x64 fast call stack allocation.

calling-only.asm

four_or_less_integer_parameters:

  ; our function to call:
  ; blah(int, int, int, int)

  ; allocate space for the 4 home volatile registers (rcx, rdx, r8 and r9) and aling to 16 bytes.
  sub rsp, 0x28
  
  ; move your argument from left to right into registers
  mov r9d, 0x10
  mov r8d, 0x20
  mov rdx, 0x30
  mov rcx, 0x40
  call blah
  
  ; free up space
  add rsp, 0x28
  
  ; exit sub-routine
  retn
  
  
  
four_or_less_mixed_type_arguments:

  ; our function to call:
  ; blah(int, float, int, int)

  ; still allocate space for 4 home registers (rcx, rdx, r8, r9) and align to 16 bytes
  sub rsp, 0x28
  
  ; move your argument from left to right into registers
  mov r9d, 0x10
  mov r8d, 0x20
  mov xmm1, dword ptr ds:[actual_float_address]
  mov ecx, 0x30
  call blah
  
  ; clean up stack
  add rsp, 0x28
  
  ; exit the sub-routine
  retn
  
five_or_more_integer_arguments:

  ; our function to call:
  ; blah(int, int, int, int, int)

  ; still allocate space for 4 home registers (rcx, rdx, r8, r9), 2 stack arguments and align to 16 bytes.
  sub rsp, 0x38
  
  ; setup stack arguments and register arguments
  mov dword ptr ss:[rsp+0x20], 0x10
  mov r9d, 0x20
  mov r8d, 0x30
  mov rdx, 0x40
  mov rcx, 0x50
  call blah
  
  ; clean up stack
  add rsp, 0x38
  
  ; exit sub-routine
  retn

local-variables-only.asm

two_or_less_variables:
  
  ; allocate space for two QWORDs and another QWORD to align to 16 bytes.
  sub rsp, 0x18
  
  ; write your local variables
  mov qword ptr ss:[rsp], 0x10
  mov qword ptr ss:[rsp+0x8], 0x20
  
  ; free up the allocated space
  add rsp, 0x18
  
  ; exit the sub-routine
  retn
  
 
 four_or_less_variables
 
  ; allocate space for 4 QWORDs and another QWORD to align to 16 bytes.
  sub rsp, 0x28
  
  ; write your local variables
  mov qword ptr ss:[rsp], 0x10
  mov qword ptr ss:[rsp+0x8], 0x20
  mov qword ptr ss:[rsp+0x10], 0x30
  mov qword ptr ss:[rsp+0x18], 0x40
  
  ; free up allocated space
  add rsp, 0x28
  
  ; exit the sub-routine
  retn