Re: A86: simple math optimization

To: assembly-86@lists.ticalc.org
Subject: Re: A86: simple math optimization
From: Dan Eble <eble@cis.ohio-state.edu>
Date: Mon, 11 May 1998 21:16:46 -0400 (EDT)
Delivered-To: assembly-86-outgoing@towerguard.unix.edu.sollentuna.se
In-Reply-To: <016a01bd7d34$2babe960$02f4ffd0@matt>
Reply-To: assembly-86@lists.ticalc.org


On Mon, 11 May 1998, Matt2000 wrote:

> Yes. This routine works and has no limits, only 59 cycles. Any
> optimizations?
> 


Why didn't you count the "sla L" instructions?  By my count, it takes 91  
t-states.



>  ; 59 T Cycles
> 
>  ;HL = (16 * d) + e
>  ;      H, L, D, & A registers modified
>  ;       D or E can be from 0..255 no limits
> 
>  xor a    ; 4T  | Clear A and carry flag
>  ld h, a    ; 4T  | Clear H
>  ld l, d    ; 4T  | HL = D
> 
>  sla l
>  rl h    ; 8T  | 16-bit rotation, HL = HL * 2
>  sla l
>  rl h    ; 8T  | * 2
>  sla l
>  rl h    ; 8T  | * 2
>  sla l
>  rl h    ; 8T  | * 2, So HL = HL * 16
> 
>  ld d, a    ; 4T  | Clear D
>  add hl, de   ; 11T | HL = HL + E
> 

--------
Dan Eble (mailto:eble@cis.ohio-state.edu)
         (http://www.cis.ohio-state.edu/~eble)

"Behold, how great a matter a little fire kindleth!" -- James 3:5

References:

Re: A86: simple math optimization

From: "Matt2000" <matt2000@gte.net>