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Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Robert Finch <robfi680@gmail.com> Newsgroups: comp.arch Subject: Re: Cost of handling misaligned access Date: Thu, 20 Feb 2025 20:26:57 -0500 Organization: A noiseless patient Spider Lines: 18 Message-ID: <vp8kp3$334fu$1@dont-email.me> References: <5lNnP.1313925$2xE6.991023@fx18.iad> <vnosj6$t5o0$1@dont-email.me> <2025Feb3.075550@mips.complang.tuwien.ac.at> <volg1m$31ca1$1@dont-email.me> <voobnc$3l2dl$1@dont-email.me> <0fc4cc997441e25330ff5c8735247b54@www.novabbs.org> <vp0m3f$1cth6$1@dont-email.me> <74142fbdc017bc560d75541f3f3c5118@www.novabbs.org> <20250218150739.0000192a@yahoo.com> <0357b097bbbf6b87de9bc91dd16757e3@www.novabbs.org> <vp2sv2$1skve$1@dont-email.me> <a34ce3b43fab761d13b2432f9e255fab@www.novabbs.org> <vp518t$2bhib$1@dont-email.me> <a56e446b2e2df9f01eb558aa68279d35@www.novabbs.org> <vp5mnu$2fjhi$1@dont-email.me> <2dc33514bc664e667173b132601e6ce0@www.novabbs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Fri, 21 Feb 2025 02:27:00 +0100 (CET) Injection-Info: dont-email.me; posting-host="a1c507ec5f40defafaf6f6b644319e9f"; logging-data="3248638"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18pXMXAUMeMN8gX9YnsTvQ+/6u07oe4mt4=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:Ubz5p4gWgQOr0O4HvgjO+oNKULw= Content-Language: en-US In-Reply-To: <2dc33514bc664e667173b132601e6ce0@www.novabbs.org> Bytes: 2442 >> Admittedly part of why I have such mixed feelings on full >> compare-and-branch: >> Pro: It can offer a performance advantage (in terms of per-clock); >> Con: Branch is now beholden to the latency of a Subtract. > Con: it can't compare to a constant > Con: it can't compare floating point > compare to constant, and floating point compares are supported in Q+ so the cons are gone constant compare is supported with the constant postfix. Because bits are available in the instruction there is also a precision field. One can compare bytes and branch for instance. Q+ supports all kinds of compares including those generating bit vectors and SETxx, ZSETxx type compares. That is maybe its drawback, supporting too many things.