On Tue, Jul 24, 2018 at 05:18:41PM +0000, Segher Boessenkool wrote: > This patch allows combine to combine two insns into two. This helps > in many cases, by reducing instruction path length, and also allowing > further combinations to happen. PR85160 is a typical example of code > that it can improve. > > This patch does not allow such combinations if either of the original > instructions was a simple move instruction. In those cases combining > the two instructions increases register pressure without improving the > code. With this move test register pressure does no longer increase > noticably as far as I can tell. > > (At first I also didn't allow either of the resulting insns to be a > move instruction. But that is actually a very good thing to have, as > should have been obvious). > > Tested for many months; tested on about 30 targets. > > I'll commit this later this week if there are no objections.
Done now, with the testcase at https://gcc.gnu.org/ml/gcc-patches/2018-07/msg01856.html . Segher
