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Mon, 15 Sep 2025 09:53:10 -0700 (PDT) Received: from free.home ([187.106.43.153]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2677a5cf655sm26289965ad.4.2025.09.15.09.53.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Sep 2025 09:53:09 -0700 (PDT) Received: from livre (livre.home [172.31.160.2]) by free.home (8.15.2/8.15.2) with ESMTPS id 58FGpjoC2168892 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 15 Sep 2025 13:51:48 -0300 From: Alexandre Oliva To: gcc-patches@gcc.gnu.org Cc: Vladimir Makarov , Rainer Orth , Mike Stump , Richard Earnshaw , Tamar Christina , Kyrylo Tkachov Subject: [PATCH 2/2v2] [ira] avoid resetting ira_reg_equiv for function invariants Organization: Free thinker, does not speak for AdaCore References: Date: Mon, 15 Sep 2025 13:51:45 -0300 In-Reply-To: (Alexandre Oliva's message of "Sat, 13 Sep 2025 04:06:43 -0300") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_ABUSEAT, RCVD_IN_BARRACUDACENTRAL, RCVD_IN_DNSWL_NONE, RCVD_IN_SBL_CSS, SPF_HELO_NONE, SPF_PASS, TXREP, WEIRD_QUOTING autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces~patchwork=sourceware.org@gcc.gnu.org An aarch64 toolchain built with --enable-default-pie fails gcc.target/aarch64/sme/nonlocal_goto_[123].c because the register allocator ends up resetting equivalences, so it concludes it needs to preserve a rematerializable function invariant across a call instead of rematerializing it. Restore the find_reg_equiv_invariant_const logic that was in place before commit 55a2c3226a3e90a6d65f19710bab1ac377054234 rewrote it and added a (spurious?) requirement for non-function-invariants to retain an equivalence when other PIC-related conditions didn't apply. That requirement seems either reversed or unnecessary. Regstrapped on x86_64-linux-gnu, with and without --enable-host-pie, and on aarch64-linux-gnu, with --enable-host-pie --enable-default-pie. This version of the patch even makes sense to me! :-) Ok to install? for gcc/ChangeLog * ira.cc (setup_reg_equiv): Retain function invariant equivalences. --- gcc/ira.cc | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/gcc/ira.cc b/gcc/ira.cc index 4eebc9c4c50fb..3e15966558edf 100644 --- a/gcc/ira.cc +++ b/gcc/ira.cc @@ -4233,12 +4233,14 @@ setup_reg_equiv (void) && REGNO (SET_SRC (set)) == (unsigned int) i); x = SET_DEST (set); } - if (! function_invariant_p (x) + /* If PIC is enabled and the equiv is not a LEGITIMATE_PIC_OPERAND, + we can't use it. */ + if (! CONSTANT_P (x) || ! flag_pic /* A function invariant is often CONSTANT_P but may include a register. We promise to only pass CONSTANT_P objects to LEGITIMATE_PIC_OPERAND_P. */ - || (CONSTANT_P (x) && LEGITIMATE_PIC_OPERAND_P (x))) + || LEGITIMATE_PIC_OPERAND_P (x)) { /* It can happen that a REG_EQUIV note contains a MEM that is not a legitimate memory operand. As later