Path: ...!news.misty.com!weretis.net!feeder6.news.weretis.net!i2pn.org!i2pn2.org!.POSTED!not-for-mail From: mitchalsup@aol.com (MitchAlsup1) Newsgroups: comp.arch Subject: Re: Stealing a Great Idea from the 6600 Date: Tue, 23 Apr 2024 17:58:41 +0000 Organization: Rocksolid Light Message-ID: References: <1s042jdli35gdo092v6uaupmrcmvo0i5vp@4ax.com> <9d1fadaada2ec0683fc54688cce7cf27@www.novabbs.org> <44fdd1209496c66ba18e425370a8b50d@www.novabbs.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Info: i2pn2.org; logging-data="2135183"; mail-complaints-to="usenet@i2pn2.org"; posting-account="65wTazMNTleAJDh/pRqmKE7ADni/0wesT78+pyiDW8A"; User-Agent: Rocksolid Light X-Rslight-Posting-User: ac58ceb75ea22753186dae54d967fed894c3dce8 X-Spam-Checker-Version: SpamAssassin 4.0.0 X-Rslight-Site: $2y$10$tH69DT4UtLLefB/288Y21.5eLFkBaz8ZwM36I6o2lOHuZhjszeBm6 Bytes: 2300 Lines: 20 George Neuner wrote: > On Sun, 21 Apr 2024 00:43:21 +0000, mitchalsup@aol.com (MitchAlsup1) > wrote: >>Address arithmetic is ADD only and does not care about signs or >>overflow. There is no concept of a negative base register or a >>negative index register (or, for that matter, a negative displace- >>ment), overflow, underflow, carry, ... > Stack frame pointers often point to the middle of the frame and need > to access data using both positive and negative displacements. Yes, one accesses callee saved registers with positive displacements and local variables with negative accesses. One simply needs to know where the former stops and the later begins. ENTER and EXIT know this by the register count and by the stack allocation size. > Some GC schemes use negative displacements to access object headers. Those are negative displacements not negative bases or indexes.