x64: Fix safepoint register index calculation.

src/x64/assembler-x64.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 91 matching lines @@
     return kAllocationIndexByRegisterCode[reg.code()];
   }
 
   static Register FromAllocationIndex(int index) {
     ASSERT(index >= 0 && index < kNumAllocatableRegisters);
     Register result = { kRegisterCodeByAllocationIndex[index] };
     return result;
   }
 
   static int ToRspIndexForPushAll(Register reg) {
-    return kRspIndexForPushAllByRegisterCode[reg.code()];
+    // TODO(ager): Refactor this so we can use the right constants for
+    // this computation. Move it to the macro assembler as on ARM.
+    return kRspIndexForPushAllByRegisterCode[reg.code()] + 5;
   }
 
   static const char* AllocationIndexToString(int index) {
     ASSERT(index >= 0 && index < kNumAllocatableRegisters);
     const char* const names[] = {
       "rax",
       "rbx",
       "rdx",
       "rcx",
       "rdi",
@@ skipping 1455 matching lines @@
  private:
   Assembler* assembler_;
 #ifdef DEBUG
   int space_before_;
 #endif
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_H_