Re: [PATCH] Fix passing/returning of complex data for PowerPC 32-bit

[Luis Machado <lgustavo at codesourcery dot com>]

On 06/27/2014 07:40 PM, Luis Machado wrote:
> On 06/27/2014 11:30 AM, Mark Kettenis wrote:
> > > Date: Thu, 26 Jun 2014 06:54:59 +0100
> > > From: Luis Machado <lgustavo@codesourcery.com>
> > >
> > > The PowerPC 32-bit unified ABI states that there are two ways of passing
> > > and returning complex type data:
> > >
> > > - Pointer, in a register, to a memory area.
> > > - Data in registers.
> > >
> > > The problem is that it is not clear how to detect which variation a
> > > program is using. GDB currently does a bit of both. It uses the first
> > > mechanism for passing parameters and uses both to return data, depending
> > > on the size of the data type. It is a bit messy because GDB is not
> > > handling complex types explicitly.
> > >
> > > Checking the gdb.base/callfuncs.exp testcase for a PowerPC 32-bit
> > > target, with code built with GCC, showed a few failures related to
> > > complex types.
> > >
> > > This patch steers GDB towards what GCC seems to generate for PowerPC
> > > 32-bit and handles complex type passing/return via general registers
> > > (the second option). All failures are gone.
> > >
> > > The problem here is if some other target/compiler is using the other
> > > variation. So, for those that have a PowerPC 32-bit handy, can you
> > > confirm it works reliably? I'm thinking AIX, Darwin or some other eabi
> > > target.
> >
> > AIX uses its own inplementations (rs6000_push_dummy_call and
> > rs6000_return_value).  And we don't support Darwin on PowerPC.
>
> True. That should be a non issue then.
>
> > > Otherwise, does this look reasonable?
> >
> > I agree that the "System V" support code should support the
> > ATR-PASS-COMPLEX-IN-GPRS ABI Attribute.  This is what the Linux ABI
> > uses (it is included in ATR-LINUX) which pretty much is the direct
> > succssor of the System V ABI (which didn't specify anything about
> > complex floating-point support).
> >
> > If somebody really wants to support complex numbers on an embedded
> > system that uses ATR-PASS-COMPLEX-AS-STRUCT, they'll have to implement
> > an osabi sniffer for it and override the appropriate methods.
> >
> > Code generally looks good.  Some nits below.  The comments are a bit
> > elaborate though.  I'd cut them down a bit; see my suggestion below.
>
> I adjusted the patch and compressed the comments according to the
> suggestions.
>
> Thanks!
> Luis

It seems folks are happy with this patch (at least the interested 
parties), so i'll go ahead and commit this one in the following days 
unless i hear something back.

Thanks,
Luis