MIPS: Avoid embedding x86 NaN constant in MacroAssembler code when snapshot is created.

src/mips/macro-assembler-mips.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 3421 matching lines @@
   jmp(&done);
 
   bind(&maybe_nan);
   // Could be NaN or Infinity. If fraction is not zero, it's NaN, otherwise
   // it's an Infinity, and the non-NaN code path applies.
   Branch(&is_nan, gt, exponent_reg, Operand(scratch1));
   lw(mantissa_reg, FieldMemOperand(value_reg, HeapNumber::kMantissaOffset));
   Branch(&have_double_value, eq, mantissa_reg, Operand(zero_reg));
   bind(&is_nan);
   // Load canonical NaN for storing into the double array.
-  uint64_t nan_int64 = BitCast<uint64_t>(
-      FixedDoubleArray::canonical_not_the_hole_nan_as_double());
-  li(mantissa_reg, Operand(static_cast<uint32_t>(nan_int64)));
-  li(exponent_reg, Operand(static_cast<uint32_t>(nan_int64 >> 32)));
+  LoadRoot(at, Heap::kNanValueRootIndex);
+  lw(mantissa_reg, FieldMemOperand(at, HeapNumber::kValueOffset));
+  lw(exponent_reg, FieldMemOperand(at, HeapNumber::kValueOffset + 4));
   jmp(&have_double_value);
 
   bind(&smi_value);
   Addu(scratch1, elements_reg,
       Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag -
               elements_offset));
   sll(scratch2, key_reg, kDoubleSizeLog2 - kSmiTagSize);
   Addu(scratch1, scratch1, scratch2);
   // scratch1 is now effective address of the double element
 
@@ skipping 2295 matching lines @@
        opcode == BGTZL);
   opcode = (cond == eq) ? BEQ : BNE;
   instr = (instr & ~kOpcodeMask) | opcode;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS