> -----Original Message----- > From: Philipp Tomsich <philipp.toms...@vrull.eu> > Sent: Friday, April 14, 2023 7:06 PM > To: gcc-patches@gcc.gnu.org > Cc: Kyrylo Tkachov <kyrylo.tkac...@arm.com>; Philipp Tomsich > <philipp.toms...@vrull.eu>; Di Zhao <di.z...@amperecomputing.com> > Subject: [PATCH v2] aarch64: disable LDP via tuning structure for - > mcpu=ampere1/1a > > AmpereOne (-mcpu=ampere1) breaks LDP instructions into two uops. > Given the chance that this causes instructions to slip into the next > decoding cycle and the additional overheads when handling > cacheline-crossing LDP instructions, we disable the generation of LDP > isntructions through the tuning structure from instruction combining > (such as in peephole2). > > Given the code-density benefits in builtins and prologue/epilogue > expansion, we allow LDPs there. > > This commit: > * adds a new tuning option AARCH64_EXTRA_TUNE_NO_LDP_COMBINE > * allows -moverride=tune=... to override this > > These changes are benchmark-driven, yielding the following changes > (with a net-overall improvement): > 503.bwaves_r. -0.88% > 507.cactuBSSN_r 0.35% > 508.namd_r 3.09% > 510.parest_r -2.99% > 511.povray_r 5.54% > 519.lbm_r 15.83% > 521.wrf_r 0.56% > 526.blender_r 2.47% > 527.cam4_r 0.70% > 538.imagick_r 0.00% > 544.nab_r -0.33% > 549.fotonik3d_r. -0.42% > 554.roms_r 0.00% > ------------------------- > = total 1.79% > > Signed-off-by: Philipp Tomsich <philipp.toms...@vrull.eu> > Co-Authored-By: Di Zhao <di.z...@amperecomputing.com> Ok. Thanks, Kyrill > > gcc/ChangeLog: > > * config/aarch64/aarch64-tuning-flags.def > (AARCH64_EXTRA_TUNING_OPTION): > Add AARCH64_EXTRA_TUNE_NO_LDP_COMBINE. > * config/aarch64/aarch64.cc (aarch64_operands_ok_for_ldpstp): > Check for the above tuning option when processing loads. > > gcc/testsuite/ChangeLog: > > * gcc.target/aarch64/ampere1-no_ldp_combine.c: New test. > > --- > > Changes in v2: > - apply both to -mcpu=ampere1 and -mcpu=ampere1a > - add TODO: tag, per discussions on the mailing list > - add testcase > > gcc/config/aarch64/aarch64-tuning-flags.def | 3 +++ > gcc/config/aarch64/aarch64.cc | 18 ++++++++++++++++-- > .../aarch64/ampere1-no_ldp_combine.c | 11 +++++++++++ > 3 files changed, 30 insertions(+), 2 deletions(-) > create mode 100644 gcc/testsuite/gcc.target/aarch64/ampere1- > no_ldp_combine.c > > diff --git a/gcc/config/aarch64/aarch64-tuning-flags.def > b/gcc/config/aarch64/aarch64-tuning-flags.def > index 712895a5263..52112ba7c48 100644 > --- a/gcc/config/aarch64/aarch64-tuning-flags.def > +++ b/gcc/config/aarch64/aarch64-tuning-flags.def > @@ -44,6 +44,9 @@ AARCH64_EXTRA_TUNING_OPTION > ("cheap_shift_extend", CHEAP_SHIFT_EXTEND) > /* Disallow load/store pair instructions on Q-registers. */ > AARCH64_EXTRA_TUNING_OPTION ("no_ldp_stp_qregs", > NO_LDP_STP_QREGS) > > +/* Disallow load-pair instructions to be formed in combine/peephole. */ > +AARCH64_EXTRA_TUNING_OPTION ("no_ldp_combine", > NO_LDP_COMBINE) > + > AARCH64_EXTRA_TUNING_OPTION ("rename_load_regs", > RENAME_LOAD_REGS) > > AARCH64_EXTRA_TUNING_OPTION ("cse_sve_vl_constants", > CSE_SVE_VL_CONSTANTS) > diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc > index f4ef22ce02f..0f04ab9fba0 100644 > --- a/gcc/config/aarch64/aarch64.cc > +++ b/gcc/config/aarch64/aarch64.cc > @@ -1933,7 +1933,7 @@ static const struct tune_params ampere1_tunings = > 2, /* min_div_recip_mul_df. */ > 0, /* max_case_values. */ > tune_params::AUTOPREFETCHER_WEAK, /* autoprefetcher_model. */ > - (AARCH64_EXTRA_TUNE_NONE), /* tune_flags. */ > + (AARCH64_EXTRA_TUNE_NO_LDP_COMBINE), /* tune_flags. */ > &ere1_prefetch_tune > }; > > @@ -1971,7 +1971,7 @@ static const struct tune_params ampere1a_tunings > = > 2, /* min_div_recip_mul_df. */ > 0, /* max_case_values. */ > tune_params::AUTOPREFETCHER_WEAK, /* autoprefetcher_model. */ > - (AARCH64_EXTRA_TUNE_NONE), /* tune_flags. */ > + (AARCH64_EXTRA_TUNE_NO_LDP_COMBINE), /* tune_flags. */ > &ere1_prefetch_tune > }; > > @@ -26053,6 +26053,20 @@ aarch64_operands_ok_for_ldpstp (rtx > *operands, bool load, > enum reg_class rclass_1, rclass_2; > rtx mem_1, mem_2, reg_1, reg_2; > > + /* Allow the tuning structure to disable LDP instruction formation > + from combining instructions (e.g., in peephole2). > + TODO: Implement fine-grained tuning control for LDP and STP: > + 1. control policies for load and store separately; > + 2. support the following policies: > + - default (use what is in the tuning structure) > + - always > + - never > + - aligned (only if the compiler can prove that the > + load will be aligned to 2 * element_size) */ > + if (load && (aarch64_tune_params.extra_tuning_flags > + & AARCH64_EXTRA_TUNE_NO_LDP_COMBINE)) > + return false; > + > if (load) > { > mem_1 = operands[1]; > diff --git a/gcc/testsuite/gcc.target/aarch64/ampere1-no_ldp_combine.c > b/gcc/testsuite/gcc.target/aarch64/ampere1-no_ldp_combine.c > new file mode 100644 > index 00000000000..bc871f4481d > --- /dev/null > +++ b/gcc/testsuite/gcc.target/aarch64/ampere1-no_ldp_combine.c > @@ -0,0 +1,11 @@ > +/* { dg-options "-O3 -mtune=ampere1" } */ > + > +long > +foo (long a[]) > +{ > + return a[0] + a[1]; > +} > + > +/* We should see two ldrs instead of one ldp. */ > +/* { dg-final { scan-assembler {\tldr\t} } } */ > +/* { dg-final { scan-assembler-not {\tldp\t} } } */ > -- > 2.34.1
RE: [PATCH v2] aarch64: disable LDP via tuning structure for -mcpu=ampere1/1a
Kyrylo Tkachov via Gcc-patches Mon, 17 Apr 2023 02:56:56 -0700
- [PATCH v2] aarch64: disable LDP via tuning ... Philipp Tomsich
- RE: [PATCH v2] aarch64: disable LDP vi... Kyrylo Tkachov via Gcc-patches
- Re: [PATCH v2] aarch64: disable LD... Philipp Tomsich
- Re: [PATCH v2] aarch64: disabl... Philipp Tomsich
- RE: [PATCH v2] aarch64: di... Kyrylo Tkachov via Gcc-patches
- Re: [PATCH v2] aarch6... Philipp Tomsich