[PATCH v4] arm: Implement Armv8.1-M low overhead loops

[Kyrylo Tkachov]

Hi Andrea,

Sorry for the delay

> -----Original Message-----
> From: Gcc-patches <gcc-patches-bounces@gcc.gnu.org> On Behalf Of
> Andrea Corallo
> Sent: 24 June 2020 11:04
> To: gcc-patches@gcc.gnu.org
> Cc: Richard Earnshaw <Richard.Earnshaw@arm.com>; nd <nd@arm.com>;
> Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
> Subject: Re: [PATCH v4] arm: Implement Armv8.1-M low overhead loops
> 
> Andrea Corallo <andrea.corallo@arm.com> writes:
> 
> > Hi all,
> >
> > here the latest version of the patch to enable Armv8.1-M Mainline
> > LOB (low overhead branch) extension low overhead loops (LOL) feature
> > using the 'loop-doloop' pass.
> >
> > I posted a previous version of it during stage 4.
> >
> > Given the following function:
> >
> > void
> > loop (int *a)
> > {
> >   for (int i = 0; i < 1000; i++)
> >     a[i] = i;
> > }
> >
> > 'doloop_begin' and 'doloop_end' patterns translates into 'dls' and 'le'
> > giving:
> >
> >  loop:
> >          movw    r2, #10000
> >          movs    r3, #0
> >          subs    r0, r0, #4
> >          push    {lr}
> >          dls     lr, r2
> >  .L2:
> >          str     r3, [r0, #4]!
> >          adds    r3, r3, #1
> >          le      lr, .L2
> >          ldr     pc, [sp], #4
> >
> > bootstrapped arm-none-linux-gnueabihf, does not introduce testsuite
> regressions.
> >
> > Andrea
> 
> Hi,
> 
> double checking I spotted another test impacted by the patch that I
> missed as first.
> 
> Here the updated patch waving the check.
> 
>   Andrea
> 
> gcc/ChangeLog
> 
> 2020-06-18  Andrea Corallo  <andrea.corallo@arm.com>
>             Mihail-Calin Ionescu  <mihail.ionescu@arm.com>
>             Iain Apreotesei  <iain.apreotesei@arm.com>
> 
> 	* config/arm/arm-protos.h (arm_target_insn_ok_for_lob): New
> 	prototype.
>         * config/arm/arm.c (TARGET_INVALID_WITHIN_DOLOOP): Define.
>         (arm_invalid_within_doloop): Implement invalid_within_doloop hook.
> 	(arm_target_insn_ok_for_lob): New function.
>         * config/arm/arm.h (TARGET_HAVE_LOB): Define macro.
>         * config/arm/thumb2.md (*doloop_end_internal, doloop_begin)
> 	(dls_insn): Add new patterns.
> 	(doloop_end): Modify to select LR when LOB is available.
>         * config/arm/unspecs.md: Add new unspec.
>         * doc/sourcebuild.texi (arm_v8_1_lob_ok)
> 	(arm_thumb2_ok_no_arm_v8_1_lob): Document new target
> supports
> 	options.
> 
> gcc/testsuite/ChangeLog
> 
> 2020-06-18  Andrea Corallo  <andrea.corallo@arm.com>
>             Mihail-Calin Ionescu  <mihail.ionescu@arm.com>
>             Iain Apreotesei  <iain.apreotesei@arm.com>
> 
>         * gcc.target/arm/lob.h: New header.
>         * gcc.target/arm/lob1.c: New testcase.
>         * gcc.target/arm/lob2.c: Likewise.
>         * gcc.target/arm/lob3.c: Likewise.
>         * gcc.target/arm/lob4.c: Likewise.
>         * gcc.target/arm/lob5.c: Likewise.
>         * gcc.target/arm/lob6.c: Likewise.
> 	* gcc.target/arm/unsigned-extend-2.c: Do not run when generating
> 	low loop overhead.
> 	* gcc.target/arm/ivopts.c: Fix check for low loop overhead.
>         * lib/target-supports.exp (check_effective_target_arm_v8_1_lob)
> 	(check_effective_target_arm_thumb2_ok_no_arm_v8_1_lob): New
> procs.

Ok.
Thanks for doing this.
Kyrill