Gpc July 2005

gpc@gnu.de

25 participants
67 discussions

Inefficiency of `mod'
by Emil Jerabek 25 Oct '10

25 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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Re: GPC on i686-apple-darwin
by Waldek Hebisch 19 Jan '06

19 Jan '06

Adriaan van Os wrote: > You were quite right about -fPIC. All the failures, except emil9.pas > disappear with -fno-pic. However, many of the other tests fail with > -fno-pic, because the option disables dynamic linking on Mac OS X. The > PPC back-end has a workaround (-mdynamic-no-pic) but that doesn't seem > to work for i686-apple-darwin. > I have just realized that Darwin PIC problem have nothing to do with Linux PIC problems: Darwin does not use the binutils feature (ELF GOT relocations) that Linux uses. > Updating the linker and assembler to odcctools-20050327 had no effect > on testsuite results. > > So, I must either > - find a backport of i686-apple-darwin PIC fixes > - find a solution for gcc-3.4 bootstrap problems > - wait for gcc-4.0 support. > > Still, I am glad with the results so far. > Well, I was able build 3.3.6 based cross-compiler for i686-apple-darwin target, and I can see duplicate labels in the assembler output. It seems that 3.4.3 has changed the parts responsible for generating those labels. I have found that 3.4.[34] contain blatant bug with easy fix: --- gcc-3.4.4/gcc/config/i386/darwin.h.orig Thu Jun 16 01:10:29 2005 +++ gcc-3.4.4/gcc/config/i386/darwin.h Thu Jun 16 01:10:32 2005 @@ -43,7 +43,7 @@ /* Use the following macro for any Darwin/x86-specific command-line option translation. */ -#define SUBTARGET_OPTION_TRANSLATE_TABLE +#define SUBTARGET_OPTION_TRANSLATE_TABLE { 0, 0 } #define ASM_SPEC "-arch i386 \ %{Zforce_cpusubtype_ALL:-force_cpusubtype_ALL} \ After that I can build the compiler proper. However I get ICE when building gcc runtime. Trying gpc on knuth3.pas (to get assembler output) give me ICE. Both ICE-s seem related to generting labels needed in PIC code... So, it seems that nobody tried gcc-3.4.x for i686-darwin for almost a year (ChangeLog entry for SUBTARGET_OPTION_TRANSLATE_TABLE change is from 2004-08-23) -- Waldek Hebisch hebisch(a)math.uni.wroc.pl

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Success!
by Peter N Lewis 11 Jan '06

11 Jan '06

Thanks to all the help from Frank, Waldek, Adriaan, Gale and others, I now have all of Interarchy compiling and running under GPC. 270 files, 160,000 lines of code, 290 Mac Style object types, all compiling and working. There are probably a few glitches left here or there, but I've tested out the bulk of the program and nothing remains broken (that was not before - it is bug for bug compatible ;-). Thanks all! Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>

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gp -j4
by Peter N Lewis 23 Nov '05

23 Nov '05

I have added support to gp for compiling multiple files simultaneously (akin to the -j4 flag to make). Since I have a dual processor machine, this dropped the total compile time for Interarchy from 8.4 minutes to 6 minutes. I basically replaced ProcessDependencies and CompileIfNecessary, and hardly touched any of the rest of gp. But the sections replaced are essentially complete rewrites. It's not the most elegant of code, is still full of debugging code, is not written in gp-style, and does not currently support a command line switch, is minimally tested, and perhaps not all that efficient, but if anyone is interested, I'm happy to send them the code. Enjoy, Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>

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FillChar Suggestion
by Pascal Viandier 11 Aug '05

11 Aug '05

Hello, Do you think it is possible to modify the prcedure "FillChar()" to make it work correctly with the type String(xx)? For example the code: VAR S10 : String(10); .... FillChar(S10, 10, 'A'); WriteLn(S10); Would display: AAAAAAAAAA I ask this because I am working on (converting to GPC) a lot of existing code, with FillChar() spread everywhere (more than 1200 SUN Pascal sources), and it works as expected on strings on SUN Pascal. However, since there is no 'Capacity' field in SUN Pascal strings, it cannot be overridden. I understand this can be a big job since calling FillChar() on a record containing Strings should work as well. I think this would be a nice feature anyway, don't you? Also, if this cannot be done or desirable from your point of view, is there a way to override the build-in FillChar() for one of mine that would be called for the type String(xx) only? I know this is not an elegant workaround, but this problem causes a lot of nasty bugs in the converted programs. If I was to write the code from scratch this would not be an issue, but rewriting more than 600 000 lines of Pascal code is an even bigger challenge :-( Regards Pascal Viandier pascal(a)accovia.com

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Mac objects and Delphi classes
by Waldek Hebisch 09 Aug '05

09 Aug '05

I have put a new "cumulative" diff on my GPC web page: http://www.math.uni.wroc.pl/~hebisch/gpc/delphi14.diff and http://www.math.uni.wroc.pl/~hebisch/gpc/dbxout.diff I have added a new option `--objects-are-references' (off by default, on for Mac Pascal) which choses reference model for objects. To get Mac semantics one has to use `--objects-are-references' and `--methods-always-virtual'. Delphi support still is incomplete (most visibly GPC does not know about `TObject'), but constuctors and destructors mostly work (one can not call a destructor from within another destructor), in particular allocate and deallocate memory. Adriaan van Os wrote: > I have compared various MacPascal object diffs posted on the gpc > mailing list (to delphi3.diff) with delphi9.diff. I see that two > patches are missing in Delphi9.diff. I guess the reason is > > - the first patch is not to gpc but to gpidump > - the second patch is of later date. Thanks for remainding me about gpidump patch. There are a few fixes that I found after delphi9.diff was made, the new diff collects them all (plus a new code, mostly for Delphi). -- Waldek Hebisch hebisch(a)math.uni.wroc.pl

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const s: String(1000) passed by value?
by Peter N Lewis 03 Aug '05

03 Aug '05

It seems that const parameters of string types are passed by value, eg: program peterT4; type Str = String(1000); var gs: Str; procedure Doit( const s: Str ); begin if @s = @gs then begin WriteLn( 'OK' ); end else begin WriteLn( 'failed' ); end; end; begin Doit( gs ); end. fails. I checked the code and it definitely looks like it is doing a copy. I use a lot of long strings (2500) and so this seems like a serious problem to me... Thanks, Peter. -- <http://www.stairways.com/> <http://download.stairways.com/>

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Heap dimensions
by Silvio a Beccara 01 Aug '05

01 Aug '05

Hello, is it possible to increase heap dimensions? I am running a GPC program which uses "big" dynamic arrays of double precision floats (up to 200 x 500) and, while it runs fine with smaller dimensions, from 128 x 256 up I get the following error: /u/dms/abeccara/pimc/parpi/pimb: out of heap when allocating 629145608 bytes (error #853 at 8071a32) I wasn't getting this error when using an older GPC version 2.1 (20020510), based on gcc-2.95.2 19991024. I am running on 30 processors with 1 GB RAM each, so I would like to use this memory. Thanks in advance, best regards Silvio a Beccara -Trieste Italy -- Email.it, the professional e-mail, gratis per te: http://www.email.it/f Sponsor: Vuoi bere tanta acqua pura e risparmiare ben 495 euro all'anno? * Con BeviSano avrai finito di comprare acqua in bottiglia - clicca qui Clicca qui: http://adv.email.it/cgi-bin/foclick.cgi?mid=3628&d=21-7

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Saving error
by Prof. Harley Flanders 29 Jul '05

29 Jul '05

I have several partitions on my hard drive. The GNU compiler and IDE is in folder G:\dev_gpc I created a folder in partiton I; to hold my experiments: I:\gnu_examples I write a short program "Test" and save it to that folder, in partition I: It compiles with the error: Cannot open iutput file i:\gnu_examples\test.exe: No such file or directory. The same program, saved to a folder in G:\dev_gpc runs OK. A related problem: I see no way to capture error messages in to the windows clipboard, for pasting into editors -- like this one. -- =========================================== Prof. Harley Flanders 3533 Windemere Court Ann Arbor, MI 48105-2867 Home: 734 668 1546 harley(a)umich.edu ===========================================

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Ballistic program
by Prof. Harley Flanders 29 Jul '05

29 Jul '05

GNU Pascal GPC v. 2.1 (20050331) The following console program (with a slight typo) drives the compiler ballistic. program Project3; begin Writeln('Hello); Readln; end. -- =========================================== Prof. Harley Flanders 3533 Windemere Court Ann Arbor, MI 48105-2867 Home: 734 668 1546 harley(a)umich.edu ===========================================

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Gpc July 2005