Crankshaft support for StringCharFromCode.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index dbbbaa7ebddc03b00ef700fe096aec74aff46e8e..e2f21c8961bb5c43fd665986726fa123fd787544 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2978,6 +2978,56 @@ void LCodeGen::DoDeferredStringCharCodeAt(LStringCharCodeAt* instr) {
 }
 
 
+void LCodeGen::DoStringCharFromCode(LStringCharFromCode* instr) {
+  class DeferredStringCharFromCode: public LDeferredCode {
+   public:
+    DeferredStringCharFromCode(LCodeGen* codegen, LStringCharFromCode* instr)
+        : LDeferredCode(codegen), instr_(instr) { }
+    virtual void Generate() { codegen()->DoDeferredStringCharFromCode(instr_); }
+   private:
+    LStringCharFromCode* instr_;
+  };
+
+  DeferredStringCharFromCode* deferred =
+      new DeferredStringCharFromCode(this, instr);
+
+  ASSERT(instr->hydrogen()->value()->representation().IsInteger32());
+  Register char_code = ToRegister(instr->char_code());
+  Register result = ToRegister(instr->result());
+  ASSERT(!char_code.is(result));
+
+  __ cmpl(char_code, Immediate(String::kMaxAsciiCharCode));
+  __ j(above, deferred->entry());
+  __ LoadRoot(result, Heap::kSingleCharacterStringCacheRootIndex);
+  __ movq(result, FieldOperand(result,
+                               char_code, times_pointer_size,
+                               FixedArray::kHeaderSize));
+  __ CompareRoot(result, Heap::kUndefinedValueRootIndex);
+  __ j(equal, deferred->entry());
+  __ bind(deferred->exit());
+}
+
+
+void LCodeGen::DoDeferredStringCharFromCode(LStringCharFromCode* instr) {
+  Register char_code = ToRegister(instr->char_code());
+  Register result = ToRegister(instr->result());
+
+  // TODO(3095996): Get rid of this. For now, we need to make the
+  // result register contain a valid pointer because it is already
+  // contained in the register pointer map.
+  __ Set(result, 0);
+
+  __ PushSafepointRegisters();
+  __ Integer32ToSmi(char_code, char_code);
+  __ push(char_code);
+  __ CallRuntimeSaveDoubles(Runtime::kCharFromCode);
+  RecordSafepointWithRegisters(
+      instr->pointer_map(), 1, Safepoint::kNoDeoptimizationIndex);
+  __ StoreToSafepointRegisterSlot(result, rax);
+  __ PopSafepointRegisters();
+}
+
+
 void LCodeGen::DoStringLength(LStringLength* instr) {
   Register string = ToRegister(instr->string());
   Register result = ToRegister(instr->result());