[PATCH v4] arm: Implement Armv8.1-M low overhead loops
Andrea Corallo
andrea.corallo@arm.com
Wed Jun 24 10:04:19 GMT 2020
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.
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