Path: csiph.com!aioe.org!.POSTED!not-for-mail
From: "Rod Pemberton" <boo@fasdfrewar.cdm>
Newsgroups: alt.os.development
Subject: Re: What form of executable or load module for your OS?
Date: Mon, 06 Jul 2015 06:21:08 -0400
Organization: Aioe.org NNTP Server
Lines: 38
Message-ID: <op.x1ckdiopyfako5@localhost>
References: <mme4i6$a6e$1@dont-email.me> <5bb535cc-0995-4fdd-ae16-a1217c4b8e92@googlegroups.com> <mn0c7p$q8n$1@dont-email.me> <c80bcbf7-a245-45a7-bb30-21e5660c2959@googlegroups.com> <mn3749$3nl$1@dont-email.me> <75acded2-9f64-4d9f-81c2-7ec73fd72e01@googlegroups.com> <mn5dto$q6c$1@dont-email.me> <1687b850-3c16-44ec-9bd9-4eb0dc2a201b@googlegroups.com> <mn5o0b$uv1$1@dont-email.me> <op.x07tovymyfako5@localhost> <mn6vm9$g5a$1@dont-email.me> <fe6d6902-6d1a-4452-94a6-233d89db24e1@googlegroups.com> <mn73e5$3hc$1@dont-email.me> <op.x08ojxp5yfako5@localhost> <853c70d5-5652-42e9-ac0f-e4b832b56ca3@googlegroups.com> <mnc6th$qa4$1@dont-email.me> <cec50788-642e-40f0-bf0f-29c74057392f@googlegroups.com>
NNTP-Posting-Host: n4wpt9zq8xR26Ttf9mo2BA.user.speranza.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1; format=flowed; delsp=yes
Content-Transfer-Encoding: 7bit
X-Complaints-To: abuse@aioe.org
User-Agent: Opera Mail/12.16 (Linux)
X-Notice: Filtered by postfilter v. 0.8.2
Xref: aioe.org alt.os.development:8308

On Sun, 05 Jul 2015 18:15:50 -0400, Alexei A. Frounze  
<alexfrunews@gmail.com> wrote:

> For MOVZX. PUSHF/POPF not needed.
>
> MOVSX is worse:
>
> PUSH AX ; if dst != AX
> MOV AL, src
> CBW
> MOV dst, AX ; if dst != AX
> POP AX ; if dst != AX
>

It's too bad there is no PUSH reg8 ...

> There are two types of comparisons in Smaller C:
> 1. comparisons whose result is used for if/while/for:
>   if (a < b) ...
>   while (a < b) ...
>   do ... while (a < b);
>   for (...; a < b; ...) ...
> 2. all other comparisons:
>   c = a < b;
> CMP+Jcc are used in the former.
> CMP+SETcc are used in the latter.

If those are the only comparisons, what are you using MOVSX for?
Signed-arithmetic?  If so, delay using CBW until an arithmetic
operation is performed when AX is free.  Then, no need for MOVSX.


Rod Pemberton

-- 
Tolerance and socialism attracts intolerance and terrorism.  See:
France, United Kingdom, Germany, Denmark, Belgium, Netherlands, ...
UK: Strong encryption, non-issue. GR: Eurozone currency, priority.