On 01/04/2010 12:07 PM, Jakub Jelinek wrote: > On Mon, Jan 04, 2010 at 12:18:50PM +0100, Steven Bosscher wrote: >>On Mon, Jan 4, 2010 at 12:02 PM, Andrew Haley <a...@redhat.com> 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 > > That's unrelated. PR22141 is about (lack of) merging of adjacent stores of > constant values into memory, but there are no memory stores involved here, > everything is in registers, so PR22141 patch will make zero difference here. > > 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? Andrew.
