[stubs] Port String.prototype.substring to TurboFan

src/builtins/builtins-string.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.
 
 #include "src/builtins/builtins.h"
 #include "src/builtins/builtins-utils.h"
 
 #include "src/code-factory.h"
 
 namespace v8 {
@@ skipping 453 matching lines @@
     Handle<String> valid_forms =
         isolate->factory()->NewStringFromStaticChars("NFC, NFD, NFKC, NFKD");
     THROW_NEW_ERROR_RETURN_FAILURE(
         isolate,
         NewRangeError(MessageTemplate::kNormalizationForm, valid_forms));
   }
 
   return *string;
 }
 
+namespace {
+
+compiler::Node* EnsureSmiBetweenZeroAnd(CodeStubAssembler* a,
+                                        compiler::Node* value,
+                                        compiler::Node* limit) {
+  typedef CodeStubAssembler::Label Label;
+  typedef compiler::Node Node;
+  typedef CodeStubAssembler::Variable Variable;
+
+  Label out(a);
+  Variable var_result(a, MachineRepresentation::kTagged);
+
+  Label if_isinbounds(a), if_isoutofbounds(a, Label::kDeferred);
+  a->Branch(a->SmiAbove(value, limit), &if_isoutofbounds, &if_isinbounds);
+
+  a->Bind(&if_isinbounds);
+  {
+    var_result.Bind(value);
+    a->Goto(&out);
+  }
+
+  a->Bind(&if_isoutofbounds);
+  {
+    Node* const zero = a->SmiConstant(Smi::FromInt(0));
+    var_result.Bind(a->Select(a->SmiLessThan(value, zero), zero, limit));
+    a->Goto(&out);
+  }
+
+  a->Bind(&out);
+  return var_result.value();
+}
+
+}  // namespace
+
+// ES6 section 21.1.3.19 String.prototype.substring ( start, end )
+void Builtins::Generate_StringPrototypeSubstring(CodeStubAssembler* a) {
+  typedef CodeStubAssembler::Label Label;
+  typedef compiler::Node Node;
+  typedef CodeStubAssembler::Variable Variable;
+
+  Label out(a);
+
+  Variable var_start(a, MachineRepresentation::kTagged);
+  Variable var_end(a, MachineRepresentation::kTagged);
+
+  Node* const receiver = a->Parameter(0);
+  Node* const start = a->Parameter(1);
+  Node* const end = a->Parameter(2);
+  Node* const context = a->Parameter(5);
+
+  // Check that {receiver} is coercible to Object and convert it to a String.
+  Node* const string =
+      a->ToThisString(context, receiver, "String.prototype.charCodeAt");
+
+  Node* const length = a->LoadStringLength(string);
+  Node* const zero = a->SmiConstant(Smi::FromInt(0));
+
+  // Conversion and bounds-checks for {start}.
+  {
+    Node* const start_int =
+        a->ToInteger(context, start, CodeStubAssembler::kTruncateMinusZero);
+    var_start.Bind(EnsureSmiBetweenZeroAnd(a, start_int, length));
+  }
+
+  // Conversion and bounds-checks for {end}.
+  {
+    var_end.Bind(length);
+    a->GotoIf(a->WordEqual(end, a->UndefinedConstant()), &out);
+
+    Node* const end_int =
+        a->ToInteger(context, end, CodeStubAssembler::kTruncateMinusZero);
+    var_end.Bind(EnsureSmiBetweenZeroAnd(a, end_int, length));
+
+    Label if_endislessthanstart(a);
+    a->Branch(a->SmiLessThan(var_end.value(), var_start.value()),
+              &if_endislessthanstart, &out);
+
+    a->Bind(&if_endislessthanstart);
+    {
+      Node* const tmp = var_end.value();
+      var_end.Bind(var_start.value());
+      var_start.Bind(tmp);
+      a->Goto(&out);
+    }
+  }
+
+  a->Bind(&out);
+  {
+    Node* result =
+        a->SubString(context, string, var_start.value(), var_end.value());
+    a->Return(result);
+  }
+}
+
 // ES6 section 21.1.3.25 String.prototype.toString ()
 void Builtins::Generate_StringPrototypeToString(CodeStubAssembler* assembler) {
   typedef compiler::Node Node;
 
   Node* receiver = assembler->Parameter(0);
   Node* context = assembler->Parameter(3);
 
   Node* result = assembler->ToThisValue(
       context, receiver, PrimitiveType::kString, "String.prototype.toString");
   assembler->Return(result);
@@ skipping 81 matching lines @@
   }
 
   iterator->set_string(isolate->heap()->empty_string());
 
   return *isolate->factory()->NewJSIteratorResult(
       isolate->factory()->undefined_value(), true);
 }
 
 }  // namespace internal
 }  // namespace v8