From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ej1-f45.google.com (mail-ej1-f45.google.com [209.85.218.45]) by sourceware.org (Postfix) with ESMTPS id 93B9838618D7; Wed, 5 May 2021 19:37:04 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 93B9838618D7 Received: by mail-ej1-f45.google.com with SMTP id r9so4673091ejj.3; Wed, 05 May 2021 12:37:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=t4yA9NVHOqxmcVl+BAwaKCX0UnFh2xV25QwaDUceXyc=; b=fzLssd9sdAc1EC4VPr0xQh5p0hBwt/msOgnzlWnoloP4CUN/Wz+tMReKbxsZIDwlZG CS8qcU4R8KhCulJRSXwrjR3uUxrKNQOzhRbIxMJ1u2QiaTWfPfboBOOI+5OBdQoxCnRC mxjES3HOQOogHd0eGEAjXycCe6UXpwJ7DTMFJhbz/JczdbxTJE2W90/tR4DaHqzDRyP6 a/dmjf3Nr4yteojYCllXbXHTD+PZeHvIXSX8MlP3tvFx9cHeO6DpdLYaLOlGE/Cf/jSU EIPtX7WU4XmS6tjszsn/PtDXvqP3T/+WTq2SXXy0874I6KsCqKs2W/NhyDOsy3t6zkjW s8Jw== X-Gm-Message-State: AOAM533OoTWShS47Nngr0Hw5BDE6cWIUw4PE7eBTctGjS5uDGVIT3qg/ 6+RRl+ToASYiI/bIjUMYNlDh8CF84UmUI7Z8 X-Google-Smtp-Source: ABdhPJzZL/Rq/Y/6rjYNYLsWEauak2ippuzlQvX6fOO/miSJfQkc9U0WtsoQsD/COnofESu2FMnVtg== X-Received: by 2002:a17:906:fb04:: with SMTP id lz4mr430171ejb.66.1620243423398; Wed, 05 May 2021 12:37:03 -0700 (PDT) Received: from beast.fritz.box (62-178-148-172.cable.dynamic.surfer.at. [62.178.148.172]) by smtp.gmail.com with ESMTPSA id t7sm60531eds.26.2021.05.05.12.37.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 May 2021 12:37:03 -0700 (PDT) From: Christoph Muellner To: gcc-patches@gcc.gnu.org Cc: Jim Wilson , Kito Cheng , Christoph Muellner Subject: [PATCH v2 04/10] RISC-V: Use STORE instead of AMOSWAP for atomic stores [PR 100265] Date: Wed, 5 May 2021 21:36:45 +0200 Message-Id: <20210505193651.2075405-5-cmuellner@gcc.gnu.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210505193651.2075405-1-cmuellner@gcc.gnu.org> References: <20210505193651.2075405-1-cmuellner@gcc.gnu.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.4 required=5.0 tests=BAYES_00, FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, GIT_PATCH_0, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Wed, 05 May 2021 19:37:05 -0000 Using AMOSWAP as atomic store does not allow us to do sub-word accesses. Further, it is not consistent with our atomic_load () implementation. The benefit of AMOSWAP is that the resulting code sequence will be smaller (comapred to FENCE+STORE), however, this does not weight out for the lack of sub-word accesses. Additionally, HW implementors have claimed that an optimal implementation AMOSWAP is slightly more expensive than FENCE+STORE. So let's use STORE instead of AMOSWAP. gcc/ PR 100265 * config/riscv/sync.md (atomic_store): Remove. --- gcc/config/riscv/sync.md | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/gcc/config/riscv/sync.md b/gcc/config/riscv/sync.md index aeeb2e854b68..efd49745a8e2 100644 --- a/gcc/config/riscv/sync.md +++ b/gcc/config/riscv/sync.md @@ -57,17 +57,6 @@ ;; Atomic memory operations. -;; Implement atomic stores with amoswap. Fall back to fences for atomic loads. -(define_insn "atomic_store" - [(set (match_operand:GPR 0 "memory_operand" "=A") - (unspec_volatile:GPR - [(match_operand:GPR 1 "reg_or_0_operand" "rJ") - (match_operand:SI 2 "const_int_operand")] ;; model - UNSPEC_ATOMIC_STORE))] - "TARGET_ATOMIC" - "amoswap.%A2 zero,%z1,%0" - [(set (attr "length") (const_int 8))]) - (define_insn "atomic_" [(set (match_operand:GPR 0 "memory_operand" "+A") (unspec_volatile:GPR -- 2.31.1