Revert "[vm/ffi] Optimize Pointer operations for statically known types"

This reverts commit 3712ed2.

Reason for revert: Breaks Arm32 precompiled.
Issue: #38737

Original change's description:
> [vm/ffi] Optimize Pointer operations for statically known types
> 
> This CL optimizes Pointer operations in hot loops for Pointer<NativeInteger/NativeDouble/Pointer> (not for structs).
> 
> Design: go/dart-ffi-pointers-il
> 
> It provides roughly a 100x speedup for the FfiMemory benchmark. The next 5x speedup is to get rid of allocations due to `load` and `store` not being inlined.
> 
> FFI API is changed to enable optimizations:
> 
> * Disable dynamic invocations of Pointer.load / Pointer.store.
> * Disallow implicit downcast of argument passed to Pointer.store.
> * Stop zeroing out Pointer.address on Pointer.free().
> 
> Issue: #38172
> 
> Related issues:
> Closes: #35902 (Disallowing dynamic invocations of Pointer ops.)
> Closes: #37385 (Function variance checking.)
> 
> Change-Id: I96058d8b5b49052eb6999f084372e6f08b4f6f17
> Cq-Include-Trybots: luci.dart.try:vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64-try,app-kernel-linux-debug-x64-try,vm-kernel-linux-debug-ia32-try,vm-dartkb-linux-debug-simarm64-try,vm-kernel-win-debug-x64-try,vm-kernel-win-debug-ia32-try,vm-dartkb-linux-debug-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-dartkb-linux-release-x64-abi-try,vm-kernel-precomp-android-release-arm64-try
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/117547
> Commit-Queue: Daco Harkes <[email protected]>
> Reviewed-by: Martin Kustermann <[email protected]>

[email protected],[email protected],[email protected]

Change-Id: I3b7923ace45beaa9f99119e9ea20c1e52b429ad8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Issue: #38172
Cq-Include-Trybots: luci.dart.try:vm-ffi-android-debug-arm-try, vm-ffi-android-debug-arm64-try, app-kernel-linux-debug-x64-try, vm-kernel-linux-debug-ia32-try, vm-dartkb-linux-debug-simarm64-try, vm-kernel-win-debug-x64-try, vm-kernel-win-debug-ia32-try, vm-dartkb-linux-debug-x64-try, vm-kernel-precomp-linux-debug-x64-try, vm-dartkb-linux-release-x64-abi-try, vm-kernel-precomp-android-release-arm64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/120582
Reviewed-by: Daco Harkes <[email protected]>
Commit-Queue: Daco Harkes <[email protected]>

Author: dcharkes

pkg/vm/lib/transformations/ffi.dart

@@ -154,22 +154,6 @@ const nonSizeAlignment = <Abi, Map<NativeType, int>>{
   Abi.wordSize32Align64: {},
 };
 
-/// Load, store, and elementAt are rewired to their static type for these types.
-const List<NativeType> optimizedTypes = [
-  NativeType.kInt8,
-  NativeType.kInt16,
-  NativeType.kInt32,
-  NativeType.kInt64,
-  NativeType.kUint8,
-  NativeType.kUint16,
-  NativeType.kUint32,
-  NativeType.kUnit64,
-  NativeType.kIntptr,
-  NativeType.kFloat,
-  NativeType.kDouble,
-  NativeType.kPointer,
-];
-
 /// [FfiTransformer] contains logic which is shared between
 /// _FfiUseSiteTransformer and _FfiDefinitionTransformer.
 class FfiTransformer extends Transformer {
@@ -194,7 +178,6 @@ class FfiTransformer extends Transformer {
   final Procedure loadMethod;
   final Procedure storeMethod;
   final Procedure offsetByMethod;
-  final Procedure elementAtMethod;
   final Procedure asFunctionMethod;
   final Procedure asFunctionInternal;
   final Procedure lookupFunctionMethod;
@@ -205,10 +188,6 @@ class FfiTransformer extends Transformer {
   final Procedure abiMethod;
   final Procedure pointerFromFunctionProcedure;
   final Procedure nativeCallbackFunctionProcedure;
-  final Map<NativeType, Procedure> loadMethods;
-  final Map<NativeType, Procedure> storeMethods;
-  final Map<NativeType, Procedure> elementAtMethods;
-  final Procedure loadStructMethod;
 
   /// Classes corresponding to [NativeType], indexed by [NativeType].
   final List<Class> nativeTypesClasses;
@@ -230,7 +209,6 @@ class FfiTransformer extends Transformer {
         loadMethod = index.getMember('dart:ffi', 'Pointer', 'load'),
         storeMethod = index.getMember('dart:ffi', 'Pointer', 'store'),
         offsetByMethod = index.getMember('dart:ffi', 'Pointer', 'offsetBy'),
-        elementAtMethod = index.getMember('dart:ffi', 'Pointer', 'elementAt'),
         addressOfField = index.getMember('dart:ffi', 'Struct', 'addressOf'),
         structFromPointer =
             index.getMember('dart:ffi', 'Struct', 'fromPointer'),
@@ -250,20 +228,7 @@ class FfiTransformer extends Transformer {
             index.getTopLevelMember('dart:ffi', '_nativeCallbackFunction'),
         nativeTypesClasses = nativeTypeClassNames
             .map((name) => index.getClass('dart:ffi', name))
-            .toList(),
-        loadMethods = Map.fromIterable(optimizedTypes, value: (t) {
-          final name = nativeTypeClassNames[t.index];
-          return index.getTopLevelMember('dart:ffi', "_load$name");
-        }),
-        storeMethods = Map.fromIterable(optimizedTypes, value: (t) {
-          final name = nativeTypeClassNames[t.index];
-          return index.getTopLevelMember('dart:ffi', "_store$name");
-        }),
-        elementAtMethods = Map.fromIterable(optimizedTypes, value: (t) {
-          final name = nativeTypeClassNames[t.index];
-          return index.getTopLevelMember('dart:ffi', "_elementAt$name");
-        }),
-        loadStructMethod = index.getTopLevelMember('dart:ffi', '_loadStruct');
+            .toList();
 
   /// Computes the Dart type corresponding to a ffi.[NativeType], returns null
   /// if it is not a valid NativeType.

pkg/vm/lib/transformations/ffi_use_sites.dart

@@ -30,8 +30,7 @@ import 'ffi.dart'
         NativeType,
         kNativeTypeIntStart,
         kNativeTypeIntEnd,
-        FfiTransformer,
-        optimizedTypes;
+        FfiTransformer;
 
 /// Checks and replaces calls to dart:ffi struct fields and methods.
 void transformLibraries(
@@ -317,6 +316,8 @@ class _FfiUseSiteTransformer extends FfiTransformer {
         return StaticInvocation(asFunctionInternal,
             Arguments([node.receiver], types: [dartType, nativeSignature]));
       } else if (target == loadMethod) {
+        // TODO(dacoharkes): should load and store be generic?
+        // https://github.com/dart-lang/sdk/issues/35902
         final DartType dartType = node.arguments.types[0];
         final DartType pointerType = node.receiver.getStaticType(env);
         final DartType nativeType = _pointerTypeGetTypeArg(pointerType);
@@ -326,20 +327,11 @@ class _FfiUseSiteTransformer extends FfiTransformer {
         _ensureNativeTypeSized(nativeType, node, target.name);
         _ensureNativeTypeToDartType(nativeType, dartType, node,
             allowStructs: true);
-
-        // TODO(37773): When moving to extension methods we can get rid of
-        // this rewiring.
-        final Class nativeClass = (nativeType as InterfaceType).classNode;
-        final NativeType nt = getType(nativeClass);
-        final typeArguments = [
-          if (nt == NativeType.kPointer) _pointerTypeGetTypeArg(nativeType)
-        ];
-        return StaticInvocation(
-            optimizedTypes.contains(nt) ? loadMethods[nt] : loadStructMethod,
-            Arguments([node.receiver], types: typeArguments));
       } else if (target == storeMethod) {
-        final Expression storeValue = node.arguments.positional.single;
-        final DartType dartType = storeValue.getStaticType(env);
+        // TODO(dacoharkes): should load and store permitted to be generic?
+        // https://github.com/dart-lang/sdk/issues/35902
+        final DartType dartType =
+            node.arguments.positional[0].getStaticType(env);
         final DartType pointerType = node.receiver.getStaticType(env);
         final DartType nativeType = _pointerTypeGetTypeArg(pointerType);
 
@@ -349,32 +341,6 @@ class _FfiUseSiteTransformer extends FfiTransformer {
         _ensureNativeTypeValid(nativeType, node);
         _ensureNativeTypeSized(nativeType, node, target.name);
         _ensureNativeTypeToDartType(nativeType, dartType, node);
-
-        // TODO(37773): When moving to extension methods we can get rid of
-        // this rewiring.
-        final Class nativeClass = (nativeType as InterfaceType).classNode;
-        final NativeType nt = getType(nativeClass);
-        final typeArguments = [
-          if (nt == NativeType.kPointer) _pointerTypeGetTypeArg(nativeType)
-        ];
-        return StaticInvocation(storeMethods[nt],
-            Arguments([node.receiver, storeValue], types: typeArguments));
-      } else if (target == elementAtMethod) {
-        // TODO(37773): When moving to extension methods we can get rid of
-        // this rewiring.
-        final DartType pointerType = node.receiver.getStaticType(env);
-        final DartType nativeType = _pointerTypeGetTypeArg(pointerType);
-        final Class nativeClass = (nativeType as InterfaceType).classNode;
-        final NativeType nt = getType(nativeClass);
-        if (optimizedTypes.contains(nt)) {
-          final typeArguments = [
-            if (nt == NativeType.kPointer) _pointerTypeGetTypeArg(nativeType)
-          ];
-          return StaticInvocation(
-              elementAtMethods[nt],
-              Arguments([node.receiver, node.arguments.positional[0]],
-                  types: typeArguments));
-        }
       }
     } on _FfiStaticTypeError {
       // It's OK to swallow the exception because the diagnostics issued will
@@ -395,7 +361,9 @@ class _FfiUseSiteTransformer extends FfiTransformer {
     final DartType shouldBeElementType =
         convertNativeTypeToDartType(containerTypeArg, allowStructs);
     if (elementType == shouldBeElementType) return;
-    // We disable implicit downcasts, they will go away when NNBD lands.
+    // Both subtypes and implicit downcasts are allowed statically.
+    if (env.isSubtypeOf(shouldBeElementType, elementType,
+        SubtypeCheckMode.ignoringNullabilities)) return;
     if (env.isSubtypeOf(elementType, shouldBeElementType,
         SubtypeCheckMode.ignoringNullabilities)) return;
     diagnosticReporter.report(