On May 2, 2012, at 2:29 PM, Eric Christopher wrote: > > On May 2, 2012, at 2:23 PM, Eli Friedman <[email protected]> wrote: > >> On Wed, May 2, 2012 at 2:07 PM, Chad Rosier <[email protected]> wrote: >>> The attached patch allows inline assembly to inherit the readnone/readonly >>> function attribute from the caller. This allows the attributes to be >>> retained after function inlining. In turn, CSE is able to do it's magic on >>> inline assembly statements. >>> >>> An orthogonal solution would be to add support for the const keyword for >>> inline assembly (e.g., asm const("mov $0x12345678, %0" : "=r" (ptr)); ). >> >> It's not obvious to me that this is safe... __attribute((const)) means >> that a function doesn't cause expose any side-effects, not that it >> doesn't have any internal state. >> > > Perhaps a way to give a statement an attribute then?
I think this is what I proposed as the orthogonal approach. However, assuming what Eli suggest below is correct, then this is not necessary. We can detect constness. Chad > >> Note that there's another way we can compute readnone for the given >> inline asm: an inline asm can be marked readnone if it doesn't have >> any memory operands, isn't volatile, and doesn't clobber memory. > > In this case it's a read from memory so it'd be readonly... but the point is > good. > > -eric _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
