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Received: from VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) by AM0PR04MB6883.eurprd04.prod.outlook.com (2603:10a6:208:17f::14) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6064.27; Thu, 2 Feb 2023 11:29:51 +0000 Received: from VE1PR04MB6560.eurprd04.prod.outlook.com ([fe80::e138:4fc3:705c:d178]) by VE1PR04MB6560.eurprd04.prod.outlook.com ([fe80::e138:4fc3:705c:d178%6]) with mapi id 15.20.6064.024; Thu, 2 Feb 2023 11:29:51 +0000 Message-ID: <7c6e61f4-b61c-a451-ba13-914c2e7f0dcf@suse.com> Date: Thu, 2 Feb 2023 12:29:49 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH][Binutils]AArch64 gas: relax ordering constriants on enabling and disabling feature extensions Content-Language: en-US To: Tamar Christina Cc: nd@arm.com, Richard.Earnshaw@arm.com, marcus.shawcroft@arm.com, binutils@sourceware.org References: From: Jan Beulich In-Reply-To: Content-Type: text/plain; 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This removes the restriction from gas as well giving users less > friction. Hmm, specifying negative before positive settings may mean the negative ones don't take effect at all (because of feature dependencies). While the same of course is true the other way around as well, silently accepting supposedly disabled insns is imo quite a bit more risky than complaining about supposedly enabled ones: The programmer may unknowingly produce a bad binary. This is even more so that the dependencies can't be considered set in stone - bugs may be found which require adjustments to them. There actually is an example of something which may want adjusting: Both F32MM and F64MM take SVE as prereq. While SVE can't easily be a prereq to I8MM (because there are also SIMD insn forms), it's unclear why SIMD - itself being a prereq to SVE - isn't a prereq to I8MM. > @@ -10269,31 +10265,20 @@ aarch64_parse_features (const char *str, const aarch64_feature_set **opt_p, > > if (optlen >= 2 && startswith (str, "no")) > { > - if (adding_value != 0) > - adding_value = 0; > + adding_value = 0; > optlen -= 2; > str += 2; > } > else if (optlen > 0) > { > - if (adding_value == -1) > - adding_value = 1; > - else if (adding_value != 1) > - { > - as_bad (_("must specify extensions to add before specifying " > - "those to remove")); > - return false; > - } > + adding_value = 1; > } > - > - if (optlen == 0) > + else if (optlen == 0) > { > as_bad (_("missing architectural extension")); > return 0; > } This "if" -> "else if" transformation looks not only unrelated to me, but actually slightly wrong: The message now won't trigger anymore when there just "+no" was specified. Jan