[regexp] Remove code flushing support

Regexp code flushing support has been unintentionally disabled for quite a
while without any signals on our benchmarks. This CL completely removes
support.

BUG=v8:6569

Change-Id: Ic018a115c38387ff5610b34d3c09cb360e30ad3f
Reviewed-on: https://chromium-review.googlesource.com/559331Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46401}

src/builtins/builtins-regexp-gen.cc

@@ -377,10 +377,22 @@ Node* RegExpBuiltinsAssembler::RegExpExecInternal(Node* const context,
   }
 
   // Check that the irregexp code has been generated for the actual string
-  // encoding. If it has, the field contains a code object otherwise it contains
-  // smi (code flushing support).
+  // encoding. If it has, the field contains a code object; and otherwise it
+  // contains the uninitialized sentinel as a smi.
 
   Node* const code = var_code.value();
+#ifdef DEBUG
+  {
+    Label next(this);
+    GotoIfNot(TaggedIsSmi(code), &next);
+
+    CSA_ASSERT(this,
+               SmiEqual(code, SmiConstant(JSRegExp::kUninitializedValue)));
+    Goto(&next);
+
+    BIND(&next);
+  }
+#endif
   GotoIf(TaggedIsSmi(code), &runtime);
   CSA_ASSERT(this, HasInstanceType(code, CODE_TYPE));
 

src/factory.cc

@@ -2763,8 +2763,6 @@ void Factory::SetRegExpIrregexpData(Handle<JSRegExp> regexp,
   store->set(JSRegExp::kFlagsIndex, Smi::FromInt(flags));
   store->set(JSRegExp::kIrregexpLatin1CodeIndex, uninitialized);
   store->set(JSRegExp::kIrregexpUC16CodeIndex, uninitialized);
-  store->set(JSRegExp::kIrregexpLatin1CodeSavedIndex, uninitialized);
-  store->set(JSRegExp::kIrregexpUC16CodeSavedIndex, uninitialized);
   store->set(JSRegExp::kIrregexpMaxRegisterCountIndex, Smi::kZero);
   store->set(JSRegExp::kIrregexpCaptureCountIndex,
              Smi::FromInt(capture_count));

src/objects-debug.cc

@@ -1095,24 +1095,17 @@ void JSRegExp::JSRegExpVerify() {
 
       FixedArray* arr = FixedArray::cast(data());
       Object* one_byte_data = arr->get(JSRegExp::kIrregexpLatin1CodeIndex);
-      // Smi : Not compiled yet (-1) or code prepared for flushing.
-      // JSObject: Compilation error.
+      // Smi : Not compiled yet (-1).
       // Code/ByteArray: Compiled code.
       CHECK(
-          one_byte_data->IsSmi() ||
+          (one_byte_data->IsSmi() && Smi::cast(one_byte_data)->value() ==
+                                         JSRegExp::kUninitializedValue) ||
           (is_native ? one_byte_data->IsCode() : one_byte_data->IsByteArray()));
       Object* uc16_data = arr->get(JSRegExp::kIrregexpUC16CodeIndex);
-      CHECK(uc16_data->IsSmi() ||
+      CHECK((uc16_data->IsSmi() &&
+             Smi::cast(uc16_data)->value() == JSRegExp::kUninitializedValue) ||
             (is_native ? uc16_data->IsCode() : uc16_data->IsByteArray()));
 
-      Object* one_byte_saved =
-          arr->get(JSRegExp::kIrregexpLatin1CodeSavedIndex);
-      CHECK(one_byte_saved->IsSmi() || one_byte_saved->IsString() ||
-            one_byte_saved->IsCode());
-      Object* uc16_saved = arr->get(JSRegExp::kIrregexpUC16CodeSavedIndex);
-      CHECK(uc16_saved->IsSmi() || uc16_saved->IsString() ||
-             uc16_saved->IsCode());
-
       CHECK(arr->get(JSRegExp::kIrregexpCaptureCountIndex)->IsSmi());
       CHECK(arr->get(JSRegExp::kIrregexpMaxRegisterCountIndex)->IsSmi());
       break;

src/objects.h

@@ -5652,14 +5652,6 @@ class JSRegExp: public JSObject {
     }
   }
 
-  static int saved_code_index(bool is_latin1) {
-    if (is_latin1) {
-      return kIrregexpLatin1CodeSavedIndex;
-    } else {
-      return kIrregexpUC16CodeSavedIndex;
-    }
-  }
-
   DECL_CAST(JSRegExp)
 
   // Dispatched behavior.
@@ -5691,22 +5683,14 @@ class JSRegExp: public JSObject {
   // fails, this fields hold an exception object that should be
   // thrown if the regexp is used again.
   static const int kIrregexpUC16CodeIndex = kDataIndex + 1;
-
-  // Saved instance of Irregexp compiled code or bytecode for Latin1 that
-  // is a potential candidate for flushing.
-  static const int kIrregexpLatin1CodeSavedIndex = kDataIndex + 2;
-  // Saved instance of Irregexp compiled code or bytecode for UC16 that is
-  // a potential candidate for flushing.
-  static const int kIrregexpUC16CodeSavedIndex = kDataIndex + 3;
-
   // Maximal number of registers used by either Latin1 or UC16.
   // Only used to check that there is enough stack space
-  static const int kIrregexpMaxRegisterCountIndex = kDataIndex + 4;
+  static const int kIrregexpMaxRegisterCountIndex = kDataIndex + 2;
   // Number of captures in the compiled regexp.
-  static const int kIrregexpCaptureCountIndex = kDataIndex + 5;
+  static const int kIrregexpCaptureCountIndex = kDataIndex + 3;
   // Maps names of named capture groups (at indices 2i) to their corresponding
   // (1-based) capture group indices (at indices 2i + 1).
-  static const int kIrregexpCaptureNameMapIndex = kDataIndex + 6;
+  static const int kIrregexpCaptureNameMapIndex = kDataIndex + 4;
 
   static const int kIrregexpDataSize = kIrregexpCaptureNameMapIndex + 1;
 
@@ -5716,15 +5700,6 @@ class JSRegExp: public JSObject {
 
   // The uninitialized value for a regexp code object.
   static const int kUninitializedValue = -1;
-
-  // The compilation error value for the regexp code object. The real error
-  // object is in the saved code field.
-  static const int kCompilationErrorValue = -2;
-
-  // When we store the sweep generation at which we moved the code from the
-  // code index to the saved code index we mask it of to be in the [0:255]
-  // range.
-  static const int kCodeAgeMask = 0xff;
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(JSRegExp::Flags)

src/regexp/jsregexp.cc

@@ -330,28 +330,14 @@ bool RegExpImpl::CompileIrregexp(Handle<JSRegExp> re,
   Isolate* isolate = re->GetIsolate();
   Zone zone(isolate->allocator(), ZONE_NAME);
   PostponeInterruptsScope postpone(isolate);
-  // If we had a compilation error the last time this is saved at the
-  // saved code index.
+#ifdef DEBUG
   Object* entry = re->DataAt(JSRegExp::code_index(is_one_byte));
-  // When arriving here entry can only be a smi, either representing an
-  // uncompiled regexp, a previous compilation error, or code that has
-  // been flushed.
+  // When arriving here entry can only be a smi representing an uncompiled
+  // regexp.
   DCHECK(entry->IsSmi());
   int entry_value = Smi::cast(entry)->value();
-  DCHECK(entry_value == JSRegExp::kUninitializedValue ||
-         entry_value == JSRegExp::kCompilationErrorValue ||
-         (entry_value < JSRegExp::kCodeAgeMask && entry_value >= 0));
-
-  if (entry_value == JSRegExp::kCompilationErrorValue) {
-    // A previous compilation failed and threw an error which we store in
-    // the saved code index (we store the error message, not the actual
-    // error). Recreate the error object and throw it.
-    Object* error_string = re->DataAt(JSRegExp::saved_code_index(is_one_byte));
-    DCHECK(error_string->IsString());
-    Handle<String> error_message(String::cast(error_string));
-    ThrowRegExpException(re, error_message);
-    return false;
-  }
+  DCHECK_EQ(JSRegExp::kUninitializedValue, entry_value);
+#endif
 
   JSRegExp::Flags flags = re->GetFlags();