On Mon, 2007-03-19 at 11:38 -0700, Linus Torvalds wrote: > > On Mon, 19 Mar 2007, Eric W. Biederman wrote: > > > > True. You can use all of the call clobbered registers. > > Quite often, the biggest single win of inlining is not so much the code > size (although if done right, that will be smaller too), but the fact that > inlining DOES NOT CLOBBER AS MANY REGISTERS!
Thanks Linus. *This* was the reason that the current hand-coded calls only clobber % eax. It was a compromise between native (no clobbers) and others (might need a reg). Now, since we decided to allow paravirt_ops operations to be normal C (ie. the patching is optional and done late), we actually push and pop % ecx and %edx. This makes the call site 10 bytes long, which is a nice size for patching anyway (enough for a movl $0, <addr>, a-la lguest's cli, or movw $0, %gs:<addr> if we supported SMP). The current 6 paravirt ops which are patched cover the vast majority of calls (until the Xen patches, then we need ~4 more?). Jeremy chose to expand patching to cover *all* paravirt ops, rather than just the new hot ones, and that's where we tipped over the ugliness threshold. Cheers, Rusty. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
