| Message ID | AM5PR0802MB2610174A4992D4C2809BB5C283260@AM5PR0802MB2610.eurprd08.prod.outlook.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Mar 16, 2017 at 10:22 AM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote: > Many supported cores implement fusion of AES instructions. When fusion > happens it can give a significant performance gain. If not, scheduling > fusion candidates next to each other has almost no effect on performance. > Due to the high benefit/low cost it makes sense to enable AES fusion with > -mcpu=generic so that cores that support it always benefit. Any objections? I am ok with this due to our new cores support this and there was no performance lost for ThunderX1. Thanks, Andrew > > Bootstrapped on AArch64, no regressions. > > ChangeLog: > 2017-03-16 Wilco Dijkstra <wdijkstr@arm.com> > > * gcc/config/aarch64/aarch64.c (generic_tunings): Add AES fusion. > > -- > diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c > index 728ce7029f1e2b5161d9f317d10e564dd5a5f472..c8cf7169a5d387de336920b50c83761dc0c96f3a 100644 > --- a/gcc/config/aarch64/aarch64.c > +++ b/gcc/config/aarch64/aarch64.c > @@ -536,7 +536,7 @@ static const struct tune_params generic_tunings = > &generic_approx_modes, > 4, /* memmov_cost */ > 2, /* issue_rate */ > - AARCH64_FUSE_NOTHING, /* fusible_ops */ > + (AARCH64_FUSE_AES_AESMC), /* fusible_ops */ > 8, /* function_align. */ > 8, /* jump_align. */ > 4, /* loop_align. */
On Thu, Mar 16, 2017 at 11:01 AM, Andrew Pinski <apinski@cavium.com> wrote: > On Thu, Mar 16, 2017 at 10:22 AM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote: >> Many supported cores implement fusion of AES instructions. When fusion >> happens it can give a significant performance gain. If not, scheduling >> fusion candidates next to each other has almost no effect on performance. >> Due to the high benefit/low cost it makes sense to enable AES fusion with >> -mcpu=generic so that cores that support it always benefit. Any objections? No objection. I'm not currently tracking performance of -mcpu=generic on falkor, so I'm not very concerned about changes to the generic tuning structure. Jim
On Thu, Mar 16, 2017 at 08:26:42PM -0700, Jim Wilson wrote: > On Thu, Mar 16, 2017 at 11:01 AM, Andrew Pinski <apinski@cavium.com> wrote: > > On Thu, Mar 16, 2017 at 10:22 AM, Wilco Dijkstra <Wilco.Dijkstra@arm.com> wrote: > >> Many supported cores implement fusion of AES instructions. When fusion > >> happens it can give a significant performance gain. If not, scheduling > >> fusion candidates next to each other has almost no effect on performance. > >> Due to the high benefit/low cost it makes sense to enable AES fusion with > >> -mcpu=generic so that cores that support it always benefit. Any objections? > > No objection. I'm not currently tracking performance of -mcpu=generic > on falkor, so I'm not very concerned about changes to the generic > tuning structure. Thanks for the feedback Jim, Andrew. This patch is OK for trunk. As Richard pointed out on the branch costs thread, if we had a bug here we'd likely have seen it by now on those cores which do enable the fusion. Thanks, James
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index 728ce7029f1e2b5161d9f317d10e564dd5a5f472..c8cf7169a5d387de336920b50c83761dc0c96f3a 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -536,7 +536,7 @@ static const struct tune_params generic_tunings = &generic_approx_modes, 4, /* memmov_cost */ 2, /* issue_rate */ - AARCH64_FUSE_NOTHING, /* fusible_ops */ + (AARCH64_FUSE_AES_AESMC), /* fusible_ops */ 8, /* function_align. */ 8, /* jump_align. */ 4, /* loop_align. */
Many supported cores implement fusion of AES instructions. When fusion happens it can give a significant performance gain. If not, scheduling fusion candidates next to each other has almost no effect on performance. Due to the high benefit/low cost it makes sense to enable AES fusion with -mcpu=generic so that cores that support it always benefit. Any objections? Bootstrapped on AArch64, no regressions. ChangeLog: 2017-03-16 Wilco Dijkstra <wdijkstr@arm.com> * gcc/config/aarch64/aarch64.c (generic_tunings): Add AES fusion. --