Re: patch for printing 64-bit values in i386 registers; STABS format

[Andrew Cagney <ac131313 at redhat dot com>]

>    Date: Fri, 25 Apr 2003 23:32:47 -0400
>    From: Andrew Cagney <ac131313 at redhat dot com>
>
>    > I'm afraid I don't understand, and I still don't see your reasoning
>    > against this approach.
>
>    It isn't necessary, just like register convertible and register 
>    raw/virtual size; .... that go before it, also were not necessary.  And 
>    now all these years later, GDB is still yet to expunge.
>
> I still don't see how you can get rid of the register convertible
> stuff.  On the i386 I still need it for variables stuffed into the
> floating point registers.

That case is fine.  A while ago I split the mechanism in half:

- given a single FP register convert the type into its true form
- the MIPS jungle of combining sub-parts and adjacent FP and integer 
register values

>    Until someone does the right think - add support for values scattered 
>    across registers and memory - hacks should be confined to architecture 
>    specific code.
>
> But even if someone does add support for values scattered across
> multiple registers and/or memory, we still need the architecture
> method I proposed.  There simply is too much debugging info out there
> that can't express values being scattered across multiple registers.

The stabs reader will need to be modified so that it generates a proper 
location description.  Note that it is STABS centric.  dwarf2 doesn't 
need that mechanism since (presumably) GCC is generating the correct 
info (....).

> And I don't think the hack you proposed is a good idea.  I think it's
> better to add a new architecture method with a clear purpose than
> abuse an existing mechanism for something that it wasn't quite
> intended for.  Even if the architecture method in question would only
> be used by a single target.

This is one of the intended purposes of this mechanism, and as I 
indicated, is needed by MIPS.  Being able to project an arbitrary [debug 
info] view of the registers onto the raw register buffer.

BTW, what happens when there is an attempt to write a long long value? 
GDB again assumes that it can write to contigious registers - the reason 
why REGISTER_BYTE can't be killed.

Andrew