Re: GCC 3.3.1 -O2 problem with sqrt.c

[Sanjiv Kumar Gupta <sanjiv dot gupta at oracle dot com>]

Ian Lance Taylor wrote:

> Sanjiv Kumar Gupta <skgnu@yahoo.com> writes:
>
>
> > I am using gcc 3.3.1 release as my port, and looks
> > like I have hit a problem with greg.
>
>
> You neglected to mention what target you are using.
Ian, the port is for a 32-bit RISC and not complete yet,
hence still not contributed.
This probably makes difficult for you to suggest any
fix, but I still asked in case I could get any pointers
for investigation.

> > I couldn't understand why the insns 620 and 621 are
> > being generated here as DI moves.
>
>
> I'm not sure specifically why it got a DI move here, but it doesn't
> look wrong.  It's treating the struct named parts as DImode.
>
>
> > This is creating problem since insn 621 gets splitted
> > after reload into two SI moves,i.e. @(r21, -8) and
> > @(r21, -4).
> > This renders insns 619 as dead and hence insns 618 and
> > insn 429 as dead, which are eliminated by flow2.
>
>
> It does look rather suspicious, but it's hard to know whether it is
> wrong without seeing the value in r1.
r1 looks unrelated to struct members, and is being used by the
ifcvt pass to expand some comparison insns.


> Does the behaviour change if you use -fno-strict-aliasing?  (I can't
> remember what the default was in 3.3.1).
>
> Ian
The behaviour doesn't changes with -fno-strict-aliasing or 
-fstrict-aliasing.

Thanks
Sanjiv