On Fri, Nov 14, 2014 at 2:35 AM, James Greenhalgh <james.greenha...@arm.com> wrote: > > Hi, > > We currently do not set any interesting default values for jump and function > alignment in AArch64. I've made the formula for these values derive from > the issue rate of the processor as so: > > jumps: 4 * processor issue-rate (rounded down to nearest power of two) > functions: 4 * processor issue-rate (rounded up to nearest power of two) > > This is sensible for the ARMv8-a implementations I tested on. An > alternative patch would make these values new fields in the tuning > tables.
I had submitted an alternative patch a few hours ago which allows the tuning structure say what alignment is wanted for all three: https://gcc.gnu.org/ml/gcc-patches/2014-11/msg01615.html > > This happens to work well for some benchmarks and doesn't harm others. > The benefit swings depending on the existing alignment and the knock-on > effects. > > Bootstrapped on aarch64-none-linux-gnu with no issues. > > Does anyone have any thoughts or preferences as to how we set these > values in future? If not, OK For trunk? Also I notice you don't align loops, was that an oversight or just you did not think it was needed? Thanks, Andrew > > Thanks, > James > > --- > 2014-11-14 James Greenhalgh <james.greenha...@arm.com> > > * config/aarch64/aarch64.c (aarch64_override_options): Set default > alignments for functions and jumps.
