On 01/08/11 10:11, Jakub Jelinek wrote: > On Mon, Aug 01, 2011 at 11:44:04AM +0800, Jiangning Liu wrote: >> It's quite necessary to solve the general problem in middle-end rather than >> in back-end. > > That's what we disagree on. All back-ends but ARM are able to handle it > right, why can't ARM too? The ABI rules for stack handling in the epilogues > are simply too diverse and complex to be handled easily in the scheduler.
Because the vast majority of back-ends (ie those without red zones) shouldn't have to deal with this mess. This is something the MI code should be able to work out and deal with itself. Then the compiler will at least generate safe code, rather than randomly moving things about and allowing potentially unsafe writes/reads from beyond the allocated stack region. We should build the compiler defensively, but then allow for more aggressive optimizations to disable the defences when the back-end wants to take on the responsibility. Not the other way around. R.
