Re: Languages that give "hints" to the compiler

jfisher@hplabsz.hpl.hp.com (Josh Fisher)
Thu, 21 Jul 1994 15:26:35 GMT

          From comp.compilers

Related articles
Languages that give "hints" to the compiler jhummel@cy4.ICS.UCI.EDU (Joe Hummel) (1994-07-18)
Re: Languages that give "hints" to the compiler wisej@acf4.nyu.edu (1994-07-29)
Re: Languages that give "hints" to the compiler tgl@netcom.com (1994-07-19)
Re: Languages that give "hints" to the compiler jfisher@hplabsz.hpl.hp.com (1994-07-21)
Re: Languages that give "hints" to the compiler rfg@netcom.com (1994-07-31)
Languages that give "hints" to the compiler ssimmons@convex.com (1994-08-01)
Re: Languages that give "hints" to the compiler jls@summit.novell.com (1994-08-02)
Re: Languages that give "hints" to the compiler rfg@netcom.com (1994-08-03)
| List of all articles for this month |

Newsgroups: comp.compilers
From: jfisher@hplabsz.hpl.hp.com (Josh Fisher)
Keywords: Fortran, history, optimize
Organization: Hewlett-Packard Laboratories, Palo Alto, CA
References: 94-07-066
Date: Thu, 21 Jul 1994 15:26:35 GMT

Our esteemed moderator wrote:
>[The original FORTRAN compiler had a FREQUENCY statement that let you give
>a hint to the compiler how many times a DO loop would run or which was the
>most likely branch of an IF. It disappeared in Fortran II. Legend says
>that the final nail in its coffin was when someone found that it was
>implemented backwards and nobody had noticed. -John]


I believe it was Lois Haibt at Yorktown who 10 years ago told me the story
in response to my mentioning the branch frequency directive in the Yale
Bulldog Compiler. As I recall, she said she'd released the 7090? code
generator--it used the FREQ statement for some different treatment of the
index register--and then went on vacation. While she was out, someone
upstream from her code reversed the sense. She found it herself a year
and a half later.


This was in the days of suspicion of compilers and hacking of object code.
No one ever caught it; she never got a bug report.


-- Josh Fisher // HP Labs Cambridge Research
--


Post a followup to this message

Return to the comp.compilers page.
Search the comp.compilers archives again.