Implement logical assignment

https://tc39.es/proposal-logical-assignment/

Bug: v8:10372
Change-Id: I538d54af6b4b24d450d1398c74f76dd57fdb0147
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2158119Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67330}

src/flags/flag-definitions.h

@@ -220,7 +220,8 @@ DEFINE_IMPLICATION(harmony_weak_refs_with_cleanup_some, harmony_weak_refs)
   V(harmony_weak_refs_with_cleanup_some,                                       \
     "harmony weak references with FinalizationRegistry.prototype.cleanupSome") \
   V(harmony_regexp_match_indices, "harmony regexp match indices")              \
-  V(harmony_top_level_await, "harmony top level await")
+  V(harmony_top_level_await, "harmony top level await")                        \
+  V(harmony_logical_assignment, "harmony logical assignment")
 
 #ifdef V8_INTL_SUPPORT
 #define HARMONY_INPROGRESS(V)                       \

src/init/bootstrapper.cc

@@ -4246,6 +4246,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_dynamic_import)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_import_meta)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_regexp_sequence)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_top_level_await)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_logical_assignment)
 
 #ifdef V8_INTL_SUPPORT
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_intl_add_calendar_numbering_system)

src/interpreter/bytecode-generator.cc

@@ -4142,9 +4142,23 @@ void BytecodeGenerator::VisitCompoundAssignment(CompoundAssignment* expr) {
     }
   }
 
-  BinaryOperation* binop = expr->AsCompoundAssignment()->binary_operation();
+  BinaryOperation* binop = expr->binary_operation();
   FeedbackSlot slot = feedback_spec()->AddBinaryOpICSlot();
-  if (expr->value()->IsSmiLiteral()) {
+  BytecodeLabel short_circuit;
+  if (binop->op() == Token::NULLISH) {
+    BytecodeLabel nullish;
+    builder()
+        ->JumpIfUndefinedOrNull(&nullish)
+        .Jump(&short_circuit)
+        .Bind(&nullish);
+    VisitForAccumulatorValue(expr->value());
+  } else if (binop->op() == Token::OR) {
+    builder()->JumpIfTrue(ToBooleanMode::kConvertToBoolean, &short_circuit);
+    VisitForAccumulatorValue(expr->value());
+  } else if (binop->op() == Token::AND) {
+    builder()->JumpIfFalse(ToBooleanMode::kConvertToBoolean, &short_circuit);
+    VisitForAccumulatorValue(expr->value());
+  } else if (expr->value()->IsSmiLiteral()) {
     builder()->BinaryOperationSmiLiteral(
         binop->op(), expr->value()->AsLiteral()->AsSmiLiteral(),
         feedback_index(slot));
@@ -4154,9 +4168,9 @@ void BytecodeGenerator::VisitCompoundAssignment(CompoundAssignment* expr) {
     VisitForAccumulatorValue(expr->value());
     builder()->BinaryOperation(binop->op(), old_value, feedback_index(slot));
   }
-
   builder()->SetExpressionPosition(expr);
   BuildAssignment(lhs_data, expr->op(), expr->lookup_hoisting_mode());
+  builder()->Bind(&short_circuit);
 }
 
 // Suspends the generator to resume at the next suspend_id, with output stored

src/parsing/parse-info.cc

@@ -38,6 +38,7 @@ UnoptimizedCompileFlags::UnoptimizedCompileFlags(Isolate* isolate,
   set_collect_source_positions(!FLAG_enable_lazy_source_positions ||
                                isolate->NeedsDetailedOptimizedCodeLineInfo());
   set_allow_harmony_top_level_await(FLAG_harmony_top_level_await);
+  set_allow_harmony_logical_assignment(FLAG_harmony_logical_assignment);
 }
 
 // static

src/parsing/parse-info.h

@@ -66,7 +66,8 @@ class Zone;
   V(is_oneshot_iife, bool, 1, _)                         \
   V(collect_source_positions, bool, 1, _)                \
   V(allow_harmony_top_level_await, bool, 1, _)           \
-  V(is_repl_mode, bool, 1, _)
+  V(is_repl_mode, bool, 1, _)                            \
+  V(allow_harmony_logical_assignment, bool, 1, _)
 
 class V8_EXPORT_PRIVATE UnoptimizedCompileFlags {
  public:

src/parsing/parser-base.h

@@ -2750,6 +2750,11 @@ ParserBase<Impl>::ParseAssignmentExpressionCoverGrammar() {
   Token::Value op = peek();
 
   if (!Token::IsArrowOrAssignmentOp(op)) return expression;
+  if ((op == Token::ASSIGN_NULLISH || op == Token::ASSIGN_OR ||
+       op == Token::ASSIGN_AND) &&
+      !flags().allow_harmony_logical_assignment()) {
+    return expression;
+  }
 
   // Arrow functions.
   if (V8_UNLIKELY(op == Token::ARROW)) {

src/parsing/scanner-inl.h

@@ -364,14 +364,14 @@ V8_INLINE Token::Value Scanner::ScanSingleToken() {
           return Select(token);
 
         case Token::CONDITIONAL:
-          // ? ?. ??
+          // ? ?. ?? ??=
           Advance();
           if (c0_ == '.') {
             Advance();
             if (!IsDecimalDigit(c0_)) return Token::QUESTION_PERIOD;
             PushBack('.');
           } else if (c0_ == '?') {
-            return Select(Token::NULLISH);
+            return Select('=', Token::ASSIGN_NULLISH, Token::NULLISH);
           }
           return Token::CONDITIONAL;
 
@@ -471,16 +471,16 @@ V8_INLINE Token::Value Scanner::ScanSingleToken() {
           return Token::DIV;
 
         case Token::BIT_AND:
-          // & && &=
+          // & && &= &&=
           Advance();
-          if (c0_ == '&') return Select(Token::AND);
+          if (c0_ == '&') return Select('=', Token::ASSIGN_AND, Token::AND);
           if (c0_ == '=') return Select(Token::ASSIGN_BIT_AND);
           return Token::BIT_AND;
 
         case Token::BIT_OR:
-          // | || |=
+          // | || |= ||=
           Advance();
-          if (c0_ == '|') return Select(Token::OR);
+          if (c0_ == '|') return Select('=', Token::ASSIGN_OR, Token::OR);
           if (c0_ == '=') return Select(Token::ASSIGN_BIT_OR);
           return Token::BIT_OR;
 

src/parsing/token.h

@@ -31,6 +31,9 @@ namespace internal {
 /* Binary operators */
 /* ADD and SUB are at the end since they are UnaryOp */
 #define BINARY_OP_TOKEN_LIST(T, E) \
+  E(T, NULLISH, "??", 3)           \
+  E(T, OR, "||", 4)                \
+  E(T, AND, "&&", 5)               \
   E(T, BIT_OR, "|", 6)             \
   E(T, BIT_XOR, "^", 7)            \
   E(T, BIT_AND, "&", 8)            \
@@ -97,9 +100,6 @@ namespace internal {
   /* IsBinaryOp() relies on this block of enum values */           \
   /* being contiguous and sorted in the same order! */             \
   T(COMMA, ",", 1)                                                 \
-  T(NULLISH, "??", 3)                                              \
-  T(OR, "||", 4)                                                   \
-  T(AND, "&&", 5)                                                  \
                                                                    \
   /* Unary operators, starting at ADD in BINARY_OP_TOKEN_LIST  */  \
   /* IsUnaryOp() relies on this block of enum values */            \
@@ -297,8 +297,8 @@ class V8_EXPORT_PRIVATE Token {
   }
 
   static Value BinaryOpForAssignment(Value op) {
-    DCHECK(base::IsInRange(op, ASSIGN_BIT_OR, ASSIGN_SUB));
-    Value result = static_cast<Value>(op - ASSIGN_BIT_OR + BIT_OR);
+    DCHECK(base::IsInRange(op, ASSIGN_NULLISH, ASSIGN_SUB));
+    Value result = static_cast<Value>(op - ASSIGN_NULLISH + NULLISH);
     DCHECK(IsBinaryOp(result));
     return result;
   }

test/cctest/test-parsing.cc

@@ -261,9 +261,6 @@ TEST(ArrowOrAssignmentOp) {
 bool TokenIsBinaryOp(Token::Value token) {
   switch (token) {
     case Token::COMMA:
-    case Token::NULLISH:
-    case Token::OR:
-    case Token::AND:
 #define T(name, string, precedence) case Token::name:
       BINARY_OP_TOKEN_LIST(T, EXPAND_BINOP_TOKEN)
 #undef T

test/mjsunit/harmony/logical-assignment.js

+// Copyright 2020 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony-logical-assignment
+
+{
+  let x = null;
+  let y = 0;
+  x ??= y ||= 5;
+
+  assertEquals(x, 5);
+  assertEquals(y, 5);
+}
+
+
+{
+  let x = null;
+  let y = 4;
+  x ??= y ||= 5;
+
+  assertEquals(x, 4);
+  assertEquals(y, 4);
+}
+
+{
+  let x = 1;
+  let y = 0;
+  x &&= y ||= 5;
+
+  assertEquals(x, 5);
+  assertEquals(y, 5);
+}
+
+{
+  let x = 0;
+  let y = 0;
+  x &&= y ||= 5;
+
+  assertEquals(x, 0);
+  assertEquals(y, 0);
+}

test/test262/test262.status

@@ -659,44 +659,6 @@
   'built-ins/AsyncFromSyncIteratorPrototype/return/absent-value-not-passed': [FAIL],
   'built-ins/AsyncFromSyncIteratorPrototype/throw/absent-value-not-passed': [FAIL],
 
-  # https://bugs.chromium.org/p/v8/issues/detail?id=10394
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-bigint': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-lhs-before-rhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-no-set': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-no-set-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-non-extensible': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-non-writeable': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-non-writeable-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-unresolved-lhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-unresolved-rhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-assignment-operator-unresolved-rhs-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-and-whitespace': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-bigint': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-lhs-before-rhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-no-set': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-no-set-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-non-extensible': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-non-writeable': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-non-writeable-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-unresolved-lhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-unresolved-rhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-unresolved-rhs-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-nullish-whitespace': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-bigint': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-lhs-before-rhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-no-set': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-no-set-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-non-extensible': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-non-writeable': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-non-writeable-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-unresolved-lhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-unresolved-rhs': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-assignment-operator-unresolved-rhs-put': [FAIL],
-  'language/expressions/logical-assignment/lgcl-or-whitespace': [FAIL],
-
   # https://bugs.chromium.org/p/v8/issues/detail?id=10397
   'language/statements/for-await-of/iterator-close-throw-get-method-abrupt': [FAIL],
   'language/statements/for-of/iterator-close-throw-get-method-abrupt': [FAIL],
@@ -716,7 +678,10 @@
   # https://github.com/tc39/ecma262/pull/889
   'annexB/language/function-code/block-decl-func-skip-arguments': [FAIL],
 
-  # https://bugs.chromium.org/p/v8/issues/detail?id=6538
+  # Non-simple assignment targets are runtime errors instead of syntax errors for web compat.
+  'language/expressions/logical-assignment/lgcl-or-assignment-operator-non-simple-lhs': [FAIL],
+  'language/expressions/logical-assignment/lgcl-and-assignment-operator-non-simple-lhs': [FAIL],
+  'language/expressions/logical-assignment/lgcl-nullish-assignment-operator-non-simple-lhs': [FAIL],
 
   ############################ INVALID TESTS #############################
 

test/test262/testcfg.py

@@ -63,6 +63,7 @@ FEATURE_FLAGS = {
   'class-methods-private': '--harmony-private-methods',
   'class-static-methods-private': '--harmony-private-methods',
   'AggregateError': '--harmony-promise-any',
+  'logical-assignment-operators': '--harmony-logical-assignment',
 }
 
 SKIPPED_FEATURES = set([])