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| From | James Kuyper <jameskuyper@verizon.net> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Understandability |
| Date | 2015-05-14 22:51 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <mj3mtf$at8$1@dont-email.me> (permalink) |
| References | (13 earlier) <9ae7e6d2-f4ec-49f9-9a8f-276403ac1ef3@googlegroups.com> <miusbt$hio$1@dont-email.me> <4f6b6478-8841-482d-ab39-07bbce61a5ed@googlegroups.com> <mj00fb$i44$1@dont-email.me> <d1836c48-c7bb-4aac-ad37-2fa079968ed5@googlegroups.com> |
On 05/14/2015 01:27 PM, David Kleinecke wrote: > On Wednesday, May 13, 2015 at 10:10:14 AM UTC-7, James Kuyper wrote: >> On 05/13/2015 12:31 PM, David Kleinecke wrote: >>> On Tuesday, May 12, 2015 at 11:54:00 PM UTC-7, David Brown wrote: >> ... >>>> If I remember the history of this thread correctly (and perhaps I >>>> remember /incorrectly/), the key objection was that you wrote "Gnu is >>>> right to call their work a collection. It is really a fiction that gcc >>>> is a free-standing program." You followed this with a series of >>>> misconceptions about gcc and the way it works. >> >> What followed the "fiction" comment was: >>> There are two parts - the front >>> and back ends. The front end produces a "source program" in an >>> intermediate language which the back end "assembles" into machine >>> code. GNU, I believe, uses a Lisplike language called RTL. One way to >>> make gcc a true program would be to make the back end a subroutine >>> called at the end of front processing. A pipe might be a better idea. >> >> So those sentences presumably contain the misconceptions David was >> talking about. >> >>> I protest once again. I believe I understand what gcc is doing. If you >>> feel I have "misconceptions" please tell me what they are. It is possible >>> I do have misconceptions. >> >> Two of the very first responses told you what Keith Thompson and David >> Browne thought were misconceptions expressed in those sentences: >> >> On 05/02/2015 04:11 PM, Keith Thompson wrote: >>> There are more than two. >> ... >>> I don't know a whole lot about gcc's internal workings, but I don't >>> believe it writes its intermediate representation to a file. It does >>> generate an assembly language program, but that's the output of the >>> "back end". >> >> Your response to that message neither acknowledged nor disputed those >> points, but only discussed other issues. >> >> On 05/04/2015 03:15 AM, David Brown wrote: >>> Three parts - there is also the "middle end". (And the assembler and >>> linker come in addition - they are normally from binutils rather than >> gcc.) >> ... >>> Nope. The "front end" is specific to the source code language, such >>> as C, C++, Fortran, etc. It produces an intermediate language >>> (GIMPLE), which is passed on to the "middle end" where much of the >>> optimisation work takes place. >>> >>> The middle-end is /mostly/ independent of both the back-end target and >>> the front-end language, but there is a certain amount of cross-talk >>> between the parts. (llvm has a similar theoretical structure, but has >>> much cleaner separation between the parts.). The output from the >>> middle-end is another intermediate language (RTL). >>> >>> The back-end handles the target-specific register allocation and code >>> generation. The result is assembly, not machine code - an external >>> assembler (usually "gas" from binutils) is called to generate the >>> machine code. Then another external program (usually "ln" from >>> binutils) is called to link the object code and static libraries into >>> an executable. >>> >>> (Things are a little more complicated when using link-time >>> optimisation, but lets skip that for now.) >> ... >>> Pipes /are/ the usual way of passing data and options between the >>> passes inside gcc. Intermediary files are only stored if you ask for >>> them (typically for debugging gcc itself). >> >> David's remarks received no response from anybody that I can see. >> >> Were either Keith or David wrong about the discrepancies between your >> description and reality on those issues? None of the subsequent >> discussion gave me that impression. It just wandered over into a >> discussion of other issues. >> -- >> James Kuyper > > I didn't see any differences from what I said. Expansions - yes. You said there were two parts; both Keith and David agreed that there were three parts. In a sense, that's "merely" an expansion - but it's also a difference, and in particular, it is a kind of difference that justifies describing your version as a misconception, if their version is correct. You said the output from the front end was in RTL; David says that it's GIMPLE. If he's correct, that also counts as a misconception on your part. You said that the output of the back end is machine code. David said that it's assembly code. If he's right, that also counts as a misconception on your part. Both of those two changes imply major differences in what kind of work the front and back ends do. You said that using a pipe would be a better idea; in context, that can only mean "a better idea than the way that gcc currently does it", which in turn implies that you thought that gcc doesn't use a pipe. Both Keith and David pointed out that it does use a pipe. If they're correct, that also counts as a misconception on your part. I said, repeatedly, "if ... correct", only because I can't confirm any of those points from personal knowledge - but I have no real reason to doubt either Keith or David on this matter. If those four misconceptions occurred in the context of a much larger discussion, they wouldn't matter much. However, those four points constitute a large fraction, possibly the majority, of the (mis)information contained in those sentences. > But > differences - no. I based my depiction of gcc on the Wikipedia article. > Maybe I condensed it too much to make people happy. I don't see how dropping the middle end, converting GIMPLE into RTL, changing assembly code to machine code, and implying that pipes are not used, when in fact they are, counts as "condensation". -- James Kuyper
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Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-01 17:55 -0700
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-01 19:41 -0700
Re: Understandability wssimms@gmail.com - 2015-05-01 20:45 -0700
Re: Understandability Bartc <bc@freeuk.com> - 2015-05-02 10:38 +0100
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-02 09:15 -0700
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-04 09:26 +0200
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-04 12:52 -0700
Re: Understandability Noob <root@127.0.0.1> - 2015-05-02 14:21 +0200
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-02 09:13 -0700
Re: Understandability Ian Collins <ian-news@hotmail.com> - 2015-05-03 08:07 +1200
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-02 13:11 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-03 10:50 -0700
Re: Understandability Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-03 13:26 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-04 12:29 -0700
Re: Understandability Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-05 05:47 -0700
Re: Understandability raltbos@xs4all.nl (Richard Bos) - 2015-05-08 21:10 +0000
Re: Understandability Ian Collins <ian-news@hotmail.com> - 2015-05-09 09:17 +1200
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-08 14:32 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-09 09:13 -0700
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-09 16:48 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-10 11:05 -0700
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-11 08:48 +0200
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-11 09:55 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-11 17:52 -0400
Re: Understandability glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-11 22:54 +0000
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-12 08:49 +0200
Re: Understandability Morris Dovey <mrdovey@iedu.com> - 2015-05-12 02:15 -0500
Re: Understandability Phil Carmody <pc+usenet@asdf.org> - 2015-05-25 03:15 +0300
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-25 00:45 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-25 10:26 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-11 10:06 -0700
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-12 08:59 +0200
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-12 08:37 -0700
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-13 08:53 +0200
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-13 08:16 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-13 09:49 -0700
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-13 10:53 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-14 10:35 -0700
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-13 09:31 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-13 13:10 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-14 10:27 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-14 22:51 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-15 10:02 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-15 13:37 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-16 09:18 -0700
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-16 23:56 +0200
Re: Understandability gazelle@shell.xmission.com (Kenny McCormack) - 2015-05-17 12:45 +0000
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-17 09:16 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-17 12:47 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-18 10:54 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-18 15:00 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-19 09:49 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-19 13:10 -0400
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-16 19:01 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-17 09:30 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-17 12:58 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-18 10:54 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-18 14:56 -0400
Re: Understandability David Kleinecke <dkleinecke@gmail.com> - 2015-05-19 09:46 -0700
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-19 13:16 -0400
Re: Understandability Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 18:23 +0100
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-19 14:02 -0400
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-19 00:11 +0200
Re: Understandability James Kuyper <jameskuyper@verizon.net> - 2015-05-18 18:28 -0400
Re: Understandability Keith Thompson <kst-u@mib.org> - 2015-05-15 10:52 -0700
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-13 21:53 +0200
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-09 16:18 +0200
Re: Understandability Noob <root@127.0.0.1> - 2015-05-09 18:31 +0200
Re: Understandability raltbos@xs4all.nl (Richard Bos) - 2015-05-17 10:44 +0000
Re: Understandability glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-17 15:53 +0000
Re: Understandability David Brown <david.brown@hesbynett.no> - 2015-05-04 09:15 +0200
Re: Understandability Waldek Hebisch <hebisch@math.uni.wroc.pl> - 2015-05-16 00:28 +0000
Re: Understandability Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-03 10:58 -0700
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