Crankshaft support for StringCharFromCode.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 8dd35b6b8394251c79842b7a56e4097d82b5cd5b..5ade3d64a20f4c82ea624f27378dfe206164bcf6 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3098,6 +3098,56 @@ 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));
+
+  __ cmp(char_code, Operand(String::kMaxAsciiCharCode));
+  __ b(hi, deferred->entry());
+  __ LoadRoot(result, Heap::kSingleCharacterStringCacheRootIndex);
+  __ add(result, result, Operand(char_code, LSL, kPointerSizeLog2));
+  __ ldr(result, FieldMemOperand(result, FixedArray::kHeaderSize));
+  __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
+  __ cmp(result, ip);
+  __ b(eq, 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.
+  __ mov(result, Operand(0));
+
+  __ PushSafepointRegisters();
+  __ SmiTag(char_code);
+  __ push(char_code);
+  __ CallRuntimeSaveDoubles(Runtime::kCharFromCode);
+  RecordSafepointWithRegisters(
+      instr->pointer_map(), 1, Safepoint::kNoDeoptimizationIndex);
+  __ StoreToSafepointRegisterSlot(r0, result);
+  __ PopSafepointRegisters();
+}
+
+
 void LCodeGen::DoStringLength(LStringLength* instr) {
   Register string = ToRegister(instr->InputAt(0));
   Register result = ToRegister(instr->result());