From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-sender-0.a4lg.com (mail-sender-0.a4lg.com [IPv6:2401:2500:203:30b:4000:6bfe:4757:0]) by sourceware.org (Postfix) with ESMTPS id 324F73858428 for ; Wed, 7 Sep 2022 05:54:16 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 324F73858428 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=irq.a4lg.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=irq.a4lg.com Received: from [127.0.0.1] (localhost [127.0.0.1]) by mail-sender-0.a4lg.com (Postfix) with ESMTPSA id D40EC300089; Wed, 7 Sep 2022 05:54:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=irq.a4lg.com; s=2017s01; t=1662530053; bh=5yMHJipb1zLlYPeYWST564w709gylt4Sbi+CnmTzpnY=; h=From:To:Cc:Subject:Date:Message-Id:Mime-Version: Content-Transfer-Encoding; b=Fo5UAQNUQKu9BWTLLksYYyY6H/rZGurLMAl7rvgME86ZX8TR2B/D2tL5SEDjvLG6g baO6OuXS17icrnWI6tLWntuWDkWhaYkoBH6Z+NJk/V0fzom9JIYLRz7ZrdTuJde9+j IyEY/HPHzAbvxBPrFWO/Ae13ob5vsEZ+125LA/vM= From: Tsukasa OI To: Tsukasa OI , Nelson Chu , Kito Cheng , Palmer Dabbelt Cc: binutils@sourceware.org Subject: [PATCH 0/3] RISC-V: Fix CSR accessibility and implications Date: Wed, 7 Sep 2022 05:53:55 +0000 Message-Id: Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-6.4 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Tracker on GitHub: While I'm reorganizing "b-ext*" and "k-ext*" tests (to make sure that they are able to be removed since there are neither 'B' nor 'K' extensions), I found something interesting. If we assemble a file with "csrr a0, seed" (uses "seed" CSR from the 'Zkr' extension) with "-march=rv32i_zkr", it causes an error to require 'Zicsr'. Yes, current GNU Binutils does not imply 'Zicsr' from 'Zkr' so that adding 'Zkr' extension alone is not enough to access corresponding CSRs (current version requires an option like "-march=rv32i_zicsr_zkr"). "k-ext.d" does not give 'Zicsr' either (and does not test the seed CSR) and adding the line "csrr a0, seed" to this test file resulted the same. That means something. If an extension adds CSR(s), we should imply 'Zicsr' from that extension (just like 'F'). So, we have to imply 'Zicsr' from following extensions: - 'H' - 'Zkr' - 'Zve32x' (I'll talk later) - 'Smstateen' - 'Sscofpmf' - 'Sstc' 'Zkr' is fixed in PATCH 2/3 and 'H' and 'S*' are fixed in PATCH 3/3. The only remaining extension is 'Zve32x' but I need to talk more to explain actual changes (specific to vectors) in PATCH 1/3. On the current version of GNU Binutils, CSRs with CSR_CLASS_V means they require the 'V' extension. However, there are a few vector subextensions that implement vector subsets (intended for embedded processors). - 'Zve64d' (superset of 'Zve64f') - 'Zve64f' (superset of 'Zve32f' and 'Zve64x') - 'Zve64x' (superset of 'Zve32x') - 'Zve32f' (superset of 'Zve32x') - 'Zve32x' : Graph: Dependency graph of some vector/FP extensions : : +-------> D --------> F -----> Zicsr : | ^ ^ : | | | : V ---> Zve64d ---> Zve64f ---> Zve64x : | | : V V : Zve32f ---> Zve32x : | : | : +---> (Zicsr [added in PATCH 1/3]) They also require general purpose vector CSRs (vstart, vl, vtype and vlenb). So, corresponding CSR_CLASS_V with the 'V' extension is inappropriate (they should require 'Zve32x' instead, the minimum vector subset). Remaining CSRs are: - vxsat - vxrm - vcsr They are related to fixed-point arithmetic and 18.2 "Zve*: Vector Extensions for Embedded Processors" says: > All Zve* extensions support all vector fixed-point arithmetic instructions > (Vector Fixed-Point Arithmetic Instructions), except that vsmul.vv and > vsmul.vx are not supported for EEW=64 in Zve64*. So, their minimum requirement shall be also 'Zve32x', not 'V'. As a consequence, we can conclude that changing requirements of CSR_CLASS_V from 'V' to 'Zve32x' is sufficient to avoid CSR accessibility warnings. Also, 'Zve32x' must imply 'Zicsr' (just like the rest) to avoid CSR instruction errors. This is only effective on 'Zve32x' and 'Zve64x' because, for instance, 'Zve32f' implies 'F' and 'F' implies 'Zicsr' (see the graph above). I didn't rename CSR_CLASS_V to CSR_CLASS_ZVE32X because the name gets difficult and there's already INSN_CLASS_V (effectively requires 'Zve32x' with some exceptions). Tsukasa OI (3): RISC-V: Fix vector CSR requirements and imply RISC-V: Imply 'Zicsr' from 'Zkr' RISC-V: Imply 'Zicsr' from some privileged extensions bfd/elfxx-riscv.c | 6 +++++ gas/config/tc-riscv.c | 2 +- gas/testsuite/gas/riscv/csr-version-1p10.l | 28 ++++++++++---------- gas/testsuite/gas/riscv/csr-version-1p11.l | 28 ++++++++++---------- gas/testsuite/gas/riscv/csr-version-1p12.l | 28 ++++++++++---------- gas/testsuite/gas/riscv/csr-version-1p9p1.l | 28 ++++++++++---------- gas/testsuite/gas/riscv/march-imply-h.d | 6 +++++ gas/testsuite/gas/riscv/vector-csrs-zve32f.d | 21 +++++++++++++++ gas/testsuite/gas/riscv/vector-csrs-zve32x.d | 21 +++++++++++++++ gas/testsuite/gas/riscv/vector-csrs-zve64d.d | 21 +++++++++++++++ gas/testsuite/gas/riscv/vector-csrs-zve64f.d | 21 +++++++++++++++ gas/testsuite/gas/riscv/vector-csrs-zve64x.d | 21 +++++++++++++++ gas/testsuite/gas/riscv/vector-csrs.s | 12 +++++++++ gas/testsuite/gas/riscv/zkr.d | 10 +++++++ gas/testsuite/gas/riscv/zkr.s | 2 ++ 15 files changed, 198 insertions(+), 57 deletions(-) create mode 100644 gas/testsuite/gas/riscv/march-imply-h.d create mode 100644 gas/testsuite/gas/riscv/vector-csrs-zve32f.d create mode 100644 gas/testsuite/gas/riscv/vector-csrs-zve32x.d create mode 100644 gas/testsuite/gas/riscv/vector-csrs-zve64d.d create mode 100644 gas/testsuite/gas/riscv/vector-csrs-zve64f.d create mode 100644 gas/testsuite/gas/riscv/vector-csrs-zve64x.d create mode 100644 gas/testsuite/gas/riscv/vector-csrs.s create mode 100644 gas/testsuite/gas/riscv/zkr.d create mode 100644 gas/testsuite/gas/riscv/zkr.s base-commit: f555b327d41ed72ffae28caae550f5f86312db43 -- 2.34.1