June 2005 - 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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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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GPC and Mac implicit pointer objects
by Waldek Hebisch 23 Jul '05

23 Jul '05

As I wrote I updated may implementation of Delphi classes to gpc-20050331. Now, I have put a patch at: http://www.math.uni.wroc.pl/~hebisch/gpc/delphi3.diff With the patch, when one chooses Mac Pascal as a dialect, object model should be compatible with Mac Pascal: -- objects are pointers -- all methods are virtual (that was already implemented in gpc-20050331) -- overriding a method requires `override' keyword -- you can allocate memory for objects with `New' and deallocate it with `Dispose' In default mode the `class' keyword is recognized and allows you to declare Delphi classes. ATM Delphi constructors works only in simplest case (you can not call a constructor inside a (different) constructor). Destructors do not deallocate memory (but `Dispose' applied to a Delphi class will deallocate memory). Also, Delphi builtin `TObject' is unimplemented. This is experimatal (and incomplete) implementation. I would like to get some feedback about missing features. Also, if I got semantics of implemented parts correctly. ATM I know only about one missing Mac objects feature (which is almost surely due to my lack of knowledge about Mac Pascal): GPC requires all methods to be defined in the same unit as the object (TCL sources implement methods in different units). And of course test programs are welcome. -- Waldek Hebisch hebisch(a)math.uni.wroc.pl

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gcc-3.4.4
by Russell Whitaker 22 Jul '05

22 Jul '05

Hi Now that gcc-3.4.4 is out, thought I'd try it with gcc-20050331. Using gcc-3.4.3.diff, got these rejects: gcc.c.rej varasm.c.rej version.c.rej That last one I needed to patch version.c manualy so gcc would compile. After I did it, wondered if it might be beter to patch gpc instead? Since have 2 cpu's, tried "make -j3 bootstrap". The c part ran ok, it quit in the rts with an error message. "make bootstrap" & installed with no problem: Reading specs from /usr/local/lib/gcc/i686-pc-linux-gnu/3.4.4/specs Configured with: ../gcc-3.4.4/configure --enable-languages=c,c++,pascal Thread model: posix gpc version 20050331, based on gcc-3.4.4 Ran gpc's test using gcc-3.3.5 and then gcc-3.4.4, got one new fail: avo7.pas And ran the tests with "time make": gcc-3.3.5 gcc-3.4.4 ---------- ---------- real 22m24.452s 20m49.896s user 11m40.872s 10m52.583s system 10m25.648s 9m41.803s And that's it Russ

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GPC on OS 10.4
by Aleck Brinkman 04 Jul '05

04 Jul '05

Has anybody successfully installed GPC on Mac OS 10.4 (Tiger)? Thanks. Aleck Brinkman Temple University

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Dropping some misfeatures in for-loops and `absolute' variables
by Frank Heckenbach 02 Jul '05

02 Jul '05

GPC accepts the following program, but produces quite silly results: program Foo; var a: array [1 .. 2] of Integer value (0, 0); i: Integer; begin i := 1; for a[i] := 1 to 10 do begin WriteLn (i, ' ', a[i]); if a[i] = 5 then i := 2 end end. The problem is that it evaluates the index i each time, not once before the loop. It would be possible to fix it, but do we really want that? Neither BP nor CP/EP allow it, they allow only identifiers in for-loops. Waldek and I see no need for such a feature. (If it made it possible to nest a compile-time-unknown number of `for' loops, I could see some point, but of course, it doesn't.) So, would anybody mind dropping this misfeature, and requiring an identifier in for-loop counters? The same (and probably a lot of other weird stuff) can be achieved with "extended" `absolute' variables, such as: program Foo; var a: array [1 .. 2] of Integer value (0, 0); i: Integer; {$local W-} c: Integer absolute a[i]; {$endlocal} begin i := 1; for c := 1 to 10 do begin WriteLn (i, ' ', c); if a[i] = 5 then i := 2 end end. We support `absolute' for BP compatibility, but IMHO then we should restrict it to what BP requires, i.e. really absolute addresses, or the address of entire variables or parameters. I suppose (hope) few users actually knew about the extended (mis)features GPC allowed, so I hope we can drop them. (If not, we probably should change semantics to evaluate the address once, and not on each usage, as is done now, so if you rely on this behaviour, you might have to change your code anyway -- if nothing else helps, you can always achieve the same effect with type-casting of pointers.) BP compatible code will not be affected. Any objections? Frank -- Frank Heckenbach, frank(a)g-n-u.de http://fjf.gnu.de/ GnuPG and PGP keys: http://fjf.gnu.de/plan (7977168E)

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$no-methods-always-virtual
by Adriaan van Os 30 Jun '05

30 Jun '05

Peter N. Lewis pointed me to the following: {$methods-always-virtual} {allowed} {$no-methods-always-virtual} {error message} program P; begin end. GPC accepts {$methods-always-virtual} as a directive in source code, but it rejects {$no-methods-always-virtual}. Is there a special reason why ? The value of the flag changes also (I think) when switching from {$mac-pascal} to {$gnu-pascal}. Regards, Adriaan van Os

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Fw: Wikipedia
by Frank Heckenbach 29 Jun '05

29 Jun '05

Scott A. Moore wrote me: > So I've been upgrading the Pascal pages on Wikipedia > recently. I can't help but notice that GPC is almost entirely > unmentioned. Even many DEAD Pascal editions have a page. > > Just a thought. Thanks for the notice, Scott. Anyone here on the list feels like writing a bit (http://en.wikipedia.org/wiki/Pascal_programming_language)? Of course, you can also write on the pages for other languages that you know. Frank -- Frank Heckenbach, frank(a)g-n-u.de http://fjf.gnu.de/ GnuPG and PGP keys: http://fjf.gnu.de/plan (7977168E)

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Question on a warning
by Pascal Viandier 28 Jun '05

28 Jun '05

Hello, When compiling a Pascal source with gpc, I receive the following warning: gpc -g -O0 -D_DEBUG --setlimit=2000 --unit-path=gpi:gpc --gpi-destination-path=gpi --implementation-only -D_DBG -Icommon/include -Imain/include -I/data2/informix-7.31.UD6/include -I/data2/informix-7.31.UD6/incl/esql -I/usr/local/devapps/ISAM/include -c common/src/fdb.pas -o obj/dbg/fdb.o common/src/fdb.pas: In procedure `CreeFDB': common/src/fdb.pas:1041: warning: `for' loop counter is threatened in a subroutine And here is the code that triggers the warning: FOR I := PosARec TO NbChamps DO BEGIN IF ((Champs[I].TipeNb > 1) AND (I <> PosARec)) THEN BEGIN WRITELN('Error: Array in an Array of Records! (line:', Line,')'); RETURN; END; Champs[I].Pos := Champs[I].Pos + AjusARec; Champs[I].TipeNb := TipeNb; Champs[I].DifByte := NbByteARec; END; The code inside the 'for' loop does not call any subroutine, except WriteLn and Return (conditionally) and they don't make any use of the counter. I wonder how the loop counter may be threatened in any way... My question is: did I missed something, or is gpc so delicate that one cannot use a 'for' loop counter outside of the loop for other purpose (that's the case here, the 'for' loop in the middle of a procedure)? How gpc determines that a 'for' loop counter may be altered in the body of the loop? Thanks Pascal Viandier pascal(a)accovia.com

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error: `prefkeys.gpi' must be recompiled?
by Peter N Lewis 28 Jun '05

28 Jun '05

I'm using gp, and it is giving me the following error: /Source/InterarchySupportBundle.p:18: error: `prefkeys.gpi' must be recompiled Clearly this is actually a gpc error. I've attached a -v3 output from gp. Interestingly, it ends with: /Source/PrefKeys.p: recompiling because interface of `GPCMacOSAll.pas' has changed /Source/InterarchySupportBundle.p: recompiling because an interface used indirectly has changed and then proceeds to compile InterarchySupportBundle.p, so GPC may well be quite correct that PrefKeys.p does indeed need recompiling and gp either skipped it for some reason or is doing it in the wrong order. Any ideas as to why this might happen or what I should look in to to try to debug the cause? I'm guessing that the cyclic dependencies (in the implementation section) are causing problems. Peter. gp -v3 -g -gstabs -O0 --uses=GPCMacOSAll --no-check-platform -DINTERARCHY -Wall --unit-path=/Developer/Pascal/GPCPInterfaces:/Source/PNLLibraries:/Source/MacOSXSupport:/Source:/Build --object-path=/IAObjects --unit-destination-path=/IAObjects --Pascal=--include=/Source/PNLLibraries/Prefix.GPC --c=-no-cpp-precomp --c=-I/Developer/Headers/FlatCarbon --c=-I/usr/include/libxml2 --c=-flat_namespace /Source/URLFiles.p gpc -dumpmachine gpc -dumpversion gpc -print-file-name=units gpc --print-needed-options -x Preprocessed-Pascal /var/tmp/GPaaa00594 Needed option for GPC: -D__ppc__ Needed option for GPC: -D__POWERPC__ Needed option for GPC: -D__NATURAL_ALIGNMENT__ Needed option for GPC: -D__MACH__ Needed option for GPC: -D__APPLE__ /Source/URLFiles.p: compiling because target files not found or not up to date /Source/BaseGlobals.p: compiling because target files not found or not up to date /Source/Logs.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyCleverAlerts.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyInternetConfig.p: recompiling interface because source has changed /Source/PNLLibraries/MyInternetConfig.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyKeychain.p: compiling implementation because target files not found or not up to date /Source/PNLLibraries/MyScrap.p: compiling implementation because target files not found or not up to date /Source/PNLLibraries/MyAEUtils.p: compiling implementation because target files not found or not up to date /Source/Utils.p: compiling because target files not found or not up to date /Source/Permissions.p: compiling because target files not found or not up to date /Source/DisplayWindow.p: compiling because target files not found or not up to date /Source/FileMapping.p: compiling implementation because target files not found or not up to date /Source/InterarchyIcons.p: compiling because target files not found or not up to date /Source/PrefKeys.p: compiling implementation because target files not found or not up to date /Source/ReportPrinting.p: compiling implementation because target files not found or not up to date /Source/TransferMode.p: compiling because target files not found or not up to date /Source/Transcript.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyCarbonEvents.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyControls.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyNotifier.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyProcesses.p: recompiling interface because source has changed /Source/PNLLibraries/MyProcesses.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyUnicode.p: compiling because target files not found or not up to date /Source/InterarchyInterface.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyDrag.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyWindow.p: compiling because target files not found or not up to date /Source/ActionToolbarItem.p: compiling because target files not found or not up to date /Source/EditWith.p: compiling because target files not found or not up to date /Source/Resume.p: compiling because target files not found or not up to date /Source/TransferActions.p: compiling because target files not found or not up to date /Source/TransferProgress.p: compiling because target files not found or not up to date /Source/URLMapping.p: compiling because target files not found or not up to date /Source/ViewWith.p: compiling because target files not found or not up to date /Source/GenericBookmarkWindow.p: compiling because target files not found or not up to date /Source/TransferNotificationCenter.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyTextDisplayWindow.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyAppearance.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyHIToolbar.p: compiling because target files not found or not up to date /Source/BookmarkManager.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyApplication.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyEditTextToolbarItem.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyHIView.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyNavigation.p: compiling because target files not found or not up to date /Source/PNLLibraries/MySegmentedView.p: compiling because target files not found or not up to date /Source/SendRecordedCommand.p: compiling because target files not found or not up to date /Source/TemporaryFiles.p: compiling because target files not found or not up to date /Source/CheckWebWindow.p: compiling because target files not found or not up to date /Source/DirectoryList.p: compiling because target files not found or not up to date /Source/DirectoryPathList.p: compiling because target files not found or not up to date /Source/DirectoryRemoveList.p: compiling because target files not found or not up to date /Source/DirectorySpecList.p: compiling because target files not found or not up to date /Source/HTTPPathList.p: compiling because target files not found or not up to date /Source/HTTPPathSuccess.p: compiling because target files not found or not up to date /Source/MirrorCache.p: compiling because target files not found or not up to date /Source/MirrorFileCollection.p: compiling because target files not found or not up to date /Source/MirrorFTPDiskPathList.p: compiling because target files not found or not up to date /Source/MirrorPutMembers.p: compiling because target files not found or not up to date /Source/MirrorPutPathList.p: compiling because target files not found or not up to date /Source/MirrorReportWindow.p: compiling because target files not found or not up to date /Source/PNLLibraries/MySuspendedEvents.p: compiling because target files not found or not up to date /Source/NotifyUser.p: compiling because target files not found or not up to date /Source/ParseFTPList.p: compiling because target files not found or not up to date /Source/ParseHTMLFile.p: compiling because target files not found or not up to date /Source/Transfer.p: compiling because target files not found or not up to date /Source/TransferUtils.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyCustomControl.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyDataBrowser.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyTextDisplay.p: compiling because target files not found or not up to date /Source/AutoUploadsEngine.p: compiling because target files not found or not up to date /Source/BookmarksBar.p: compiling because target files not found or not up to date /Source/ChasingArrows.p: compiling because target files not found or not up to date /Source/FTPDiskScriptingSupport.p: compiling because target files not found or not up to date /Source/FTPDisksEngine.p: compiling because target files not found or not up to date /Source/QueueManager.p: compiling because target files not found or not up to date /Source/ScheduledBookmarksEngine.p: compiling because target files not found or not up to date /Source/SplitViewControl.p: compiling because target files not found or not up to date /Source/StartupItems.p: compiling because target files not found or not up to date /Source/FileActions.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyCharsets.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyTXNControl.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyPlayAsyncSound.p: compiling because target files not found or not up to date /Source/HostInfoMapping.p: compiling implementation because target files not found or not up to date /Source/HostUploadPermissionsMapping.p: compiling implementation because target files not found or not up to date /Source/PNLLibraries/MyDataBrowserColumnView.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyDataBrowserIconView.p: compiling because target files not found or not up to date /Source/PNLLibraries/MyFind.p: compiling because target files not found or not up to date /Source/ScheduleWindow.p: compiling because target files not found or not up to date /Source/PrefKeys.p: recompiling because interface of `GPCMacOSAll.pas' has changed /Source/InterarchySupportBundle.p: recompiling because an interface used indirectly has changed Compiling InterarchySupportBundle.p (603) gpc -D__ppc__ -D__POWERPC__ -D__NATURAL_ALIGNMENT__ -D__MACH__ -D__APPLE__ -g -gstabs -O0 -DINTERARCHY -Wall --unit-path=/Developer/Pascal/GPCPInterfaces:/Source/PNLLibraries:/Source/MacOSXSupport:/Source:/Build --object-path=/IAObjects --include=/Source/PNLLibraries/Prefix.GPC -I /IAObjects -I /IAObjects/ -I /Developer/Pascal/GPCPInterfaces -I /Source/PNLLibraries -I /Source/MacOSXSupport -I /Source -I /Build -I /IAObjects/ -I . -I /Developer/Pascal/gpc-20050331/lib/gcc/powerpc-apple-darwin8.1.0/3.4.3/units -I /Source/ --unit-path=/Source/ --gpi-destination-path=/IAObjects/ --unit-path=/IAObjects/ --no-automake -c -o /IAObjects/InterarchySupportBundle.o /Source/InterarchySupportBundle.p --uses=GPCMacOSAll /Source/InterarchySupportBundle.p:18: error: `prefkeys.gpi' must be recompiled -- <http://www.stairways.com/> <http://download.stairways.com/>

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