On Wed, Jul 1, 2020 at 8:40 PM <jiejie_r...@c-sky.com> wrote: > GCC seems to overlap register bewteen DEST and SOURCE in different > machine mode, > Is there any target hooks to control this feature ? > I use <Constraint Modifier> ‘&’ to forbid register allocator to > overlap bewteen DEST and SOURCE, > but there are some redundancy instructions in the result code :(
& is the correct solution in general. Presumably this is about your draft v0.7.1 vector port. This port uses an unspec in every pattern. This limits the compiler's ability to optimize code. You might get better results if you eliminated as many of the unspecs as you can. You might want to check TARGET_MODES_TIEABLE_P though this is mostly about casts and moves not register allocation. Jim
