From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-x529.google.com (mail-ed1-x529.google.com [IPv6:2a00:1450:4864:20::529]) by sourceware.org (Postfix) with ESMTPS id D705A3858C53 for ; Fri, 1 Apr 2022 06:47:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D705A3858C53 Received: by mail-ed1-x529.google.com with SMTP id a17so1793841edm.9 for ; Thu, 31 Mar 2022 23:47:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Bty1ArJnMN4suMGMdyfGSTvvJ+CDL0J1AHsDgr73S9Y=; b=mDpZhGw0bNjCbtI/kaAw7aRe2aZU4++kkNa3W1o9WVieG3fQyX4lMZCqaEYFqomgkP OEp53kMmUSVvZAWORRpsMRTX8sy7M9M0X76J+ZAl4HpnK40erwbiTNVPfjpX0ZCGAaAk 0fRdzCQT01i1/4GbEWQ9qXpWYccXJlY/4bW2juDl420np7OisfARUy07yYP8gf22Siy1 G5r9CZ/XyzBG34xOSbueiFukIvXl2SFKj56K2gH4QOwKxS5BSqScJZMX+DGo+pN1oDrE QMa1nN8yBbciV8KMx8eGTHWmmHkggOxY1ExqHZfvCw9NH5DkjAghwoylNEFZdoxDQKtv jplQ== X-Gm-Message-State: AOAM530TN906zOnf0oCz0RYsCDfoxE83DSiwmukUPTT+nZHET3ubgEM6 Mr3CU9Mg/D6FIBIlBPT/7fdYYKb9vsinKCDI/dQ= X-Google-Smtp-Source: ABdhPJxCSu5S+Jr2vTnBrYOOuSnuKxS9wTp/OBi/NA+7LEziEjgwqW6Z67tHckWbLn5TCyQQtTdFNMCQFkig4LddFt4= X-Received: by 2002:a05:6402:2688:b0:419:5dde:4700 with SMTP id w8-20020a056402268800b004195dde4700mr20058631edd.124.1648795675402; Thu, 31 Mar 2022 23:47:55 -0700 (PDT) MIME-Version: 1.0 References: <20220331055117.6942-1-hongtao.liu@intel.com> In-Reply-To: From: Richard Biener Date: Fri, 1 Apr 2022 08:47:44 +0200 Message-ID: Subject: Re: [PATCH] Split vector load from parm_del to elemental loads to avoid STLF stalls. To: Hongtao Liu Cc: liuhongt , GCC Patches Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Apr 2022 06:47:59 -0000 On Fri, Apr 1, 2022 at 8:29 AM Hongtao Liu wrote: > > On Thu, Mar 31, 2022 at 6:45 PM Richard Biener via Gcc-patches > wrote: > > > > On Thu, Mar 31, 2022 at 7:51 AM liuhongt wrote: > > > > > > Since cfg is freed before machine_reorg, just do a rough calculation > > > of the window according to the layout. > > > Also according to an experiment on CLX, set window size to 64. > > > > > > Currently only handle V2DFmode load since it doesn't need any scratch > > > registers, and it's sufficient to recover cray performance for -O2 > > > compared to GCC11. > > > > > > Bootstrap and regtest on x86_64-pc-linux-gnu{-m32,}. > > > No impact for SPEC2017(same binary for both O2 and Ofast). > > > Ok for trunk? > > > > > > gcc/ChangeLog: > > > > > > PR target/101908 > > > * config/i386/i386.cc (ix86_split_stlf_stall_load): New > > > function > > > (ix86_reorg): Call ix86_split_stlf_stall_load. > > > > > > gcc/testsuite/ChangeLog: > > > > > > * gcc.target/i386/pr101908-1.c: New test. > > > * gcc.target/i386/pr101908-2.c: New test. > > > --- > > > gcc/config/i386/i386.cc | 47 ++++++++++++++++++++++ > > > gcc/testsuite/gcc.target/i386/pr101908-1.c | 12 ++++++ > > > gcc/testsuite/gcc.target/i386/pr101908-2.c | 12 ++++++ > > > 3 files changed, 71 insertions(+) > > > create mode 100644 gcc/testsuite/gcc.target/i386/pr101908-1.c > > > create mode 100644 gcc/testsuite/gcc.target/i386/pr101908-2.c > > > > > > diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc > > > index 5a561966eb4..f9169b04d43 100644 > > > --- a/gcc/config/i386/i386.cc > > > +++ b/gcc/config/i386/i386.cc > > > @@ -21933,7 +21933,53 @@ ix86_seh_fixup_eh_fallthru (void) > > > emit_insn_after (gen_nops (const1_rtx), insn); > > > } > > > } > > > +/* Split vector load from parm_decl to elemental loads to avoid STLF > > > + stalls. */ > > > +static void > > > +ix86_split_stlf_stall_load () > > > +{ > > > + basic_block bb; > > > + unsigned window = 0; > > > + FOR_EACH_BB_FN (bb, cfun) > > > + { > > > + rtx_insn *insn; > > > + FOR_BB_INSNS (bb, insn) > > > + { > > > + if (!NONDEBUG_INSN_P (insn)) > > > + continue; > > > + window++; > > > + /* Insert 64 vaddps %xmm18, %xmm19, %xmm20(no dependence between each > > > + other, just emulate for pipeline) before stalled load, stlf stall > > > + case is as fast as no stall cases on CLX. > > > + Since CFG is freed before machine_reorg, just do a rough > > > + calculation of the window according to the layout. */ > > > + if (window > 64) > > > + return; > > > > I wonder if we should also return for any_uncondjump_p (insn) > > (not sure if that captures returnjump_p), or maybe just explicitely > > allow any_condjump_p and reject other PC setters. > > > I guess it doesn't include call. > > Likewise we might want to stop at a LABEL that can be backwards reached. > > > I think checking load from parm_decl can somehow avoid split load in a > loop(assume optimizer will hoist that out). > > I suppose people more familiar with cfgrtl can suggest something better. > > > > > + rtx set = single_set (insn); > > > + if (!set) > > > + continue; > > > + rtx src = SET_SRC (set); > > > + if (!MEM_P (src) > > > + /* Only handle V2DFmode load since it doesn't need any scratch > > > + register. */ > > > + || GET_MODE (src) != E_V2DFmode > > > + || !MEM_EXPR (src) > > > + || TREE_CODE (get_base_address (MEM_EXPR (src))) != PARM_DECL) > > > > I wonder if we have (easy) ways to detect whether XEXP (src, 0) is > > frame/stack based > > rather than requiring a MEM_EXPR. There is may_be_sp_based_p () > may_be_sp_based_p just checks stack pointer which is not suitable after RA. > > exported from alias.c > > for example, but I'm not sure whether that works after RA & frame elimination. > > > > > + continue; > > > + > > > + rtx zero = CONST0_RTX (V2DFmode); > > > + rtx dest = SET_DEST (set); > > > + rtx m = adjust_address (src, DFmode, 0); > > > + emit_insn_before (gen_sse2_loadlpd (dest, zero, m), insn); > > > > Can SSE1 also do this? > X86 does have movlps and movhps, but the problem is movlps load 64bit > memory to xmm w/o change upper bits which may cause partial register > dependence. So do we need to guard this transform on SSE2 availability then? > > > > > + m = adjust_address (src, DFmode, 8); > > > + PATTERN (insn) = gen_sse2_loadhpd (dest, dest, m); > > > + INSN_CODE (insn) = -1; > > > + gcc_assert (recog_memoized (insn) != -1); > > > > I think we want to dump something into dump_file when we split an insn here. > Good idea. > > > > > + } > > > + } > > > + > > > +} > > > /* Implement machine specific optimizations. We implement padding of returns > > > for K8 CPUs and pass to avoid 4 jumps in the single 16 byte window. */ > > > static void > > > @@ -21948,6 +21994,7 @@ ix86_reorg (void) > > > > > > if (optimize && optimize_function_for_speed_p (cfun)) > > > { > > > + ix86_split_stlf_stall_load (); > > > if (TARGET_PAD_SHORT_FUNCTION) > > > ix86_pad_short_function (); > > > > btw. this function suggests we do have edges, so doing something "better" > > than FOR_EACH_BB_FN, aka walking blocks in layout order, might be > > possible after all. For example ix86_avoid_jump_mispredicts just walks > > the function by looking at get_insns(), that might be more closely what > > "as laid out" is. > I prefer to use get_insns (). > > > > > else if (TARGET_PAD_RETURNS) > > > diff --git a/gcc/testsuite/gcc.target/i386/pr101908-1.c b/gcc/testsuite/gcc.target/i386/pr101908-1.c > > > new file mode 100644 > > > index 00000000000..33d9684f0ad > > > --- /dev/null > > > +++ b/gcc/testsuite/gcc.target/i386/pr101908-1.c > > > @@ -0,0 +1,12 @@ > > > +/* { dg-do compile } */ > > > +/* { dg-options "-O2 -msse2 -mno-avx" } */ > > > +/* { dg-final { scan-assembler-not {(?n)movhpd[ \t]} } } */ > > > + > > > +struct X { double x[2]; }; > > > +typedef double v2df __attribute__((vector_size(16))); > > > + > > > +v2df __attribute__((noipa)) > > > +foo (struct X* x, struct X* y) > > > +{ > > > + return (v2df) {x->x[1], x->x[0] } + (v2df) { y->x[1], y->x[0] }; > > > +} > > > diff --git a/gcc/testsuite/gcc.target/i386/pr101908-2.c b/gcc/testsuite/gcc.target/i386/pr101908-2.c > > > new file mode 100644 > > > index 00000000000..45060b73c06 > > > --- /dev/null > > > +++ b/gcc/testsuite/gcc.target/i386/pr101908-2.c > > > @@ -0,0 +1,12 @@ > > > +/* { dg-do compile } */ > > > +/* { dg-options "-O2 -msse2 -mno-avx" } */ > > > +/* { dg-final { scan-assembler-times {(?n)movhpd[ \t]+} "2" } } */ > > > + > > > +struct X { double x[4]; }; > > > +typedef double v2df __attribute__((vector_size(16))); > > > + > > > +v2df __attribute__((noipa)) > > > +foo (struct X x, struct X y) > > > +{ > > > + return (v2df) {x.x[1], x.x[0] } + (v2df) { y.x[1], y.x[0] }; > > > +} > > > -- > > > 2.18.1 > > > > > > > -- > BR, > Hongtao