> Ignoring what the ISO C language spec says, are there any modern hardware platforms (say: ARM64 and X86-64) that do not use two's complement to implement sign

> Ignoring what the ISO C language spec says, are there any modern hardware platforms (say: ARM64 and X86-64) that do not use two's complement to implement signed integers? This is not how compilers work. Optimization happens based on language semantics, not on what platforms do.