C OFFSET(i)
C Expands to 4*i, or to the empty string if i is zero
define(`OFFSET', `ifelse($1,0,,eval(4*$1))')

dnl LREG(reg) gives the 8-bit register corresponding to the given 32-bit register.
define(`LREG',`ifelse(
	$1, %eax, %al,
	$1, %ebx, %bl,
	$1, %ecx, %cl,
	$1, %edx, %dl)')dnl

define(`HREG',`ifelse(
	$1, %eax, %ah,
	$1, %ebx, %bh,
	$1, %ecx, %ch,
	$1, %edx, %dh)')dnl