Optionally use 31-bits SMI value for 64-bit system

src/x64/debug-x64.cc

 // Copyright 2012 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 109 matching lines @@
     for (int i = 0; i < kNumJSCallerSaved; i++) {
       int r = JSCallerSavedCode(i);
       Register reg = { r };
       ASSERT(!reg.is(kScratchRegister));
       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);
+#if !V8_USE_31_BITS_SMI_VALUE
         __ Integer32ToSmi(reg, reg);
         __ push(reg);
         __ sar(kScratchRegister, Immediate(32));
         __ Integer32ToSmi(kScratchRegister, kScratchRegister);
         __ push(kScratchRegister);
+#else
+        __ shr(reg, Immediate(63));
+        __ shll(reg, Immediate(1));
+        __ push(reg);
+        __ shl(kScratchRegister, Immediate(1));
+        __ push(kScratchRegister);
+#endif
       }
     }
 
 #ifdef DEBUG
     __ RecordComment("// Calling from debug break to runtime - come in - over");
 #endif
     __ Set(rax, 0);  // No arguments (argc == 0).
     __ movq(rbx, ExternalReference::debug_break(masm->isolate()));
 
     CEntryStub ceb(1);
     __ CallStub(&ceb);
 
     // Restore the register values from the expression stack.
     for (int i = kNumJSCallerSaved - 1; i >= 0; i--) {
       int r = JSCallerSavedCode(i);
       Register reg = { r };
       if (FLAG_debug_code) {
         __ Set(reg, kDebugZapValue);
       }
       if ((object_regs & (1 << r)) != 0) {
         __ pop(reg);
       }
       // Reconstruct the 64-bit value from two smis.
       if ((non_object_regs & (1 << r)) != 0) {
         __ pop(kScratchRegister);
+#if !V8_USE_31_BITS_SMI_VALUE
         __ SmiToInteger32(kScratchRegister, kScratchRegister);
         __ shl(kScratchRegister, Immediate(32));
         __ pop(reg);
         __ SmiToInteger32(reg, reg);
         __ or_(reg, kScratchRegister);
+#else
+        __ shr(kScratchRegister, Immediate(1));
+        __ pop(reg);
+        __ shl(reg, Immediate(62));
+        __ or_(reg, kScratchRegister);
+#endif
       }
     }
 
     // Read current padding counter and skip corresponding number of words.
     __ pop(kScratchRegister);
     __ SmiToInteger32(kScratchRegister, kScratchRegister);
     __ lea(rsp, Operand(rsp, kScratchRegister, times_pointer_size, 0));
 
     // Get rid of the internal frame.
   }
@@ skipping 179 matching lines @@
 
 const bool Debug::kFrameDropperSupported = true;
 
 #undef __
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64