Path: utzoo!utgpu!news-server.csri.toronto.edu!torsqnt!lethe!becker!ncrcan!brambo!wwg
From: wwg@brambo.UUCP (Warren W. Gay VE3WWG)
Newsgroups: comp.sys.ibm.pc.programmer
Subject: Re: No Aliasing Compile Option
Keywords: Microsoft 6.0 C update woes alias
Message-ID: <893@brambo.UUCP>
Date: 4 Jun 90 17:15:46 GMT
References: <1990May19.141401.4350@ux1.cso.uiuc.edu> <265861D7.3293@tct.uucp> <1913@cod.NOSC.MIL> <265A8814.1465@tct.uucp>
Reply-To: wwg@brambo.UUCP (Warren W. Gay VE3WWG)
Organization: Bramalea Software Inc., Bramalea, Ont.
Lines: 55

>In article <265A8814.1465@tct.uucp> chip@tct.uucp (Chip Salzenberg) writes:
>[[ Please note that the -Ox flag of MSC 6.0 is now safe.  However,
>   unsafe aliasing optimization is still available with the -Oa flag.
>   The target of my criticism is the use of -Oa in compiling
>   advertising benchmarks. ]]
>...bunch of stuff removed...
>
>Nevertheless, I stand by my assertion that the use of a "benchmark
>flag" (-Oa) is reprehensible on Microsoft's part--doubly so, since
>they didn't print in large friendly letters, THIS BENCHMARK IS
>COMPILED WITH A NO-ALIASING OPTION THAT YOU MAY NOT BE ABLE TO USE FOR
>YOUR OWN CODE.


I'm coming into this fray rather late, but hey-- at least they didn't
use the "#asm" optimization feature! :-)

You are arguing at cross purposes. Unless u are in agreement about what
is being measured, the argument is pointless.

	"What should the benchmark measure?"

The possibilities include:

	1.	Default compiles.
	2.	Safe optimized compiles.
	3.	Flat out capability.


I believe that all 3 measurements are useful. Measurement # 2 is 
probably the most important, especially when existing code is to be
RE-compiled and/or ported. If only one set of benchmarks are going to be
published, then I tend to think that this should be the figure to publish
(but again, we have to agree on what is being measured first).

However, if I was to purchase a product, and assuming that I also want to
spend the time tweaking (or can justify doing so), then the all out, flat
out "measurements" are also highly significant. This becomes a test of
the "capability" of the compiler-- just how far can it go if I NEED it.

If I went with "safe optimization" only compiler (or options), then I'd
be forced to go to MASM more often. Given the choices-- I'd much rather
use a "subset C" when I need to, then be stuck to a principle.

*flame*suit*on*

After all, referring thru a pointer is equally valid C code. So why INSIST
on aliasing in the first place?  ;-)

*flame*suit*off*

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