January 2009 - Gpc

Inefficiency of `mod'
by Emil Jerabek 26 Oct '10

26 Oct '10

Hi, during some debugging I noticed that GPC generates very hairy code for the `mod' operator with signed arguments. A closer look revealed that the code contains a lot of branching on conditions which can be determined on compile time, and most surprisingly, the value of X mod Y is recomputed _twice_, if X is negative. (I've attached a commented assembler dump.) This may be partially a back-end problem (CSE?), but I feel there's something wrong in the relevant code in gpc-common.c (build_pascal_binary_op) as well. `exp1 mod exp2' gets translated into something like exp2 <= 0 ? error : exp1 >= 0 ? exp1 mod exp2 : ((-exp1) mod exp2) == 0 ? 0 : exp2 - (-exp1) mod exp2 This arranges that both arguments supplied to the "internal mod" are non-negative, but this information is not passed on -- the arguments are still declared as signed types, which apparently makes the back-end to produce the mess it does. I've done a little test: the following replacement for `mod', which differs from the built-in one essentially just by the type-casts to `Cardinal', inline operator xmod (X, Y: Integer) = Z: Integer; begin if Y <= 0 then RuntimeError (714); if X >= 0 then Z := Cardinal (X) mod Y else begin Z := Cardinal (-X) mod Y; if Z <> 0 then Z := Y - Z end end; indeed generates a better code, it measures about 15% faster for positive X and more than twice faster for negative X. YMMV. If this is possible in user code, it should work in the compiler internals as well :) The result type of the whole `mod' expression looks dubious too. IIUIC, `exp1 mod exp2' inherits the type of exp1. Now, the result of `mod' is guaranteed to be nonnegative and to fit in the type of exp2 (or more precisely, it is in 0 .. High (type of (exp2)) - 1), whereas it needn't have anything to do with the type of exp1: consider var X, Z: Integer; Y: LongInt; begin X := -8; Y := High (LongInt); Z := X mod Y { -> overflow } end Or am I missing something? Emil (BTW, where is fjf434c.pas?)

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GPC support for AIX 6?
by Gert Doering 16 Feb '10

16 Feb '10

Hi Gnu Pascal list, we're currently using IBM's xpc pascal compiler on IBM AIX 5.3. New machines are being shipped with AIX 6, and IBM's xpc is no longer supported there - for the time being, it actuall works (the xpc frontend generated intermediate code, and the second stage compiler still groks it). Management is not happy about this, as it might break any day, and I have been asked to "provide GPC" on AIX 6. Googling seems to suggest that the earliest release of GCC to work on AIX 6 is gcc 4.2.4 This mailing list's archive suggests that GPC and GCC 4.2 do not yet work together, due to larger efforts required due to backend changes (Waldek's mail from March 12, 2008). I reported this to management ("there is no GPC on AIX 6"), and they came back with the question "if we pay one of the GPC developers to do a GPC port to a recent GCC, to support AIX 6, how much would that cost?". Here we go - I'm posing this question to you. Is one of you capable and willing to make GPC work on AIX 6? And if yes, what would your conditions be (estimated time to do this, estimated costs)? (I can't promise anything, but will report back to management and they will decide...) thanks, gert -- Gert Doering gd(a)medat.de MEDAT Muenchen Tel: 089/126808-0 Fax: -50

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New (gpc-20060325)
by Waldek Hebisch 08 Dec '09

08 Dec '09

I have put a new gpc snapshot at: http://www.math.uni.wroc.pl/~hebisch/gpc-20060325.tar.bz2 Main change is preliminary gcc-4.0.x support. The other changes are rather small. Note that for "production use" 3.4.x and 3.3.x backend are prefered. Also, using 2.8.1, 2.95.3 and 3.2.3 backend should work, but is depreciated. For more detail see: http://www.math.uni.wroc.pl/~hebisch/gpc/NEWS-20060325 and http://www.math.uni.wroc.pl/~hebisch/gpc/Fixed-20060325 -- Waldek Hebisch hebisch(a)math.uni.wroc.pl

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Re: Linux Binaries and Makefile
by Kevan Hashemi 30 Mar '09

30 Mar '09

Dear Prof O, > On your "desktop" in Linux? That sounds odd to me. Everything I do is a bit odd. > If you don't know what you're doing, yes. That's precisely my point: I don't know what I'm doing. > An exaggeration. As I said, on a modern PC (e.g., an Athlon XP 3800), it > only takes a few minutes I was not refering to "compile time". I was referring to "Where on earth do I get a non-broken version of sed? What is sed anyway? Why won't patch work on this machine with these diff files? Is it patch that's not working or is it just that I'm a retard? What does it mean that the .tar.bz.tar archive is in an unrecognizable format?" Compiling GPC will be four hours work for me, minimum. > If you find one, it may not work. So far, that 20041218 distribution of binaries has worked on every single one of the two dozen machines we have loaded it onto. Why would the 20070904 distribution fail to work? Yours, Kevan -- Kevan Hashemi, Electrical Engineer Physics Department, Brandeis University http://alignment.hep.brandeis.edu/

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Re: Write doesn't work with CRT
by Alexey Kotlyarov 25 Jan '09

25 Jan '09

> Depending on what you want to do, > either > writeln("sqrt(-1)"); > or > writeln(sqrt(1)); > works. I'm sorry, I haven't made it clear the first time. So: With CRT, all writeln do nothing. For example: uses crt; begin writeln('OK') end. produces nothing. uses crt; begin writeln('OK'); writeln(sqrt(-1)) end. produces just the error message from sqrt(-1), NOT 'OK'. Same programs without "uses crt;" both include 'OK' (the latter before the error message). > > You might try: > > program testcrt; > uses gpc, crt; > begin > writeln('OK'); > sleep(10); > writeln(sqrt(-1)); > end. Now I understand more about the problem. If I put the CRT unit in, each write will actually be to some virtual screen appearing on top of my console and disappearing after program finished. As all test programs above finish quickly, I simply can't see it. Therefore, this sample: program testcrt; uses gpc, crt; begin writeln('OK'); readln end. works as expected, but there is nothing left on the console after it ran. Is this by design? Because I might have programs which use CRT for every kind of things and I still must see their output.

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Write doesn't work with CRT
by Alexey Kotlyarov 25 Jan '09

25 Jan '09

Being compiled version of GPC installed on Ubuntu, the following very simple program fails to produce any output: program testcrt; uses crt; begin writeln('OK'); writeln(sqrt(-1)); { error } end. $ gpc --automake testcrt.pas -o testcrt $ ./testcrt ./testcrt: argument to `SqRt' is < 0 (error #708 at 40b6c6) Notice the absence of OK. Similarly, removing error line makes program produce no output. Removing 'uses crt;' restores normal behavior. Version info and such: $ gpc --version gpc 20070904, based on gcc-4.1.3 20080420 (prerelease) (Ubuntu 2.1-4.1.2-22ubuntu1) Copyright (C) 2006 Free Software Foundation, Inc. $ uname -a Linux flower2 2.6.27-11-generic #1 SMP Fri Jan 23 13:58:13 UTC 2009 x86_64 GNU/Linux Any ideas of how to fix this?

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LLVM
by Adriaan van Os 25 Jan '09

25 Jan '09

I would like to draw your all attention to the LLVM compiler infrastructure <http://llvm.org/>. I hear good things about it from people writing compiler front-ends for it. There is also the clang front-end <http://clang.llvm.org/> project. LLVM may in the future replace GCC in many software projects. It may be a good idea to get somehow involved. Regards, Adriaan van Os

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X CODE 3.1 AND INTEGRATION PROBLEMS
by MICHAEL MCNEESE 21 Jan '09

21 Jan '09

I recently added GNU Pascal to my inventory of languages in X Code 3.1 along with the integration kit. Unfortunately, Pascal does not show up in the X Code enviroment. Its possible that upon installation the it simply is not indexed properly. Does anyone have any suggestions? mike

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New version?
by leledumbo 06 Jan '09

06 Jan '09

Will there be any new version of gpc? Or at least the latest one (20070904) with gcc 4.2.X or 4.3.X integration? -- View this message in context: http://www.nabble.com/New-version--tp21308910p21308910.html Sent from the Gpc mailing list archive at Nabble.com.

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Linux Binaries and Makefile
by Kevan Hashemi 01 Jan '09

01 Jan '09

Dear GPC, The African Chief maintains the Windows version of GPC, now using 20070904 sources. Adriaan maintains the MacOS version, now using 20070904 sources. I think the outstanding question for Prince and me is the Linux version. There is no binary distribution of the 20070904 GPC that I can find. I use the 20041218 version on Linux. I suppose most Linux users are happy to compile GPC from sources. But I'm not a Linux expert: I just port my code to Linux for my Linux users. So I'm stuck with 20041218, and my code has to remain compatible with the older GPC. (I have a bunch of compiler directives to get the module names right.) Suppose I wanted to compile the 20070904 sources on Linux. How would I go about it? Yours, Kevan -- Kevan Hashemi, Electrical Engineer Physics Department, Brandeis University http://alignment.hep.brandeis.edu/

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