https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85160
--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> --- Author: segher Date: Mon Jul 30 13:18:17 2018 New Revision: 263067 URL: https://gcc.gnu.org/viewcvs?rev=263067&root=gcc&view=rev Log: combine: Allow combining two insns to two insns 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). PR rtl-optimization/85160 * combine.c (is_just_move): New function. (try_combine): Allow combining two instructions into two if neither of the original instructions was a move. Modified: trunk/gcc/ChangeLog trunk/gcc/combine.c
