Implemented one-char cache lookup in generated code.

src/x64/codegen-x64.cc

Index: src/x64/codegen-x64.cc
diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index d2df5a875fe962c57d3d01d7d1f3b5ff806787c6..b7a5de816a6cff7f3826741f35261c8ad23bd866 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -3877,6 +3877,49 @@ void CodeGenerator::GenerateFastCharCodeAt(ZoneList<Expression*>* args) {
 }
 
 
+void CodeGenerator::GenerateCharFromCode(ZoneList<Expression*>* args) {
+  Comment(masm_, "[ GenerateCharFromCode");
+  ASSERT(args->length() == 1);
+
+  Load(args->at(0));
+  frame_->Dup();
+  Result code = frame_->Pop();
+  code.ToRegister();
+  ASSERT(code.is_valid());
+
+  Result temp = allocator()->Allocate();
+  ASSERT(temp.is_valid());
+
+  JumpTarget slow_case;
+  JumpTarget exit;
+
+  // Fast case of Heap::LookupSingleCharacterStringFromCode.
+  Condition is_smi = __ CheckSmi(code.reg());
+  slow_case.Branch(NegateCondition(is_smi), not_taken);
+
+  __ SmiToInteger32(kScratchRegister, code.reg());
+  code.Unuse();
+  __ cmpl(kScratchRegister, Immediate(String::kMaxAsciiCharCode));
+  slow_case.Branch(above, not_taken);
+
+  __ Move(temp.reg(), Factory::single_character_string_cache());
+  __ movq(temp.reg(), Operand(temp.reg(),

[Mads Ager (chromium), 2010/02/26 17:59:06]

FieldOperand to get rid of the "- kHeapObjectTag" in the offset.

[Vitaly Repeshko, 2010/02/26 20:14:48]

Done.

+                              kScratchRegister, times_pointer_size,
+                              FixedArray::kHeaderSize - kHeapObjectTag));
+  __ Cmp(temp.reg(), Factory::undefined_value());

[Mads Ager (chromium), 2010/02/26 17:59:06]

You should use CompareRoot here to use the root array.

[Vitaly Repeshko, 2010/02/26 20:14:48]

Done.

+  slow_case.Branch(equal, not_taken);
+
+  frame_->SetElementAt(0, &temp);
+  exit.Jump();
+
+  slow_case.Bind();
+  Result result = frame_->CallRuntime(Runtime::kCharFromCode, 1);
+  frame_->Push(&result);
+
+  exit.Bind();
+}
+
+
 void CodeGenerator::GenerateIsNonNegativeSmi(ZoneList<Expression*>* args) {
   ASSERT(args->length() == 1);
   Load(args->at(0));