PowerPC : GCC2 optimises better than GCC4???

[Andrew Haley]

On 01/04/2010 04:17 PM, Nathan Froyd wrote:
> On Mon, Jan 04, 2010 at 04:08:17PM +0000, Andrew Haley wrote:
>> On 01/04/2010 12:07 PM, Jakub Jelinek wrote:
>>> IMHO we really should have some late tree pass that converts adjacent
>>> bitfield operations into integral operations on non-bitfields (likely with
>>> alias set of the whole containing aggregate), as at the RTL level many cases
>>> are simply too many instructions for combine etc. to optimize them properly,
>>> while at the tree level it could be simpler.
>>
>> 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.