Introduce PushInt64AsTwoSmis and PopInt64AsTwoSmis macro instructions for X64

R=danno@chromium.org

Review URL: https://codereview.chromium.org/22348005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16376 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/debug-x64.cc

@@ -123,14 +123,8 @@ static void Generate_DebugBreakCallHelper(MacroAssembler* masm,
       if ((object_regs & (1 << r)) != 0) {
         __ push(reg);
       }
-      // Store the 64-bit value as two smis.
       if ((non_object_regs & (1 << r)) != 0) {
-        __ movq(kScratchRegister, reg);
-        __ Integer32ToSmi(reg, reg);
-        __ push(reg);
-        __ sar(kScratchRegister, Immediate(32));
-        __ Integer32ToSmi(kScratchRegister, kScratchRegister);
-        __ push(kScratchRegister);
+        __ PushInt64AsTwoSmis(reg);
       }
     }
 
@@ -155,12 +149,7 @@ static void Generate_DebugBreakCallHelper(MacroAssembler* masm,
       }
       // Reconstruct the 64-bit value from two smis.
       if ((non_object_regs & (1 << r)) != 0) {
-        __ pop(kScratchRegister);
-        __ SmiToInteger32(kScratchRegister, kScratchRegister);
-        __ shl(kScratchRegister, Immediate(32));
-        __ pop(reg);
-        __ SmiToInteger32(reg, reg);
-        __ or_(reg, kScratchRegister);
+        __ PopInt64AsTwoSmis(reg);
       }
     }
 

src/x64/macro-assembler-x64.cc

@@ -2196,6 +2196,30 @@ void MacroAssembler::AddSmiField(Register dst, const Operand& src) {
 }
 
 
+void MacroAssembler::PushInt64AsTwoSmis(Register src, Register scratch) {
+  movq(scratch, src);
+  // High bits.
+  shr(src, Immediate(64 - kSmiShift));
+  shl(src, Immediate(kSmiShift));
+  push(src);
+  // Low bits.
+  shl(scratch, Immediate(kSmiShift));
+  push(scratch);
+}
+
+
+void MacroAssembler::PopInt64AsTwoSmis(Register dst, Register scratch) {
+  pop(scratch);
+  // Low bits.
+  shr(scratch, Immediate(kSmiShift));
+  pop(dst);
+  shr(dst, Immediate(kSmiShift));
+  // High bits.
+  shl(dst, Immediate(64 - kSmiShift));
+  or_(dst, scratch);
+}
+
+
 void MacroAssembler::JumpIfNotString(Register object,
                                      Register object_map,
                                      Label* not_string,

src/x64/macro-assembler-x64.h

@@ -720,6 +720,14 @@ class MacroAssembler: public Assembler {
   }
 
   void Push(Smi* smi);
+
+  // Save away a 64-bit integer on the stack as two 32-bit integers
+  // masquerading as smis so that the garbage collector skips visiting them.
+  void PushInt64AsTwoSmis(Register src, Register scratch = kScratchRegister);
+  // Reconstruct a 64-bit integer from two 32-bit integers masquerading as
+  // smis on the top of stack.
+  void PopInt64AsTwoSmis(Register dst, Register scratch = kScratchRegister);
+
   void Test(const Operand& dst, Smi* source);