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Re: [PATCH] __builtin_frame_address(0) doesn't work without the frame pointer
- From: Denis Zaitsev <zzz at cd-club dot ru>
- To: gcc at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Cc: Richard Earnshaw <rearnsha at arm dot com>, Richard Henderson <rth at redhat dot com>,David Edelsohn <dje at watson dot ibm dot com>
- Date: Wed, 17 Jul 2002 07:23:23 +0600
- Subject: Re: [PATCH] __builtin_frame_address(0) doesn't work without the frame pointer
- References: <20020712005110.A21602@natasha.zzz.zzz> <200207150911.KAA04192@cam-mail2.cambridge.arm.com>
On Mon, Jul 15, 2002 at 10:11:06AM +0100, Richard Earnshaw wrote:
> > On Wed, Jul 10, 2002 at 03:56:21PM +0100, Richard Earnshaw wrote:
> > > > On Tue, Jul 09, 2002 at 06:11:17PM +0100, Richard Earnshaw wrote:
> > > > > ARM certainly does. But that has special code to copy the return address
> > > > > for frame 0 into a pseudo if the return address is needed.
> > > >
> > > > We're talking about __builtin_frame_address, not
> > > > __builtin_return_address.
> > > >
> > >
> > > Ooops. Then the ARM is definitely a candidate, since it has a variable
> > > offset between frame_pointer_rtx and hard_frame_pointer_rtx which depends
> > > on the number of registers that require saving.
> > >
> >
> > Yes, ARM seems to be a subject... BTW, why it was choosed for ARM
> > such a stack layout, that the soft frame pointer points into the
> > middle of what usually the stack frame is?
>
> GCC's model of the frame pointer points to the bottom of the stack after
> the registers have been pushed, but before the stack is adjusted for local
> variables. The ARM APCS model of the frame pointer points to the top of
> the saved register area (this is normally four less than the stack-pointer
> address at the point when control reaches the called function).
The comment at the line 7957 of 3.1/gcc/config/arm.c shows something
not exactly that... Why?