On Thu, 17 Oct 2013 22:40:32 +0800 Jiang Liu <[email protected]> wrote:
> >>> You could make the code more concise by limiting your patching ability to > >>> branch immediates. Then a nop is simply a branch to the next instruction > >>> (I > >>> doubt any modern CPUs will choke on this, whereas the architecture > >>> requires > >>> a NOP to take time). > >> I guess a NOP should be more effecient than a "B #4" on real CPUs:) > > > > Well, I was actually questioning that. A NOP *has* to take time (the > > architecture prevents implementations from discaring it) whereas a static, > > unconditional branch will likely be discarded early on by CPUs with even > > simple branch prediction logic. > I naively thought "NOP" is cheaper than a "B" :( > Will use a "B #1" to replace "NOP". > Really?? What's the purpose of a NOP then? It seems to me that an architecture is broken if a NOP is slower than a static branch. -- Steve -- 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/
