[builtins] Create StringToNumber helper.

Move StringToNumber builtin implementation to helper function in
CodeStubAssembler.

BUG=

Review-Url: https://codereview.chromium.org/2293943002
Cr-Commit-Position: refs/heads/master@{#39249}

src/builtins/builtins-conversion.cc

@@ -110,35 +110,13 @@ void Builtins::Generate_NonPrimitiveToPrimitive_String(
 }
 
 void Builtins::Generate_StringToNumber(CodeStubAssembler* assembler) {
-  typedef CodeStubAssembler::Label Label;
   typedef compiler::Node Node;
   typedef TypeConversionDescriptor Descriptor;
 
   Node* input = assembler->Parameter(Descriptor::kArgument);
   Node* context = assembler->Parameter(Descriptor::kContext);
 
-  Label runtime(assembler);
-
-  // Check if string has a cached array index.
-  Node* hash = assembler->LoadNameHashField(input);
-  Node* bit = assembler->Word32And(
-      hash, assembler->Int32Constant(String::kContainsCachedArrayIndexMask));
-  assembler->GotoIf(assembler->Word32NotEqual(bit, assembler->Int32Constant(0)),
-                    &runtime);
-
-  assembler->Return(assembler->SmiTag(
-      assembler->BitFieldDecode<String::ArrayIndexValueBits>(hash)));
-
-  assembler->Bind(&runtime);
-  {
-    // Note: We cannot tail call to the runtime here, as js-to-wasm
-    // trampolines also use this code currently, and they declare all
-    // outgoing parameters as untagged, while we would push a tagged
-    // object here.
-    Node* result =
-        assembler->CallRuntime(Runtime::kStringToNumber, context, input);
-    assembler->Return(result);
-  }
+  assembler->Return(assembler->StringToNumber(context, input));
 }
 
 // ES6 section 7.1.3 ToNumber ( argument )
@@ -183,9 +161,7 @@ void Builtins::Generate_NonNumberToNumber(CodeStubAssembler* assembler) {
     assembler->Bind(&if_inputisstring);
     {
       // The {input} is a String, use the fast stub to convert it to a Number.
-      // TODO(bmeurer): Consider inlining the StringToNumber logic here.
-      Callable callable = CodeFactory::StringToNumber(assembler->isolate());
-      assembler->TailCallStub(callable, context, input);
+      assembler->Return(assembler->StringToNumber(context, input));
     }
 
     assembler->Bind(&if_inputisoddball);

src/code-stub-assembler.cc

@@ -2215,6 +2215,31 @@ Node* CodeStubAssembler::StringFromCharCode(Node* code) {
   return var_result.value();
 }
 
+Node* CodeStubAssembler::StringToNumber(Node* context, Node* input) {
+  Label runtime(this, Label::kDeferred);
+  Label end(this);
+
+  Variable var_result(this, MachineRepresentation::kTagged);
+
+  // Check if string has a cached array index.
+  Node* hash = LoadNameHashField(input);
+  Node* bit =
+      Word32And(hash, Int32Constant(String::kContainsCachedArrayIndexMask));
+  GotoIf(Word32NotEqual(bit, Int32Constant(0)), &runtime);
+
+  var_result.Bind(SmiTag(BitFieldDecode<String::ArrayIndexValueBits>(hash)));
+  Goto(&end);
+
+  Bind(&runtime);
+  {
+    var_result.Bind(CallRuntime(Runtime::kStringToNumber, context, input));
+    Goto(&end);
+  }
+
+  Bind(&end);
+  return var_result.value();
+}
+
 Node* CodeStubAssembler::BitFieldDecode(Node* word32, uint32_t shift,
                                         uint32_t mask) {
   return Word32Shr(Word32And(word32, Int32Constant(mask)),

src/code-stub-assembler.h

@@ -355,6 +355,11 @@ class CodeStubAssembler : public compiler::CodeAssembler {
   // Return the single character string with only {code}.
   compiler::Node* StringFromCharCode(compiler::Node* code);
 
+  // Type conversion helpers.
+  // Convert a String to a Number.
+  compiler::Node* StringToNumber(compiler::Node* context,
+                                 compiler::Node* input);
+
   // Returns a node that is true if the given bit is set in |word32|.
   template <typename T>
   compiler::Node* BitFieldDecode(compiler::Node* word32) {