iAPX86 code for ABS (using Microsof

[mcdonald at uxe.cso.uiuc.edu]

>I remember a review of Microsoft's C compiler for MS-DOS that stated it
>produced no-conditional-jump-abs-code. The function to convert an integer
>to a positive integer was performed without a conditional jump (i.e. JS or
>something). I'm very interested in this piece of code, so if someone
>who does have a Microsoft C-compiler could try something like
>  main()
>  { int a,b;
>    a=-10;
>    b=abs(a);
>  }

Here is the result of cl -c -Ox -Fa test.c, excluding the header and trailer:

; a = -10
	mov	WORD PTR [bp-2],-10	;a
; b = abs(a)
	mov	ax,-10
	cwd	
	xor	ax,dx
	sub	ax,dx
	mov	WORD PTR [bp-4],ax	;b

So your review was correct!  I assume that they do this odd thing in
order to not empty instruction prefetch queues????????????????

Doug McDonald