Re: Unsaved register?

[Geoff Keating <geoffk at geoffk dot org>]

> Date: Tue, 29 May 2001 16:21:45 -0700 (PDT)
> From: Erik Walthinsen <omega@temple-baptist.com>
> cc: <gcc-bugs@gcc.gnu.org>
> 
> On 29 May 2001, Geoff Keating wrote:
> 
> > Sure.  Your inline asm clobbers various registers by making the
> > function call, and you haven't mentioned them.
> I thought that a function call was implicitely supposed to restore all the
> state it clobbers?  It's a full C function, no asm at all.  How is the
> calling code supposed to know which registers are going to be clobbered?

There is an ABI that specifies what registers a call may clobber.

> I haven't seen anything in the docs about describing to gcc what registers
> a call might clobber, how does one do that?

GCC doesn't know it's a call, all it knows is that it is some
assembler.  You explain the clobbers just as for any other chunk of assembler.

-- 
- Geoffrey Keating <geoffk@geoffk.org>