[builtins] String.prototype.slice as a CSA builtin.

BUG=v8:6370

Review-Url: https://codereview.chromium.org/2870013004
Cr-Commit-Position: refs/heads/master@{#45275}

src/bootstrapper.cc

@@ -1810,6 +1810,8 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
 #endif  // V8_INTL_SUPPORT
     SimpleInstallFunction(prototype, "replace",
                           Builtins::kStringPrototypeReplace, 2, true);
+    SimpleInstallFunction(prototype, "slice", Builtins::kStringPrototypeSlice,
+                          2, false);
     SimpleInstallFunction(prototype, "split", Builtins::kStringPrototypeSplit,
                           2, true);
     SimpleInstallFunction(prototype, "substr", Builtins::kStringPrototypeSubstr,

src/builtins/builtins-definitions.h

@@ -853,6 +853,8 @@ namespace internal {
   CPP(StringPrototypeLocaleCompare)                                            \
   /* ES6 #sec-string.prototype.replace */                                      \
   TFJ(StringPrototypeReplace, 2, kSearch, kReplace)                            \
+  /* ES6 #sec-string.prototype.slice */                                        \
+  TFJ(StringPrototypeSlice, SharedFunctionInfo::kDontAdaptArgumentsSentinel)   \
   /* ES6 #sec-string.prototype.split */                                        \
   TFJ(StringPrototypeSplit, 2, kSeparator, kLimit)                             \
   /* ES6 #sec-string.prototype.substr */                                       \

src/code-stub-assembler.cc

@@ -3548,7 +3548,9 @@ Node* AllocAndCopyStringCharacters(CodeStubAssembler* a, Node* context,
 }  // namespace
 
 Node* CodeStubAssembler::SubString(Node* context, Node* string, Node* from,
-                                   Node* to) {
+                                   Node* to, SubStringFlags flags) {
+  DCHECK(flags == SubStringFlags::NONE ||
+         flags == SubStringFlags::FROM_TO_ARE_BOUNDED);
   VARIABLE(var_result, MachineRepresentation::kTagged);
   ToDirectStringAssembler to_direct(state(), string);
   Label end(this), runtime(this);
@@ -3559,8 +3561,13 @@ Node* CodeStubAssembler::SubString(Node* context, Node* string, Node* from,
 
   // Make sure that both from and to are non-negative smis.
 
-  GotoIfNot(TaggedIsPositiveSmi(from), &runtime);
-  GotoIfNot(TaggedIsPositiveSmi(to), &runtime);
+  if (flags == SubStringFlags::NONE) {
+    GotoIfNot(TaggedIsPositiveSmi(from), &runtime);
+    GotoIfNot(TaggedIsPositiveSmi(to), &runtime);
+  } else {
+    CSA_ASSERT(this, TaggedIsPositiveSmi(from));
+    CSA_ASSERT(this, TaggedIsPositiveSmi(to));
+  }
 
   Node* const substr_length = SmiSub(to, from);
   Node* const string_length = LoadStringLength(string);
@@ -3661,8 +3668,14 @@ Node* CodeStubAssembler::SubString(Node* context, Node* string, Node* from,
 
   BIND(&original_string_or_invalid_length);
   {
-    // Longer than original string's length or negative: unsafe arguments.
-    GotoIf(SmiAbove(substr_length, string_length), &runtime);
+    if (flags == SubStringFlags::NONE) {
+      // Longer than original string's length or negative: unsafe arguments.
+      GotoIf(SmiAbove(substr_length, string_length), &runtime);
+    } else {
+      // with flag SubStringFlags::FROM_TO_ARE_BOUNDED, the only way we can
+      // get here is if substr_length is equal to string_length.
+      CSA_ASSERT(this, SmiEqual(substr_length, string_length));
+    }
 
     // Equal length - check if {from, to} == {0, str.length}.
     GotoIf(SmiAbove(from, SmiConstant(Smi::kZero)), &runtime);

src/code-stub-assembler.h

@@ -805,9 +805,15 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
                          ParameterMode parameter_mode = SMI_PARAMETERS);
   // Return the single character string with only {code}.
   Node* StringFromCharCode(Node* code);
+
+  enum class SubStringFlags { NONE, FROM_TO_ARE_BOUNDED };
+
   // Return a new string object which holds a substring containing the range
   // [from,to[ of string.  |from| and |to| are expected to be tagged.
-  Node* SubString(Node* context, Node* string, Node* from, Node* to);
+  // If flags has the value FROM_TO_ARE_BOUNDED then from and to are in
+  // the range [0, string-length)
+  Node* SubString(Node* context, Node* string, Node* from, Node* to,
+                  SubStringFlags flags = SubStringFlags::NONE);
 
   // Return a new string object produced by concatenating |first| with |second|.
   Node* StringAdd(Node* context, Node* first, Node* second,

src/debug/debug-evaluate.cc

@@ -584,6 +584,7 @@ bool BuiltinHasNoSideEffect(Builtins::Name id) {
     case Builtins::kStringPrototypeIncludes:
     case Builtins::kStringPrototypeIndexOf:
     case Builtins::kStringPrototypeLastIndexOf:
+    case Builtins::kStringPrototypeSlice:
     case Builtins::kStringPrototypeStartsWith:
     case Builtins::kStringPrototypeSubstr:
     case Builtins::kStringPrototypeSubstring:

src/js/string.js

@@ -52,48 +52,6 @@ function StringSearch(pattern) {
 }
 
 
-// ECMA-262 section 15.5.4.13
-function StringSlice(start, end) {
-  CHECK_OBJECT_COERCIBLE(this, "String.prototype.slice");
-
-  var s = TO_STRING(this);
-  var s_len = s.length;
-  var start_i = TO_INTEGER(start);
-  var end_i = s_len;
-  if (!IS_UNDEFINED(end)) {
-    end_i = TO_INTEGER(end);
-  }
-
-  if (start_i < 0) {
-    start_i += s_len;
-    if (start_i < 0) {
-      start_i = 0;
-    }
-  } else {
-    if (start_i > s_len) {
-      return '';
-    }
-  }
-
-  if (end_i < 0) {
-    end_i += s_len;
-    if (end_i < 0) {
-      return '';
-    }
-  } else {
-    if (end_i > s_len) {
-      end_i = s_len;
-    }
-  }
-
-  if (end_i <= start_i) {
-    return '';
-  }
-
-  return %_SubString(s, start_i, end_i);
-}
-
-
 // ES6 draft, revision 26 (2014-07-18), section B.2.3.2.1
 function HtmlEscape(str) {
   return %RegExpInternalReplace(/"/g, TO_STRING(str), "&quot;");
@@ -334,8 +292,6 @@ utils.InstallFunctions(GlobalString.prototype, DONT_ENUM, [
   "padStart", StringPadStart,
   "repeat", StringRepeat,
   "search", StringSearch,
-  "slice", StringSlice,
-
   "link", StringLink,
   "anchor", StringAnchor,
   "fontcolor", StringFontcolor,