Re: [arm] possible bug in G++ 3.4.x

[Vladimir Ivanov <vladitx at nucleusys dot com>]

Hello,

[Richard]:
	Does this mean that GCC-3.4.x won't be fixed?

[Paul]:
	Is this problem present also in CSL-3.4.x branch?

Best regards,
  -- Vladimir

On Tue, 1 Mar 2005, Richard Earnshaw wrote:

> On Mon, 2005-02-28 at 12:51, Vladimir Ivanov wrote:
> > Hello all,
> >
> > While compiling this:
> >  	http://sourceforge.net/projects/raytracer/
> >
> > I think I've spotted a bug in ARM port of G++.
> >
> > The problem is that many method functions tend to save all callee-saved FP
> > registers, while they use few or none of them.
> >
> > Here's a small snippet from "base3d.cpp" file:
> >
> > 00000528 <_ZN6Base3d8rotateV1Ed>:
> >       528:       e1a0c00d        mov     ip, sp
> >       52c:       e92ddff0        stmdb   sp!, {r4, r5, r6, r7, r8, r9, sl, fp, ip, lr, pc}
> >       530:       ed2d420c        sfm     f4, 4, [sp, #-48]!
> >       534:       e24cb004        sub     fp, ip, #4      ; 0x4
> >       538:       e24dd0cc        sub     sp, sp, #204    ; 0xcc
> >       53c:       e59f3288        ldr     r3, [pc, #648]  ; 7cc <.text+0x7cc>
> >       ...
> >
> > Function uses only F0 register, although F4-F7 are saved/restored. This
> > leads to great speed penalty, especially when coprocessors like Crunch
> > have many registers.
> >
> > PowerPC port shows no such problem, so I think it's something in ARM port.
> >
> > Sorry I cannot provide small enough example, C++ is not my area of
> > expertise.
>
> [I tried to reply to this yesterday, but the response has failed to show
> up here.  I suspect it was mailer problems at my end, but if you get
> this twice I apologise.]
>
> I think this is most likely a consequence of SJLJ exceptions.  It should
> be fixed when we move to the EABI unwinding tables.
>
> R.