Treat a '!' preceding a function literal as eager-compile hint.

Some minifiers use the pattern !function ... () for JS code that should
be immediately executed. This change recognizes that pattern and treats
it equally to parenthesized functions.

A bit more background info is in the referenced bug.

R=verwaest@chromium.org
BUG=v8:5643

Review-Url: https://codereview.chromium.org/2509143003
Cr-Commit-Position: refs/heads/master@{#41114}

src/parsing/parser-base.h

@@ -458,16 +458,12 @@ class ParserBase {
       return &non_patterns_to_rewrite_;
     }
 
-    bool next_function_is_parenthesized() const {
-      return next_function_is_parenthesized_;
+    bool next_function_is_likely_called() const {
+      return next_function_is_likely_called_;
     }
 
-    void set_next_function_is_parenthesized(bool parenthesized) {
-      next_function_is_parenthesized_ = parenthesized;
-    }
-
-    bool this_function_is_parenthesized() const {
-      return this_function_is_parenthesized_;
+    void set_next_function_is_likely_called() {
+      next_function_is_likely_called_ = true;
     }
 
    private:
@@ -508,13 +504,12 @@ class ParserBase {
 
     ZoneList<typename ExpressionClassifier::Error> reported_errors_;
 
-    // If true, the next (and immediately following) function literal is
-    // preceded by a parenthesis.
-    bool next_function_is_parenthesized_;
-
-    // The value of the parents' next_function_is_parenthesized_, as it applies
-    // to this function. Filled in by constructor.
-    bool this_function_is_parenthesized_;
+    // Record whether the next (=== immediately following) function literal is
+    // preceded by a parenthesis / exclamation mark.
+    // The FunctionState constructor will reset a parents'
+    // next_function_is_likely_called_ to prevent it from being 'reused' in the
+    // next function literal.
+    bool next_function_is_likely_called_;
 
     friend Impl;
     friend class Checkpoint;
@@ -1466,13 +1461,10 @@ ParserBase<Impl>::FunctionState::FunctionState(
       return_expr_context_(ReturnExprContext::kInsideValidBlock),
       non_patterns_to_rewrite_(0, scope->zone()),
       reported_errors_(16, scope->zone()),
-      next_function_is_parenthesized_(false),
-      this_function_is_parenthesized_(false) {
+      next_function_is_likely_called_(false) {
   *function_state_stack = this;
   if (outer_function_state_) {
-    this_function_is_parenthesized_ =
-        outer_function_state_->next_function_is_parenthesized_;
-    outer_function_state_->next_function_is_parenthesized_ = false;
+    outer_function_state_->next_function_is_likely_called_ = false;
   }
 }
 
@@ -1789,8 +1781,9 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParsePrimaryExpression(
       }
       // Heuristically try to detect immediately called functions before
       // seeing the call parentheses.
-      function_state_->set_next_function_is_parenthesized(peek() ==
-                                                          Token::FUNCTION);
+      if (peek() == Token::FUNCTION) {
+        function_state_->set_next_function_is_likely_called();
+      }
       ExpressionT expr = ParseExpressionCoverGrammar(true, CHECK_OK);
       Expect(Token::RPAREN, CHECK_OK);
       return expr;
@@ -2944,6 +2937,12 @@ typename ParserBase<Impl>::ExpressionT ParserBase<Impl>::ParseUnaryExpression(
 
     op = Next();
     int pos = position();
+
+    // Assume "! function ..." indicates the function is likely to be called.
+    if (op == Token::NOT && peek() == Token::FUNCTION) {
+      function_state_->set_next_function_is_likely_called();
+    }
+
     ExpressionT expression = ParseUnaryExpression(CHECK_OK);
     impl()->RewriteNonPattern(CHECK_OK);
 

src/parsing/parser.cc

@@ -2530,7 +2530,7 @@ FunctionLiteral* Parser::ParseFunctionLiteral(
   }
 
   FunctionLiteral::EagerCompileHint eager_compile_hint =
-      function_state_->next_function_is_parenthesized()
+      function_state_->next_function_is_likely_called()
           ? FunctionLiteral::kShouldEagerCompile
           : default_eager_compile_hint();
 

test/cctest/BUILD.gn

@@ -91,6 +91,7 @@ v8_executable("cctest") {
     "interpreter/test-source-positions.cc",
     "libplatform/test-tracing.cc",
     "libsampler/test-sampler.cc",
+    "parsing/test-parse-decision.cc",
     "parsing/test-scanner-streams.cc",
     "parsing/test-scanner.cc",
     "print-extension.cc",

test/cctest/cctest.gyp

@@ -112,6 +112,7 @@
       'heap/test-spaces.cc',
       'libplatform/test-tracing.cc',
       'libsampler/test-sampler.cc',
+      'parsing/test-parse-decision.cc',
       'parsing/test-scanner-streams.cc',
       'parsing/test-scanner.cc',
       'print-extension.cc',

test/cctest/parsing/test-parse-decision.cc

+// Copyright 2016 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.
+
+// Test specific cases of the lazy/eager-parse decision.
+//
+// Note that presently most unit tests for parsing are found in
+// cctest/test-parsing.cc.
+
+#include <unordered_map>
+
+#include "include/v8.h"
+#include "src/api.h"
+#include "src/handles-inl.h"
+#include "src/isolate.h"
+#include "src/utils.h"
+
+#include "test/cctest/cctest.h"
+
+using namespace v8::internal;
+
+TEST(EagerlyCompileImmediateUseFunctions) {
+  if (!FLAG_lazy) return;
+
+  // Test parenthesized, exclaimed, and regular functions. Make sure these
+  // occur both intermixed and after each other, to make sure the 'reset'
+  // mechanism works.
+  const char src[] =
+      "function normal() { var a; }\n"             // Normal: Should lazy parse.
+      "(function parenthesized() { var b; })()\n"  // Parenthesized: Pre-parse.
+      "!function exclaimed() { var c; }() \n"      // Exclaimed: Pre-parse.
+      "function normal2() { var d; }\n"
+      "(function parenthesized2() { var e; })()\n"
+      "function normal3() { var f; }\n"
+      "!function exclaimed2() { var g; }() \n"
+      "function normal4() { var h; }\n";
+
+  Isolate* isolate = CcTest::i_isolate();
+  HandleScope scope(isolate);
+  LocalContext env;
+
+  // Compile src & record the 'compiled' state of all top level functions in
+  // is_compiled.
+  std::unordered_map<std::string, bool> is_compiled;
+  {
+    v8::Local<v8::Script> api_script = v8_compile(src);
+    Handle<JSFunction> toplevel_fn = v8::Utils::OpenHandle(*api_script);
+    Handle<Script> script =
+        handle(Script::cast(toplevel_fn->shared()->script()));
+
+    WeakFixedArray::Iterator iter(script->shared_function_infos());
+    while (SharedFunctionInfo* shared = iter.Next<SharedFunctionInfo>()) {
+      std::unique_ptr<char[]> name = String::cast(shared->name())->ToCString();
+      is_compiled[name.get()] = shared->is_compiled();
+    }
+  }
+
+  DCHECK(is_compiled.find("normal") != is_compiled.end());
+
+  DCHECK(is_compiled["parenthesized"]);
+  DCHECK(is_compiled["parenthesized2"]);
+  DCHECK(is_compiled["exclaimed"]);
+  DCHECK(is_compiled["exclaimed2"]);
+  DCHECK(!is_compiled["normal"]);
+  DCHECK(!is_compiled["normal2"]);
+  DCHECK(!is_compiled["normal3"]);
+  DCHECK(!is_compiled["normal4"]);
+}