CheckBothNonNegativeSmi 1363 src/x64/macro-assembler-x64.cc   Condition both_smi = CheckBothNonNegativeSmi(src1, src2);
CheckBothNonNegativeSmi  462 src/x64/macro-assembler-x64.h   Condition CheckBothNonNegativeSmi(Register first, Register second);