[vm/ffi] Make elementAt an extension method

The CFE rewrite for structs, unions, and abi-specific integers is now
done on the extension methods.
The other native types are implemented in the extension methods
directly.

TEST=test/ffi

Closes: #50714
Change-Id: I578325733e3cd66200e80949d47ff12a13115b99
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/276102
Reviewed-by: Slava Egorov <[email protected]>
Commit-Queue: Daco Harkes <[email protected]>

Author: dcharkes

pkg/vm/lib/transformations/ffi/common.dart

@@ -113,7 +113,7 @@ const Map<NativeType, int> nativeTypeSizes = <NativeType, int>{
   NativeType.kBool: 1,
 };
 
-/// Load, store, and elementAt are rewired to their static type for these types.
+/// Load and store are rewired to their static type for these types.
 const List<NativeType> optimizedTypes = [
   NativeType.kBool,
   NativeType.kInt8,
@@ -201,16 +201,19 @@ class FfiTransformer extends Transformer {
   final Procedure allocatorAllocateMethod;
   final Procedure castMethod;
   final Procedure offsetByMethod;
-  final Procedure elementAtMethod;
   final Procedure addressGetter;
   final Procedure structPointerGetRef;
   final Procedure structPointerSetRef;
   final Procedure structPointerGetElemAt;
   final Procedure structPointerSetElemAt;
+  final Procedure structPointerElementAt;
+  final Procedure structPointerElementAtTearoff;
   final Procedure unionPointerGetRef;
   final Procedure unionPointerSetRef;
   final Procedure unionPointerGetElemAt;
   final Procedure unionPointerSetElemAt;
+  final Procedure unionPointerElementAt;
+  final Procedure unionPointerElementAtTearoff;
   final Procedure structArrayElemAt;
   final Procedure unionArrayElemAt;
   final Procedure arrayArrayElemAt;
@@ -219,6 +222,8 @@ class FfiTransformer extends Transformer {
   final Procedure abiSpecificIntegerPointerSetValue;
   final Procedure abiSpecificIntegerPointerElemAt;
   final Procedure abiSpecificIntegerPointerSetElemAt;
+  final Procedure abiSpecificIntegerPointerElementAt;
+  final Procedure abiSpecificIntegerPointerElementAtTearoff;
   final Procedure abiSpecificIntegerArrayElemAt;
   final Procedure abiSpecificIntegerArraySetElemAt;
   final Procedure asFunctionMethod;
@@ -246,7 +251,6 @@ class FfiTransformer extends Transformer {
   final Map<NativeType, Procedure> loadUnalignedMethods;
   final Map<NativeType, Procedure> storeMethods;
   final Map<NativeType, Procedure> storeUnalignedMethods;
-  final Map<NativeType, Procedure> elementAtMethods;
   final Procedure loadAbiSpecificIntMethod;
   final Procedure loadAbiSpecificIntAtIndexMethod;
   final Procedure storeAbiSpecificIntMethod;
@@ -363,8 +367,6 @@ class FfiTransformer extends Transformer {
             index.getProcedure('dart:ffi', 'Allocator', 'allocate'),
         castMethod = index.getProcedure('dart:ffi', 'Pointer', 'cast'),
         offsetByMethod = index.getProcedure('dart:ffi', 'Pointer', '_offsetBy'),
-        elementAtMethod =
-            index.getProcedure('dart:ffi', 'Pointer', 'elementAt'),
         addressGetter =
             index.getProcedure('dart:ffi', 'Pointer', 'get:address'),
         compoundTypedDataBaseField =
@@ -397,6 +399,10 @@ class FfiTransformer extends Transformer {
             index.getProcedure('dart:ffi', 'StructPointer', '[]'),
         structPointerSetElemAt =
             index.getProcedure('dart:ffi', 'StructPointer', '[]='),
+        structPointerElementAt =
+            index.getProcedure('dart:ffi', 'StructPointer', 'elementAt'),
+        structPointerElementAtTearoff = index.getProcedure('dart:ffi',
+            'StructPointer', LibraryIndex.tearoffPrefix + 'elementAt'),
         unionPointerGetRef =
             index.getProcedure('dart:ffi', 'UnionPointer', 'get:ref'),
         unionPointerSetRef =
@@ -405,6 +411,10 @@ class FfiTransformer extends Transformer {
             index.getProcedure('dart:ffi', 'UnionPointer', '[]'),
         unionPointerSetElemAt =
             index.getProcedure('dart:ffi', 'UnionPointer', '[]='),
+        unionPointerElementAt =
+            index.getProcedure('dart:ffi', 'UnionPointer', 'elementAt'),
+        unionPointerElementAtTearoff = index.getProcedure('dart:ffi',
+            'UnionPointer', LibraryIndex.tearoffPrefix + 'elementAt'),
         structArrayElemAt = index.getProcedure('dart:ffi', 'StructArray', '[]'),
         unionArrayElemAt = index.getProcedure('dart:ffi', 'UnionArray', '[]'),
         arrayArrayElemAt = index.getProcedure('dart:ffi', 'ArrayArray', '[]'),
@@ -418,6 +428,12 @@ class FfiTransformer extends Transformer {
             index.getProcedure('dart:ffi', 'AbiSpecificIntegerPointer', '[]'),
         abiSpecificIntegerPointerSetElemAt =
             index.getProcedure('dart:ffi', 'AbiSpecificIntegerPointer', '[]='),
+        abiSpecificIntegerPointerElementAt = index.getProcedure(
+            'dart:ffi', 'AbiSpecificIntegerPointer', 'elementAt'),
+        abiSpecificIntegerPointerElementAtTearoff = index.getProcedure(
+            'dart:ffi',
+            'AbiSpecificIntegerPointer',
+            LibraryIndex.tearoffPrefix + 'elementAt'),
         abiSpecificIntegerArrayElemAt =
             index.getProcedure('dart:ffi', 'AbiSpecificIntegerArray', '[]'),
         abiSpecificIntegerArraySetElemAt =
@@ -462,10 +478,6 @@ class FfiTransformer extends Transformer {
           return index.getTopLevelProcedure(
               'dart:ffi', "_store${name}Unaligned");
         }),
-        elementAtMethods = Map.fromIterable(optimizedTypes, value: (t) {
-          final name = nativeTypeClassNames[t];
-          return index.getTopLevelProcedure('dart:ffi', "_elementAt$name");
-        }),
         loadAbiSpecificIntMethod =
             index.getTopLevelProcedure('dart:ffi', "_loadAbiSpecificInt"),
         loadAbiSpecificIntAtIndexMethod = index.getTopLevelProcedure(

pkg/vm/lib/transformations/ffi/use_sites.dart

@@ -123,7 +123,10 @@ mixin _FfiUseSiteTransformer on FfiTransformer {
         node.isExtensionMember &&
         (node == allocationTearoff ||
             node == asFunctionTearoff ||
-            node == lookupFunctionTearoff));
+            node == lookupFunctionTearoff ||
+            node == abiSpecificIntegerPointerElementAtTearoff ||
+            node == structPointerElementAtTearoff ||
+            node == unionPointerElementAtTearoff));
     final result = super.visitProcedure(node);
     _inFfiTearoff = false;
     return result;
@@ -201,6 +204,28 @@ mixin _FfiUseSiteTransformer on FfiTransformer {
         ensureNativeTypeValid(nativeType, node, allowCompounds: true);
 
         return _replaceSetRef(node);
+      } else if (target == abiSpecificIntegerPointerElementAt ||
+          target == structPointerElementAt ||
+          target == unionPointerElementAt) {
+        final pointer = node.arguments.positional[0];
+        final index = node.arguments.positional[1];
+        final pointerType =
+            pointer.getStaticType(staticTypeContext!) as InterfaceType;
+        ensureNativeTypeValid(pointerType, pointer,
+            allowCompounds: true, allowInlineArray: true);
+        final DartType nativeType = node.arguments.types[0];
+
+        ensureNativeTypeValid(nativeType, node, allowCompounds: true);
+
+        Expression? inlineSizeOf = _inlineSizeOf(nativeType as InterfaceType);
+        if (inlineSizeOf != null) {
+          // Generates `receiver.offsetBy(inlineSizeOfExpression)`.
+          return InstanceInvocation(InstanceAccessKind.Instance, pointer,
+              offsetByMethod.name, Arguments([multiply(index, inlineSizeOf)]),
+              interfaceTarget: offsetByMethod,
+              functionType: Substitution.fromInterfaceType(pointerType)
+                  .substituteType(offsetByMethod.getterType) as FunctionType);
+        }
       } else if (target == structArrayElemAt || target == unionArrayElemAt) {
         final DartType nativeType = node.arguments.types[0];
 
@@ -704,60 +729,6 @@ mixin _FfiUseSiteTransformer on FfiTransformer {
           ..fileOffset = node.fileOffset);
   }
 
-  @override
-  visitInstanceInvocation(InstanceInvocation node) {
-    final modifiedExpression = _visitInstanceInvocation(node);
-    if (node == modifiedExpression) {
-      return super.visitInstanceInvocation(node);
-    }
-    // We've just created this node. We're likely not going to need to transform
-    // this node itself. Visit its sub expressions.
-    return super.defaultExpression(modifiedExpression);
-  }
-
-  /// Replaces nodes if they match. Does not invoke any super visit.
-  Expression _visitInstanceInvocation(InstanceInvocation node) {
-    if (_inFfiTearoff) {
-      return node;
-    }
-    final Member target = node.interfaceTarget;
-    try {
-      if (target == elementAtMethod) {
-        final DartType pointerType =
-            node.receiver.getStaticType(staticTypeContext!);
-        final DartType nativeType = _pointerTypeGetTypeArg(pointerType)!;
-
-        ensureNativeTypeValid(nativeType, node, allowCompounds: true);
-
-        Expression? inlineSizeOf = _inlineSizeOf(nativeType as InterfaceType);
-        if (inlineSizeOf != null) {
-          // Generates `receiver.offsetBy(inlineSizeOfExpression)`.
-          return InstanceInvocation(
-              InstanceAccessKind.Instance,
-              node.receiver,
-              offsetByMethod.name,
-              Arguments(
-                  [multiply(node.arguments.positional.single, inlineSizeOf)]),
-              interfaceTarget: offsetByMethod,
-              functionType:
-                  Substitution.fromInterfaceType(pointerType as InterfaceType)
-                          .substituteType(offsetByMethod.getterType)
-                      as FunctionType);
-        }
-      }
-    } on FfiStaticTypeError {
-      // It's OK to swallow the exception because the diagnostics issued will
-      // cause compilation to fail. By continuing, we can report more
-      // diagnostics before compilation ends.
-    }
-
-    return node;
-  }
-
-  DartType? _pointerTypeGetTypeArg(DartType pointerType) {
-    return pointerType is InterfaceType ? pointerType.typeArguments[0] : null;
-  }
-
   void _ensureIsStaticFunction(Expression node) {
     if ((node is StaticGet && node.target is Procedure) ||
         (node is ConstantExpression &&

runtime/tools/ffi/sdk_lib_ffi_generator.dart

@@ -192,6 +192,9 @@ $platform$truncate$alignment  external $dartType operator [](int index);
   /// The $property at `address + ${sizeTimes}index`.
 $platform$truncate$alignment  external void operator []=(int index, $dartType value);
 
+  /// Pointer arithmetic (takes element size into account).
+  external Pointer<$nativeType> elementAt(int index);
+
 $asTypedList
 }
 
@@ -237,7 +240,7 @@ void generatePatchExtension(
   if (container == "Pointer") {
     buffer.write("""
 extension ${nativeType}Pointer on Pointer<$nativeType> {
- @patch
+  @patch
   $dartType get value => _load$nativeType(this, 0);
 
   @patch
@@ -249,6 +252,9 @@ extension ${nativeType}Pointer on Pointer<$nativeType> {
   @patch
   operator []=(int index, $dartType value) => _store$nativeType(this, ${sizeTimes}index, value);
 
+  @patch
+  Pointer<$nativeType> elementAt(int index) => Pointer.fromAddress(address + ${sizeTimes}index);
+
 $asTypedList
 }
 
@@ -329,9 +335,12 @@ class Config {
   final int elementSize;
   final Version? since;
   const Config(
-      this.nativeType, this.dartType, this.typedListType, this.elementSize,
-      {Version? since})
-      : since = since;
+    this.nativeType,
+    this.dartType,
+    this.typedListType,
+    this.elementSize, {
+    Version? since,
+  }) : since = since;
 }
 
 const String kDoNotEmit = "donotemit";