Joe Buck <[EMAIL PROTECTED]> writes: > On Fri, Feb 23, 2007 at 11:09:29AM -0500, Vladimir N. Makarov wrote: > > Yes, that is the current state of 4.1 and 4.2 branches (as of > > yesterday). I don't think we will see a change with the reverted > > alaising patches for itanium because conservative aliasing most probably > > will be compensated by itanium hardware (itanium speculation insn > > support was added for 4.2). > > Perhaps I'm missing something obvious, but often conservative aliasing > results in reading lots of extra data from memory. How can speculation > compensate for that? It seems that the best you can do is reduce the > penalty, if you can do something in parallel with the extra I/O.
On an in-order processor, the biggest effect of conservative aliasing is not so much extra memory reads as it is poor scheduling of existing memory reads. And better speculation can improve scheduling in general. Ian
