This sounds like a dumb question I know. However the following code
snippet results in many more machine instructions under 4.4.2 than under
2.9.5 (I am running a cygwin->PowerPC cross):
typedef unsigned int U32;
typedef union
{
U32 R;
struct
{
U32 BF1:2;
U32 :8;
> >> Is there any way to improve this behaviour? I have been using 2.9.5
> very
> >> successfully for years and am now looking at 4.4.2, but have many
> such
> >> examples in my code (for clarity of commenting and maintainability).
> >
> > This is very strange. On x86_64, gcc 4.4.1 generates
> >
>
> On Mon, Jan 04, 2010 at 12:18:50PM +0100, Steven Bosscher wrote:
> > > This optimization is done by the first RTL cse pass. I can't
> understand
> > > why it's not being done for your target. I guess this will need a
> > > powerpc expert.
> >
> > Known bug, see http://gcc.gnu.org/PR22141
>
> T
>>> Yabbut, how come RTL cse can handle it in x86_64, but PPC not?
>>
>> Probably because the RTL on x86_64 uses and's and ior's, but PPC uses
>> set's of zero_extract's (insvsi).
>
> Aha! Yes, that'll probably be it. It should be easy to fix cse to
> recognize those too.
>
> Andrew
I'm not fam
>>> Aha! Yes, that'll probably be it. It should be easy to fix cse to
>>> recognize those too.
>> I'm not familiar with the gcc source yet, but just in case I get the
>> time to look at this, could anyone give me a file/line ref to dive
>> into and examine?
> Would you believe cse.c? :-)
Ha!
