X64: Added register holding Smi::FromInt(1).

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 882ee652960e2c4dac8b1c9af6c47ef6c20e70e3..a256ab82bd4a57a413c5f5176bfe9bb251bcc2a2 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -47,8 +47,11 @@ enum AllocationFlags {
 // Default scratch register used by MacroAssembler (and other code that needs
 // a spare register). The register isn't callee save, and not used by the
 // function calling convention.
-static const Register kScratchRegister = { 10 };  // r10.
-static const Register kRootRegister = { 13 };     // r13
+static const Register kScratchRegister = { 10 };      // r10.
+static const Register kSmiConstantRegister = { 15 };  // r15 (callee save).
+static const Register kRootRegister = { 13 };         // r13 (callee save).
+// Value of smi in kSmiConstantRegister.
+static const int kSmiConstantRegisterValue = 1;
 
 // Convenience for platform-independent signatures.
 typedef Operand MemOperand;
@@ -202,6 +205,12 @@ class MacroAssembler: public Assembler {
   // ---------------------------------------------------------------------------
   // Smi tagging, untagging and operations on tagged smis.
 
+  void InitializeSmiConstantRegister() {
+    movq(kSmiConstantRegister,
+         reinterpret_cast<uint64_t>(Smi::FromInt(kSmiConstantRegisterValue)),
+         RelocInfo::NONE);
+  }
+
   // Conversions between tagged smi values and non-tagged integer values.
 
   // Tag an integer value. The result must be known to be a valid smi value.
@@ -469,11 +478,12 @@ class MacroAssembler: public Assembler {
 
   // Basic Smi operations.
   void Move(Register dst, Smi* source) {
-    Set(dst, reinterpret_cast<int64_t>(source));
+    LoadSmiConstant(dst, source);
   }
 
   void Move(const Operand& dst, Smi* source) {
-    Set(dst, reinterpret_cast<int64_t>(source));
+    Register constant = GetSmiConstant(source);
+    movq(dst, constant);
   }
 
   void Push(Smi* smi);
@@ -820,6 +830,14 @@ class MacroAssembler: public Assembler {
  private:
   bool generating_stub_;
   bool allow_stub_calls_;
+
+  // Returns a register holding the smi value. The register MUST NOT be
+  // modified. It may be the "smi 1 constant" register.
+  Register GetSmiConstant(Smi* value);
+
+  // Moves the smi value to the destination register.
+  void LoadSmiConstant(Register dst, Smi* value);
+
   // This handle will be patched with the code object on installation.
   Handle<Object> code_object_;