Crankshaft support for StringCharFromCode.

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2989 matching lines @@
       instr->pointer_map(), 2, Safepoint::kNoDeoptimizationIndex);
   if (FLAG_debug_code) {
     __ AbortIfNotSmi(eax);
   }
   __ SmiUntag(eax);
   __ StoreToSafepointRegisterSlot(result, eax);
   __ PopSafepointRegisters();
 }
 
 
+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, String::kMaxAsciiCharCode);
+  __ j(above, deferred->entry());
+  __ Set(result, Immediate(Factory::single_character_string_cache()));
+  __ mov(result, FieldOperand(result,
+                              char_code, times_pointer_size,
+                              FixedArray::kHeaderSize));
+  __ cmp(result, Factory::undefined_value());
+  __ 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, Immediate(0));
+
+  __ PushSafepointRegisters();
+  __ SmiTag(char_code);
+  __ push(char_code);
+  __ CallRuntimeSaveDoubles(Runtime::kCharFromCode);
+  RecordSafepointWithRegisters(
+      instr->pointer_map(), 1, Safepoint::kNoDeoptimizationIndex);

[fschneider, 2011/03/14 11:34:17]

I think it is ok to have no deoptimization index here, but you need to be sure
that we never get a deoptimization when calling the runtime. (e.g. when runtime
code calls JS code which can always cause a forced deopt)

Otherwise it is always safe to assign a lazy deoptimization environment.

[Vitaly Repeshko, 2011/03/14 14:15:50]

Thanks for the explanation! But if this runtime functions re-enters JS, then we
have a more severe problem because we declared that StringFromCharCode has no
visible side effects.

+  __ StoreToSafepointRegisterSlot(result, eax);
+  __ PopSafepointRegisters();
+}
+
+
 void LCodeGen::DoStringLength(LStringLength* instr) {
   Register string = ToRegister(instr->string());
   Register result = ToRegister(instr->result());
   __ mov(result, FieldOperand(string, String::kLengthOffset));
 }
 
 
 void LCodeGen::DoInteger32ToDouble(LInteger32ToDouble* instr) {
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister() || input->IsStackSlot());
@@ skipping 850 matching lines @@
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32