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Groups > comp.lang.forth > #56661
| From | anton@mips.complang.tuwien.ac.at (Anton Ertl) |
|---|---|
| Newsgroups | comp.lang.forth |
| Subject | Re: LLVM and Forth |
| Date | 2017-04-03 13:52 +0000 |
| Organization | Institut fuer Computersprachen, Technische Universitaet Wien |
| Message-ID | <2017Apr3.155215@mips.complang.tuwien.ac.at> (permalink) |
| References | (2 earlier) <ac4976d7-955a-45e3-9cdd-e339e15acbc2@googlegroups.com> <ZqGdnRes4qCBI33FnZ2dnUU7-VednZ2d@supernews.com> <065e774c-c5fb-4e68-9489-00b5357142d6@googlegroups.com> <81ee5375-fdd8-471f-89a7-6c1043ba2307@googlegroups.com> <2b5e56ca-8952-4cf7-84a6-462b49d7093a@googlegroups.com> |
krishna.myneni@ccreweb.org writes:
>On Monday, April 3, 2017 at 3:10:00 AM UTC-5, minf...@arcor.de wrote:
>> So there is no undefined code. I have never encountered C Compiler proble=
>ms because kernels are small and the resulting C code is straightforward an=
>d doesn't use any esoteric constructs. KISS is always a good pronciple.
It does not help against nasal demons. You can get them in just a few
characters, and with code that most people would see as
straighforward. E.g., try to write rotl32(int x, unsigned n) or
memmove() in C.
>The new C standard apparently has p=
>lenty of such undefined behaviors, sacrificing language safety for the sake=
> of compiler optimization. From the LLVM project blog:
>
>"Undefined behavior exists in C-based languages because the designers of C =
>wanted it to be an extremely efficient low-level programming language. In c=
>ontrast, languages like Java (and many other 'safe' languages) have eschewe=
>d undefined behavior because they want safe and reproducible behavior acros=
>s implementations, and willing to sacrifice performance to get it. While ne=
>ither is "the right goal to aim for," if you're a C programmer you really s=
>hould understand what undefined behavior is."
>
>http://blog.llvm.org/2011/05/what-every-c-programmer-should-know.html
Yes, the nasal demon fans claim that they invite nasal demons for
performance reasons, but they rarely, if ever provide empirical
evidence of the performance effects.
That's because the performance effects of nasal demon "optimizations"
are so small that most production programmers would boycott the newer
C compilers with more nasal demons if they knew it. However, Wang et
al. actually measured the performance effect: Even on the SPECint
benchmarks, which are in a privileged position (GCC and LLVM
maintainers optimize for them and don't dare miscompile them, and
therefore they don't have to be "sanitized", which could reduce their
performance), the speedup is <2%.
>Personally, I think the extra CPU power of modern processors should be weig=
>hted much more towards language safety rather than maximal efficiency.
This is a false dichotomy. Nasal demons hurt efficiency: If you want
to avoid undefined behaviour, you avoid many efficient idioms; in
addition, you have to invest lots of time in "sanitizing" your
program, and you miss that time when it comes to making your program
faster; plus, every change to your program (such as implementing an
optimization idea) incurs the danger of introducing undefined
behaviour into your carefully sanitized program, so better not go
there.
This is actually not specific to newer C standards. Older C standards
also had lots of undefined behaviour. The problem is actually in the
newer C compilers and their maintainers, who think it is a good idea
to put nasal demons in their compilers.
- anton
--
M. Anton Ertl http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
New standard: http://www.forth200x.org/forth200x.html
EuroForth 2016: http://www.euroforth.org/ef16/
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LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-01 06:36 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-01 14:57 +0000
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-01 11:55 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-02 15:24 +0000
Re: LLVM and Forth rickman <gnuarm@gmail.com> - 2017-04-01 11:21 -0400
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-01 11:57 -0700
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-02 04:02 -0500
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-02 06:35 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-02 14:41 +0000
Re: LLVM and Forth minforth@arcor.de - 2017-04-03 01:09 -0700
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-03 05:32 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-03 13:52 +0000
Re: LLVM and Forth minforth@arcor.de - 2017-04-03 07:59 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-03 16:08 +0000
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-03 12:22 -0500
Re: LLVM and Forth Paul Rubin <no.email@nospam.invalid> - 2017-04-03 20:10 -0700
Re: LLVM and Forth minforth@arcor.de - 2017-04-03 22:19 -0700
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-04 16:12 +0200
Re: LLVM and Forth Walter Banks <walter@bytecraft.com> - 2017-04-05 17:27 -0400
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-03 14:29 +0000
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-03 03:17 -0500
Re: LLVM and Forth minforth@arcor.de - 2017-04-03 05:04 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-03 12:55 +0000
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-03 10:08 -0500
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-03 17:05 +0000
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-04 11:29 -0500
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-04 19:11 +0200
Re: LLVM and Forth Paul Rubin <no.email@nospam.invalid> - 2017-04-04 21:29 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-05 15:01 +0000
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-05 18:42 +0100
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-06 04:01 -0500
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-06 18:48 +0000
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-06 18:42 -0700
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-07 04:02 -0500
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-08 21:18 -0700
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-08 22:43 +0000
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-08 20:54 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-09 14:53 +0000
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-10 00:38 +0000
Re: LLVM and Forth James Kuyper <jameskuyper@verizon.net> - 2017-04-09 22:46 -0400
Re: LLVM and Forth Robert Wessel <robertwessel2@yahoo.com> - 2017-04-09 22:27 -0500
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-10 12:36 +0000
Re: LLVM and Forth Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-10 14:09 +0100
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-10 13:07 +0000
Re: LLVM and Forth Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-04-10 16:18 +0100
Re: LLVM and Forth "James R. Kuyper" <jameskuyper@verizon.net> - 2017-04-10 11:51 -0400
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-12 21:32 +0000
Re: LLVM and Forth "James R. Kuyper" <jameskuyper@verizon.net> - 2017-04-12 18:29 -0400
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-12 15:29 -0700
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-13 02:55 +0200
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-10 18:38 -0700
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-10 11:54 -0500
Re: LLVM and Forth Paul Rubin <no.email@nospam.invalid> - 2017-04-10 10:17 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-03 17:02 +0100
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-03 10:03 -0700
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-04 03:25 -0700
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-04 11:24 +0000
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-04 04:55 -0700
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-04 12:28 +0000
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-04 16:16 +0000
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-04 15:38 +0200
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-04 16:06 +0200
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-04 17:57 -0700
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-05 00:44 -0400
Re: LLVM and Forth minforth@arcor.de - 2017-04-05 00:00 -0700
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-05 08:47 -0700
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-05 11:04 -0500
Re: LLVM and Forth john <anon@example.com> - 2017-04-05 18:04 +0100
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-05 13:04 -0700
Re: LLVM and Forth Paul Rubin <no.email@nospam.invalid> - 2017-04-05 18:20 -0700
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-05 20:14 -0700
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-06 12:33 +0000
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-06 10:49 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 18:55 +0100
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-06 20:41 +0000
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 21:47 +0100
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 21:56 +0100
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-06 23:59 -0400
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-06 17:10 -0700
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-07 03:33 -0400
Re: LLVM and Forth Spiros Bousbouras <spibou@gmail.com> - 2017-04-08 22:48 +0000
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-09 15:06 -0400
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-08 22:45 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-09 14:27 +0000
Re: LLVM and Forth Joel Rees <joel.rees@gmail.com> - 2017-04-09 21:26 -0700
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-09 13:35 -0400
Re: LLVM and Forth Paul Rubin <no.email@nospam.invalid> - 2017-04-09 14:07 -0700
Re: LLVM and Forth minforth@arcor.de - 2017-04-05 12:16 -0700
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-05 20:27 -0700
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-06 05:24 -0400
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-06 03:26 -0700
Re: LLVM and Forth minforth@arcor.de - 2017-04-06 04:05 -0700
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-06 06:50 -0500
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-06 05:23 -0400
Re: LLVM and Forth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-06 04:44 -0500
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 10:57 +0100
Re: LLVM and Forth peter.m.falth@gmail.com - 2017-04-05 05:29 -0700
Re: LLVM and Forth "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-04-14 02:04 +0000
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 14:03 +0200
Re: LLVM and Forth "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-04-16 00:44 +0000
Re: LLVM and Forth alex@rivadpm.com - 2017-04-16 05:53 -0700
Re: LLVM and Forth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-16 15:43 +0000
Re: LLVM and Forth "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-04-16 22:27 +0000
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-18 02:45 +0200
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-18 18:26 +0100
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-20 19:51 +0200
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-20 19:08 +0100
Re: LLVM and Forth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-20 20:42 +0200
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-20 20:29 +0100
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-20 20:48 +0100
Re: LLVM and Forth "Rudy Velthuis" <newsgroups@rvelthuis.de> - 2017-04-21 11:49 +0000
Re: LLVM and Forth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-03 20:39 -0400
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-02 21:15 +0100
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-02 15:18 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-03 13:07 +0100
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-03 09:45 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-03 22:52 +0100
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-03 15:25 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 09:35 +0100
Re: LLVM and Forth antispam@math.uni.wroc.pl - 2017-04-06 01:36 +0000
Re: LLVM and Forth minforth@arcor.de - 2017-04-05 22:00 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 09:52 +0100
Re: LLVM and Forth hughaguilar96@gmail.com - 2017-04-06 20:15 -0700
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-03 05:20 -0700
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-03 17:11 +0100
Re: LLVM and Forth Alex <alex@rivadpm.com> - 2017-04-06 17:43 +0100
Re: LLVM and Forth krishna.myneni@ccreweb.org - 2017-04-06 10:53 -0700
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