On Fri, Jun 3, 2016 at 3:51 AM, Wilco Dijkstra <wilco.dijks...@arm.com> wrote: > Increase loop alignment on Cortex cores to 8 and set function alignment to > 16. This makes things consistent across big.LITTLE cores, improves > performance of benchmarks with tight loops and reduces performance variations > due to small changes in code layout. It looks almost all AArch64 cores agree > on alignment of 16 for function, and 8 for loops and branches, so we should > change -mcpu=generic as well if there is no disagreement - feedback welcome.
This is actually might be better for ThunderX than the current set of values for ThunderX. I have tried 16 alignment for functions to see if it is better but it should not hurt ThunderX that much as we have a 128 byte cache line anyways. Thanks, Andrew > > OK for commit? > > ChangeLog: > > 2016-05-03 Wilco Dijkstra <wdijk...@arm.com> > > * gcc/config/aarch64/aarch64.c (cortexa53_tunings): > Increase loop alignment to 8. Set function alignment to 16. > (cortexa35_tunings): Likewise. > (cortexa57_tunings): Increase loop alignment to 8. > (cortexa72_tunings): Likewise. > > --- > > diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c > index > 12e5017a6d4b0ab15dcf932014980fdbd1a598ee..6ea10a187a1f895a399515b8cd0da0be63be827a > 100644 > --- a/gcc/config/aarch64/aarch64.c > +++ b/gcc/config/aarch64/aarch64.c > @@ -424,9 +424,9 @@ static const struct tune_params cortexa35_tunings = > 1, /* issue_rate */ > (AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD > | AARCH64_FUSE_MOVK_MOVK | AARCH64_FUSE_ADRP_LDR), /* fusible_ops */ > - 8, /* function_align. */ > + 16, /* function_align. */ > 8, /* jump_align. */ > - 4, /* loop_align. */ > + 8, /* loop_align. */ > 2, /* int_reassoc_width. */ > 4, /* fp_reassoc_width. */ > 1, /* vec_reassoc_width. */ > @@ -449,9 +449,9 @@ static const struct tune_params cortexa53_tunings = > 2, /* issue_rate */ > (AARCH64_FUSE_AES_AESMC | AARCH64_FUSE_MOV_MOVK | AARCH64_FUSE_ADRP_ADD > | AARCH64_FUSE_MOVK_MOVK | AARCH64_FUSE_ADRP_LDR), /* fusible_ops */ > - 8, /* function_align. */ > + 16, /* function_align. */ > 8, /* jump_align. */ > - 4, /* loop_align. */ > + 8, /* loop_align. */ > 2, /* int_reassoc_width. */ > 4, /* fp_reassoc_width. */ > 1, /* vec_reassoc_width. */ > @@ -476,7 +476,7 @@ static const struct tune_params cortexa57_tunings = > | AARCH64_FUSE_MOVK_MOVK), /* fusible_ops */ > 16, /* function_align. */ > 8, /* jump_align. */ > - 4, /* loop_align. */ > + 8, /* loop_align. */ > 2, /* int_reassoc_width. */ > 4, /* fp_reassoc_width. */ > 1, /* vec_reassoc_width. */ > @@ -502,7 +502,7 @@ static const struct tune_params cortexa72_tunings = > | AARCH64_FUSE_MOVK_MOVK), /* fusible_ops */ > 16, /* function_align. */ > 8, /* jump_align. */ > - 4, /* loop_align. */ > + 8, /* loop_align. */ > 2, /* int_reassoc_width. */ > 4, /* fp_reassoc_width. */ > 1, /* vec_reassoc_width. */ >
