From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,81b62fa6e95ab58b X-Google-Attributes: gid103376,public From: kilgallen@eisner.decus.org (Larry Kilgallen) Subject: Re: aliased & packed? Date: 1997/05/13 Message-ID: <1997May13.154714.1@eisner>#1/1 X-Deja-AN: 241338020 X-Nntp-Posting-Host: eisner.decus.org References: <5l5llv$4e@lotho.delphi.com> <1997May13.065907.1@eisner> X-Nntp-Posting-User: KILGALLEN X-Trace: 863552842/18607 Organization: LJK Software Newsgroups: comp.lang.ada Date: 1997-05-13T00:00:00+00:00 List-Id: In article , bobduff@world.std.com (Robert A Duff) writes: > Is this really true? I mean, if you access one byte at the start of a > word (using byte instructions on the 21164), then won't the next seven > be sitting there in the cache waiting for you? Good point. I don't know what they have in there, but probably they have that. Of course registers are still faster than cache. > And it seems like more than a couple of instructions to shift and mask > an 8-byte word (I mean, using 21064 instructions only), in the case > where the byte you want is dynamic (i.e. you're indexing randomly into > an array of bytes -- on the other hand, most array accesses are probably > sequential). >From what I have seen (several years ago), the register-to-register instructions on Alpha look quite weird but many of them have clever uses in such operations. The instruction set was designed with heavy input from compiler writers. Larry Kilgallen