From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rock.gnat.com (rock.gnat.com [205.232.38.15]) by sourceware.org (Postfix) with ESMTPS id 290973858C78; Tue, 1 Mar 2022 20:15:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 290973858C78 Received: from localhost (localhost.localdomain [127.0.0.1]) by filtered-rock.gnat.com (Postfix) with ESMTP id D929C1160C3; Tue, 1 Mar 2022 15:15:55 -0500 (EST) X-Virus-Scanned: Debian amavisd-new at gnat.com Received: from rock.gnat.com ([127.0.0.1]) by localhost (rock.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id TDXjd91Cv0oP; Tue, 1 Mar 2022 15:15:55 -0500 (EST) Received: from free.home (tron.gnat.com [IPv6:2620:20:4000:0:46a8:42ff:fe0e:e294]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by rock.gnat.com (Postfix) with ESMTPS id 273501160C1; Tue, 1 Mar 2022 15:15:54 -0500 (EST) Received: from livre (livre.home [172.31.160.2]) by free.home (8.15.2/8.15.2) with ESMTPS id 221KFk1I879528 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 1 Mar 2022 17:15:47 -0300 From: Alexandre Oliva To: Richard Biener Cc: Jeff Law , Vladimir Makarov , zsojka@seznam.cz, GCC Patches , wilson@gcc.gnu.org Subject: Re: [PR103302] skip multi-word pre-move clobber during lra Organization: Free thinker, does not speak for AdaCore References: <74d2af86-c1c4-0842-b319-09e76b3bf633@gmail.com> <4bf89538-8c3c-59a7-378b-d02982e6a5ea@gmail.com> <03226f85-0334-1840-94f9-6c618175f974@gmail.com> Errors-To: aoliva@lxoliva.fsfla.org Date: Tue, 01 Mar 2022 17:15:45 -0300 In-Reply-To: (Alexandre Oliva's message of "Wed, 23 Feb 2022 19:39:35 -0300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 X-Spam-Status: No, score=-12.2 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, 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: Tue, 01 Mar 2022 20:15:58 -0000 On Feb 23, 2022, Alexandre Oliva wrote: > On Feb 21, 2022, Richard Biener wrote: >>> Ok to revert commit r12-5852-g50e8b0c9bca6cdc57804f860ec5311b641753fbb >> OK. Please re-open the bug as appropriate. > Thanks. I've reopened it. Here's what I'm installing. I'm not > reverting the testcase, since it stopped failing even before the patch > was put in. And now here's a patch that fixes the underlying issue. Undo multi-word optional reloads correctly From: Alexandre Oliva Unlike e.g. remove_inheritance_pseudos, undo_optional_reloads didn't deal with subregs, so instead of removing multi-word moves, it replaced the reload pseudo with the original pseudo. Besides the redundant move, that retained the clobber of the dest, that starts a multi-word move. After the remap, the sequence that should have become a no-op move starts by clobbering the original pseudo and then moving its pieces onto themselves. The problem is the clobber: it makes earlier sets of the original pseudo to be regarded as dead: if the optional reload sequence was an output reload, the insn for which the output reload was attempted may be regarded as dead and deleted. I've arranged for undo_optional_reloads to accept SUBREGs and use get_regno, like remove_inheritance_pseudo, adjusted its insn-removal loop to tolerate iterating over a removed clobber, and added logic to catch any left-over reload clobbers that could trigger the problem. for gcc/ChangeLog * lra-constraints.cc (undo_optional_reloads): Recognize and drop insns of multi-word move sequences, tolerate removal iteration on an already-removed clobber, and refuse to substitute original pseudos into clobbers. --- gcc/lra-constraints.cc | 37 ++++++++++++++++++++++++------------- 1 file changed, 24 insertions(+), 13 deletions(-) diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc index b2c4590153c4c..5cd89e7eeddc2 100644 --- a/gcc/lra-constraints.cc +++ b/gcc/lra-constraints.cc @@ -7261,15 +7261,17 @@ undo_optional_reloads (void) continue; src = SET_SRC (set); dest = SET_DEST (set); - if (! REG_P (src) || ! REG_P (dest)) + if ((! REG_P (src) && ! SUBREG_P (src)) + || (! REG_P (dest) && ! SUBREG_P (dest))) continue; - if (REGNO (dest) == regno + if (get_regno (dest) == (int) regno /* Ignore insn for optional reloads itself. */ - && REGNO (lra_reg_info[regno].restore_rtx) != REGNO (src) + && (get_regno (lra_reg_info[regno].restore_rtx) + != get_regno (src)) /* Check only inheritance on last inheritance pass. */ - && (int) REGNO (src) >= new_regno_start + && get_regno (src) >= new_regno_start /* Check that the optional reload was inherited. */ - && bitmap_bit_p (&lra_inheritance_pseudos, REGNO (src))) + && bitmap_bit_p (&lra_inheritance_pseudos, get_regno (src))) { keep_p = true; break; @@ -7291,18 +7293,22 @@ undo_optional_reloads (void) bitmap_copy (insn_bitmap, &lra_reg_info[regno].insn_bitmap); EXECUTE_IF_SET_IN_BITMAP (insn_bitmap, 0, uid, bi2) { + /* We may have already removed a clobber. */ + if (!lra_insn_recog_data[uid]) + continue; insn = lra_insn_recog_data[uid]->insn; if ((set = single_set (insn)) != NULL_RTX) { src = SET_SRC (set); dest = SET_DEST (set); - if (REG_P (src) && REG_P (dest) - && ((REGNO (src) == regno - && (REGNO (lra_reg_info[regno].restore_rtx) - == REGNO (dest))) - || (REGNO (dest) == regno - && (REGNO (lra_reg_info[regno].restore_rtx) - == REGNO (src))))) + if ((REG_P (src) || SUBREG_P (src)) + && (REG_P (dest) || SUBREG_P (dest)) + && ((get_regno (src) == (int) regno + && (get_regno (lra_reg_info[regno].restore_rtx) + == get_regno (dest))) + || (get_regno (dest) == (int) regno + && (get_regno (lra_reg_info[regno].restore_rtx) + == get_regno (src))))) { if (lra_dump_file != NULL) { @@ -7310,7 +7316,7 @@ undo_optional_reloads (void) INSN_UID (insn)); dump_insn_slim (lra_dump_file, insn); } - delete_move_and_clobber (insn, REGNO (dest)); + delete_move_and_clobber (insn, get_regno (dest)); continue; } /* We should not worry about generation memory-memory @@ -7319,6 +7325,11 @@ undo_optional_reloads (void) we remove the inheritance pseudo and the optional reload. */ } + if (GET_CODE (PATTERN (insn)) == CLOBBER + && REG_P (SET_DEST (insn)) + && get_regno (SET_DEST (insn)) == (int) regno) + /* Refuse to remap clobbers to preexisting pseudos. */ + gcc_unreachable (); lra_substitute_pseudo_within_insn (insn, regno, lra_reg_info[regno].restore_rtx, false); lra_update_insn_regno_info (insn); -- Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/ Free Software Activist GNU Toolchain Engineer Disinformation flourishes because many people care deeply about injustice but very few check the facts. 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