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[209.132.180.131]) by mx.google.com with ESMTPS id c10-v6si1047292plm.342.2018.01.22.05.47.10 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Jan 2018 05:47:11 -0800 (PST) Received-SPF: pass (google.com: domain of gcc-patches-return-471794-patch=linaro.org@gcc.gnu.org designates 209.132.180.131 as permitted sender) client-ip=209.132.180.131; Authentication-Results: mx.google.com; dkim=pass header.i=@gcc.gnu.org header.s=default header.b=S5+EsZNC; spf=pass (google.com: domain of gcc-patches-return-471794-patch=linaro.org@gcc.gnu.org designates 209.132.180.131 as permitted sender) smtp.mailfrom=gcc-patches-return-471794-patch=linaro.org@gcc.gnu.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=linaro.org DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:from :to:cc:subject:date:message-id:in-reply-to:references; q=dns; s= default; b=PZHh2DnnMorwaJr9mtvhmyURLyzaehVVhxC13k/+1ziusJVGlxbX/ SWJ5B+SM2GeQ4gtPZjx+EQQaZlTH7MT3+os+neK6JmpYlR2h68qp8Mf5yoVbVqS2 m4yFUs/kP34wQtgfknzcFOOM2+F7J8IIQpwD1OHwMJpILlhpjva9fs= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:from :to:cc:subject:date:message-id:in-reply-to:references; s= default; bh=7UozLNxZKwTsk7zH9vgcEd9n2F0=; b=S5+EsZNClta+WDPUaEHf trnEgZV6r6otyU06M8q5AhmwFc9yBrjUpeM3Qdqvewe0c3PHDMhAAQivrFnJLIJ1 ZNji0M5bw5Sf/MrfkOmiKmP9YWD6UmxgGe2yxIvKbhZ9HULNRtAda5QqsPHvYyqe cjalCsVrOkITiYo02NXrQCE= Received: (qmail 2218 invoked by alias); 22 Jan 2018 13:46:44 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Delivered-To: mailing list gcc-patches@gcc.gnu.org Received: (qmail 2007 invoked by uid 89); 22 Jan 2018 13:46:42 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-26.9 required=5.0 tests=BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mail-qt0-f196.google.com Received: from mail-qt0-f196.google.com (HELO mail-qt0-f196.google.com) (209.85.216.196) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 22 Jan 2018 13:46:40 +0000 Received: by mail-qt0-f196.google.com with SMTP id s3so20760659qtb.10 for ; Mon, 22 Jan 2018 05:46:40 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=gfYXY2eHE95so7+/JAKoMHzgkxx6x3RL2T9g0DQxL04=; b=JRDBatPlh2QEZlWh2SAT3P27PxEnEC3D7/kfpmCGQFNeuQYJ+Dkl6dQmHGJzyzAhDV gUw0nFY1ujL2LJWB7rKvzZNXmfjphcFY/jT0fy4Z3swoE64dxeC507tqTf3GjY9seYg0 VSgYZNW1ljRkw4Wt3t0m1Zt0fqOUQvqfi04gYFO+gxkuFIeVydoDnjd6/+QWrYUxDSry hfDG05urjK6bzZghi2CUCXG0mSu6idwbkcbWCIGMpXu1e1fPluCFR6J9xl8aUcdydEmU wFImjh2uNuqVoLuXTlov3bi9YF5VMMvlcJN02bGerKT2A2BM2mkrZ+teX6747i0MIyPa aY+A== X-Gm-Message-State: AKwxytdMd5SVINkYnWDIDPE/S65Xok6g4q2oacnKh3XTjLtiPGvRmhnY dhiR11yGO8L/PGA7aT/UkKxioq9u+Zk= X-Received: by 10.237.49.134 with SMTP id 6mr11563522qth.178.1516628798444; Mon, 22 Jan 2018 05:46:38 -0800 (PST) Received: from localhost.localdomain ([177.180.105.91]) by smtp.gmail.com with ESMTPSA id s39sm10492452qth.67.2018.01.22.05.46.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 22 Jan 2018 05:46:37 -0800 (PST) From: Luis Machado To: gcc-patches@gcc.gnu.org Cc: james.greenhalgh@arm.com, Richard.Earnshaw@arm.com Subject: [PATCH 2/2] Introduce prefetch-dynamic-strides option. Date: Mon, 22 Jan 2018 11:46:10 -0200 Message-Id: <1516628770-25036-3-git-send-email-luis.machado@linaro.org> In-Reply-To: <1516628770-25036-1-git-send-email-luis.machado@linaro.org> References: <1516628770-25036-1-git-send-email-luis.machado@linaro.org> X-IsSubscribed: yes The following patch adds an option to control software prefetching of memory references with non-constant/unknown strides. Currently we prefetch these references if the pass thinks there is benefit to doing so. But, since this is all based on heuristics, it's not always the case that we end up with better performance. For Falkor there is also the problem of conflicts with the hardware prefetcher, so we need to be more conservative in terms of what we issue software prefetch hints for. This also aligns GCC with what LLVM does for Falkor. Similarly to the previous patch, the defaults guarantee no change in behavior for other targets and architectures. I've regression-tested and bootstrapped it on aarch64-linux. No problems found. Ok? 2018-01-22 Luis Machado Introduce option to control whether the software prefetch pass should issue prefetch hints for non-constant strides. gcc/ * config/aarch64/aarch64-protos.h (cpu_prefetch_tune) : New const unsigned int field. * config/aarch64/aarch64.c (generic_prefetch_tune): Update to include prefetch_dynamic_strides. (exynosm1_prefetch_tune): Likewise. (thunderxt88_prefetch_tune): Likewise. (thunderx_prefetch_tune): Likewise. (thunderx2t99_prefetch_tune): Likewise. (qdf24xx_prefetch_tune): Likewise. Set prefetch_dynamic_strides to 0. (aarch64_override_options_internal): Update to set PARAM_PREFETCH_DYNAMIC_STRIDES. * doc/invoke.texi (prefetch-dynamic-strides): Document new option. * params.def (PARAM_PREFETCH_DYNAMIC_STRIDES): New. * params.h (PARAM_PREFETCH_DYNAMIC_STRIDES): Define. * tree-ssa-loop-prefetch.c (should_issue_prefetch_p): Account for prefetch-dynamic-strides setting. --- gcc/config/aarch64/aarch64-protos.h | 3 +++ gcc/config/aarch64/aarch64.c | 11 +++++++++++ gcc/doc/invoke.texi | 10 ++++++++++ gcc/params.def | 9 +++++++++ gcc/params.h | 2 ++ gcc/tree-ssa-loop-prefetch.c | 10 ++++++++++ 6 files changed, 45 insertions(+) -- 2.7.4 diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h index 8736bd9..22bd9ae 100644 --- a/gcc/config/aarch64/aarch64-protos.h +++ b/gcc/config/aarch64/aarch64-protos.h @@ -230,6 +230,9 @@ struct cpu_prefetch_tune const int l1_cache_size; const int l1_cache_line_size; const int l2_cache_size; + /* Whether software prefetch hints should be issued for non-constant + strides. */ + const unsigned int prefetch_dynamic_strides; /* The minimum constant stride beyond which we should use prefetch hints for. */ const int minimum_stride; diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c index 0ed9f14..713b230 100644 --- a/gcc/config/aarch64/aarch64.c +++ b/gcc/config/aarch64/aarch64.c @@ -547,6 +547,7 @@ static const cpu_prefetch_tune generic_prefetch_tune = -1, /* l1_cache_size */ -1, /* l1_cache_line_size */ -1, /* l2_cache_size */ + 1, /* prefetch_dynamic_strides */ -1, /* minimum_stride */ -1 /* default_opt_level */ }; @@ -557,6 +558,7 @@ static const cpu_prefetch_tune exynosm1_prefetch_tune = -1, /* l1_cache_size */ 64, /* l1_cache_line_size */ -1, /* l2_cache_size */ + 1, /* prefetch_dynamic_strides */ -1, /* minimum_stride */ -1 /* default_opt_level */ }; @@ -567,6 +569,7 @@ static const cpu_prefetch_tune qdf24xx_prefetch_tune = 32, /* l1_cache_size */ 64, /* l1_cache_line_size */ 1024, /* l2_cache_size */ + 0, /* prefetch_dynamic_strides */ 2048, /* minimum_stride */ 3 /* default_opt_level */ }; @@ -577,6 +580,7 @@ static const cpu_prefetch_tune thunderxt88_prefetch_tune = 32, /* l1_cache_size */ 128, /* l1_cache_line_size */ 16*1024, /* l2_cache_size */ + 1, /* prefetch_dynamic_strides */ -1, /* minimum_stride */ 3 /* default_opt_level */ }; @@ -587,6 +591,7 @@ static const cpu_prefetch_tune thunderx_prefetch_tune = 32, /* l1_cache_size */ 128, /* l1_cache_line_size */ -1, /* l2_cache_size */ + 1, /* prefetch_dynamic_strides */ -1, /* minimum_stride */ -1 /* default_opt_level */ }; @@ -597,6 +602,7 @@ static const cpu_prefetch_tune thunderx2t99_prefetch_tune = 32, /* l1_cache_size */ 64, /* l1_cache_line_size */ 256, /* l2_cache_size */ + 1, /* prefetch_dynamic_strides */ -1, /* minimum_stride */ -1 /* default_opt_level */ }; @@ -10467,6 +10473,11 @@ aarch64_override_options_internal (struct gcc_options *opts) aarch64_tune_params.prefetch->l2_cache_size, opts->x_param_values, global_options_set.x_param_values); + if (aarch64_tune_params.prefetch->prefetch_dynamic_strides == 0) + maybe_set_param_value (PARAM_PREFETCH_DYNAMIC_STRIDES, + aarch64_tune_params.prefetch->prefetch_dynamic_strides, + opts->x_param_values, + global_options_set.x_param_values); if (aarch64_tune_params.prefetch->minimum_stride >= 0) maybe_set_param_value (PARAM_PREFETCH_MINIMUM_STRIDE, aarch64_tune_params.prefetch->minimum_stride, diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 1cb1ef5..541c24c 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -10567,6 +10567,16 @@ The size of L1 cache, in kilobytes. @item l2-cache-size The size of L2 cache, in kilobytes. +@item prefetch-dynamic-strides +Whether the loop array prefetch pass should issue software prefetch hints +for strides that are non-constant. In some cases this may be +beneficial, though the fact the stride is non-constant may make it +hard to predict when there is clear benefit to issuing these hints. + +Set to 1, the default, if the prefetch hints should be issued for non-constant +strides. Set to 0 if prefetch hints should be issued only for strides that +are known to be constant and below @option{prefetch-minimum-stride}. + @item prefetch-minimum-stride Minimum constant stride, in bytes, to start using prefetch hints for. If the stride is less than this threshold, prefetch hints will not be issued. diff --git a/gcc/params.def b/gcc/params.def index bf2d12c..c564178 100644 --- a/gcc/params.def +++ b/gcc/params.def @@ -790,6 +790,15 @@ DEFPARAM (PARAM_L2_CACHE_SIZE, "The size of L2 cache.", 512, 0, 0) +/* Whether software prefetch hints should be issued for non-constant + strides. */ + +DEFPARAM (PARAM_PREFETCH_DYNAMIC_STRIDES, + "prefetch-dynamic-strides", + "Whether software prefetch hints should be issued for non-constant " + "strides.", + 1, 0, 1) + /* The minimum constant stride beyond which we should use prefetch hints for. */ diff --git a/gcc/params.h b/gcc/params.h index 96012db..8aa960a 100644 --- a/gcc/params.h +++ b/gcc/params.h @@ -196,6 +196,8 @@ extern void init_param_values (int *params); PARAM_VALUE (PARAM_L1_CACHE_LINE_SIZE) #define L2_CACHE_SIZE \ PARAM_VALUE (PARAM_L2_CACHE_SIZE) +#define PREFETCH_DYNAMIC_STRIDES \ + PARAM_VALUE (PARAM_PREFETCH_DYNAMIC_STRIDES) #define PREFETCH_MINIMUM_STRIDE \ PARAM_VALUE (PARAM_PREFETCH_MINIMUM_STRIDE) #define USE_CANONICAL_TYPES \ diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c index 112ccac..de2acc8 100644 --- a/gcc/tree-ssa-loop-prefetch.c +++ b/gcc/tree-ssa-loop-prefetch.c @@ -992,6 +992,16 @@ prune_by_reuse (struct mem_ref_group *groups) static bool should_issue_prefetch_p (struct mem_ref *ref) { + /* Do we want to issue prefetches for non-constant strides? */ + if (!cst_and_fits_in_hwi (ref->group->step) && PREFETCH_DYNAMIC_STRIDES == 0) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "Skipping non-constant step for reference %u:%u\n", + ref->group->uid, ref->uid); + return false; + } + /* Some processors may have a hardware prefetcher that may conflict with prefetch hints for a range of strides. Make sure we don't issue prefetches for such cases if the stride is within this particular