{"id":2223774,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2223774/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/aeCQ_tJTTwe51o3B@tucnak/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/1.1/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null},"msgid":"","date":"2026-04-16T07:34:22","name":"i386: Fix up TARGET_AVOID_FALSE_DEP_FOR_BMI APX NF splitters [PR124892]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"19e3a8eb1aa70ac63f1a5139a8c68dce6e3aedf9","submitter":{"id":671,"url":"http://patchwork.ozlabs.org/api/1.1/people/671/?format=json","name":"Jakub Jelinek","email":"jakub@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/aeCQ_tJTTwe51o3B@tucnak/mbox/","series":[{"id":500094,"url":"http://patchwork.ozlabs.org/api/1.1/series/500094/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500094","date":"2026-04-16T07:34:22","name":"i386: Fix up TARGET_AVOID_FALSE_DEP_FOR_BMI APX NF splitters [PR124892]","version":1,"mbox":"http://patchwork.ozlabs.org/series/500094/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2223774/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2223774/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=PPo/LIp1;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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Thu, 16 Apr 2026 07:34:25 +0000 (UTC)","from tucnak.zalov.cz (localhost [127.0.0.1])\n by tucnak.zalov.cz (8.18.1/8.18.1) with ESMTPS id 63G7YNRU887659\n (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT);\n Thu, 16 Apr 2026 09:34:23 +0200","(from jakub@localhost)\n by tucnak.zalov.cz (8.18.1/8.18.1/Submit) id 63G7YMcg887656;\n Thu, 16 Apr 2026 09:34:22 +0200"],"DKIM-Filter":["OpenDKIM Filter v2.11.0 sourceware.org 539724BA2E1F","OpenDKIM Filter v2.11.0 sourceware.org 1E03A4BA543C"],"DMARC-Filter":"OpenDMARC Filter v1.4.2 sourceware.org 1E03A4BA543C","ARC-Filter":"OpenARC Filter v1.0.0 sourceware.org 1E03A4BA543C","ARC-Seal":"i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1776324872; cv=none;\n b=h4t/lEIvR4ZSyN2+uF7oWoSr3H0rqZxoWDy/ReqU3tYLnCrmirPqkqlYZD93qpjKfXC8bkH8IlYg0WfSfAWXONo7d+hiQPpXsmss8GXzji3hqonifORrhvoRyFREMMhRmYceO/HOmnFPEIYCrGrtLNtE7EvPHRo+5G18bAX25mw=","ARC-Message-Signature":"i=1; a=rsa-sha256; d=sourceware.org; s=key;\n t=1776324872; c=relaxed/simple;\n bh=rrNDadLfo67UVOz6SPTCEbIXg1cPF4byOfz6K7NAdJs=;\n h=DKIM-Signature:Date:From:To:Subject:Message-ID:MIME-Version;\n b=hu3i/rWoT9tcJYzbPLdnBRV1X6DkkQsBMeX0l9BQbYU0HIQHSJFXsH5+t3MCG7+ikix0aPSQvmNHVH82X3if58YZWqx23KSR36IdcABaCHWCXqTrJF6zW6Ezn+49ZkUFfyxbfwPE035FadJQkmLI5Im25gkeE9cGUnyCZOBq+jE=","ARC-Authentication-Results":"i=1; server2.sourceware.org","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1776324871;\n h=from:from:reply-to:reply-to:subject:subject:date:date:\n message-id:message-id:to:to:cc:cc:mime-version:mime-version:\n content-type:content-type; bh=wvo3uHANLt8X65vgj5UvXm7T/6SM9km46RYf+YH+AM0=;\n b=PPo/LIp1ps27D7CT/4zBmKXJUTK1wZZYgl2JUREkI1+QuSsG64/8WWsA4V6ema1X+d5oJC\n 77XVIFErY3bcjrBtb9NdlRK5MOjBmulmbMtbdnLT0IQ9vfUby9cKfaH7senKjXa8/oVySM\n 4bvW4iyVRu2cUJqVhcSJ0wmPEkmQ4OU=","X-MC-Unique":"lRi6J_GoOYySJN31OL6m0w-1","X-Mimecast-MFC-AGG-ID":"lRi6J_GoOYySJN31OL6m0w_1776324867","Date":"Thu, 16 Apr 2026 09:34:22 +0200","From":"Jakub Jelinek ","To":"Uros Bizjak , Hongtao Liu ","Cc":"gcc-patches@gcc.gnu.org","Subject":"[PATCH] i386: Fix up TARGET_AVOID_FALSE_DEP_FOR_BMI APX NF splitters\n [PR124892]","Message-ID":"","MIME-Version":"1.0","X-Scanned-By":"MIMEDefang 3.4.1 on 10.30.177.111","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"7Uhokyor60QpnxxLIcsK_MyirXIX7nC7Xq7G_86EPS0_1776324867","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain; charset=us-ascii","Content-Disposition":"inline","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Reply-To":"Jakub Jelinek ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"Hi!\n\nThe following testcase is miscompiled because the 3\nTARGET_AVOID_FALSE_DEP_FOR_BMI APX NF splitters use ix86_expand_clear.\nAll other uses of ix86_expand_clear are on either splitters where we know\nsomething clobbers flags register or sets it at the end of pattern (so\nclearly flags register is not live across the pattern) or in\ndefine_peephole2 where we explicitly check peep2_regno_dead_p (?, FLAGS_REG).\nNow, ix86_expand_clear handles right the QI/HImode cases by setting SImode\ninstead and based on TARGET_USE_MOV0 and/or optimize_insn_for_size_p\ndecides whether to use xor reg, reg form or mov $0, reg.\nNow, for these 3 APX NF splitters there is actually no flags clobber nor set\nin the pattern and because it is a splitter, we don't know if flags register\nis live across it (likely yes, otherwise why the APX NF pattern would be\nused) or not. So, we can't use ix86_expand_clear which could clobber flags.\nAs the splitters are only SWI48, we don't have to worry about QI/HImode\nclearing and so IMHO just want to always use the mov $0, reg form by hand.\nIf flags actually isn't live across it, we have\n;; Attempt to always use XOR for zeroing registers (including FP modes).\n(define_peephole2\n [(set (match_operand 0 \"general_reg_operand\")\n (match_operand 1 \"const0_operand\"))]\n \"GET_MODE_SIZE (GET_MODE (operands[0])) <= UNITS_PER_WORD\n && (! TARGET_USE_MOV0 || optimize_insn_for_size_p ())\n && peep2_regno_dead_p (0, FLAGS_REG)\"\n [(parallel [(set (match_dup 0) (const_int 0))\n (clobber (reg:CC FLAGS_REG))])]\n \"operands[0] = gen_lowpart (word_mode, operands[0]);\")\npeephole2 which would turn the mov $0, reg back to xor reg, reg.\n\nBootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n\n2026-04-16 Jakub Jelinek \n\n\tPR target/124892\n\t* config/i386/i386.md (clz2_lzcnt_nf,\n\t__nf, popcount2_nf): Emit explicit\n\tset of (match_dup 0) to (const_int 0) without flags clobber instead of\n\tusing ix86_expand_clear.\n\n\t* gcc.target/i386/apx-pr124892.c: New test.\n\n\n\tJakub","diff":"--- gcc/config/i386/i386.md.jj\t2026-03-27 10:17:13.854335308 +0100\n+++ gcc/config/i386/i386.md\t2026-04-15 18:35:23.740482534 +0200\n@@ -21859,11 +21859,12 @@ (define_insn_and_split \"clz2_lzcnt\n \"&& TARGET_AVOID_FALSE_DEP_FOR_BMI && epilogue_completed\n && optimize_function_for_speed_p (cfun)\n && !reg_mentioned_p (operands[0], operands[1])\"\n- [(parallel\n+ [(set (match_dup 0) (const_int 0))\n+ (parallel\n [(set (match_dup 0)\n \t (clz:SWI48 (match_dup 1)))\n (unspec [(match_dup 0)] UNSPEC_INSN_FALSE_DEP)])]\n- \"ix86_expand_clear (operands[0]);\"\n+ \"\"\n [(set_attr \"prefix_rep\" \"1\")\n (set_attr \"type\" \"bitmanip\")\n (set_attr \"mode\" \"\")])\n@@ -22020,11 +22021,12 @@ (define_insn_and_split \"_\n \"&& TARGET_AVOID_FALSE_DEP_FOR_BMI && epilogue_completed\n && optimize_function_for_speed_p (cfun)\n && !reg_mentioned_p (operands[0], operands[1])\"\n- [(parallel\n+ [(set (match_dup 0) (const_int 0))\n+ (parallel\n [(set (match_dup 0)\n \t (unspec:SWI48 [(match_dup 1)] LT_ZCNT))\n (unspec [(match_dup 0)] UNSPEC_INSN_FALSE_DEP)])]\n- \"ix86_expand_clear (operands[0]);\"\n+ \"\"\n [(set_attr \"type\" \"\")\n (set_attr \"prefix_0f\" \"1\")\n (set_attr \"prefix_rep\" \"1\")\n@@ -22666,11 +22668,12 @@ (define_insn_and_split \"popcount2_\n \"&& TARGET_AVOID_FALSE_DEP_FOR_BMI && epilogue_completed\n && optimize_function_for_speed_p (cfun)\n && !reg_mentioned_p (operands[0], operands[1])\"\n- [(parallel\n+ [(set (match_dup 0) (const_int 0))\n+ (parallel\n [(set (match_dup 0)\n \t (popcount:SWI48 (match_dup 1)))\n (unspec [(match_dup 0)] UNSPEC_INSN_FALSE_DEP)])]\n- \"ix86_expand_clear (operands[0]);\"\n+ \"\"\n [(set_attr \"prefix_rep\" \"1\")\n (set_attr \"type\" \"bitmanip\")\n (set_attr \"mode\" \"\")])\n--- gcc/testsuite/gcc.target/i386/apx-pr124892.c.jj\t2026-04-15 18:44:16.052606262 +0200\n+++ gcc/testsuite/gcc.target/i386/apx-pr124892.c\t2026-04-15 18:44:50.020039751 +0200\n@@ -0,0 +1,20 @@\n+/* PR target/124892 */\n+/* { dg-do run { target { apxf && { lzcnt && { ! ia32 } } } } } */\n+/* { dg-options \"-O2 -frename-registers\" } */\n+\n+[[gnu::noipa, gnu::target (\"apxf\"), gnu::target (\"lzcnt\")]] char\n+foo (unsigned u)\n+{\n+ return __builtin_stdc_bit_ceil (u);\n+}\n+\n+int\n+main ()\n+{\n+ if (!__builtin_cpu_supports (\"apxf\"))\n+ return 0;\n+ if (!__builtin_cpu_supports (\"lzcnt\"))\n+ return 0;\n+ if (foo (7) != 8)\n+ __builtin_abort ();\n+}\n","prefixes":[]}