(Inst->getOperand());
+  auto loc = getOpLocation(Inst->getLoc());
+  auto newPackType = cast<PackType>(getOpASTType(Inst->getIndexedPackType()));
+
+  auto newComponentStartIndex =
+    getOpStructuralPackIndex(Inst->getIndexedPackType(),
+                             Inst->getComponentStartIndex());
+
+  recordClonedInstruction(
+      Inst, getBuilder().createPackPackIndex(loc, newComponentStartIndex,
+                                             newIndexValue, newPackType));
+}
+
+template <typename ImplClass>
+void SILCloner<ImplClass>::visitScalarPackIndexInst(
+    ScalarPackIndexInst *Inst) {
+  getBuilder().setCurrentDebugScope(getOpScope(Inst->getDebugScope()));
+
+  auto loc = getOpLocation(Inst->getLoc());
+  auto newPackType = cast<PackType>(getOpASTType(Inst->getIndexedPackType()));
+
+  auto newComponentIndex =
+    getOpStructuralPackIndex(Inst->getIndexedPackType(),
+                             Inst->getComponentIndex());
+
+  recordClonedInstruction(
+      Inst, getBuilder().createScalarPackIndex(loc, newComponentIndex,
+                                               newPackType));
+}
+
 template <typename ImplClass>
 void SILCloner<ImplClass>::visitOpenPackElementInst(
     OpenPackElementInst *Inst) {