[PING] PPC - Printing Decimal 128 types out of registers

[Luis Machado <luisgpm at linux dot vnet dot ibm dot com>]

Hi,

I'm looking forward to refresh this patch, would anyone have comments on
it? It's been a while since i first submitted this one.

Best regards,

On Mon, 2007-11-26 at 19:40 -0200, Luis Machado wrote:
> Hi there,
> 
> Did anyone have a chance to go through this one?
> 
> Regards,
> Luis
> 
> On Wed, 2007-11-07 at 16:33 -0200, Luis Machado wrote:
> > Hi folks,
> > 
> > I'm continuing the work to enhance DFP type support on GDB. DFP types
> > are nativelly supported on the Power6 processor, thus they are stored in
> > registers as so. This patch handles the printing and setting of
> > Decimal128 types directly out of/in the registers.
> > 
> > A Decimal128 type is stored using pairs of Floating Point registers, and
> > it always starts in an even-numbered register. So, we could, for
> > example, have a Decimal128 var taking up FPR0-FPR1, FPR10-FPR11, but
> > never FPR1-FPR2 or FPR23-24.
> > 
> > Right now GDB isn't able to print those vars as it doesn't know they
> > take up more than one register.
> > 
> > The idea to overcome this was to create a new set of 16 Decimal128-typed
> > pseudo-registers called DL (Standing for "D"ecimal "L"ong Double) that
> > would represent all 16 pairs of Floating Point Registers.. By using a
> > pseudo-register mechanism, we're able to force the DL/FPR registers to
> > map directly into the FPR/DL registers.
> > 
> > Benefits of this change include:
> > 
> > * Better printing support for Decimal128 types. We just print the
> > register as is. No need to include casting tricks and arrays to print
> > that value.
> > 
> > * Straightforward way of setting Decimal128 values directly in the
> > registers. We just "set $dl0=1.23dl", for example, and it's
> > automatically set.
> > 
> > * Overview of the state of 16 Decimal128 registers using the "info reg
> > all" command.
> > 
> > 
> > Supporting the patch there is also a number of other modifications, as
> > listed:
> > 
> > * DFP types are now global since they were included as predefined types
> > in the "target-descriptions.c" file.
> > 
> > * A simple testcase making sure the registers are working as expected.
> > 
> > * Piece of documentation for the GDB manual.
> > 
> > * Fix to display a 128-bit hex literal representation of Decimal128
> > types (using "info reg").
> > 
> > Also note that this support will be available for both ppc64 and ppc32.
> > 
> > Looking forward to have comments and suggestions for improvements.
> > 
> > Regards,
> > Luis
-- 
Luis Machado
Software Engineer 
IBM Linux Technology Center