Gpc May 2008

gpc@gnu.de

4 participants
6 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?)

10 16

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

7 44

turn off lazyIO on disk files
by Wolfgang Helbig 04 Jul '08

04 Jul '08

Hi, the program, Don Knuth's TeX adapted to GPC version 2.1, does heavy I/O on text files. I noticed a very high percentage of system time. I believe this is due to lazy I/O, which seems to be unbuffered. GPC should apply lazy/IO when the text file comes from the keyboard, but to use buffered I/O when it comes from the disk. Is there a way to turn off lazy/IO on nonterminal text files? Greetings, Wolfgang Helbig

3 2

Re: Mac OS X Pascal Interfaces version 2.1
by Adriaan van Os 06 May '08

06 May '08

> Updated Mac OS X Pascal Interfaces, version 2.1 (release H), can be downloaded from > <http://www.microbizz.nl/gpc.html>. The direct link is <http://www.microbizz.nl/GPCInterfacesH.dmg> The installer package missed a file (PLibraries/GPCMacOS.a). The file has been added. Regards, Adriaan van Os

1 0

Mac OS X Pascal Interfaces version 2.1
by Adriaan van Os 06 May '08

06 May '08

Updated Mac OS X Pascal Interfaces, version 2.1 (release H), can be downloaded from <http://www.microbizz.nl/gpc.html>. The direct link is <http://www.microbizz.nl/GPCInterfacesH.dmg> The installer package contains Mac OS X Pascal interface units for GNU Pascal, FreePascal and MetroWerks CodeWarrior Pascal. A lot of work went into this new release, units were added or updated and several bugs have been fixed. There are now 330 Pascal interface units. For GPC on Mac OS X, this release requires the recently released gpc346u2 compiler (and a soon-to-be released new GPC Xcode kit). Please report bugs to <gpc(a)microbizz.nl>. The Pascal Interfaces team: Peter N. Lewis <peter(a)stairways.com.au> Jonas Maebe <jonas.maebe(a)elis.ugent.be> Adriaan van Os <http://www.microbizz.nl/gpc.html> Gale Paeper <gpaeper(a)empirenet.com>

1 0

pascal strings in the gnu assembler
by steven.borley 05 May '08

05 May '08

Hope this is not considered too off-topic as it about the gnu assemble (gnu-as). I beg forgiveness on grounds that's its Pascal related. In my assembly code I'm trying to place string constants in memory (length byte followed by ASCII string with no trailing zero byte) The following is failing with "Error: illegal relocation size: 1" FOO: .byte ((BAR - . - 2) & 0x7F) ; calculate length .ascii "foo" BAR: .word 0x1234 ; dummy for this example I could just hard code the length, except I eventually want this as macro as I have several hundred strings. And unfortunately this part of the code has to be in assembler, for various reasons. I assume the error is because ((BAR - . - 2) & 0x7F) resolves to a two byte type even although we can see its value would always fit within a byte. It didn't seem a particularly unusually thing to want to do so I'm hoping someone can point me in the right direction with this. Regards, Steven

3 2

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Gpc May 2008