Gpc June 2008

gpc@gnu.de

3 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

GPC and the Linux Standard Base
by Yang Lao 12 Jun '08

12 Jun '08

I wonder if any version of gpc for linux is compliant or conformant with the Linux Standard Base. When I run your hello program through their lsbappchk it gives messages like this: FAIL Symbol isnanl is used, but is not included in LSB 3.2 (Core & C++ & Desktop)

2 2

[Fwd: GCC 4.3.1 Released]
by Adriaan van Os 09 Jun '08

09 Jun '08

-------- Original Message -------- Subject: GCC 4.3.1 Released Date: Mon, 9 Jun 2008 03:49:31 -0400 From: Jakub Jelinek <jakub(a)redhat.com> Reply-To: Jakub Jelinek <jakub(a)redhat.com> To: gcc-announce(a)gcc.gnu.org, gcc(a)gcc.gnu.org GCC 4.3.1 has been released. GCC 4.3.1 is a bug-fix release, containing fixes for regressions in GCC 4.3.0 relative to previous GCC releases. See: http://gcc.gnu.org/gcc-4.3/changes.html and particularly http://gcc.gnu.org/gcc-4.3/changes.html#4.3.1 for more information about changes in GCC 4.3.1. This release is available from the FTP servers listed here: http://www.gnu.org/order/ftp.html The release is in gcc/gcc-4.3.1/ subdirectory. As always, a vast number of people contributed to this GCC release -- far too many to thank individually!

1 0

[Fwd: GCC 4.2.4 Released]
by Adriaan van Os 09 Jun '08

09 Jun '08

-------- Original Message -------- Subject: GCC 4.2.4 Released Date: Wed, 21 May 2008 15:13:16 +0000 (UTC) From: Joseph S. Myers <joseph(a)codesourcery.com> Reply-To: gcc(a)gcc.gnu.org To: gcc-announce(a)gcc.gnu.org, gcc(a)gcc.gnu.org GCC 4.2.4 has been released. GCC 4.2.4 is a bug-fix release, containing fixes for regressions in GCC 4.2.3 relative to previous GCC releases. This release is available from the FTP servers listed at: http://www.gnu.org/order/ftp.html Please do not contact me directly regarding questions or comments about this release. Instead, use the resources available from http://gcc.gnu.org. As always, a vast number of people contributed to this GCC release -- far too many to thank individually!

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Gpc June 2008