[M3devel] bit field operations for insert/extract

[Tony Hosking]

Are they wrong?  Seems strange that they worked previously!

On Nov 23, 2010, at 1:46 PM, Jay K wrote:

> None yet. But notice the endian checks around the insert_mn or extract_mn uses in cg.m3.
> The change would be to remove those.
> 
>  - Jay
> 
> 
> Subject: Re: [M3devel] bit field operations for insert/extract
> From: hosking at cs.purdue.edu
> Date: Tue, 23 Nov 2010 09:37:00 -0500
> CC: m3devel at elegosoft.com
> To: jay.krell at cornell.edu
> 
> Refresh my memory.  What m3front change did you make?
> 
> 
> On Nov 23, 2010, at 3:33 AM, Jay K wrote:
> 
> Tony, I'm going to try again to use bitfield operations for extract_mn.
> And insert_mn.
> I think I know what went wrong before for extract_mn: just remove the endian check in m3front.
> But I'm going to be sure test p240 covers it well.
> 
> The easy part, duh, your original extract_mn was correct I think, just, again, missing the m3front change.
> 
> Insert_mn is less obvious.
> I started writing it... bitfield_ref..modify_expr...uh, seems suspicious, to be modifying an existing value.
> 
> I guess it's more like, that, but with a temp that starts with the full value of x:
>  create temp
>  modify(temp, x)
>  modify(bitfield_ref(temp, count, offset), y);
>  m3_load(temp) 
> 
> ?
> 
> I'll try something like that.
> It seems unfortunate.
> Maybe we can know if x is already a value and not a variable?
> 
> 
>  - Jay
> 
> 

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