Re: new problems with "-fforce-addr"

[Steve Kargl <sgk at troutmask dot apl dot washington dot edu>]

On Wed, Oct 03, 2007 at 09:55:49AM +0200, Manfred Schwarb wrote:
> Hi,
> 
> In contrary to my mail on September 1, my problem seems still to be present.
> This time in another library, but I encounter the very same symptoms (gfortran of yesterday).
> gfortran -O3 -march=pentium4 -mfpmath=sse -msse3 is OK,
> gfortran -O3 -march=pentium4 -mfpmath=sse -msse3 -fforce-addr produces wrong code.
> 
> Again "-fforce-addr" in combination with "-O1" is OK, and output of -fdump-tree-optimized of the
> broken one is identical to the working one.
> As this is the second time I encounter this, it happens only with some combination of optimization
> and other compilers don't have problems to compile this code, I think it's a real bug in gcc/gfortran.
> 
> If nobody on this list has an idea how to narrow this issue, I will post an mail to gcc@, as perhaps 
> it is not frontend related, but some more general optimization issue.
> 
> Regards,
> Manfred

Given the description

`-fforce-addr'
     Force memory address constants to be copied into registers before
     doing arithmetic on them.
 
Whatever you're seeing is a probably a middle or backend problem.

What does this option buy you?  Faster execution?  Does the
problem occur with -O2 because with my codes the difference
between -O2 and -O3 is in the noise?


-- 
Steve