https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77359
--- Comment #13 from Dominik Vogt <vogt at linux dot vnet.ibm.com> --- > What do you mean by size of a stack slot? On s390, if we have one "int" variables on the stack, this uses a "slot" 4 bytes. The stack pointer maintains an 8 byte alignmet though, i.e. SP is changec by 8. If we have two "int" on the stack, they use a 4 byte slot each, and the SP is still changed by just 8. The 4 bytes is what the s390 Abi calls a stack "slot" which is the minimum allocation unit for variables on the stack, i.e. whatever a variable needs is rouded up to a multiple of 4. When this is done, the final sum of needed stack space (including the dynamic stack area) is rounded up to STACK_BOUNDARY. Actually I don't know if any other target has something similar.