From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id EAA81385841D; Tue, 23 Jan 2024 07:08:53 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org EAA81385841D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1705993733; bh=NJU3t57O8hwcH9MuHWwYCuMdGxYqXT+AK33tPGCq9Pk=; h=From:To:Subject:Date:In-Reply-To:References:From; b=qRG2YCj6780QYSxsqtgeb7dlyvhbjavz8aMuISziJXbqhllHN8CICX2zk4JOGZ8gA 0nI37MJl3kKYqrs9PKYpAt7+lWIuG9ZRtTSgffxpI1vsuGevkduY0KQH6gCOqn71+k Yg4xqEEOme2e5V58qb+A3y21h9mwzN1XiFjR1/kw= From: "cvs-commit at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/113255] [11/12/13/14 Regression] wrong code with -O2 -mtune=k8 Date: Tue, 23 Jan 2024 07:08:52 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 13.2.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: cvs-commit at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 11.5 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113255 --- Comment #12 from GCC Commits --- The master branch has been updated by Richard Biener : https://gcc.gnu.org/g:a98d5130a6dcff2ed4db371e500550134777b8cf commit r14-8346-ga98d5130a6dcff2ed4db371e500550134777b8cf Author: Richard Biener Date: Mon Jan 15 12:55:20 2024 +0100 rtl-optimization/113255 - base_alias_check vs. pointer difference When the x86 backend generates code for cpymem with the rep_8byte strathegy for the 8 byte aligned main rep movq it needs to compute an adjusted pointer to the source after doing a prologue aligning the destination. It computes that via src_ptr + (dest_ptr - orig_dest_ptr) which is perfectly fine. On RTL this is then 8: r134:DI=3Dconst(`g'+0x44) 9: {r133:DI=3Dframe:DI-0x4c;clobber flags:CC;} REG_UNUSED flags:CC 56: r129:DI=3Dconst(`g'+0x4c) 57: {r129:DI=3Dr129:DI&0xfffffffffffffff8;clobber flags:CC;} REG_UNUSED flags:CC REG_EQUAL const(`g'+0x4c)&0xfffffffffffffff8 58: {r118:DI=3Dr134:DI-r129:DI;clobber flags:CC;} REG_DEAD r134:DI REG_UNUSED flags:CC REG_EQUAL const(`g'+0x44)-r129:DI 59: {r119:DI=3Dr133:DI-r118:DI;clobber flags:CC;} REG_DEAD r133:DI REG_UNUSED flags:CC but as written find_base_term happily picks the first candidate it finds for the MINUS which means it picks const(`g') rather than the correct frame:DI. This way find_base_term (but also the unfixed find_base_value used by init_alias_analysis to initialize REG_BASE_VALUE) performs pointer analysis isn't sound. The following restricts the handling of multi-operand operations to the case we know only one can be a pointer. This for example causes gcc.dg/tree-ssa/pr94969.c to miss some RTL PRE (I've opened PR113395 for this). A more drastic patch, removing base_alias_check results in only gcc.dg/guality/pr41447-1.c regressing (so testsuite coverage is bad). I've looked at gcc.dg/tree-ssa tests and mostly scheduling changes are present, the cc1plus .text size is only 230 bytes worse. With the this less drastic patch below most scheduling changes are gone. x86_64 might not the very best target to test for impact, but test coverage on other targets is unlikely to be very much better. PR rtl-optimization/113255 * alias.cc (find_base_term): Remove PLUS/MINUS handling when both operands are not CONST_INT_P. * gcc.dg/torture/pr113255.c: New testcase.=