> - on ARM, the "y" operand is evaluated mod 32 > - on x86, if y is greater than 31, the result is 0 You mixed them up, didn't you ? AFAIK, ARM does set all

> - on ARM, the "y" operand is evaluated mod 32 > - on x86, if y is greater than 31, the result is 0 You mixed them up, didn't you ? AFAIK, ARM does set all bits to 0 if the shift if greater than 31, but it only uses the lowest byte of the shift amount register, so it feels like a mod 256. x86[^1] does mask the lower 5 bits of the shift amount, so it feels like a mod 32. And the amount can only be 8 bits, so a 32-bit C variable must be truncated somehow. [1] except on 8086, there is no mask there, so no modulo.