gmane.comp.gcc.devel

Re: optimizations with -mcpu=cortex-a8, -mtune=cortex-a8

Ian Lance Taylor — 2008-08-21T14:45:09

gcc< at >gcc.gnu.org is the wrong mailing list for this sort of question. It should be asked on gcc-help< at >gcc.gnu.org. Please take any followups there. Thanks. In this case it's fairly likely that the default CPU for your compiler is something similar to cortex-a8. The differences between CPUs are often fairly subtle, and may not cause a change in the generated code for most, or sometimes any, programs. Ian

Re: [PATCH] Update libtool to latest git tip

Paolo Bonzini — 2008-08-21T14:29:26

Why? Regressions, or just no time? Actual approval depends on your answer to this question, but the patch is technically okay. Can you commit it to the src repository too? There is some regeneration to do there too. Paolo

Re: Something general (beginner related)

Manuel López-Ibáñez — 2008-08-21T10:33:50

2008/8/20 Nils Pipenbrinck cubic.org>: We know and we agree and we would like this to improve. Believe me, it was worse just 2 years ago. It is slowly improving but we need more help. Or even your own pass could be the pseudo-pass. This is a good place to start improving documentation: http://gcc.gnu.org/wiki/WritingANewPass You do not need any approval to modify all this and you can always ask in this list for some reviewers afterwards. Yes, but hired developers are not paid to do this and volunteers are typically interested on investing their limited free time in other things. This is catch22 that you are already experiencing: If you are a total newbie, you do not feel confident to write any documentation. If you are experienced, you want to implement things rather than write documentation that you do not need anymore. http://gcc.gnu.org/wiki/GTY http://gcc.gnu.org/wiki/Memory_management?highlight=%28gty%29 http://gcc.gnu.org/wiki/GCC_glossary?highlight=%28gty%29 We actually have lots of documentation but it is not very inter-connected, complete or condensed. We appreciate any help on this. We would accept patches that just improve the comments in the source-code (as long as they are correct and submitted properly). Cheers, Manuel.

Re: How to use gcc source and try new optmization techniques

Manuel López-Ibáñez — 2008-08-21T10:17:12

Rohan, Welcome to GCC and I hope you achieve what you want. I would recommend you check our wiki: http://gcc.gnu.org/wiki which has some very useful links: http://gcc.gnu.org/wiki/GettingStarted It is a wiki, so feel free to correct mistakes, improve stuff and add links. If you want to create a page for your project, please do so. Seema, I see a link to the workshop but not a link to the GCC resource center you linked. Would you like adding one under "Tutorials, HOWTOs". Cheers, Manuel. 2008/8/21 Seema Ravandale gmail.com>:

Re: [graphite] Get graphite backend working again [scalar variable handling]

Albert Cohen — 2008-08-21T07:57:54

You are correct. It is sufficient to substitute the SSA variables wherever they appear, as it is done now. Albert

optimizations with -mcpu=cortex-a8, -mtune=cortex-a8

Dasgupta, Romit — 2008-08-21T06:56:58

Hi, I came across the -mpcu=cortex-a8 option in the codesourcery gcc. When I added that to build the Linux kernel, I found that there are no differences in the kernel code with and without the options. The following are the gcc options that where used to build the kernel. Am I missing something? -nostdinc -isystem /data/arm-2007q3/bin/../lib/gcc/arm-none-linux-gnueabi/4.2.1/include -mlittle-endian -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Os -fno-stack-protector -marm -fno-omit-frame-pointer -mapcs -mno-sched-prolog -mabi=aapcs-linux -mno-thumb-interwork -march=armv7a -mcpu=cortex-a8 -mtune=cortex-a8 -msoft-float -Uarm -fno-omit-frame-pointer -fno-optimize-sibling-calls -g -Wdeclaration-after-statement -Wno-pointer-sign Thanks, -Romit

Re: How to use gcc source and try new optmization techniques

Seema Ravandale — 2008-08-21T05:35:10

Hi Rohan, I have already worked on cfg data structure, plugin "data flow pass" on cfg. For this purpose, following links would be useful. http://www.cse.iitb.ac.in/~uday/gcc-workshop/?file=downloads more info can be available at http://www.cse.iitb.ac.in/grc/ - Seema On Thu, Aug 21, 2008 at 6:51 AM, Pranav Bhandarkar gmail.com> wrote:

Re: How to use gcc source and try new optmization techniques

Pranav Bhandarkar — 2008-08-21T01:21:03

Hi, I may not have correctly understood your questions but from what I understand I think you mean to ask how you could easily plug in your optimization pass into GCC so as to test your implementation of some optimization. Well, the way to do that would be to understand the pass structure and decide where in the order of passes should your pass be inserted i.e after which and before which other pass should your optimization pass fit in. Look at passes.c to see how the order of passes is specified. Once you have told the compiler when to execute your pass (primarily through passes.c) and provided your optimization has been correctly implemented in the context of GCC you should be good to go. HTH, Pranav On Wed, Aug 20, 2008 at 7:45 PM, Rohan Sreeram yahoo.com> wrote:

How to use gcc source and try new optmization techniques

Rohan Sreeram — 2008-08-21T00:45:25

Hi, I am a student in Utah State University researching on compilers optimization techniques. I wanted to know how I could use gcc for experimenting with optimization. Here is what I intend to do: 1) Understand the control flow graphs being generated by GCC, which I could build using the -fdump-tree-cfg option. 2) Write code that could convert CFG to a different graph. 3) Use this new graph for optimization. 4) Use the optimized graph to generate machine code (say Intel architecture for now). Please let me know how I could leverage the GCC code for this purpose, and if you any suggestions/comments for me you are most welcome ! :) Thanks, Rohan

Re: [graphite] Google Summer of Code 2008 is over - Thank you

Sebastian Pop — 2008-08-20T23:52:42

Hi Tobias, On Wed, Aug 20, 2008 at 4:45 PM, Tobias Grosser fim.uni-passau.de> wrote: I would like to say a big thank you for your contributions. It was a pleasure to work with you during this SOC, and I hope to have your valuable opinion, remarks and patches for loop optimizations and parallelization on top of the graphite infrastructure. Sebastian

gcc-4.2-20080820 is now available

2008-08-20T22:43:27

Snapshot gcc-4.2-20080820 is now available on ftp://gcc.gnu.org/pub/gcc/snapshots/4.2-20080820/ and on various mirrors, see http://gcc.gnu.org/mirrors.html for details. This snapshot has been generated from the GCC 4.2 SVN branch with the following options: svn://gcc.gnu.org/svn/gcc/branches/gcc-4_2-branch revision 139353 You'll find: gcc-4.2-20080820.tar.bz2 Complete GCC (includes all of below) gcc-core-4.2-20080820.tar.bz2 C front end and core compiler gcc-ada-4.2-20080820.tar.bz2 Ada front end and runtime gcc-fortran-4.2-20080820.tar.bz2 Fortran front end and runtime gcc-g++-4.2-20080820.tar.bz2 C++ front end and runtime gcc-java-4.2-20080820.tar.bz2 Java front end and runtime gcc-objc-4.2-20080820.tar.bz2 Objective-C front end and runtime gcc-testsuite-4.2-20080820.tar.bz2 The GCC testsuite Diffs from 4.2-20080813 are available in the diffs/ subdirectory. When a particular snapshot is ready for public consumption the LATEST-4.2 link is updated and a message is sent to the gcc list. Please do not use a snapshot before it has been announced that way.

[graphite] Google Summer of Code 2008 is over - Thank you

Tobias Grosser — 2008-08-20T21:45:18

Hi gcc community, hi graphities, since Monday Google Summer of Code 2008 is over and I would like to write a little bit about my SOC project. First of all I would like to thank Sebastian for being my mentor. It was really fun to work with you. I never felt alone and always got great mail or phone response, if I was not sure where to go. And also thanks to all the other gcc and graphite people, that contributed to graphite and helped me working on my GSoC project. I got many valuable mails and bug reports helping me improving my code. What I really liked was the good integration in the graphite team, so that from the first days I felt like home. I got all support I needed and our weekly (except exceptions) phone conferences helped me to get to know the team better. Now I know some of you by hearing your voice, but it would be even better to see you once in real live! I also would like to thank Laurent for the CompileFarm account. A very useful service for gcc development. In the last weeks I realized a little problem in my graphite work. As I worked so well with the graphite folks, I just completely forgot to use the gcc mailing lists and to get in touch with the countless gcc developers. So I apologize for this and will try to change this now. As a starter I would like to inform you, what I have done during the last 4 months: What I wanted to do: ==================== […] At the moment the general shape of the GRAPHITE framework is quite clear and people have started to work on different areas. While they reached new areas of development, it became quite clear, that the GRAPHITE frontend, the translation from GIMPLE to GRAPHITE has some serious drawbacks, which stop people to continue their development fast and efficiently. During Summer of Code I would like to solve these problems and build a solid basis for further graphite development. […] More on my proposal at: http://students.fim.uni-passau.de/~grosser/gcc_soc/ What is done: ============= 1. SCoP detection ----------------- We scan the CFG to detect all parts, that we can transform to the polyhedral representation (GRAPHITE). * This pass works and is verified by the graphite and polyhedron test suites. * We detect conditions containing (<=, <, >, >=), perfect loop nests with single exit, and allow parameters in loop borders and conditons. 2. GIMPLE => GRAPHITE --------------------- Now the control flow of the detected SCoPs is translated to the polyhedral representation. This means loop borders and conditions are inserted into a matrix, that tells us for which values of the loop indeces the bbs are executed. * Works for all detected SCoPs 3. Cloog Output --------------- Cloog is the library we use to regenerate the CFG. We insert the polyhedral model and get an ast, describing the loop structure after applied optimizations. Cloog is also able to optimize in control structures (e.g. move conditions out of loops) so even without optimizations passes we get optimizations. * Works for all detected SCoPs 4. Loop blocking ---------------- * I wrote a first experimental pass, to show how graphite transformations work. So GRAPHITE has now a front end, that is able to detect most of the common loop nests and get them into the graphite representation. In Polyhedron e.g. we detect already 411 SCoPs with 536 loops and 1303 bbs. These are 15% of all loops (3587). And there is many space for improvements. What is left to be done: ======================== 1. SCoP detection ----------------- * Conditional statements containing “||” or “&&”. * Switch statements. * Loops with multiple exits. * Iterative optimization to maximize SCoP size. 2. GIMPLE => GRAPHITE --------------------- * Conditional statements containing “||” or “&&”. * Switch statements. * Loops with multiple exits. * Allow scev parameter detection in SCoPs, that are not surrounded by a loop. 3. Graphite middle end ---------------------- Here we reach hardly touched ground, where a large number of optimizations are possible. For example: * Dependency detection * Loop splitting * Loop fusing * … * Automatic parallization I will keep on working on graphite, the next weeks on the import and after that heading to some of the open tasks. So even if Google Summer of Code has finished. I do not want to say “Goodbye”, but “Hello” to you. I am looking forward to work with you on gcc and graphite! See you Tobi

Re: Better GCC diagnostics

Robert Dewar — 2008-08-20T19:52:11

The error mechanism in Ada is very extensive, probably would be quite a bit of work to find out how to interface effectively to this API, but something that would be nice to do in the long run.

Re: Creating own Backend: Segmentation fault in mark_jump_label_1

Ian Lance Taylor — 2008-08-20T17:34:48

Um, yes. Sorry, and thanks for the correction. Ian

Re: Creating own Backend: Segmentation fault in mark_jump_label_1

Joe Buck — 2008-08-20T17:19:40

I think you meant to say "We can answer precise and detailed ...".

RE: [graphite] Use of loops_mappings (SVN r138161)

Sjodin, Jan — 2008-08-20T16:30:58

I think we got confused about the existing implementation. The concern was that a transform could affect multiple GBBs/loops, but everything is done to individual GBBs so that is not the case. We should remove the loops_mapping instead since the existing implementation is simpler. I tired to remove the loops_mapping and use the GBB_LOOPS instead and all the tests pass. - Jan

Re: Better GCC diagnostics

Arnaud Charlet — 2008-08-20T16:09:12

Well, clearly, the preprocessor and handling of #include is very C/C++ specific, and not used by Ada or Fortran. As for diagnostics, Ada does use its own mechanism, mainly because it's much more powerful than the one in libcpp, and handles e.g. multiple locations related to cascaded generic package instantiations (C++ templates), as well as many other goodies already described by Robert is previous messages. It has also handled column info from day one (and we would not want any of the e.g. -fshow-column stuff: why would you *not* want to display column information ? :-) So from GNAT's point of view, what's the point in duplicating all this work done and written in Ada in another less capable language (which would also make it more painful for GNAT developers to use), in particular if this capability is only available in very recent GCC versions. Arno

Re: Better GCC diagnostics

Manuel López-Ibáñez — 2008-08-20T16:00:48

2008/8/20 Arnaud Charlet adacore.com>: Not just that, probably Fortran/Ada are already duplicating stuff that is in libcpp or they are implementing their own version of stuff that C/C++ are lacking (caret diagnostics? character encodings?). Cheers, Manuel.

Re: Better GCC diagnostics

Arnaud Charlet — 2008-08-20T15:54:47

Agreed. Other modules may find these APIs very handy. Currently many features are only available very deep or hidden inside libcpp implementation that could be useful in other contexts (such as e.g. getting source file dependency information). Arno

Re: Better GCC diagnostics

Manuel López-Ibáñez — 2008-08-20T15:52:01

2008/8/20 Tom Tromey redhat.com>: It is essentially. However, all the internal things are exposed all over the place for no good reason. This is in gcc/c-lex.c /* #define callback for DWARF and DWARF2 debug info. */ static void cb_define (cpp_reader *pfile, source_location loc, cpp_hashnode *node) { - const struct line_map *map = linemap_lookup (line_table, loc); - (*debug_hooks->define) (SOURCE_LINE (map, loc), + (*debug_hooks->define) (location_source_line (location_manager, loc), (const char *) cpp_macro_definition (pfile, node)); } This is in tree.h -expanded_location -expand_location (source_location loc) -{ - expanded_location xloc; - if (loc == 0) - { - xloc.file = NULL; - xloc.line = 0; - xloc.column = 0; - xloc.sysp = 0; - } - else - { - const struct line_map *map = linemap_lookup (line_table, loc); - xloc.file = map->to_file; - xloc.line = SOURCE_LINE (map, loc); - xloc.column = SOURCE_COLUMN (map, loc); - xloc.sysp = map->sysp != 0; - }; - return xloc; -} +#define expand_location(LOC) location_expand (location_manager, (LOC)) + Moreover, the location_manager probably should be separated from CCP. If we want to implement re-opening files and reading strings given locations, then opening/reading files should also be moved out of CCP to its own module/namespace/object. Cheers, Manuel.

Re: Better GCC diagnostics

Tom Tromey — 2008-08-20T15:17:49

Manuel> If I ever get the time, I would like to abstract our line-map Manuel> implementation within a "location_manager" object and API but Manuel> I don't think this conflicts directly with your work. I am curious to know how this would be different from what we have now. I think the line-map API is rather ugly, personally, but it seems to me that a "struct line_maps" is essentially a location manager object. Tom