[vm] Implementation of NullCheck for bytecode

Bug: #38840
Change-Id: I56af108096355a0486d45f88e795908ce712db4b
Fixes: #38840
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/121904
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Commit-Queue: Liam Appelbe <liama@google.com>

Author: liamappelbe

pkg/vm/lib/bytecode/assembler.dart

@@ -571,8 +571,8 @@ class BytecodeAssembler {
     _emitInstructionD(Opcode.kAllocateClosure, rd);
   }
 
-  void emitCheckReceiverForNull(int rd) {
+  void emitNullCheck(int rd) {
     emitSourcePosition();
-    _emitInstructionD(Opcode.kCheckReceiverForNull, rd);
+    _emitInstructionD(Opcode.kNullCheck, rd);
   }
 }

pkg/vm/lib/bytecode/dbc.dart

@@ -258,8 +258,8 @@ enum Opcode {
 
   // Null operations.
   kEqualsNull,
-  kCheckReceiverForNull,
-  kCheckReceiverForNull_Wide,
+  kNullCheck,
+  kNullCheck_Wide,
 
   // Int operations.
   kNegateInt,
@@ -468,7 +468,7 @@ const Map<Opcode, Format> BytecodeFormats = const {
       Encoding.k0, const [Operand.none, Operand.none, Operand.none]),
   Opcode.kEqualsNull: const Format(
       Encoding.k0, const [Operand.none, Operand.none, Operand.none]),
-  Opcode.kCheckReceiverForNull: const Format(
+  Opcode.kNullCheck: const Format(
       Encoding.kD, const [Operand.lit, Operand.none, Operand.none]),
   Opcode.kNegateInt: const Format(
       Encoding.k0, const [Operand.none, Operand.none, Operand.none]),

pkg/vm/lib/bytecode/gen_bytecode.dart

@@ -3251,8 +3251,7 @@ class BytecodeGenerator extends RecursiveVisitor<Null> {
     // correct noSuchMethod for method call.
     if (checkForNull) {
       asm.emitPush(receiverTemp);
-      asm.emitCheckReceiverForNull(
-          cp.addSelectorName(node.name, InvocationKind.method));
+      asm.emitNullCheck(cp.addSelectorName(node.name, InvocationKind.method));
     }
 
     _genInstanceCall(null, InvocationKind.getter, node.interfaceTarget,
@@ -3309,8 +3308,7 @@ class BytecodeGenerator extends RecursiveVisitor<Null> {
       final int receiverTemp = locals.tempIndexInFrame(node);
       _genArguments(node.receiver, args, storeReceiverToLocal: receiverTemp);
       asm.emitPush(receiverTemp);
-      asm.emitCheckReceiverForNull(
-          cp.addSelectorName(node.name, InvocationKind.method));
+      asm.emitNullCheck(cp.addSelectorName(node.name, InvocationKind.method));
     } else {
       _genArguments(node.receiver, args);
     }
@@ -3344,8 +3342,7 @@ class BytecodeGenerator extends RecursiveVisitor<Null> {
         final int receiverTemp = locals.tempIndexInFrame(node);
         asm.emitStoreLocal(receiverTemp);
         asm.emitPush(receiverTemp);
-        asm.emitCheckReceiverForNull(
-            cp.addSelectorName(node.name, InvocationKind.getter));
+        asm.emitNullCheck(cp.addSelectorName(node.name, InvocationKind.getter));
       }
       _genDirectCall(directCall.target, argDesc, 1, isGet: true, node: node);
     } else {
@@ -3367,8 +3364,7 @@ class BytecodeGenerator extends RecursiveVisitor<Null> {
       asm.emitStoreLocal(temp);
       _generateNode(node.value);
       asm.emitPush(temp);
-      asm.emitCheckReceiverForNull(
-          cp.addSelectorName(node.name, InvocationKind.setter));
+      asm.emitNullCheck(cp.addSelectorName(node.name, InvocationKind.setter));
     } else {
       _generateNode(node.value);
     }
@@ -3477,6 +3473,15 @@ class BytecodeGenerator extends RecursiveVisitor<Null> {
     }
   }
 
+  @override
+  visitNullCheck(NullCheck node) {
+    _generateNode(node.operand);
+    final operandTemp = locals.tempIndexInFrame(node);
+    asm.emitStoreLocal(operandTemp);
+    asm.emitPush(operandTemp);
+    asm.emitNullCheck(cp.addObjectRef(null));
+  }
+
   @override
   visitNullLiteral(NullLiteral node) {
     asm.emitPushNull();

pkg/vm/lib/bytecode/local_vars.dart

@@ -1289,6 +1289,11 @@ class _Allocator extends RecursiveVisitor<Null> {
   visitInstantiation(Instantiation node) {
     _visit(node, temps: 3);
   }
+
+  @override
+  visitNullCheck(NullCheck node) {
+    _visit(node, temps: 1);
+  }
 }
 
 class LocalVariableIndexOverflowException

pkg/vm/testcases/bytecode/closures.dart.expect

@@ -1611,7 +1611,7 @@ Bytecode {
   InterfaceCall        CP#2, 1
   PopLocal             r2
   Push                 r0
-  CheckReceiverForNull CP#4
+  NullCheck            CP#4
   InterfaceCall        CP#5, 1
   Push                 r1
   Push                 r2
@@ -1648,7 +1648,7 @@ Bytecode {
   InterfaceCall        CP#3, 1
   PopLocal             r2
   Push                 r0
-  CheckReceiverForNull CP#5
+  NullCheck            CP#5
   InterfaceCall        CP#6, 1
   Push                 r1
   Push                 r2
@@ -1687,7 +1687,7 @@ Bytecode {
   InterfaceCall        CP#5, 1
   PopLocal             r2
   Push                 r0
-  CheckReceiverForNull CP#7
+  NullCheck            CP#7
   InterfaceCall        CP#8, 1
   Push                 r1
   Push                 r2

runtime/vm/compiler/frontend/bytecode_flow_graph_builder.cc

@@ -1427,7 +1427,7 @@ void BytecodeFlowGraphBuilder::BuildAssertSubtype() {
   code_ <<= instr;
 }
 
-void BytecodeFlowGraphBuilder::BuildCheckReceiverForNull() {
+void BytecodeFlowGraphBuilder::BuildNullCheck() {
   if (is_generating_interpreter()) {
     UNIMPLEMENTED();  // TODO(alexmarkov): interpreter
   }

runtime/vm/constants_kbc.h

@@ -689,8 +689,8 @@ namespace dart {
   V(MoveSpecial_Wide,                    A_Y, WIDE, num, xeg, ___)             \
   V(BooleanNegateTOS,                      0, ORDN, ___, ___, ___)             \
   V(EqualsNull,                            0, ORDN, ___, ___, ___)             \
-  V(CheckReceiverForNull,                  D, ORDN, lit, ___, ___)             \
-  V(CheckReceiverForNull_Wide,             D, WIDE, lit, ___, ___)             \
+  V(NullCheck,                             D, ORDN, lit, ___, ___)             \
+  V(NullCheck_Wide,                        D, WIDE, lit, ___, ___)             \
   V(NegateInt,                             0, ORDN, ___, ___, ___)             \
   V(AddInt,                                0, ORDN, ___, ___, ___)             \
   V(SubInt,                                0, ORDN, ___, ___, ___)             \

runtime/vm/interpreter.cc

@@ -2698,7 +2698,7 @@ RawObject* Interpreter::Call(RawFunction* function,
   }
 
   {
-    BYTECODE(CheckReceiverForNull, D);
+    BYTECODE(NullCheck, D);
     SP -= 1;
 
     if (UNLIKELY(SP[0] == null_value)) {