On Fri, Oct 28, 2011 at 9:48 AM, David Miller <da...@davemloft.net> wrote: > > g++.dg/init/copy7.C makes sure that memcpy() is not emitted with > src and dst equal.
The testcase is bogus and should be removed. See the patch I posted (and the PR). Unfortunately the patch didn't get any review yet. > The fix installed absolutely relies upon a backend implementing > the movmem pattern, and essentially that such a pattern will > always succeed to emit for arbitrary circumstances. No, it doesn't. And you can trigger similar C testcases to fail on x86_64 as well. > However 1) not all platforms implement the pattern, it is not > required, therefore it cannot be relied upon for correct code > generation and 2) even those that implement this pattern have certain > restrictions which could legitimately be triggered and thus cause the > memcpy() with src and dst equal to still be emitted. > > Sparc is currently failing this testcase for reason #1, but it would > be trivial to make minor modifications to the copy7.C test case to get > it to fail on a score of several targets as well (even those that > provide a movmem pattern). > > So we should either install a more complete fix or open the bug back > up. We should remove the testcase. Richard.
